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Beyond bones & stones

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Lee Berger’s son, Matthew, found the ~1.9 million year old hominin remains of female adult and a juvenilemale in cave deposits at Malapa, South Africa. The remains have been analyzed and been published inScience today, and so far this finding is the big fossil hominid of 2010. The skull of the juvenile is the coverimage for this week’s issue of Science.

Australopithecus sediba on the coverof Science

Today’s paleoanthropology new is what was eluded to by a commenter last month. I talked to somecolleagues about what the commenter could have been referring to back then, and they told me Berger’sgonna be releasing his findings on UW88-50. I didn’t report on it then because of several reasons, one ofwhich was time constraints but also because I really didn’t have much information on the fossils. There’s a lotmore press out today about it and while, I don’t have much time to digest it all, I figured I’ll at least share itwith you in case you’ve been living under a rock.

The remains have been given a new species classification, Australopithecus sediba and are probablydescendants of Australopithecus africanus. Like every other new fossil hominin species, there’s an array ofarchaic and modern features. The small teeth, projecting nose, very advanced pelvis, along with the long legsare the more modern features. The archaic features are the long arms and small brain case. What is specialabout Australopithecus sediba is that the hominin fossil record is pretty sparse around 1.9 million years agoand this fossil helps fill that gap.

Check out the news coverage, BBC, ABC News…

Australopithecus sediba (UW88-50) of Malapa, South Africa « Anthropol... http://anthropology.net/2010/04/08/australopithecus-sediba-uw88-50-of-...

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Photo: Brett Eloff, courtesy of LeeBerger and the University of the

Witwatersrand

Australopithecus sediba (specimenUW88-50)

Australopithecus sediba on thecover of Science

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Berger, L., de Ruiter, D., Churchill, S., Schmid, P., Carlson, K., Dirks, P., & Kibii, J. (2010).Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa Science, 328(5975), 195-204 DOI: 10.1126/science.1184944

Dirks, P., Kibii, J., Kuhn, B., Steininger, C., Churchill, S., Kramers, J., Pickering, R., Farber, D.,Meriaux, A., Herries, A., King, G., & Berger, L. (2010). Geological Setting and Age ofAustralopithecus sediba from Southern Africa Science, 328 (5975), 205-208 DOI:10.1126/science.1184950

Written by Kambiz Kamrani

April 8, 2010 at 7:09 pm

Posted in Physical Anthropology

Tagged with Australopithecus sediba, lee berger, paleoantropology, UW88-50

« Unearthed finger bone points to the possible discovery of an unknown hominin56 Family Portraits From East Asia »

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The “a. sediba” …

Is just another Australopithecus (1.78 – 1.9 million years ago ) that would have been contemporarywith H.erectus.

It may not even be a new speciesof Australopithecus.

3 2 Rate This

1.


2 of 8 3/7/2012 11:28 PM

Uill Frasiel

April 9, 2010 at 2:49 am

Reply

There were many australopithicines;a.Bosei,A.Robustus,A.Aferensis,A.Aafricanus and I’mthinking that the morphological differences were probably due to certain environmental stressorswithin the regions they occupied.So I presume that they are just Australopithicines.There werevariations even among Homo Sapiens Neanderthalensis as some of them were quite large andpowerful and others somewhat smaller;they to existed in various regions of Europe and they,asprobably all life forms,are subjected to stressors.These stressors may possibly be both externaland internal-and I have no clue as to the time when early man could react by thinking.And,ofcourse,being able to think is not an absolute solution to a species survival.Homo habilis was ahandyman and I would guess that this would have to be,due to the use of hands and tools,justbefore H.Erectus,the fire bringer.The way scientists could make an educated guess concerningthe new find would be to examine the shape and size of the frontal lobes within the frontal andparietal areas of the cranium.By the way,Stephen J. Gould,I Believe was a notedastrophycisist(not sure of spelling).This is off subject,but he was interveiwed about Einsteinsrelativity theory,and he stated,”you know,I still can’t figure how he thought of that”. I hope ourspecies survives(if we are a species).We are intelligent,and this does help,however,it asmentioned above,is not absolute.This is probably wrong in some areas,as I’m not apaleoanthropologist.I’m just an amateur astrophotographer and I think we are all special andpossibly unique.I wonder, who was the first hominid to have just a ghost of a thought-Who amI,is there nothing more.

0 0 Rate This

mark

August 4, 2011 at 11:53 pm

Reply

Missing link or new species?There are few branches on the bush of apes and old world monkeys but there is a genealogicalsequence of branching in the evolution of apes and humans.The late Stephen Jay Gould for one helped me to understand the proper metaphor is bush not ladderand this help me to understand why the search for a “missing link” between advanced apes andincipient human is so meaningless.A continuous chain may lack a crucial connection, but a branching bush bears no single link at a crucialthreshold between no and yes. Rather, each branching point successively restricts the range of closestrelatives, the ancestors of all apes being separate from monkeys, forebears of the orangutan from thechimp-gorilla-human- complex, finally precursors of chimps from the ancestors of humans. No branchpoint can have special status as the missing link and all represent lateral relationships of diversification,not vertical sequences of transformation.There is a common precuror to primates further down the branching bush.An interested in paleoentology can be rewarded with reference to S J Gould 1993, Eight Little Piggies.

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It is wonderful to be finding more hominids but I still don’t quite understand why there are so fewfossils maybe we just haven’t been here long enough in large numbers.

1 1 Rate This

Garry Prockter

April 9, 2010 at 7:59 pm

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Harsh-Berger:http://www.nature.com/news/2010/100408/full/news.2010.171.html

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Occam's Razor

April 10, 2010 at 5:29 am

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3.

Another species of human lineages? Australopithecines around 1.8 mya? How many species of humanlineages did we have? Are they all really different species? I think this article raises more questions thananswers for understanding human evolution. One thing that we know quite for sure is existence of agreater biological variation existed in the past than we have today.

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anthrogenetics

April 10, 2010 at 5:15 pm

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4.

Thanks for the link, Occam’s Razor. I think the following comment there sums it up: ‘The new fossilhas a suite of characters which confirm that there is no clear boundary between Australopithecusafricanus and Homo’.

“How many species of human lineages did we have? Are they all really different species?”

I doubt very much the new discovery is actually a different species. All species vary over theirgeographic range, and I’d presume Australopithecus did too. Even today the inhabitants of South Africadiffer in appearance from those of East Africa, and especially from those of West Africa in spite of theBantu expansion.

“Rather, each branching point successively restricts the range of closest relatives”

The fact that various Australopithecus populations possess different aspects of the later Homo genus

5.


4 of 8 3/7/2012 11:28 PM

suggests to me that human evolution was more complicated even than a simple ‘bush’. It suggestsmixing and (dare I say it?) hybridization.

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terryt

April 11, 2010 at 7:41 pm

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it is my opinion early hominid lineage will show much more variation then late (and usually then later).simply because like with most animals the geographical distribution (or(..) habitat) would tend to bemore limited and the environmental effects for the species therefore more pronounced. as such i missany comparative indications about the paleo-environmental setting. it would be interesting to know ifthe claim of a new species is supported by indications of a different habitat from other australopitheci.as it stands i am sceptical. to mention one example, it is said that the pelvis is very advanced, yet only arather small fraction of one is found and probably not intact. i am nevertheless very interested in whatelse will follow and be found,since we don’t know much about austr.it occured to me also the specimen appears somewhat archaic for the apparent dating. almost suggestinga remnant population. of that however i am not to sure, the one or few habilis fossils are not much of asolid sample either. btw how i read the article the assumption that animal were drawn by the smell ofwater concerned other animal fossils then hominids found in the same eroded cave system. hominidscould for example be drawn to close by the noise of trapped and wounded animals.

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onyx

April 12, 2010 at 3:39 am

Reply

6.

[...] Anthropology.net. Australopithecus sediba (UW88-50) of Malapa, South Africa.(paleoanthropology) Okay.. the last one for A. sediba. I promise. But there are some cool photos and anslightly different perspective on the story. Nothing shocking… just a different angle. [...]

0 1 Rate This

90th Edition of the Four Stone Hearth!

April 15, 2010 at 9:00 am

Reply

7.

wonderful article. we did the interview in easy science between our character sibo and matthew

1 0 Rate This

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Sanderson Peter

July 1, 2010 at 2:00 am

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alluded to, not eluded..eluded is to escape from ..sorry, grammar nerds read this too, not justanthropology ones!

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deirdre milks

September 9, 2010 at 12:23 am

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9.

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Human Evolution | Search | Dictionary

Australopithecus africanusThe Taung Child specimen

Photo: Guérin Nicolas

"Mrs. Ples" (click to enlarge)Photo: Luna04

Dart with Taung skull

"Mrs. Ples"Photo: Guérin Nicolas

Taung ChildBeak gouges?

(click to enlarge)Photo: Lee Berger

Online Biology Dictionary

The material attributed to this hominid has been found in only four caves:Taung, Sterkfontein, Makapansgat, and Gladysvale, all in northwesternSouth Africa. The fossils are from two to three million years old.

The first Australopithecus africanus specimen —or australopithecine of any kind — everdiscovered was the Taung Child, (sometimescalled the "Taung Baby" — the individual inquestion was three-and-a-half years old) ofwhich the facial portion of the skull iswell-preserved (see figure below right). It wasfound in a box of rocks from the cave at Taungby anatomist Raymond Dart of the University of

the Witwatersrand in Johannesburg. He at first could see only a brain castprotruding from a chunk of stone, but he saw immediately that a primatewas in question, and painstakingly chipped the embedded face free of therock matrix.

Dart (1925) immediately claimed the specimen represented a very earlyhuman ancestor. The scientific establishment, however, long rejected hisclaim. Accepted wisdom at the time said humans had come into being inAsia.

The most complete skull of an Australopithecusafricanus adult ever found (dating to 2.15 mya),a specimen (STS 5) nicknamed "Mrs. Ples" (seefigure at right), was discovered in 1947 by Dart'sfriend, Robert Broom and John T. Robinson atSterkfontein (see figure below right). Ples isshort for Plesianthropus, the defunct genus towhich the skull was originally assigned. Manyadditional Australopithecus africanus fossils continue to be found at Sterkfontein (seepicture of excavation), but no others have ever been found at Taung, despite intensivesearch.

In a recent paper (Berger 2006), paleontologist Lee Berger provides strong evidence thatmarks in the eye sockets of the Taung Child are damage caused by birds of prey. The studyshows it's likely that an eagle brought the child to the site where the skull was discovered,and that this is the reason for the absence of other australopithecine remains at Taung. Themarks that have been interpreted as beak damage caused when eagles ripped out theunfortunate child's eyes are indicated in the figure at left.

Similar to its northern precursor, Australopithecus afarensis, which is known from eastAfrica, Australopithecus africanus was bipedal with arms a bit longer than its legs. Bothwere gracile australopithecines with relatively slender builds.

†

Australopithecus africanus – Raymond Dart's baby http://www.macroevolution.net/australopithecus-africanus.html

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A. africanus is known onlyfrom nw South Africa

More about Australopithecus africanus >>

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Biology Dictionary >>

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Habitat: Savanna-forest mosaic.

Synonym: Plesianthropus transvaalensis.

Etymology: The name of this hominid is constructed from the Latinprefix australo-, the Greek suffix -pithecus, and the Latin wordafricanus meaning from or of Africa.

Note: The skull of the Taung Child is strikingly similar to skullsattributed to the far more recent Homo floresiensis.

Work cited: Dart, R. A. 1925. Australopithecus africanus: theman-ape of South Africa. Nature, 115: 195-199. (793 Kb download of Dart's first report of the discovery of theTaung skull)

Ardipithecus ramidus >>

Australopithecus afarensis >>

Australopithecus anamensis >>

Australopithecus bahrelghazali >>

Australopithecus garhi >>

Australopithecus sediba >>

Kenyanthropus platyops >>

Paranthropus aethiopicus >>

Paranthropus boisei >>

Paranthropus robustus >>

Orrorin tugenensis >>

Sahelanthropus tchadensis >>

Homo habilis >>

Homo rudolfensis >>

Homo erectus >>

Homo ergaster >>

Homo cepranensis >>

Homo heidelbergensis >>

Homo rhodesiensis>>

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Homo neanderthalensis>>

Homo georgicus >>

Australopithecus africanus had a cranial capacity of about 450 cc, a brain size that puts it on a par with a ratherbrainy modern chimpanzee.

Experts who argue Australopithecus africanus was an ancestor of modern humanssay it was somewhat more human-like with respect to cranial characteristics thanwas Australopithecus afarensis. However, it also had apelike traits such as curvedfingers suited for climbing trees. Such simian features suggest to some researchersthat A. africanus evolved into Paranthropus robustus, one of the robustautralopithecines, not Homo.

However — whether the facts are consistent with the idea that australopithecineswere direct ancestors of humans or not — Raymond Dart's work, together with thatof Robert Broom and the Leakeys, succeeded in convincing the scientific world thatDarwin had been right in asserting humankind had its origins in Africa.

The focus remains on that continent today, though the exact role of theaustralopithecines in human evolution has yet to be resolved.

Interesting facts and information about other ancient hominids:

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Origins of Humankind

The Hominid Family Tree

Orrorin tugenensis(6 mya)Ardipithecus ramidus(4.4 mya)Australipithecus anamensis(4.2 to 3.9 mya)Australipithecus afarensis(3.6 to 2.9 mya)Kenyanthropus platyops(3.5 to 3.3 mya)

Australipithecus africanus(3 to 2 mya)Australipithecus aethiopicus(2.7 to 2.3 mya)Australipithecus garhi(2.5 mya)Australipithecus boisei(2.3 to 1.4 mya)Homo habilis(2.3 to 1.6 mya)

Homo erectus(1.8 to 0.3 mya)Australipithecus robustus(1.8 to 1.5 mya)Homo heidelbergensis(600 to 100 tya)Homo neanderthalensis(250 to 30 tya)Homo sapiens(100 tya to present)

mya = millions of years ago tya = thousands of years ago

Australopithecus africanus (3 to 2 million years ago)

Species Description:

Australopithecus africanus was nearly identical in body and brain size to A. afarensis.Like A. afarensis, A. africanus also showed marked differences in size between malesand females. Although the teeth and jaws of A. africanus were much larger thanmodern human teeth, they are still more similar to ours than to the teeth of apes. Theupper and lower jaws of A. africanus were also fully rounded in front, like those ofmodern humans, and their canine teeth were smaller on average than those of A.afarensis. Australopithecus africanus individuals probably inhabited open woodlands,where they would have foraged for fruits, seeds, and roots.

Fossil Finds:

Taung ChildEstimated age: 3 to 2 million yearsDate of discovery: 1924Location: Taung, South Africa

Collected by workers in a lime quarry, this was the first Australopithecus fossilever discovered. The scientific community initially rejected the identification ofthis partial skull, saying that it was some sort of extinct ape species ratherthan an early form of hominid.

Mrs. PlesEstimated age: 3 to 2 million yearsDate of discovery: 1947Location: Sterkfontein, South Africa

This adult cranium, most likely from a female A. africanus, is the bestspecimen of the species discovered so far.

STS 14Estimated age: 3 to 2 million yearsDate of discovery: 1947Location: Sterkfontein, South Africa

These remains of a small adult female include a nearly completevertebral column, a pelvis, some rib fragments, and part of afemur. The pelvis is far more humanlike than apelike and is strongevidence that A. africanus was bipedal.

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This page was last updated on 6/17/00.

Introduction

The species of Australopithecus africanus was named in a February, 1925, issue of Nature by Raymond Dart.R. Dart was one of the pioneers of paleoanthropology, and created quite a furor over the naming of the fossilspecimen (the Taung Child skull and endocast) as a hominid. The standard line at the time by some of thepowerful figures in the field (e.g., A. Keith and O. Abel) was that the ancestors of humans should be found inEurope, and should have an enlarged brain and an apelike jaw (as was the case in the Piltdown Man hoax).The claim that the specimen was a hominid was rejected by those who saw the material as that of a youngchimpanzee or gorilla. This view was not helped by the difficulty in acquiring casts, the material was distantfrom many in the field (few of which ever travelled to actually view the material), and most importantly, wasthat of a juvenile. Juveniles are often misrepresentative of adult states, and most researchers claimed that theTaung Child would have developed into a chimpanzee or gorilla ancestor.

Due to the hostile or indifferent response of his peers, Dart never followed up the find with furtherexcavations, and no other specimens of the species have been found at Taung. Dart dedicated himself todeveloping the anatomy department at the University of Witwatersrand, and it would be twenty years laterwhen sites like Sterkfontein were found that corroborated Darts ideas.

Though the genus designation mixed both Latin ("australo") and Greek ("pithecus"), the genus name hasbecome accepted as the label by which the group of pre-Homo hominids in Africa have come to be known.Dart claimed that A. africanus was bipedal due to the position of the foramen magnum, and was vindicatedby later finds, such as STS 14, which showed unequivocally that africanus was an obligate biped.

Diagnostic Features

The earliest africanus material comes from sites such as Sterkfontein, Makapansgat, Gladysvale, and Taung.This material dates to the end of the Early Pliocene, mostly between 2.9-2.4 myr, with the SterkfonteinMember 2 material (possibly afarensis or other species) being the earliest known possible africanus, dating toabout 3.5 myr. The Sterkfontein material are problematic, as there may be intrusions from later strata, andthere is a heterogenous mixture of earlier and more modern faunal species, and thus, this material may be asyoung as 1.0 myr.

Most postcrania material attributed to africanus is well within the range of variation of the afarensis material,however, the limb proportions may be different. STS 14 is a 2.5 myr old specimen from Sterkfontein. Thisspecimen is particularly important as it includes both os coxa, as well as many of the vertebrae. This findshowed unequivocally that these hominids were bipedal, and were not simply apes, vindicating RaymondDart. Features of STS 14 that align it with a more humanlike locomotor capacity include:

The iliac blade is short and wide.There is a well-developed sciatic notch.There is a strong anterior inferior iliac spine.

Australopithecus africanus http://www.modernhumanorigins.net/africanus.html

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STS 14 has six lumbar vertebrae (whereas modern humans have five, and chimps usually have three). With anincreased number of lumbar vertebrae (the ancestral condition, as in cercopithecoids), bipedalism may havebeen the ancestral condition (from a very small-bodied primate?). While it is ver similar in morphology(relative to its size), there are also differences. This specimen differs from modern human in that:

There is a forward projecting anterior superior iliac spine.A very small articular surface for the sacrum.A marked outward flare of the iliac blades.

There is a fairly large sample of africanus teeth known (though not as large a smaple as the afarensismaterial). The material shows several important differences when compared to afarensis that include:

Postcanine teeth are larger, more bulbously cusped, and relatively broader (the size difference is greaterin the later erupting teeth of each type), and may have somewhat thicker enamel, especially on thetooth walls.Dm1 is larger and more squared, with more equal sized cusps.The anterior lower premolars are always bicuspid, usually with equal or close to equal sized cusps, andwear more similarly to the other premolars.The anterior lower premolars have greater enamel thickness.Compared intrasex, the africanus central incisors show no reduction but the other anterior teeth areusually smaller. The ranges almost completely overlap, however, and there are very large canines andincisors in both samples.No canines wear to have cutting edges (canine-premolar diatemata are rare), even though a few arelarge enough to project beyond the level of the other teeth (this is much more common in the afarensissample).

Although the canines are reduced compared with the earlier Plocene samples, their roots - especially those ofthe maxilla teeth - are still long and robust. The canines also wear more rapidly than the afarensis material,with the wear almost always on the tips. There is significant sexual dimorphism in the canines, although not asmuch as any of the apes, while there is sexual dimorphism on the level of gorillas in the postcanine material.This pattern of big teeth seems to have been influenced by the africanus diet and chewing pattern. A. Walkerand M. Wolpoff claim that the africanus chewing pattern is similar to modern hunter-gatherer groups, withthe molars and premolars designed to last a lifetime of wear and tear (the oldest individuals dying at about thetime they have no crowns left in their mouth - max age about 35). The diet of these South African hominidsseems to have been seasonal, with emphasis on a frugivory diet, with much seeds and other hard objects beingmasticated.

There is a good sized sample of africanus crania, allowing reasonably strong comments to be made on thematerials affinities to other material. Some of the better-known specimens include STS 5 (Mrs. Ples), a 2.5myr cranium of an adult male with a brain about 485 cc, STS 71, a 2.5 myr male partial cranium with anestimated 428 cc brain, STW 505, an indovidual with a brain esimated to have been 625 cc, and the typespecimen of africanus, the Taung Child. The facial features of the africanus material are a mixture of moremodern and archaic ones, with similarity to (and important differences between) the afarensis material. Someof these features (relative to afarensis include:

Retraction of the palate from a position in front of the face to under it.Forward shift of the zygomatic processes of the maxilla, the zygomatic bone, and the front of themasseter muscle, creating the zygomatic prominence.Expansion of the anterior part of the temporalis muscle.A broader nasal aperture.Anterior pillars extending above the canine roots, of variable expression creating thickened lateral nasalmargins.


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Structural changes in the jaw related to expanding premolars and molars, as well as incisor and(especially) canine reduction and decreased emphasis on anterior loading.

Conclusions

The africanus material is seen as different things by different people. Some see this as a regional variation orsubspecies of afarensis, some see it as two completely different species, and some consider the africanusmaterial to be the descendants of afarensis. Another important question that has been, is, and will probablyalways be debated is the question of whether the africanus material represents two or more species, asexually dimorphic species, or a very variable species (especially with regards to inter-era speculation). Theaccepted view seems to be that they deserve separate species status due to both their differences from theafarensis material and their geographic separation from them. However, a very important question in debateis whether or not this species contributed to the modern human lineage.

Bibliography

This bibliography contains the sources of the information cited above, as well as any sources that couldprovide any other information on the subject. If you know of any other sources that are pertinent to A.africanus, please e-mail me the citation in the format used below, and I will add it to the list. Any problemswith information I presented above can be sent to me here. I don't want to provide disinformation, and anycorrections are gladly accepted (with proper documentation of what is wrong and why, with sources). Thanks!

Abitbol, M.M. 1995. "Reconstruction of the STS 14 (Australopithcus africanus) pelvis" In American Journalof Physical Anthropology, vol. 96, pp. 143-158.

Aiello, L., and C. Dean. 1990. An Introduction to Human Evolutionary Anatomy. London: Academic Press.

Berger, L.R., and R.J. Clarke. 1995. "Eagle involvement of the Taung child fauna." In Journal of HumanEvolution, vol. 29, pp. 275-299.

Broom, R. 1925. "Some notes on the Taungs skull." In Nature, vol. 115, pp. 569-571.

Broom, R. 1947. "Discovery of a new skull of the South African ape-man, Plesianthropus." In Nature, vol.159, pp. 672.

Broom, R. and J.T. Robinson. 1949 "A new mandible of the ape-man Plesianthropus transvaalensis." InAmerican Journal of Physical Anthropology, vo. 7, pp. 123-127.

Broom, R., J.T. Robinson, and G.W.H. Schepers. 1950. "Sterkfontein Ape-man Plesianthropus" In Memoirsof the Transvaal Museum, no. 4.

Clarke, R.J. 1996. "The genus Paranthropus: What's in a name?" In Contemporary Issues in HumanEvolution., ed. by W.E. Meikle, F.C. Howell, and N.G. Jablonski, pp. ?-?. San Francisco: California Academyof Science.

Dart, R. 1925. "Australopithecus africanus. The man-ape of South Africa." In Nature, vol. 115, pp. 195-199.

Dart, R. 1967. Adventures with the Missing Link. Philidelphia: The Institutes Press.

Johanson, D., and B. Edgar. 1996. From Lucy to Language. New York: Simon and Schuster Editions.

Jones, S., R. Martin, and D. Pilbeam, eds. 1992. The Cambridge Encyclopedia of Human Evolution.


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Cambridge: Cambridge University Press.

McHenry, H. 1994. "Behavioral ecological implications of early hominid body size." In Journal of HumanEvolution, vol. 27, pp. 77-87.

McHenry, H. 1998. "Body proportions in Australopithecus afarensis and A. africanus and the origin of thegenus Homo." In Journal of Human Evolution, vol. 35, pp. 1-22.

Rak, Y. 1983. The Australopithecine face. New York: Academic Press.

Robinson, J.T. 1956. The Dentition of the Australopithecinae. Transvaal Museum Memoir No. 9, pp. 1-179.

Robinson, J.T. 1972. Early Hominid Posture and Locomotion. Chicago: University of Chicago Press.

Tobias, P.V. 1992. "New researches at Sterkfontein and Taung with a note on Piltdown and its relavence to thehistory of paleo-anthropology." In Transactions of the Royal Society of South Africa, vol. 48, pp. 1-14.

Wolpoff, M. 1999. Paleoanthropology. second edition. Boston: McGraw-Hill.

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Possible New Human Ancestor Discovered

By Brandon KeimEmail AuthorApril 8, 2010 | 10:53 am | Categories: Miscellaneous

Two 1.9 million-year-old skeletons found in a South African cave have added a new and intriguingmember to the primate family.Dubbed Australopithecus sediba, it has many features — including long legs and a protruding nose— common to Homo, the genus that eventually spawned humans. Other features, such as extra-longforearms and flexible feet, date from deep in our primate past.

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Paleontologists disagree over whether A. sediba is a direct human ancestor, or just looks like one.But whatever their lineage, the fossils provide rare insight into a period shrouded in paleontologicalmystery.“We feel that A. sediba might be a Rosetta Stone for defining for the first time what the genus Homois,” said paleontologist Lee Berger of the University of Witwatersrand. “They’re going to be aremarkable window, a time machine.”The skeletons, described April 8 in Science, were found — with a bit of help from Google Earth —two years ago in a South African cave, where they fell two million years ago.On one side of that date in the fossil timeline are the various species of Australopithecus, the firstgreat apes to walk on two feet. On the timeline’s other side is the genus Homo, the first creaturesone would recognize — with all due respect to Lucy’s famous A. afarensis — as close to human.In between is uncertainty. The fossil record is mostly bare. Some of the Australopithecus lineagesplit, with one branch becoming Homo. But the identity of that lineage, and the characteristics ofearly Homo, are unknown.According to Berger’s team, A. sediba‘s combination of old and new features make it a likelydescendant of A. africanus — one of Lucy’s direct descendants — and either a direct ancestor ofearly Homo and ultimately us, or what Berger calls “a very close side branch.”“It sits at a very critical moment in time,” said Berger. It “fills a critical gap in the line.”

Other paleontologists say Berger’s fossilsare a marvelous find. But as expected in a field where entire fossil records spanning millions ofyears could fit on a coffee table, and where the mostly missing A. sediba skeletons are consideredremarkably complete, the new hominid’s taxonomical position is being interpreted in manydifferent ways.While the Australopithecus designation is correct, “the proposed link between A. sediba and earlyHomo is forced and tenuous at best,” said William Jungers, a Stony Brook Universitypaleoanthropologist. He doesn’t consider a juvenile specimen — the most complete of the twoskeletons comes from the human equivalent of a teenager — a reliable indicator of adult features.To this criticism, Berger said the teen’s brain had “clearly reached about 95 to 98 percent of adult


2 of 13 3/7/2012 11:46 PM

capacity.” Few changes would be expected in its cranial size and shape, which are critical incharacterizing a primate species.Jungers also noted that the first Homo fossils predate A. sediba by 500,000 years, while Homoergaster had reached western Asia just 200,000 years after A. sediba‘s known date. Both thesefigures suggest that Homo was established well before A. sediba came along, said Rick Potts, curatorof anthropology at the Smithsonian National Museum of Natural History.“The connection with the origin of Homo doesn’t seem to hold much water,” said Potts, and theconfluence of some A. sediba traits with Homo is just coincidence. “Evolution produces a universeof features that are combined and recombined,” he said.According to Berger, however, A. sediba may have older roots than they think. “The site we found issimply a point in time. It doesn’t represent the first appearance of this species,” he said.Meanwhile, Arizona State University paleoanthropologist William Kimbel argued that A. sedibashould have been classified as Homo, though it may not have been a direct human ancestor.“In my way of thinking, it belongs in Homo because of the brow ridge, the face, the pelvis,” he said.“It’s true that it has the small brain and long upper limbs indicative of Australopithecus, but thoseare signs of its ancestry, not its future.”These arguments may be settled as more A. sediba skeletons emerge. Berger is currently assemblingat least two. However, taxonomic debates may ultimately prove less important than the questions A.sediba provokes.Already the fossils suggest that Australopithecus didn’t morph suddenly into Homo, but adapted ingradual, piecemeal fashion. What pressures led to these adaptations — and their relationship to tooluse, cognitive developments, dietary shifts and climate changes — have yet to be determined.“The significance is in the patterns and insights it provides,” said Kimbel. “These specimens fall atthe young end of a very puzzling million-year period in hominin evolution.”Whether or not A. sediba is our ancestor, “it could help us understand the dynamics that led to thesplit producing the lineage culminating ultimately in us,” said Kimbel.Images: Lee Berger/ScienceSee Also:Nov. 24, 1974: Humanity, Meet Lucy. She’s Your MomLucy 2.0: Famous Fossil Hominid Goes DigitalHumanity Has New 4.4 Million-Year-Old Baby MamaHobbits May Belong on New Branch of Our Family TreeBone Crunching Debunks ‘First Monkey’ Ida Fossil HypeCitations: “Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa.”By Lee R. Berger, Darryl J. deRuiter, Steven E. Churchill, Peter Schmid, Kristian J. Carlson, PaulH. G. M. Dirks, Job M. Kibii. Science, Vol. 328 No. 5975, April 9, 2010.“Geological Setting and Age of Australopithecus sediba from Southern Africa.” By Paul H. G. M.Dirks, Job M. Kibii, Brian F. Kuhn, Christine Steininger, Steven E. Churchill, Jan D. Kramers, RobynPickering, Daniel L. Farber, Anne-Sophie Mériaux, Andy I. R. Herries, Geoffrey C. P. King, Lee R.Berger. Science, Vol. 328 No. 5975, April 9, 2010.Brandon Keim’s Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon iscurrently working on a book about ecological tipping points.You Might LikeRelated Links by Contextly

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3 of 13 3/7/2012 11:46 PM

July 28, 1998

By JOHN NOBLE WILFORD

n analysis of African fossils, including a few new specimens, has revealed apuzzling anatomical difference between two major species of the early human

family, one from southern and the other from eastern Africa. The discoverers of thedifference suggest that the evolution of the human body thus was more complicatedthan previously understood, possibly requiring some rearrangement of branches onthe family tree.

Writing in the current issue of the Journal of HumanEvolution, two paleoanthropologists, Dr. Henry M.McHenry and Dr. Lee R. Berger, reported finding thatAustralopithecus africanus, which lived in southernAfrica, had more archaic, apelike arms and legs than theearlier A. afarensis. That species, which lived between3.9 and 3 million years ago in East Africa (mostly thenations of Tanzania, Kenya and Ethiopia today) and is

best known from the skeleton popularly called Lucy, had more humanlike limbs.Both were capable of upright walking.

"This is not what would be expected from progressive evolution," the scientists saidof their findings. McHenry is a paleoanthropologist at the University of California atDavis, and Berger is at the University of Witwatersrand in Johannesburg.

The australopithecines included several species of hominids transitional betweenapes and humans. Since the Lucy discovery in the early 1970's, most specialists inhuman origins have come to accept the afarensis as the likely ancestral species in thelineage leading to the human genus, Homo, about 2.5 million years ago.

For Lucy and her kind to evolve into descendants with more apelike limbs, thescientists said, evolution would have to go backward, which rarely happens. Onepossible explanation for such an evolutionary reversal, they said, might have been toadapt to a more arboreal environment.

In a popular account of the findings in the August issue of National Geographicmagazine, Berger said it was more likely that africanus did not descend fromafarensis but that the two species evolved separately. They were apparently "sisterspecies that share a missing-link ancestor."

New Fossils Seem to Point Backward On the Human Evolutionary Trail http://www.nytimes.com/library/national/science/072898sci-fossil.html

1 of 2 3/8/2012 12:03 AM

Thus, only one of them could have been a direct ancestor of humans, Berger said,and africanus seemed more likely to have been that ancestor. It had developed alarger brain and somewhat more humanlike face and teeth than afarensis. Althoughthe fossil evidence is scrappy, the first members of the Homo genus, Homo habilis,appeared to have had long arms and short legs, not unlike africanus.

McHenry agreed that africanus appeared to be "close to the ancestor of Homo."Throwing down the gauntlet before paleontologists working in East Africa, Bergersaid, "That reinforces my own conviction that Homo emerged from africanus insouthern Africa and migrated north."

If africanus turned out to be on the main trunk of the family tree, then afarensiswould be relegated to a dead-end branch, Berger said, culminating in A. boisei,which died out about a million years ago.

The analysis was based on a comparison of more than 100 fossil bones from alimestone quarry at Sterkfontein, South Africa, and arid badlands at Hadar, Ethiopia,where Lucy was excavated. The bones included the skeletons of Lucy herself and amale africanus. McHenry's main contribution was the development of a technique ofinferring body weight and the length and diameter of limb bones from an analysis ofa tiny fragment of a joint.

Like several other paleoanthropologists, Dr. Eric Delson of the American Museum ofNatural History in New York said he found the research "a very intriguing piece ofwork and thought-provoking," but cautioned that it was too early to be redrawing thefamily tree. He said the fossil record for H. habilis was too scant to tie it to the A.africanus lineage.

Dr. Bernard Wood, a paleoanthropologist at George Washington University, said theanalysis of joints in determining limb sizes was "quite ingenious, but the results arenot earth-shattering." He was not surprised, for instance, that the findings did notappear to fit neatly into a pattern of progressive and linear relationships in evolution.

"My own view is that nature would have carried out many experiments," Wood said,referring to patterns of parallel evolution in which different lineages could arrive atdifferent stages of development at different times. "We are still only scratching thesurface of the complexity of human origins," he said, adding that it was unlikely theancestor-descendant relationships would ever be reconstructed.

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New Fossils Seem to Point Backward On the Human Evolutionary Trail http://www.nytimes.com/library/national/science/072898sci-fossil.html

2 of 2 3/8/2012 12:03 AM

Australopithecus sediba: A NewSpecies of Homo-Like Australopithfrom South AfricaLee R. Berger,1,2* Darryl J. de Ruiter,3,1 Steven E. Churchill,4,1 Peter Schmid,5,1Kristian J. Carlson,1,6 Paul H. G. M. Dirks,2,7 Job M. Kibii1

Despite a rich African Plio-Pleistocene hominin fossil record, the ancestry of Homo and its relationto earlier australopithecines remain unresolved. Here we report on two partial skeletons with anage of 1.95 to 1.78 million years. The fossils were encased in cave deposits at the Malapa site inSouth Africa. The skeletons were found close together and are directly associated with craniodentalremains. Together they represent a new species of Australopithecus that is probably descendedfrom Australopithecus africanus. Combined craniodental and postcranial evidence demonstratesthat this new species shares more derived features with early Homo than any other australopithspecies and thus might help reveal the ancestor of that genus.

The origin of the genus Homo is widelydebated, with several candidate ancestorsbeing proposed in the genus Australopith-

ecus (1–3) or perhaps Kenyanthropus (4). Theearliest occurrence of fossils attributed to Homo(H. aff.H. habilis) at 2.33 million years ago (Ma)in Ethiopia (5) makes it temporally antecedent toall other known species of the genus Homo.Within early Homo, the hypodigms and phylo-genetic relationships between H. habilis andanother early species, H. rudolfensis, remainunresolved (6–8), and the placement of thesespecies within Homo has been challenged (9).H. habilis is generally thought to be the ancestorof H. erectus (10–13), although this might bequestioned on the basis of the considerabletemporal overlap that existed between them(14). The identity of the direct ancestor of thegenusHomo, and thus its link to earlier Australo-pithecus, remains controversial. Herewe describetwo recently discovered, directly associated, par-tially articulated Australopithecus skeletons fromthe Malapa site in South Africa, which allow usto investigate several competing hypotheses re-garding the ancestry of Homo. These skeletonscannot be accommodated within any existingfossil taxon; thus, we establish a new species,Australopithecus sediba, on the basis of a com-

bination of primitive and derived characters of thecranium and postcranium.

The following is a description of Au. sediba:Order Primates Linnaeus 1758; suborder Anthro-poidea Mivart 1864; superfamily HominoideaGray 1825; family Hominidae Gray 1825; genusAustralopithecus DART 1925; species Australo-pithecus sediba sp. nov.

Etymology. The word sediba means “foun-tain” or “wellspring” in the seSotho language.

Holotype and paratype. Malapa Hominin1 (MH1) is a juvenile individual represented bya partial cranium, fragmented mandible, and par-tial postcranial skeleton that we designate asthe species holotype [Figs. 1 and 2, supportingonline material (SOM) text S1, figs. S1 and S2,and table S1]. The first hominin specimen re-covered from Malapa was the right clavicle ofMH1 (UW88-1), discovered by Matthew Bergeron 15 August 2008. MH2 is an adult individualrepresented by isolated maxillary teeth, a partialmandible, and partial postcranial skeleton that wedesignate as the species paratype. AlthoughMH1is a juvenile, the second molars are alreadyerupted and in occlusion. Using either a humanor an ape model, this indicates that MH1 hadprobably attained at least 95% of adult brain size(15). Although additional growth would haveoccurred in the skull and skeleton of thisindividual, we judge that it would not haveappreciably altered the morphology on whichthis diagnosis is based.

Locality. The two Au. sediba type skeletonswere recovered from the Malapa site (meaning“homestead” in seSotho), situated roughly 15 kmNNE of the well-known sites of Sterkfontein,Swartkrans, and Kromdraai in Gauteng Province,South Africa. Detailed information regardinggeology and dating of the site is in (16).

RESEARCHARTICLES

1Institute for Human Evolution, University of the Witwatersrand,Private Bag 3, Wits 2050, South Africa. 2School of Geosciences,University of theWitwatersrand, Private Bag 3, Wits 2050, SouthAfrica. 3Department of Anthropology, Texas A&M University,College Station, TX 77843, USA. 4Department of EvolutionaryAnthropology, Box 90383, DukeUniversity, Durham, NC 27708,USA. 5Anthropological Institute and Museum, University ofZürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.6Department of Anthropology, Indiana University, Bloomington,IN 47405, USA. 7School of Earth and Environmental Sciences,James Cook University, Townsville, Queensland 4811, Australia.

*To whom correspondence should be addressed. E-mail:[email protected]

Fig. 1. Craniodental elements of Au. sediba. UW88-50 (MH1) juvenile cranium in (A) superior, (B)frontal, and (C) left lateral views. (D) UW88-8 (MH1) juvenile mandible in right lateral view, (E)UW88-54 (MH2) adult mandible in right lateral view, (F) UW88-8 mandible in occlusal view, (G)UW 88-54 mandible in occlusal view, and (H) UW 88-50 right maxilla in occlusal view (scale barsare in centimeters).

www.sciencemag.org SCIENCE VOL 328 9 APRIL 2010 195

Diagnosis. Au. sediba can be distinguishedfrom other species of Australopithecus by acombination of characters presented in Table 1;comparative cranial measures are presented inTable 2. A number of derived characters separateAu. sediba from the older chronospecies Au.anamensis and Au. afarensis. Au. sediba exhibitsneither the extreme megadontia, extensive cra-nial cresting, nor facial prognathism of Au. garhi.The suite of derived features characterizingAu. aethiopicus, Au. boisei, and Au. robustus,in particular the pronounced cranial muscle mark-ings, derived facial morphology, mandibularcorpus robusticity, and postcanine megadontia,are absent in Au. sediba. The closest morpholog-ical comparison for Au. sediba is Au. africanus,as these taxa share numerous similarities in thecranial vault, facial skeleton, mandible, andteeth (Table 1). Nevertheless, Au. sediba can bereadily differentiated from Au. africanus onboth craniodental and postcranial evidence.Among the more notable differences, we ob-serve that although the cranium is small, thevault is relatively transversely expanded withvertically oriented parietal walls and widelyspaced temporal lines; the face lacks the pro-

nounced, flaring zygomatics of Au. africanus;the arrangement of the supraorbital torus, naso-alveolar region, infraorbital region, and zy-gomatics result in a derived facial mask; themandibular symphysis is vertically oriented witha slight bony chin and a weak post-incisive pla-num; and the teeth are differentiated by theweakly defined buccal grooves of the maxillarypremolars, the weakly developed median lingualridge of the mandibular canine, and the smallabsolute size of the postcanine dentition. Theseexact differences also align Au. sediba with thegenusHomo (see SOM text S2 for hypodigms usedin this study). However, we consider Au. sedibato be more appropriately positioned withinAustralopithecus, based on the following cranio-dental features: small cranial capacity, pronouncedglabelar region, patent premaxillary suture,moderate canine jugum with canine fossa, smallanterior nasal spine, steeply inclined zygomati-coalveolar crest, high masseter origin, moderatedevelopment of the mesial marginal ridge of themaxillary central incisor, and relatively closelyspaced premolar and molar cusps.

Postcranially, Au. sediba is similar to otheraustralopiths in its small body size, its relatively

long upper limbs with large joint surfaces, andthe retention of apparently primitive charac-teristics in the upper and lower limbs (table S2).Au. sediba differs from other australopiths, butshares with Homo a number of derived featuresof the os coxa, including increased buttressing ofthe ilium and expansion of its posterior portion,relative reduction in the distance between thesacroiliac and hip joints, and reduction of dis-tance from the acetabulum to the ischial tuberos-ity. These synapomorphies with Homo anticipatethe reorganization of the pelvis and lower limb inH. erectus and possibly the emergence of moreenergetically efficient walking and running inthat taxon (17). As with the associated cranialremains, the postcranium of Au. sediba is definednot by the presence of autapomorphic featuresbut by a unique combination of primitive andderived traits.

Cranium. The cranium is fragmented andslightly distorted. The minimum cranial capacityof MH1 is estimated at 420 cm3 (SOM text S4).The vault is ovoid, with transversely expanded,vertically oriented parietal walls. The widelyspaced temporal lines do not approach themidline. Postorbital constriction is slight. Theweakly arched supraorbital torus is moderatelydeveloped and laterally extended, with sharplyangled lateral corners and a weakly definedsupratoral sulcus. A robust glabelar region isevident, with only a faint depression of thesupraorbital torus at the midline. The frontalprocess of the zygomatic faces primarily laterallyand is expanded medially but not laterally. Thezygomatic prominence does not show antero-lateral expansion. The zygomatics are weaklyflared laterally, resulting in an uninterruptedfrontal profile of the facial mask that is squaredsuperiorly and tapered inferiorly. The zygomat-icoalveolar crests are long, straight, and steep-ly inclined, resulting in a high masseter origin.The root of the zygomatic begins at the anteriormargin of M1. The nasal bones are widenedsuperiorly, become narrowest about one-thirdof the way down, and flare to their widest extentat their inferior margin. The nasal bones areelevated as a prominent ridge at the internasalsuture, with an increasingly anterior projectioninferiorly. The bone surface of the maxilla re-treats gently away from the nasal aperture lat-erally, resulting in an everted margin of thesuperolateral portion of the aperture relative tothe infraorbital region. The inferolateral portionof the nasal aperture becomes bluntly rounded.The infraorbital region is slightly convex (18)and is oriented at an approximately right angleto the alveolar plane. There is a trace of a pre-maxillary suture near the superolateral marginof the nasal aperture. Prominent canine jugadelineate moderately developed canine fossae.Anterior pillars are absent. The inferior marginof the nasal aperture is marked by a steppednasal sill and a small but distinct anterior nasalspine. The subnasal region is straight in the cor-onal plane and only weakly projecting relative

Fig. 2. Associated skeletal elements of MH1 (left) and MH2 (right), in approximate anatomical position,superimposed over an illustration of an idealized Au. africanus skeleton (with some adjustment fordifferences in body proportions). The proximal right tibia of MH1 has been reconstructed from a naturalcast of the proximal metaphysis.

9 APRIL 2010 VOL 328 SCIENCE www.sciencemag.org196

RESEARCH ARTICLES

continuedon

next

page

Table1.

Listof

charactersused

todiagnose

Au.sediba.

Thesecharactersarecommonlyused

inhominin

phylogeneticstudies(11,

38–4

0)or

have

been

recorded

asdiagnosticforvarious

hominin

taxa

inthepast

(3,10

,36

).Recogn

izingthepotentialpitfalls

ofperforminga

cladistic

analysison

possibly

interdependent

characters

ofun

certainvalence,

weproduced

acladogram

from

thedata

inthistableas

atestof

theph

ylogeneticpositio

nof

Au.sediba(fig.

S3).Our

mostparsimonious

cladogram

places

Au.sediba

atthestem

oftheHom

oclade.

Num

bers

inparenthesesin

the

first

column

referto

measurespresented

inTable

2;descriptions

ofthesecharacterstates

areprovided

inSO

Mtext

S3.Ab

breviatio

nsareas

follo

ws:

A-M,anteromedial;costasupr.,costasupraorbita

lis;interm

ed.,interm

ediate;lat.,

lateral;med.,medial;mesognath.,mesognathic;mod.,moderately;

MMR,

mesialmarginal

ridge;

orthogn.,orthognathic;procum

b.,procum

bent;proj.,projectin

g;TM

J,temperoman-

dibularjoint.

Chara

cters

Au.

afaren

sisAu

.ga

rhiAu

.afr

icanu

sAu

.sed

ibaH.

habil

isH.

rudolf

ensis

H.ere

ctus

Au.

aethi

opicu

sAu

.bo

isei

Au.

robustus

Vau

ltCranialcapacity

(1)

Small

Small

Small

Small

Interm

ed.

Large

Large

Small

Small

Small

A-M

incursionof

temporallin

eson

frontal

bone

(9)

Strong

Moderate

Moderate

Weak

Weak

Weak

Weak

Strong

Strong

Strong

Positio

nof

temporallin

eson

parie

talbones

Crest

Crest

Varia

ble

Wide

Varia

ble

Wide

Wide

Crest

Crest

Crest

Compoundtemporal

nuchal

crest(m

ales)

Extensive

?Ab

sent

Absent

Varia

ble

Absent

Absent

Extensive

Varia

ble

Absent

Postorbitalconstrictio

n(5)

Marked

Moderate

Moderate

Slight

Moderate

Moderate

Slight

Marked

Marked

Marked

Pneumatizationof

temporalsquama

Extensive

?Extensive

Reduced

Reduced

Reduced

Reduced

Extensive

Varia

ble

Reduced

Facial

hafting

Low

Low

Low

Low

Low

Low

Low

High

High

High

Frontaltrigon

Present

Present

Absent

Absent

Absent

Absent

Absent

Present

Present

Present

Supraglenoid

gutter

width

Narrow

?Narrow

Narrow

Narrow

Narrow

Narrow

Wide

Wide

Wide

Horizontaldistance

betweenTM

Jand

M2/M3(6)

Long

?Long

Short

Short

Long

Short

Long

Long

Long

Parie

taltransverse

expansion/tuber

Absent

Absent

Absent

Present

Present

Present

Present

Absent

Absent

Absent

Facial

skeleton

Supraorbitalexpression

Costasupr.

Costasupr.

Interm

ed.

Torus

Torus

Interm

ed.

Torus

Costasupr.

Costasupr.

Costasupr.

Supraorbitalcontour

Less

arched

Less

arched

Varia

ble

Arched

Arched

Arched

Arched

Less

arched

Varia

ble

Arched

Glabellarregion

form

sas

prom

inentblock

No

No

Varia

ble

Yes

No

Varia

ble

No

No

Yes

Yes

Lat.halfof

infraorbital

marginblunt

andprotruding

No

?No

No

No

No

No

Yes

No

Yes

Zygomaticarch

relativeto

inferio

rorbitalmargin

Above

?Level

Level

Level

?Level

Above

Above

Above

Convexity/concavity

ofinfraorbitalregion

??

Convex

Convex

Concave

Concave

Convex

Concave

Concave

Concave

Nasal

bone

projectio

nabovefrontomaxillary

suture

Expanded

?Varia

ble

No

No

No

No

Tapered

Expanded

Expanded

Inferio

rwidth

ofprojectin

gnasalbone

(25)

Wide

?Varia

ble

Wide

Varia

ble

Narrow

Wide

Not

proj.

Not

proj.

Not

proj.

Infraorbitalforamen

height

(32)

High

?Varia

ble

High

High

?High

Low

Low

Low


RESEARCH ARTICLES

Characters

Au.

afarensis

Au.

garhi

Au.

africanu

sAu

.sediba

H.

habilis

H.

rudo

lfensis

H.

erectus

Au.

aethiopicus

Au.

boisei

Au.

robu

stus

Canine

juga

prom

inence/anterior

pillars

Prom

inent

Prom

inent

Varia

ble

Prom

inent

Varia

ble

Weak

Weak

Weak

Weak

Pillars

Patencyof

prem

axillary

suture

Obliterated

?Occasional

Trace

Obliterated

Obliterated

Obliterated

Obliterated

Obliterated

Occasional

Inferolateralnasal

aperture

margin

Sharp

Sharp

Varia

ble

Blunt

Varia

ble

Sharp

Blunt

Blunt

Varia

ble

Blunt

Eversion

ofsuperio

rnasal

aperture

margin

??

None

Slight

Slight

Slight

Slight

Slight

Varia

ble

None

Nasoalveolartriangular

fram

e/gutter

Triangular

?Triangular

Triangular

Triangular

Triangular

Triangular

Gutter

Gutter

Gutter

Nasal

cavity

entrance

Stepped

Stepped

Stepped

Stepped

Varia

ble

Stepped

Stepped

Smooth

Smooth

Smooth

Nasoalveolarclivus

contourin

coronalplane

Convex

Convex

Straight

Straight

Straight

Straight

Straight

Concave

Concave

Concave

Subnasal

projectio

n(38)

Marked

Marked

Varia

ble

Weak

Varia

ble

Weak

Weak

Marked

Moderate

Moderate

Canine

fossa

Present

Present

Present

Present

Present

Absent

Absent

Absent

Absent

Absent

Maxillaryfossula

Absent

Absent

Absent

Absent

Absent

Absent

Absent

Absent

Absent

Present

Incisorprocum

bency

Procum

b.Procum

b.Varia

ble

Vertical

Varia

ble

Vertical

Vertical

Vertical

Vertical

Vertical

Anterio

rnasalspinerel.to

nasalaperture

Absent

?An

terio

rAn

terio

rAn

terio

r?

Enlarged

Posterior

Posterior

Posterior

Expansionof

frontal

processof

zygomaticbone

Med.andlat.

?Med.andlat.

Medial

Medial

Medial

Medial

Med.andlat.

Med.andlat.

Med.andlat.

Angularindentationof

lateralorbitalmargin

??

Indented

Curved

Curved

Curved

Curved

?Curved

Curved

Zygomaticprom

inence

developm

ent

Prom

inent

?Prom

inent

Slight

Slight

?Slight

Prom

inent

Prom

inent

Prom

inent

Lateralflarin

gof

zygomaticarches

Marked

?Marked

Slight

Slight

Slight

Slight

Marked

Marked

Marked

Outlin

eof

superio

rfacial

mask

Tapered

?Tapered

Squared

Squared

Squared

Squared

Tapered

Tapered

Tapered

Zygomaticoalveolar

crest/m

alar

notch

Straight

?Straight

Straight

Notch

Notch

Notch

Straight

Straight

Straight

Infraorbitalplateangle

relativeto

alveolar

plane

Obtuse

?Obtuse

Right

Right

Right

Right

Obtuse

Obtuse

Obtuse

Zygomaticom

axillary

stepsandfossae

present

No

?No

No

No

No

No

No

No

Yes

Heightof

masseter

origin

(35)

Low

Low

High

High

Low

Low

Low

High

High

High

Malar

thickness(31)

Thin

?Thin

Thin

Thin

?Thin

Thick

Thick

Thick

Projectio

nof

zygomatics

relativeto

nasalbones

Posterior

Posterior

Varia

ble

Posterior

Posterior

Level

Posterior

Anterio

rAn

terio

rAn

terio

r

Facial

prognathism

(7)

(sellion-prosthionangle)

Prognathic

Prognathic

Varia

ble

Mesognath.

Mesognath.

Mesognath.

Orthogn.

Prognathic

Mesognath.

Mesognath.

Masseteric

positio

nrelativeto

sellion

Anterio

r?

Posterior

Posterior

Posterior

?Posterior

Anterio

rAn

terio

rAn

terio

r

Lateralanterio

rfacial

contour

Bipartite

Bipartite

Varia

ble

Straight

Varia

ble

Straight

Straight

Straight

Straight

Straight


RESEARCH ARTICLES

Characters

Au.

afarensis

Au.

garhi

Au.

africanu

sAu

.sediba

H.

habilis

H.

rudo

lfensis

H.

erectus

Au.

aethiopicus

Au.

boisei

Au.

robu

stus

Palate

Protrustionof

incisors

beyond

bi-caninelin

eYes

Yes

Yes

Yes

Yes

No

Yes

No

No

No

Anterio

rpalataldepth

Shallow

Shallow

Deep

Deep

Varia

ble

Deep

Varia

ble

Shallow

Deep

Shallow

Dentalarcade

shape

Rectangle

Rectangle

Varia

ble

Parabolic

Parabolic

Parabolic

Parabolic

Rectangle

Parabolic

Parabolic

MaxillaryI2/C

diastema

Present

Present

Absent

Absent

Varia

ble

Absent

Absent

Absent

Absent

Absent

Man

dible

Orie

ntationof

mandibular

symphysis

Receding

?Receding

Vertical

Vertical

Vertical

Vertical

Vertical

Vertical

Vertical

Bony

chin

(mentum

osseum

)Ab

sent

?Slight

Slight

Slight

Slight

Slight

Slight

Slight

Slight

Dire

ctionof

mental

foramen

opening

Varia

ble

?Varia

ble

Lateral

Lateral

Lateral

Lateral

Lateral

Lateral

Lateral

Post-in

cisive

planum

Prom

inent

?Prom

inent

Weak

Prom

inent

Weak

Weak

Prom

inent

Prom

inent

Prom

inent

Torusmarginalis

and

marginaltubercles

Prom

inent

?Moderate

Moderate

Moderate

Prom

inent

Prom

inent

?Prom

inent

Prom

inent

Mandibularcorpus

cross-sectionalarea

atM1(50)

Small

?Sm

all

Small

Small

Varia

ble

Small

Large

Large

Large

Teeth

Incisor-to-postcanineratio

(maxillary)

(60)

Large

Moderate

Moderate

Moderate

Moderate

Moderate

Large

?Sm

all

Small

Canine-to-postcanine

ratio

(maxillary/mandibular)(61,

62)

Large

Large

Large

Large

Large

Large

Large

?Sm

all

Small

Postcanine

crow

narea

(maxillary/mandibular)(57,

59)

Moderate

Large

Large

Moderate

Moderate

Large

Small

Large

Large

Large

MaxillaryI1:MMR

developm

ent,lin

gual

face

Moderate

?Moderate

Moderate

Weak

Weak

Weak

?Moderate

Moderate

MaxillaryC:

developm

ent

oflin

gual

ridges

Marked

Marked

Marked

Weak

Weak

Marked

Marked

?Marked

Weak

Maxillaryprem

olar

molarization

None

Minor

Minor

None

Minor

Minor

None

Marked

Marked

Marked

Maxillaryprem

olars:

buccal

grooves

Marked

Marked

Marked

Weak

Weak

Marked

Weak

?Weak

Weak

Medianlin

gual

ridge

ofmandibularcanine

Prom

.?

Prom

.Weak

Weak

Weak

Weak

?Weak

Weak

MandibularP 3

root

number

2?

22

12

1?

22

Protoconid/metaconid

moremesialcusp

(molars)

Equal

?Equal

Protoconid

Protoconid

Protoconid

Protoconid

?Equal

Equal

Peak

ofenam

elform

sbetweenrootsof

molars

No

?Yes

Yes

No

No

No

?No

Yes

Relativeenam

elthickness

Thick

Thick

Thick

Thick

Thick

Thick

Thick

Hyper

Hyper

Hyper

Positio

nsof

apices

oflin

gual

(LC)

andbuccal

(BC)

cuspsof

prem

olars

andmolarsrelativeto

occlusal

margin

LCat

margin,

BCslightly

lingual

LCat

margin,

BCslightly

lingual

LCslightly

buccal,BC

moderately

lingual

LCslightly

buccal,BC

moderately

lingual

LCat

margin,

BCslightly

lingual

LCat

margin,

BCslightly

lingual

LCat

margin,

BCslightly

lingual

LCmod.

buccal,BC

strongly

lingual

LCmod.

buccal,BC

strongly

lingual

LCmod.

buccal,BC

strongly

lingual


RESEARCH ARTICLES

continuedon

next

page

Table2.

Craniodental

measurementsforearly

homininsin

Africa.

Au.sediba

isrepresentedby

MH1.

Unlessotherwise

defin

ed,measurements

are

based

on(6).

Some

measureswere

unavailableforspecimensof

Au.a

farensisandAu.g

arhi,inwhich

case

thecharacterstates

inTable1wereestim

ated.S

everal

characterstates

inTable1arerecorded

asvaria

ble,

although

only

speciesaveragevalues

arepresented

here.Measurements

arein

millimetersunless

otherwiseindicated.

Descriptio

nsof

characterstates

presentedin

Table1that

arebasedon

measurements

from

thistableareprovided

inSO

Mtext

S3.Ab

breviatio

nsareas

follows:br,

bregma;ek,ectoconchion;

ekm,ectom

olare;fm

t,frontomolaretemporale;ft,frontotemporale;

g,glabella;mf,

maxillofrontale;

n,nasion;ns,nasospinale;

or,orbitale;po,porio

n;pr,

prosthion;

rhi,rhinion;

zm,zygomaxillare;

zy,zygion;zyo,

zygoorbitale.

Item

Measure

ment

descr

iption

in(6)

Measure

ment

Au.

afaren

sisAu

.afr

icanu

sAu

.sed

ibaH.

habil

isH.

rudolf

ensis

H.ere

ctus

Au.

aethi

opicu

sAu

.bo

isei

Au.

robustus

1Cranialcapacity

(cm3 )

415

442

420

631

751

900

419

515

530

29

Maximum

parie

talbreadth

9099

100

103

114

126

9499

100

311

Bi-porionicbreadth(po-po)

126

9910

410

412

712

112

511

6—

4Postorbitalconstrictio

n(narrowestpointbehind

theorbits)

7769

7376

8589

6564

735

Postorbitalconstrictio

nindex(4/14×10

0)66

7185

7072

8065

6168

6Horizontaldistance

betweenTM

JandM2 /M3

8361

4551

5857

9482

817

Facial

prognathism

(sellion-prosthionangle)

6361

6565

6872

4166

698

75Infratem

poralfossadepth

–31

2127

–37

5150

369

8Minimum

frontalbreadth(ft-ft)

4054

7066

7276

3336

3510

17Glabella

tobregma(g-br)

101

8075

8386

103

–87

–11

Frontalchord(n-br)

–84

7480

9399

–84

–12

62Supraorbitaltorusvertical

thickness

–8

88

1012

1012

913

43Superio

rfacial

height

(n-pr)

8778

6868

9076

9910

080

1449

Superio

rfacial

breadth(fmt-fm

t)11

797

8610

011

710

710

010

810

715

50Bi-orbitalbreadth(ek-ek)

8984

7889

100

9910

193

8216

52Bizygomaticbreadth(zy-zy)

157

126

102

117

–13

515

316

514

317

Zygomaticbreadthindex(14/16

×10

0)75

7484

85–

84–

6574

1853

Bimaxillarybreadth(zm-zm)

–10

384

9711

310

512

611

910

619

55Interorbitalbreadth(m

f-mf)

1819

2027

2425

2324

2420

56Orbitalbreadth(m

f-ek)

3836

3133

3939

3637

3321

57Orbitalheight

(perpendicular

to20

)34

3231

3133

3641

3330

2271

Nasal

bridge

length

(n-rhi)

–27

2618

2018

3530

2823

73Nasal

bridge

breadthsuperio

r–

58

88

1312

1411

24Nasal

bridge

breadthat

anterio

rlacrimal

crests

–11

510

–24

1911

–25

74Nasal

bridge

breadthinferio

r–

1113

1110

1811

78

26Nasal

bridge

height

(nasionsubtense

atanterio

rlacrimal

crests)

–4

98

–9

45

–27

69Nasal

height

(n-ns)

5850

4945

5752

7264

5428

70Nasal

aperture

height

(rhi-ns)

2926

2228

3930

3835

2429

68Maximum

nasalaperture

width

2323

2625

2732

3031

2530

Orbito

alveolar

height

(or-alveolar

plane)

5553

4447

5951

5369

5731

60Malar

thickness

1413

138

–12

2018

1832

Infraorbitalforamen

height

(toinferio

rorbitalmargin)

–12

1515

1416

3025

2633

Prosthionto

zygomaxillare(pr-zm

)–

6757

5569

6780

8271

34Prosthionto

zygoorbitale

(pr-zyo)

–60

5057

7570

7381

6935

Masseterorigin

height

index(33/34

×10

0)–

112

104

9692

9611

010

110

336

47Subnasaleto

prosthion(horizontalprojectio

n)28

2313

1917

1623

2726

3748

Subnasal

toprosthion(vertical

projectio

n)15

2117

1830

2112

2522

38Subnasaleprojectio

nindex(36/37

×10

0)18

710

876

106

5779

192

108

122

3994

Incisoralveolar

length

–13

1615

1416

1515

1340

96Prem

olar

alveolar

length

–15

1816

1613

2122

17


RESEARCH ARTICLES

to the facial plane. The face is mesognathic.The palate is consistently deep along its entireextent, with a parabolic dental arcade.

Mandible. Descriptions apply to the morecomplete juvenile (MH1) mandible unless other-wise stated. The nearly vertical mandibular sym-physis presents a weak lateral tubercle, resultingin a slight mental trigone, and a weak man-dibular incurvation results in a slight mentumosseum. The post-incisive planum is weaklydeveloped and almost vertical. Both mandibularcorpora are relatively gracile, with a low heightalong the alveolar margin. The extramolar sulcusis relatively narrow in both mandibles. In MH1,a moderate lateral prominence displays itsgreatest protrusion at the mesial extent of M2,with a marked decrease in robusticity to P4; inMH2 the moderate lateral prominence showsits greatest protrusion at M3, with a markeddecrease in robusticity to M2. The alveolar prom-inence is moderately deep with a notable medialprojection posteriorly. The anterior and posteriorsubalveolar fossae are continuous. The ramusof MH1 is tall and narrow, with nearly parallel,vertically oriented anterior and posterior bor-ders; the ramus of MH2 is relatively broader,with nonparallel anterior and posterior borders(fig. S2). The mandibular notch is relatively deepand narrow in MH1 and more open in MH2.The coronoid extends farther superiorly thanthe condyle. The condyle is mediolaterally broadand anteroposteriorly narrow. The endocondyloidbuttress is absent in MH1, whereas in MH2 aweak endocondyloid buttress approaches thecondyle without reaching it.

Dental size and proportions. The dentitionof the juvenile (MH1) is relatively small, whereaspreserved molars of the adult (MH2) are evensmaller (Fig. 3 and fig. S4). For MH1, themaxillary central incisor is distinguishable onlyfrom the reduced incisors of Au. robustus. Themaxillary canine is narrower than all canines ofAu. africanus except TM 1512, whereas themandibular canine falls well below the range ofAu. africanus. Premolars and molars are at thelower end of the Au. africanus range and withinthat of H. habilis–H. rudolfensis and H. erectus.Molar dimensions of the adult individual (MH2)are smaller than those of Au. africanus, areat or below the range of those of H. habilis–H. rudolfensis, and are within the range of thoseofH. erectus. Au. sedibamirrors the Au. africanuspattern of maxillary molars that increase slightlyin size posteriorly, though it differs in that themolars tend to be considerably larger in the lattertaxon. Conversely, the Au. sediba pattern variesslightly from that seen in specimens KNM-ER1813, OH 13, and OH 65 andH. erectus, where-in the molars increase from M1 to M2 but thendecrease to M3. In broad terms, the teeth ofAu. sediba are similar in size to teeth of speci-mens assigned to Homo but share the closelyspaced cusp apices seen in Australopithecus.

Postcranium. Preserved postcranial remainsof Au. sediba (table S1) denote small-bodiedIte

mMe

asure

ment

descr

iption

in(6)

Measure

ment

Au.

afaren

sisAu

.afr

icanu

sAu

.sed

ibaH.

habil

isH.

rudolf

ensis

H.ere

ctus

Au.

aethi

opicu

sAu

.bo

isei

Au.

robustus

4198

Intercaninedistance

2630

3030

3331

–29

2742

88Palate

breadth(ekm

-ekm

)68

6463

7080

6683

8267

4314

1Mandibularsymphysisheight

3938

3227

3634

–47

4244

142

Mandibularsymphysisdepth

6020

1919

2419

–28

2545

147

Mandibularcorpus

height

atP 4

3433

2830

3830

–42

3846

148

Mandibularcorpus

depthat

P 419

2118

2022

19–

2824

4714

9Cross-sectionalarea

atP 4

(calculatedas

anellipse)

511

558

382

427

653

458

–91

070

948

150

Mandibularcorpus

height

atM1

3332

2829

3630

3541

3749

151

Mandibularcorpus

depthat

M1

1921

1820

2320

2628

2650

152

Cross-sectionalarea

atM1(calculatedas

anellipse)

488

532

396

421

667

469

715

913

759

5115

4Mandibularcorpus

height

atM2

3131

2531

3630

–41

3552

155

Mandibularcorpus

depthat

M2

2225

2223

2621

–31

2853

156

Cross-sectionalarea

atM2(calculatedas

anellipse)

536

612

436

537

745

504

–98

077

054

162

Heightof

mentalforamen

relativeto

alveolar

margin

2019

1313

1713

–20

2055

Maxillaryincisorcrow

narea

(I1+I2)

143

135

109

132

137

136

–11

710

956

Maxillarycanine

crow

narea

107

104

7995

118

96–

7679

57Maxillarypostcanine

crow

narea

713

868

731

755

829

617

–10

1294

158

Mandibularcanine

crow

narea

8795

6883

–79

–72

6159

Mandibularmolar

crow

narea

550

651

536

565

668

466

–78

167

860

Maxillaryincisorto

postcanine

ratio

20.0

15.6

14.9

17.4

16.6

22.1

–11

.511

.661

Maxillarycanine

topostcanine

ratio

15.0

11.9

10.8

12.6

14.2

15.5

–7.5

8.4

62Mandibularcanine

tomolar

ratio

15.8

14.6

12.7

14.6

–16

.7–

9.2

9.0


RESEARCH ARTICLES

hominins that retain an australopith pattern oflong upper limbs, a high brachial index, andrelatively large upper limb joint surfaces(table S2). In addition to these aspects of limband joint proportions, numerous other featuresin the upper limb are shared with sibling speciesof Australopithecus (to the exclusion of laterHomo), including a scapula with a craniallyoriented glenoid fossa and a strongly developedaxillary border; a prominent conoid tubercle onthe clavicle, with a pronounced angular margin;low proximal-to-distal humeral articular propor-tions; a distal humerus with a marked crest forthe brachioradialis muscle, a large and deepolecranon fossa with a septal aperture, and amarked trochlear/capitular keel (19); an ulnawith a pronounced flexor carpi ulnaris tubercle;and long, robust, and curved manual phalangesthat preserve strong attachment sites for theflexor digitorum superficialis muscle.

Numerous features of the hip, knee, and ankleindicate that Au. sediba was a habitual biped. Interms of size and morphology, the proximal anddistal articular ends of the femur and tibia fallwithin the range of variation of specimensattributed to Au. africanus. However, severalderived features in the pelvis link the Malapaspecimens with later Homo. In the os coxa (Fig.4), Au. sediba shares with Homo a pronouncedacetabulocristal buttress; a more posterior posi-tion of the cristal tubercle; a superoinferiorlyextended posterior iliac blade, with an expandedretroauricular area; a sigmoid-shaped anterior in-ferior iliac spine; a reduced lever arm for weighttransfer between the auricular surface and theacetabulum; an enlarged and rugose iliofemoralligament attachment area; a tall and thin pubicsymphyseal face; and a relatively short ischiumwith a deep and narrow tuberoacetabular sulcus.These features are present in taxonomically un-

assigned postcranial remains from Koobi Fora(KNM-ER 3228) and Olduvai Gorge (OH 28),which have been argued to represent earlyHomo(20), as well as in earlyHomo erectus (21). An oscoxa from Swartkrans (SK 3155) has been con-sidered by some to also represent early Homo(22) but can be seen to possess the australopithpattern in most of these features. In addition,Au. sediba shares with later Homo the human-like pattern of low humeral-to-femoral diaph-yseal strength ratios, in contrast to the ape-likepattern seen in the H. habilis specimen OH 62(table S2).

Although aspects of the pelvis are derived, thefoot skeleton is more primitive overall, sharingwith other australopiths a flat talar trochleaarticular surface with medial and lateral marginswith equal radii of curvature, and a short, stout,and medially twisted talar neck with a highhorizontal angle and a low neck torsion angle

Fig. 3. Dental size of a selection of Au. sediba teeth compared to other earlyhominin taxa; see fig. S4 for additional teeth. Dental measurements weretaken as described by Wood (6). Owing to small sample sizes, H. habilis andH. rudolfensis were combined. (A) Upper central incisor mesiodistal (MD)length. (B) Upper canine MD length. (C) Lower canine MD length. (D) Squareroot of calculated [MD × BL (BL, buccolingual)] upper third premolar area.(E) Square root of calculated (MD × BL) upper second molar area. (F)Square root of calculated (MD × BL) lower second molar area. Measureswere taken on original specimens by D.J.D. for Au. africanus, Au. robustus,

and Au. sediba. Measurements for Au. afarensis, H. habilis, H. rudolfensis,and H. erectus are from (6). P4 is not fully erupted on the right side of MH1,therefore measures of the maxillary postcanine dentition are presented forthe left side only. Dental metrics for Au. sediba are as follows (MD, BL, inmillimeters): Maxillary: MH1: RI1 10.1, 6.9; LI2 7.7 (damaged), 5.1; RC9.0, 8.8; LP3 9.0, 11.2; LP4 9.2, 12.1; LM1 12.9, 12.0; LM2 12.9, 13.7;LM3 13.3, 14.1; MH2: RM3 11.3, 12.9. Mandibular: MH1: LC 8.0, 8.5; RM112.5, 11.6; RM2 14.4, 12.9; RM3 14.9, 13.8; MH2: RM1 11.8, 11.1; RM214.1, 12.2; RM3 14.2, 12.7; LM3 14.1, 12.5.


RESEARCH ARTICLES

(table S2 and fig. S5). The calcaneus is markedlyprimitive in its overall morphology: the bone isstrongly angled along the proximodistal axis,with the point of maximum inflexion occurring atan enlarged peroneal trochlea; the lateral plantartubercle is lacking; the calcaneal axis is set about45° to the transverse plane; and the calcaneocu-boid facet is vertically set and lacks an expandedposterior projection for the beak of the cuboid(23).

Discussion. The age and overall morpholo-gy of Au. sediba imply that it is most likelydescended from Au. africanus, and appears morederived toward Homo than do Au. afarensis, Au.garhi, and Au. africanus. Elsewhere in SouthAfrica, the Sterkfontein cranium Stw 53, dated to2.0 to 1.5Ma, is generally considered to representeither H. habilis (10, 24, 25) or perhaps anundiagnosed form of early Homo (26). It playedan important role in the assignment of OH 62 toH. habilis (27). However, the derived cranioden-tal morphology of Au. sediba casts doubt on theattribution of Stw 53 to early Homo [see also(28)]: Stw 53 appears to be more primitive thanMH1 in retaining closely spaced temporal lines;marked postorbital constriction; a weakly devel-oped supraorbital torus; narrow, nonprojectingnasal bones; anterior pillars; marked nasoalveolarprognathism; medial and lateral expansion of thefrontal process of the zygomatic bone; andlaterally flared zygomatics. If Stw 53 insteadrepresents Au. africanus, the assignment of OH62 to H. habilis becomes tenuous. Attribution ofthe partial skeleton KNM-ER 3735 to H. habiliswas tentatively based, in part, on a favorablecomparison with OH 62 and on the hypothesisthat there were no other contemporaneous non-

robust australopith species to which it could beassigned in East Africa (29). As a result, theinterpretation of KNM-ER 3735 as H. habilisalso becomes uncertain.

The phylogenetic significance of the co-occurrence of derived postcranial features inAu. sediba,H. erectus, and a sample of isolatedfossils generally referred to Homo sp. indet.(table S2) is not clear: The latter might repre-sent early H. erectus, it might sample the post-cranium of H. rudolfensis (which would thenimply an evolutionary pathway fromAu. sediba toH. rudolfensis to H. erectus), or it might representthe postcranium of H. habilis [which would sug-gest that OH 62 and KNM-ER 3735 (two speci-mens with ostensibly more primitive postcranialskeletons) do not belong in this taxon]. If the lat-ter possibility holds, it could suggest a phyloge-netic sequence from Au. sediba to H. habilis toH. erectus. Conversely, although the overall post-cranial morphology of Au. sediba is similar to thatof other australopiths, a number of derived featuresof the os coxa align the Malapa hominins withlater Homo (H. erectus) to the exclusion of otheraustralopiths. Additionally, Au. sediba shares asmall number of cranial traits with H. erectus thatare not exhibited in the H. habilis–H. rudolfensishypodigm, including slight postorbital constrictionand convexity of the infraorbital region (18).Following on this, MH1 compares favorably withSK 847 (H. erectus) in the development of thesupraorbital torus, nasal bones, infraorbital region,frontal process of the zygomatic, and subnasalprojection. However, MH1 differs from SK 847 inits relatively smaller size, the robust glabelar re-gion, the weakly developed supratoral sulcus, thesteeply inclined zygomaticoalveolar crests with a

high masseter origin, and the moderate caninejuga, all features aligning MH1 with Australopith-ecus. It is thus not possible to establish the precisephylogenetic position of Au. sediba in relation tothe various species assigned to early Homo. Wecan conclude that combined craniodental and post-cranial evidence demonstrates that this new spe-cies shares more derived features with earlyHomothan does any other known australopith species(Table 1 and table S2) and thus represents a candi-date ancestor for the genus, or a sister group to aclose ancestor that persisted for some time after thefirst appearance of Homo.

The discovery of a <1.95-million-year-old(16) australopith that is potentially ancestral toHomo is seemingly at odds with the recovery ofolder fossils attributed to the latter genus (5) or ofapproximately contemporaneous fossils attribut-able to H. erectus (6, 30). However, it is unlikelythat Malapa represents either the earliest or thelatest temporal appearance of Au. sediba, nordoes it encompass the geographical expanse thatthe species once occupied. We hypothesize thatAu. sediba was derived via cladogenesis fromAu. africanus (≈3.0 to 2.4 Ma), a taxon whosefirst and last appearance dates are also uncertain(31). The possibility that Au. sediba split fromAu. africanus before the earliest appearance ofHomo cannot be discounted.

Although the skull and skeleton of Au. sedibado evince derived features shared with earlyHomo, the overall body plan is that of a homininat an australopith adaptive grade. This supportsthe argument, based on endocranial volume andcraniodental morphology, that this species ismost parsimoniously attributed to the genusAustralopithecus. The Malapa specimens dem-

Fig. 4. Representative ossa coxae, in lateral view, from left to right, of Au.afarensis (AL 288-1), Au. africanus (Sts 14), Au. sediba (MH1), and H. erectus(KNM-WT 15000). The specimens are oriented so that the iliac blades all lie in theplane of the photograph (which thus leads to differences between specimens inthe orientation of the acetabula and ischial tuberosities). MH1 possesses derived,Homo-like morphology compared to other australopithecines, including a relativereduction in the weight transfer distance from the sacroiliac (yellow) to hip (circle)

joints; expansion of the retroauricular surface of the ilium (blue arrows)(determined by striking a line from the center of the sphere representing thefemoral head to the most distant point on the posterior ilium; the superior arrowmarks the terminus of this line, and the inferior arrow marks the intersection ofthis line with the most anterior point on the auricular face); narrowing of thetuberoacetabular sulcus (delimited by yellow arrows); and pronouncement of theacetabulocristal (green arrows) and acetabulosacral buttresses.


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onstrate that the evolutionary transition from asmall-bodied and perhaps more arboreal-adaptedhominin (such as Au. africanus) to a larger-bodied, possibly full-striding terrestrial biped(such asH. erectus) occurred in a mosaic fashion.Changes in functionally important aspects ofpelvic morphology, including a reduction of thesacroacetabular weight-bearing load arm andenhanced acetabulosacral buttressing (reflect-ing enhancement of the hip extensor mecha-nism), enlargement of the iliofemoral ligamentattachment (reflecting a shift in position of theline of transfer of weight to behind the center ofrotation of the hip joint), enlargement of theacetabulocristal buttress (denoting enhancementof an alternating pelvic tilt mechanism), and re-duction of the distance from the acetabulum tothe ischial tuberosity (reflecting a reduction in themoment arm of the hamstring muscles) (20, 32)occurred within the context of an otherwise aus-tralopith body plan, and seemingly before anincrease in hominin encephalization [in contrastto the argument in (33)]. Relative humeral andfemoral diaphyseal strength measures (table S2)also suggest that habitual locomotor patterns inAu. sediba involved a more modern human-likemechanical load-sharing than that seen in theH. habilis specimen OH 62 (34, 35). Mosaic evo-lutionary changes are mirrored in craniodentalmorphology, because the increasinglywide spacingof the temporal lines and reduction in post-orbital constriction that characterize Homo firstappeared in an australopith and before significantcranial expansion. Moreover, dental reduction,particularly in the postcanine dentition, precededthe cuspal rearrangement (wide spacing of post-canine tooth cusps) that marks early Homo.

The pattern of dental eruption and epiphysealfusion exhibited by MH1 indicates that its age atdeath was 12 to 13 years by human standards,whereas inMH2 the advanced degree of occlusalattrition and epiphyseal closure indicates that ithad reached full adulthood (SOM text S1). Al-though juvenile, MH1 exhibits pronounced devel-opment of the supraorbital region and canine juga,eversion of the gonial angle of the mandible, andlarge rugose muscle scars in the skeleton, all in-dicating that this was a male individual. And, al-though fully adult, the mandible and skeleton ofMH2 are smaller than in MH1, which, combinedwith the less rugose muscle scars and the shape ofthe pubic body of the os coxa, suggests that MH2was a female. In terms of dental dimensions,MH1has mandibular molar occlusal surface areas thatare 10.7% (M1) and 8.1% (M2) larger than thoseof MH2. Dimorphism in the postcranial skeletonlikewise is not great, though the juvenile status ofMH1 tends to confound efforts to assess adultbody size. The diameter of the proximal epiphysisfor the femoral head of MH1 (29.8 mm) is ap-proximately 9.1% smaller than the superoinferiordiameter of MH2's femoral head (32.7 mm). It islikely that MH1 would have experienced someappositional increase in joint size before matu-rity, thus this disparity would probably have de-

creased somewhat. The distal humeral epiphysisof MH1 is fully fused and its articular breadth(35.3 mm) is only marginally larger than that ofMH2 (35.2 mm). Thus, although the dentitionand postcranial skeleton are at odds in the de-gree of apparent size differences, the overalllevel of dimorphism, if these sex attributions arecorrect, appears slight in the Malapa homininsand was probably similar to that evinced by mod-ern humans.

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are referred to the taxon H. ergaster by some. Unlessotherwise stated, we collectively refer to H. habilis,H. rudolfensis, H. erectus, and H. ergaster materials as“early Homo.”

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Au. boisei that he refers to as a nasomaxillary basin: aconcave depression that is surrounded by a moreelevated topography. We see a similar concavity in theinfraorbital region of specimens of H. habilis–H.rudolfensis (KNM-ER 1470, KNM-ER 1805, KNM-ER1813, and OH 24), although it is not clear whetherthey represent homologous structures. In specimens ofAu. africanus, Au. sediba, and H. erectus, we recognize aslight convexity in this area.

19. Some humeri that are probably best attributed toAustralopithecus lack marked development of thetrochlear/capitular keel [or “lateral crest”: see (37)], andthus the absence of a marked crest does not reliablydifferentiate Australopithecus from Homo. However,although some specimens of early Homo (such asKNM-WT 15000) have crests that are more stronglydeveloped than those of modern humans, none exhibitthe marked crests of the australopiths. Thus, the markedcrest seen in the Malapa humeri can be seen to be sharedwith Australopithecus rather than Homo.

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Skeleton, A. Walker, R. E. F. Leakey, Eds. (Harvard Univ.Press, Cambridge, MA, 1993), pp. 221–233.

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30. L. Gabunia, A. Vekua, Nature 373, 509 (1995).31. T. D. White, in Paleoclimate and Evolution with Emphasis

on Human Origins, E. S. Vrba, G. H. Denton,T. C. Partridge, L. H. Burckle, Eds. (Yale Univ. Press,New Haven, CT, 1995), pp. 369–384.

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diaphyseal strength ratios in Au. sediba reflect arelative reinforcement of the femoral diaphysis in thecontext of femoral elongation (resulting in longerbending-moment arms) without a change in locomotorbehavior. At present, we are unable to directly assessthe absolute and relative length of the femur inAu. sediba.

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41. We thank the South African Heritage Resources Agencyfor the permits to work at the Malapa site; the Nashfamily for granting access to the Malapa site andcontinued support of research on their reserve; the SouthAfrican Department of Science and Technology, the SouthAfrican National Research Foundation, the Institute forHuman Evolution, the Palaeontological Scientific Trust,the Andrew W. Mellon Foundation, the AfricaArrayProgram, the U.S. Diplomatic Mission to South Africa,and Sir Richard Branson for funding; the University of theWitwatersrand’s Schools of Geosciences and AnatomicalSciences and the Bernard Price Institute forPalaeontology for support and facilities; the GautengGovernment, Gauteng Department of Agriculture,Conservation and Environment and the Cradle ofHumankind Management Authority; E. Mbua, P. Kiura,V. Iminjili, and the National Museums of Kenya for accessto comparative specimens; Optech and Optron; DukeUniversity; the Ray A. Rothrock Fellowship of TexasA&M University; and the University of Zurich 2009 FieldSchool. Numerous individuals have been involved in theongoing preparation and excavation of these fossils,including C. Dube, B. Eloff, C. Kemp, M. Kgasi,M. Languza, J. Malaza, G. Mokoma, P. Mukanela,T. Nemvhundi, M. Ngcamphalala, S. Jirah, S. Tshabalala,and C. Yates. Other individuals who have givensignificant support to this project include B. de Klerk,C. Steininger, B. Kuhn, L. Pollarolo, B. Zipfel, J. Kretzen,D. Conforti, J. McCaffery, C. Dlamini, H. Visser,R. McCrae-Samuel, B. Nkosi, B. Louw, L. Backwell,F. Thackeray, and M. Peltier. T. Stidham helped constructthe cladogram in fig. S3. J. Smilg facilitated computedtomography scanning of the specimens. R. Clarke andF. Kirera provided valuable discussions on these andother hominin fossils in Africa.

Supporting Online Materialwww.sciencemag.org/cgi/content/full/328/5975/195/DC1SOM Text 1 to 4Figs. S1 to S5Tables S1 and S2References

19 November 2009; accepted 26 February 201010.1126/science.1184944


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