ABOUT THE SKULLSSahelanthropus tchadensis6-7 MYA. The Sahelanthropus tchadensis skull was discovered by Michael Brunet's team in Chad in 2001 and described in Nature in 2002. Some suggest that S. tchadensis existed near the time that hominids and apes separated on their evolutionary paths. The characteristics of the cranium are a mosaic of hominid-like (short face, the size and shape of the canines), and ape-like (very large browridges and small brain case) features.

Ardipithecus ramidus4.4 MYA. Ardipithecus ramidus had a small brain, measuring between 300 and 350 cm3. This is slightly smaller than a modern bonobo or female common chimpanzee brain, but much smaller than the brain of australopithecines like Lucy (~400 to 550 cm3) and roughly 20% the size of the modern Homo sapiens brain. Like common chimpanzees, A. ramidus was much more prognathic than modern humans.The teeth of A. ramidus lacked the specialization of other apes, and suggest that it was a generalized omnivore and frugivore (fruit eater) with a diet that did not depend heavily on foliage, fibrous plant material (roots, tubers, etc.), or hard and or abrasive food. The size of the upper canine tooth in A. ramidus males was not distinctly different from that of females. The features of the upper canine in A. ramidus contrast with the sexual dimorphism observed in common chimpanzees, where males have significantly larger and sharper upper canine teeth than females.

Australopithecus afarensis “Lucy” female3.2 MYA. The Australopithecus afarensis Skull "Lucy" was discovered by D. Johanson in 1974 in Hadar, Ethiopia. Several branches of the hominid evolutionary tree that began between 2 and 3 MYA stemmed from "Lucy's" species. Although the short stature of this female, only 1.2 meters, suggests that she was immature, eruption of the third molar provides evidence that this specimen was mature, and was simply a female representative of a sexually dimorphic species. The jaw shares features with both apes and other early hominids, with the shape showing some similarities to apes, with relatively large front teeth and parallel-sided tooth rows, and the size of the canine teeth being intermediate between apes and hominids who lived later. The cheek teeth are intermediate in size between hominids who lived earlier and those who lived later. The brain of "Lucy" was relatively small and overlapped in size with living apes; however, the shape of the pelvis, along with other characteristics of the postcranial skeleton, indicates that "Lucy" walked upright. At the same time, other characteristics of the limb skeleton indicate that members of this species spent time in the trees. This combination of an ape-sized brain in a hominid adapted to upright walking adds to the evidence that bipedalism occurred before the development of a relatively large brain.Australopithecus afarensis male2.9 to 3.6 MYA. Australopithecus afarensis Skull. The australopithecines are only known from Africa and are believed to be the earliest known true hominids. None has ever been found in Europe or Asia. They had ape-sized brains; their cranial capacity ranged from 375 to 530 cc. The cranial capacity of Australopithecus afarensis had a similar range. They had strong jaws with large teeth. Like modern gorillas the adult males were much larger than the females. The babies probably took approximately the same length of time to grow up as a modern chimpanzee or gorilla.

Kenyanthropus platyops3.5 MYA. The Kenyanthropus platyops Skull KNM-WT-40000 was discovered in 1999 by J. Erus, a member of Meave Leakey's team, west of Lake Turkana, Kenya. In 2001 Leakey, et al. described the specimen in Nature. Leakey and colleagues viewed the finds as being distinct enough from Australopithecus, particularly in the marked flatness of the face, that it justifies giving them a new genus and species, Kenyanthropus platyops (meaning "flat faced hominid from Kenya"). Providing a second hominid species in the period from 3 to 3.5 MYA, the discovery of this specimen challenges A. afarensis "Lucy" as the direct ancestor of modern human.

Australopithecus africanus2.5 MYA, the Australopithecus africanus Skull Sts 5 "Mrs. Ples" was discovered in 1947 by R. Broom and J. Robinson in Sterkfontein, Transvaal, South Africa. The discovery of this nearly complete cranium of a mature specimen led to a much more positive reception of South African australopithecines as hominids. Like other early hominids, it had an ape-sized brain. The Sts 5 cranial capacity is about 485 cc. Compared to Australopithecus afarensis, it has a more rounded skull, a less projecting face, absence of cranial crests, and smaller front teeth. However, the front teeth are larger than in robust australopithecines. The cheek teeth are larger than in Australopithecus afarensis but smaller than in the robust australopithecines.

Paranthropus aethiopicus2.5 MYA. The Paranthropus aethiopicus Skull KNM-WT 17000 was discovered by A. Walker in 1985 on the west shore of Lake Turkana in northern Kenya. It was described by Walker, Leakey, Harris and Brown in Nature in 1986. The skull is commonly referred to as the "Black Skull" due to its blue-black color. Although not considered on a direct line to humans, it gives insights into early hominid evolution. Although it shares many primitive features with A. afarensis (e.g., projecting face, small cranial capacity (410 cc)), it also has features typical of australopithecine species (e.g., projecting face, large sagittal crest and jaws, and expanded cheek teeth). Given that it seems to fall between A. afarensis and A. boisei, it was given its own species name.

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Paranthropus robustus1.5 to 2 MYA. The Paranthropus robustus Skull SK-48 was discovered by Fourie in Swartkrans, South Africa in 1950 and described by R. Broom in 1952. SK-48, formerly called Paranthropus crassidens, greatly increased what is known about australopithecines. The Transvaal cave site where it was found was blasted by explosives but, remarkably, the skull survived. The skull was found with the right canine, the first premolar and all three molars intact. On the basis of the adult teeth and small sagittal crest, Broom determined the specimen to be an adult female.

Australopithecus Sediba2 MYA. The cranial capacity of MH1, which has been estimated to be at 95% of adult capacity (420 cm3), is at the higher end of the range for A. africanus and far from the lower range of early Homo (631 cm3), but the mandible and tooth size are quite gracile and similar to what one would expect to find in H. erectus; so similar are these features that, if found in isolation without other skeletal remains, they could be classified as Homo based on tooth and mandible size. However, the cusp spacing is more like Australopithecus. A. sediba had a surprisingly modern hand, whose precision grip suggests it might have been another tool-making Australopithecus. Evidence of the precision gripping and stone tool production can be seen from Homo-like features such as having a long thumb and short fingers.

Homo habilis1.9 MYA. The Homo habilis Skull KNM-ER 1813 was discovered by K. Kimeu in 1973 at Koobi, Kenya, and described by R. Leakey in Nature in 1973. The species possessed a larger brain than A. africanus or A. boisei, though smaller than Homo erectus from Java and China. The cranial bones are thinner than typical for australopithecines, and the braincase is wider and shorter. The width of the face approaches A. boisei in breadth, but is not similarly flat. The facial profile of H. habilis slopes forward but projects less than in A. africanus. Some scientists believe that the range of variation of specimens once attributed to Homo habilis is too great to represent a single species; consequently, more than one species of early Homo may have lived at the same time in East Africa.

Homo nalediThe physical characteristics of H. naledi are described as having traits similar to the genus Australopithecus, mixed with traits more characteristic of the genus Homo, and traits not known in other hominin species. The skeletal anatomy contains plesiomorphic ("ancestral") features found in the australopithecines and more Apomorphic ("derived" or traits arising separately from the ancestral state) features known from later hominins. Four skulls were discovered, thought to be two females and two males, with a cranial volume of 560 cm3 (34 cu in) for the males and 465 cm3 (28.4 cu in) for females, approximately half the volume of modern human skulls; average Homo erectus skulls are 900 cm3 (55 cu in). The H. naledi skulls are closer in cranial volume to australopithecine skulls. Nonetheless, the cranial structure is described as more similar to those found in the genus Homo than to australopithecines, particularly in its slender features, and the presence of temporal and occipital bossing, and the fact that the skulls do not narrow in behind the eye-sockets. The species' brains were markedly smaller than modern Homo sapiens, measuring between 450 and 550 cm3 (27–34 cu in).

Homo rudolfensis1.8 to 1.9 MYA. The Homo rudolfensis Skull KNM-ER 1470 was discovered by B. Ngeneo in 1972 at Koobi Fora in Kenya and described by R. Leakey in Nature in 1973. 1470 features a 750 cc braincase, too large for australopithecines, and perhaps even for habilis, and lacks the crests and heavy muscle markings that characterize australopithecine skulls, as well as lacking the brow ridges associated with Homo erectus. Several features differ from other habilis specimens (a longer face, squared upper jaw and short, shallow palate), leading some scientists to conclude that there is too great a range of characteristics within the specimens for them to be a single species. In 1986 Valerii Alexeev proposed another species within Homo, giving 1470 the scientific name Homo rudolfensis.

Homo Gautengensis1.8 MYA According to Curnoe, Homo gautengensis had big teeth suitable for chewing plant material.[8] It was "small-brained" and "large-toothed," and was "probably an ecological specialist, consuming more vegetable matter than Homo erectus, Homo sapiens, and probably even Homo habilis." It apparently produced and used stone tools and may even have made fire, as there is evidence for burnt animal bones associated with H. gautengensis' remains.Curnoe believes H. gautengensis stood just over 3 feet (0.91 m) tall and weighed about 110 pounds (50 kg). The researchers believe it lacked speech and language skills. Due to its anatomy and geological age, researchers think that it was a close relative of Homo sapiens but not necessarily a direct ancestor.

Homo ergaster1.75 MYA. Female The Homo ergaster Skull KNM-ER 3733 with dentition was discovered by B. Ngeneo in 1975 in Koobi Fora, Kenya, and described by R. Leakey in Nature in 1976. Several teeth are intact, but no mandible was ever found. Of great significance is the fact that this skull was found in the same sediment layer that A. boisei KNM-ER 406 had been six years earlier, adding to the evidence against the single species hypothesis, the notion that only one hominid species existed at any time in history. Also known as Homo erectus, KNM-ER 3733 is said to be very similar in appearance to the H. erectus finds of Peking, China, including a cranial capacity of 850 cc, keeling of the cranium and the presence of an occipital torus. Due to its features (including wear on teeth and closure of cranial sutures) and compared to KNW-WT 15000, this specimen is considered to be a mature female.Paranthropus boisei (KNM-ER 406 BH006)1.7 MYA. The Paranthropus boisei Skull KNM-ER 406 was discovered by R. Leakey at Koobi Fora, Kenya, in 1969. This discovery helped to shed light on the controversial hypothesis that all australopithecines were of the same species, and tended to support the classification of boisei as a separate species of Australopithecus. A comparison of KNM-ER 406 and KNM-ER 732 revealed that australopithecines were sexually dimorphic. Some of the features possessed by this skull are sagittal and nuchal crests (missing in KNM-ER 732), massive cheek teeth, and widely flaring cheekbones, giving the face a dish shape. An interesting feature of this specimen is a little hole on the frontal bone, which may be rare evidence in early hominids of bone disease. The cranium is virtually complete and has a capacity of 510 cc.

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Homo ergaster1.6 MYA. Male. The Homo ergaster Skull KNM-WT 15000 "Nariokotome Boy" or "Turkana Boy" was discovered by K. Kimeu in 1984 in Nariokotome, Kenya. It was first described by Brown, Harris, R. Leakey and Walker in Nature in 1985 as H. erectus. The completeness of this skull allowed scientists to get accurate measurements of brain size. Many other skeletal parts were also recovered, giving anthropologists a great deal of information regarding body size, limb proportions, age of death (probably 12 or 13 years) and whether or not language was possible. The pelvis reveals a greater ability to run than modern humans, and some reveal a closer affinity to australopithecines.

Homo erectus1 MYA to 240,000 YA. The Homo erectus Skull Peking Man is also known as Pithecanthropus pekinensis (Sinathropus). The original reconstruction was prepared by Dr. F. Weidenreich and Mrs. Lucille Swan in 1937 from the fossil remains of several different individuals found in the caves at Zhoukoudian, China. The skull is somewhat unique in that a rare metopic suture is present along the mid-line of the frontal bone. Cranial capacity averages about 1050 cc. The skull has a large brow ridge and a ridge of bone on the back of the skull.

Homo heidelbergensis125,000 to possibly 400,000 YA. The Homo heidelbergensis Skull Broken Hill 1 (Rhodesian Man) was discovered in Kabwe, Zambia (formerly Rhodesia), by miner T. Zwigelaar and originally described by A. Woodward in 1921 in Nature as Rhodesian Man (H. rhodesiensis). This is the first human ancestor to be found in Africa. The skull shares features of both Homo erectus (heavy browridge) and Homo sapiens (flatter face, large brain (1300 cc).

Archaic Homo sapiens Skhul 5 BH-032100,000 YA. The Homo sapiens Skull Skhul 5 was discovered by T. McCown near Mount Carmel, Israel in 1932. The remains of 10 individuals were excavated from Skhul cave in 1932.. The Skhul skulls show much variation in the expression of modern traits. With a cranial capacity of 1520 cc, features common to modern skulls are the high forehead, expanded frontal portion of the braincase, and rounded back of the skull. Differences from modern skulls include its more pronounced brow ridges, and prognathic lower face. Skhul 5 has been suggested as providing evidence of hybridization between humans and Neanderthals. Current evidence, indicates that Neanderthals and early modern Homo sapiens alternately occupied the Near East during cold and warm periods, respectively, for thousands of years.Homo antecessor800,000 YA H. antecessor was about 1.6-1.8 m (5½-6 feet) tall, and males weighed roughly 90 kg (200 pounds). Their brain sizes were roughly 1,000–1,150 cm³, smaller than the 1,350 cm³ average of modern humans. Due to fossil scarcity, very little more is known about the physiology of H. antecessor, yet it was likely to have been more robustthan H. heidelbergensis.[17] Based on teeth eruption pattern, the researchers think that H. antecessor had the same development stages as H. sapiens, though probably at a faster pace. Other significant features demonstrated by the species are a protruding occipital bun, a low forehead, and a lack of a strong chin.

Homo neanderthalensis50,000 YA. The first humans with proto-Neanderthal traits are believed to have existed in Eurasia as early as 350,000–600,000 years ago with the first "true Neanderthals" appearing between 200,000 and 250,000 years ago. The exact date of their extinction had been disputed but in 2014, a team led by Thomas Higham used an improved radiocarbon dating technique on material from 40 archaeological sites to show that Neanderthals died out in Europe between 41,000 and 39,000 years ago. This coincides with the start of a very cold period in Europe and is 5,000 years after Homo sapiens reached the continent. DNA evidence indicated interbreeding between Neanderthals and Homo sapiens in Europe.Comparison of the DNA of Neanderthals and Homo sapiens suggests that they diverged from a common ancestor between 350,000 and 400,000 years ago.

Homo floresiensis18,000 YA. The Homo floresiensis Skull (Flores Skull LB1) was discovered by P. Brown and his team on the island of Flores, Indonesia, in 2003 and reported in Nature in 2004. A skeleton of this species, which has been designated as female because of characteristics of the pelvis, shows that in maturity she was only about 3.3 feet tall. That such a specimen (which had an unusually small brain capacity -- 380 cc -- for its body size) was in existence only 18,000 YA could be one of the most important discoveries in decades. Stone tools were also found at this site. H. floresiensis is the subject of much debate centering around whether it is a new human species or a microcephalic human. P. Brown et al. originally proposed that the Flores hominid was the result of a long term process of isolation on an island known as "insular dwarfism.

Homo sapiens (Cro-Magnon) 10,000-30,000 YA. This Cro-Magnon Skull was discovered in 1998 in the Rhine River deposits in Southwest Germany near Mainz. Since it was dredged from a gravel pit, the stratum can only be assumed. However, the association with Mammuthus, Megaceros and Equis, as well as the state of mineralization, suggests an age of at least 10,000 to 30,000 years. It also matches the description of other Cro-Magnon type hominid fossils from the area.

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Homo sapiens (“modern”)160,000 YA-present. Oldest fossils of modern humans have been found in the Middle Awash (Herto people) and Omo regions of Ethiopia.

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