Hominin evolution

Chapter 15

Classification of humansK AnimaliaP ChordataC Mammalia3 middle ear bones, diaphragm, fur / hair, teeth , one lower jaw bone,

mammary glands (Sub-class; Eutheria)O Primates 5 digits with opposable thumbs/big toes, flat nails & sensitive to touch

large forward-facing eyes = stereoscopic vision, cones for colour & protective outer socket bone

flexible skeleton for life in trees, large brains relative to body sizesociallong gestation periods (more fetal brain growth), provide parental care(Superfamily; Hominoidea)

F Hominidae (Subfamily; Homininae)Hominins are bipedal locomotion (erect-walking), only humans and

extinct ancestors.position of foramen magnum (p.566), angle between femur & tibia (p.

570) and shape of pelvis (p.568)G Homo Different from Australopith ancestors because; Reduction in size of

teeth, increase in brain size, shortening of face & behavioural differences

S Sapiens Whites of eyes - can tell if someone is looking at you

Lucy

Tuang child

AustralopithecusGraciles Robusts

A. anamensisA. afarensisA. africanus

A. robustusA. boiseiA. aethiopicus

Possibly ancestral to the human line Cousins of the human line

Brain size: about 400ml Brain size: about 500ml

Large molars , larger canines (Herbivores) Very large molars (Herbivores)

Rounded top of skull Bony crest on top of skull of males

Adult height: 1.4 – 1.5m (male) 1.0 – 1.2m (female)

Adult height: 1.3 – 1.4m (male) 1.0 – 1.3m (female)

Paranthropus

Australopithecus Paranthropus

A. anamensisA. afarensisA. africanus

P. robustusP. boiseiP. Aethiopicus

Lucy (3.2 Myr old)• Found 1974 in the Afar Triangle in

Ethiopia by Donald Johanson• Australopithecus afarensis• Approx 1m tall when standing on

2 feet– Standing taller meant they could

see further but not faster or safer– But... save a little bit of energy and

therefore may have reared more young

– Walking also frees up chest muscles to help with development of speech

Taung child (2.2 Myr old)

• November 1924 Cape Province, South Africa - importance recognised in 1984

• Raymond Dart (Aussie professor of Anatomy)• Cranium & Mandible (jaw) possessed both ape-like

and human-like features:– concluded it was an infant from an intermediate

species– classified it as Australopithecus africanus (new species)

• Position of foramen magnum, Dart concluded that the Tuang child walked upright

What was happening 6 Myr ago?

• All came about because rainforests were dying out and grasslands were prominent

• due to tectonic plates of India & Asia colliding--> poles freezing over --> less water available --> development of the African Savannah• Spent more time on the ground & less in

trees

habilis history h

rudolfensis reconstructs r

ergaster everything e

heidelbergensis however h

erectus evolution e

neanderthalensis never n

sapiens seems (to) s

florensis flow f

HOMO

~ 2-3 Myr ago• More variation amongst upright apes (transitional species)

Paranthropus boisei ~2.2 Myr old• roots of tall reeds & termites• couldn't build shelters

Homo rudolfensis ~ 2.6 Myr ago• scavengers

Homo habilis ~2.4 Myr old• scavengers & jack of all trades• made use of first primitive stone tools (Oldowan tools; scrapers, cutters & choppers)• could therefore live off a huge variety of foods• eating meat lead to brain development (half as big again, as boisei)

• Oldest Homo fossil is dated back to 2.4 Myr ago

Australopithecus Homodecreasing tooth size

Increasing brain size

~ 1.6 Myr agoHomo erectus• Brain size: 900ml (intelligence & planning)

– Controlled use of fire– Crafting of more elaborate stone tools– Evidence of systematic hunting

• Make sounds (no spoken language)– Vertebrae suggests that less nerve tissue in spinal cord -> lack

of fine muscle control of breathing that is necessary for speech

1.8 million years agoHomo ergaster• Same as habilis (and thought to have coexisted) but from east Africa• First to be able to piece together information from the world around them• First to make hand axes (made by hitting a core stone with a hammer stone)• Demonstrated ability to learn from each other

– as shown by many generations making the same tools• Big brains used to understand one another (uses lots of Energy)

– families and friends worked together eg: finding, stalking, killing, sharing food

• It was the Homo ergaster who left Africa and crossed the Middle East into Asia (which took thousands of years)

• When they were discovered, they were now known as Homo erectus

• 1 million years later – Homo ergaster has shown no development.– stone hand axes were still used (not even spears)

40‘000 – 400‘000 years agoHomo Heidelbergensis• Intermediate between H. erectus & H. sapiens• Large brain size: 1100-1400ml• Tall: around 1.8m • More muscular than humans

Homo Neanderthalis • Europe• Short limbs - decreasing SA:Vol ratio - prevent heat loss• Wide nose stopped them from sweating• Enduring - many fractures found in fossilised bones• Tolerant to pain• Brains were nearly as big as ours• Anticipation of events (better understanding of selves) ie: childbirth• Relationships were more developed

Neanderthals vs Modern humans

• mtDNA varies by an average of 27 bases• most human mtDNA will vary only an average of 8

bases-> therefore - they were / are a different species• diverged from the line that gave rise to Homo sapiens

about 500-600 000 years ago• co-existed with Homo sapiens for tens of thousands of

years before extinction• no interbreeding during that time (separate gene

pools)

~ 18‘000 years agoHomo floresiensis• Small (around 1m), Brain size: 380ml• Close to us - similar proportions of brain size to body• Youngest fossils to be found• Alive at the same time as Homo Sapiens (and after

Neanderthals)

~ 130‘000 years ago - presentHomo sapiens• Avarage brain size: 1350 – 1400ml• Steep foreheads• Short, high, narrow skulls• Brow ridges small or absent• Small eye sockets• Pointed chin• No gap between 3rd molar and jawbone

Out of Africa / Regional continuityOut of Africa hypothesis Regional continuity hypothesisModern humans should appear first in Africa and only later in other parts of the world

Modern humans should appear throughout Africa, Asia and Europe during the same period

Transitional forms from ancestral to modern humans should be found only in Africa

Transitional forms should be found in Africa, Asia and Europe

Variation in mtDNA should be greater in African populations than in other populations

Variation in mtDNA should be about equal in human populations from all regions of the Old World

• mtDNA studies strongly support the „Out of Africa“ hypothesis

Changes in human population

• Biological evolution (lactose tolerance, body shape)

• Cultural evolution– Changes in human societies over time where

those changes are socially transmitted

• Technological evolution