1. EQ: How did humans evolve?
Human Evolution
EQ: How did humans evolve?

2. Hominins (Hominids)
Humans and our direct ancestors, since the split from chimps.
Major groups:
Australopithecines
Paranthropsus
Homo genus
Chimps are not ancestral species !! We shared a common ancestor.
Not a direct line to us !! A radiating lineage. Several hominids species co-existed.
Gorillas, chimps and hominids split about 6-8 MYA. At a generous 25 year generation time: 320,000 generations ago with strong natural selection

3. Primates

5. Hominid evolution Driven by life on the ground.
Not all traits at the same time!!
Mosiac Evolution
We walked upright for several million years before an increase in skull size

6. What Makes A Hominid? - Bipedalism
Primary feature distinguishing hominids from other hominoids is walking erect on two legs – erect bipedalism
Adaptations for bipedalism in the the partial skeleton of “Lucy,” an australopithecine ( 3.2 mya) clearly seen in the hip, spine and leg bones

7. Why did bipedalism become the primary adaptation of hominids?
Carrying behavior
Reduction of overall heat stress - facilitates heat loss through convection by exposing body to air currents, only humans have sweat glands that produce moisture to cool body
Most energy efficient way to travel long distances
Allows for better vision in open environments & defensive action against predators by freeing hands to throw objects

8. Hominid life on ground:
Bipedalism, upright walking
Jaw shape -smaller with specialized teeth with an omnivorous diet. Pronounced chin.
larger brain size, increased cerebrum
Reduced size difference between sexes
tool use, language, social behavior
Extended parent care time- longer juvenile period
More learning
Reduced sense of smell
Increased size of brain for vision and co-ordination with muscles
Eyes are larger and directed forward

10. Hominid Sites Earliest fossil hominid sites are in Africa
They now span the latest Miocene to the early Pleistocene from about 6-7 mya to about 1.6 mya
The major groups of sites are:
Ethiopia = Middle Awash valley & Hadar (Australopithecus afarensis)
Kenya = Lake Turkana
Tanzania = Olduvai Gorge
South Africa = various sites in limestone caverns centered around Sterkfontein

11. Evidence for Early Bipedalism
The record of bipedalism is most graphically preserved in the fossilized footprints at Laetoli, Tanzania!
3.6 million year old tracks left by 2 individuals were uncovered in volcanic ash by Mary Leakey ( )
Footprints were left by 2 australopithecines in damp volcanic ash of Laetoli
In the Laetoli trail, prints of the 2 individuals can be seen walking away from us
Notice how close the tracks are!

12. Laetoli Footprints
Laetoli footprints clearly show that the creatures who made them were fully bipedal
Big toe hardly diverges from the rest of the foot, unlike in apes
Gait = “heel-strike” followed by “toe-off” – the way modern humans walk

13. Laetoli Reconstruction
In this reconstruction, the 2 early hominids, identified as Australopithecus afarensis, walk bipedally across an open ash field produced by an erupting volcano
Region is wooded, but here trees are absent and the volcanic ash, wetted by a light shower of rain formed a flat shallow layer in which footprints are deeply implanted
Footprints filled up with yet more ash, and were thus preserved
Footprints reveal that, even at this early stage of human evolution, our ancestors walked upright with striding gait very similar to our own

14. Australopithecus First “humans”: Australopithecus, about 4.4 MYA.
Earliest is Australopithecus afarensis
Skull, capacity about 1/3 modern human size.
lasted 3 MY.
All fossils from Eastern and Southern Africa
Several Species of this genus including
A. afarensis, A.africanus, & A. boeisi
Very much apelike with an important feature. Was able to walk upright
Fossil evidence of hip, hands.
Australopithecus africanus was a dead end, no new lineages.

15. “Lucy” Australopithecus afarensis 3.24 million years old

17. Fig. 23.9

19. Fig. 23.6b

20. Fig. 23.6a

21. Homo habilis “Handy Man”
Homo habilis fossils from 2.5 to 1.6 MYA.
After walking upright for 2 MY these hominids now used their brains and fashioned simple stone tools.
First to use stone tools
Co-existed with the smaller-brained Australopithecus for nearly 1 MY.
Also was larger in general
Homo habilis lead to H. erectus, to H. sapiens.

22. Fig. 23.9

23. Homo ergaster Less sexual dimorphism, more pair bonding Larger brain
Slender legs, distance walking
Short straight fingers. No longer climbing trees
Smaller teeth, foods more prepared less hard chewing
More advanced tools
More habitats
MYA

24. Homo erectus
Homo erectus was the first to migrate out of Africa into Europe and Asia.
H. erectus 1.8 MYA - 300,000 YA.
gave rise to larger populations, had to continually expand to find food, hunt farther out.
Larger than H. habilis
Larger brain
Smaller face
Was the first to use fire

25. Homo heidelbergensis Descended from H. ergaster in africa, spread out.
Northern populations in Europe under ice age conditions became The Neanderthals 200, ,000 years ago in Europe
Reaming population in Africa adapted to drought conditions, became homo sapiens, spread out to rest of world.

26. Intermediate fossil between Homo habilis and H. erectus
1.7 million years old

27. Homo neanderthalensis
The Neanderthals
Probably not a direct ancestor - but another offshoot from H. erectus
200, ,000 years ago in Europe
Brain as large or larger than present day humans
Adapted to ice age
Buried dead with flowers - first evidence of religous/symbolic thinking.
Made hunting tools from stone and wood
Carnivorous

28. Neanderthal

30. Human Ancestors