1. Primates and Hominins
Week 8

2. What’s a primate? Hands and feet efficient at grasping
Flattened nails (not claws)
Relatively large brains
Color vision
Complex social behavior
Extensive parental care

3. Two main groups: Prosimians and Anthropoids

4. Prosimians Lemurs, lorises, pottos, and tarsiers Paraphyletic group
Relatively small, live in trees, active at night

5. Anthropoids
New World and Old World monkeys, gibbons, and great apes (orangutans, gorillas, chimpanzees, and humans)
Gorilla
Capuchin monkey, gibbons, gorilla (left to right)
Gibbons
Capuchin monkey

6. Anthropoids: Great Apes
= hominids
Orangutans, gorillas, chimps, and humans
Relatively large bodies, long arms, short legs, no tail, distinct walking
Gorillas and chimps knuckle walk
Orangutans fist walk
Gorillas and chimps knuckle walk
Humans are fully bipedal
Humans are Bipedal
Orangutans fist walk

7. Humans are sister to bonobos and chimpanzees.
Most recent common ancestor of chimps and humans lived in Africa 6-7 million years ago
Africa 6-7 million years ago

8. Hominins (within hominids)
=monophyletic group comprising Homo sapiens and our 20+ extinct, bipedal relatives

9. Hominins Classified into four major groups: Australopithecus
Paranthropus
Early Homo
Recent Homo

10. Australopithecus Called “gracile”- have a slight build (1.5 m, 36 kg)
Earliest specimens from South Africa
Shapes of knee, hip, and hole in skull indicate that they were bipedal
36 kg = 80 lbs

11. Paranthropus
Hypothesis that they were a monophyletic group that was a side branch during human evolution
Same height but 20 lbs heavier
Broader skulls, more “robust,” great biting power
Great responsibility

12. Early Homo Humans = species in the genus Homo
Flatter, narrower faces, smaller jaws and teeth, larger brains
Used tools

13. Recent Homo 1.2 mya – present
Flatter faces, smaller teeth, larger brains
Cro-Magnons: 30,000-year-old population
Neanderthals: extinct 40,000 years ago

14. Recent discovery in the news!
Homo naledi
In a cave in South Africa in 2015
Burial ground 30m underground, 1,500 fossil remains
relative-species/

15. It was a tight fit (interesting video):

16. What can we learn from the fossil record?
Hominins are bipedal (defining synapomorpy).
Several species from the lineage were present simultaneously during most of hominin evolution.
So why is Homo sapiens the only extant species?
Homo spp. have large brains relative to overall body size.
Why?

17. Why is Homo sapiens the only extant species in the lineage?
All other species were wiped out during an intense heat wave.
Intense competition for food and space.
The other species weren’t smart enough to survive.
They were killed by large predators.
Likely due to intense competition for food and space, also possibly due to climate change (possibly due to ice age glaciation).

18. Why is Homo sapiens the only extant species in the lineage?
All other species were wiped out during an intense heat wave.
Intense competition for food and space.
The other species weren’t smart enough to survive.
They were killed by large predators.
...compounded by ice age glaciation
Likely due to intense competition for food and space, also possibly due to climate change (possibly due to ice age glaciation).

19. 2. Why did humans evolve large brains?
Selection for the ability to reason and communicate for using language and tools.
Unpredictable climate selected for the ability to think ahead.
Social competition for scarce resources selected for larger brains.
All of the above.
D- these are all hypotheses for why humans developed such large brains relative to their body size and compared to other hominins.
However, it’s not really known.

20. 2. Why did humans evolve large brains?
Selection for the ability to reason and communicate for using language and tools.
Unpredictable climate selected for the ability to think ahead.
Social competition for scarce resources selected for larger brains.
All of the above.
D- these are all hypotheses for why humans developed such large brains relative to their body size and compared to other hominins.
However, it’s not really known, and this is also a very difficult question to test.

21. Out-of-Africa Hypothesis
Homo sapiens evolved in Africa and then dispersed.
No interbreeding with other Homo species.
Is this hypothesis supported with fossil and/or molecular evidence?

22. 3. Which of the following statements is true based on fossil evidence?
Homo sapiens, H. neanderthalensis, and H. erectus all lived in Africa at the same time.
H. sapiens and H. neanderthalensis never coexisted with each other.
H. sapiens was found throughout Europe, Asia, Africa, and Australia from 60, ,000 years ago.
H. sapiens did not originate in Africa.
A- false- H. sapiens lived in Africa from 195,000-65,000 years ago, whereas H. neanderthalis occupied Europe and the Middle East, and H. erectus was in Asia during that time.
B- false- They coexisted in Europe for several thousand years (once H. sapiens dispersed to Europe)
C- true*
D- false- H. sapiens originated in Africa and then later dispersed to the other continents.

23. 3. Which of the following statements is true based on fossil evidence?
Homo sapiens, H. neanderthalensis, and H. erectus all lived in Africa at the same time.
H. sapiens and H. neanderthalensis never coexisted with each other.
H. sapiens was found throughout Europe, Asia, Africa, and Australia from 60, ,000 years ago.
H. sapiens did not originate in Africa.
A- false- H. sapiens lived in Africa from 195,000-65,000 years ago, whereas H. neanderthalis occupied Europe and the Middle East, and H. erectus was in Asia during that time.
B- false- They coexisted in Europe for several thousand years (once H. sapiens dispersed to Europe)
C- true*
D- false- H. sapiens originated in Africa and then later dispersed to the other continents.

24. Out-of-Africa Hypothesis
Homo sapiens evolved in Africa and then dispersed.
No interbreeding with other Homo species.
Is this hypothesis supported with fossil and/or molecular evidence?
Overall, supported by fossil evidence (H. sapiens interbred with Neanderthals)

25. 4. Which of the following statements is not true based on molecular evidence?
The ancestral population of modern humans lived in Africa.
Humans left Africa in one wave.
H. sapiens and neanderthals interbred in the middle east.
H. sapiens bred with H. erectus before migrating to Australia.
A- true
B- false- migrated out of Africa in more than one wave- the first one moved east and south to Australia, and the second one moved to Europe and Asia
C- true- this happened before H. sapiens migrated to Europe and Asia
D- true- this happened during the first wave of migration

26. 4. Which of the following statements is not true based on molecular evidence?
The ancestral population of modern humans lived in Africa.
Humans left Africa in one wave.
H. sapiens and neanderthals interbred in the middle east.
H. sapiens bred with H. erectus before migrating to Australia.
A- true
B- false- migrated out of Africa in more than one wave- the first one moved east and south to Australia, and the second one moved to Europe and Asia
C- true- this happened before H. sapiens migrated to Europe and Asia
D- true- this happened during the first wave of migration

28. Out-of-Africa Hypothesis
Homo sapiens evolved in Africa and then dispersed.
No interbreeding with other Homo species.
Is this hypothesis supported with fossil and/or molecular evidence?
Overall, supported by fossil evidence (but not certain whether H. sapiens interbred with Neanderthals).
Molecular data support dispersal out of Africa, but inbreeding occurred.