Primates and Hominins Week 8

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

Two main groups: Prosimians and Anthropoids

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

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

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

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

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

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

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

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

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

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

Recent discovery in the news! Homo naledi In a cave in South Africa in 2015 Burial ground 30m underground, 1,500 fossil remains http://www.cnn.com/2015/09/10/africa/homo-naledi-human- relative-species/

It was a tight fit (interesting video):

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?

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).

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).

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.

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.

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?

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- 30,000 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.

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- 30,000 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.

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)

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

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

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.