L14- Origin of Modern Humans

Key Questions:

  1. How many waves of migration out of Africa were there?

    • likely to have several waves due to the Movius line

  2. Was there two-way gene flow between Africa and Eurasia?

    • likely

Homo ergaster/erectus spread out across Eurasia:

  • there was a high amount of environmental variation across this area

    → created a lot of intraspecific variation

Homo heidelbergensis:

  • evolved from Homo ergaster/erectus in Africa/Europe 600,000 years ago (a long time after Out of Africa)

  • spread out and colonised Africa and Europe

  • gave rise to Homo neanderthalensis in Europe 400,000 years ago

  • gave rise to Homo sapiens in Africa 200,000 years ago

Neanderthals:

  • evolved from Homo heidelbergensis in Europe/West Asia

  • lived in caves and buried the dead→ are lots of fossils

  • were adapted to live in the cold (glacial period):

    • had protruding faces with long nasal passages

    • had powerful muscles and strong bodies

  • were big-bodied, robustly built, did routine heavy work

  • had a larger brain than modern humans (1450 cc) but a similar EQ

  • both heidelbergensis and neanderthals had limited speech

    • hyoid bones, larynx structure, large hypoglossal canal (nerves)

  • produced stone tools and worked wood

  • were self-aware

    • buried dead in foetal positions, adorned bodies in jewellery

  • were found all over Western Europe and into Asia:

Models for the Evolution of Homo sapiens:

  1. Multiregional model→ discarded theory

    • ergaster/erectus spread out and evolved independently into sapiens in different regions with some gene flow

    • regional differences are deep rooted (1-2 million years ago)

  2. Out of Africa model 2

    • sapiens evolved in Africa 200,000 years ago and spread out, replacing erectus and all other Homos

    • regional differences are shallow (200,000 years ago)

What happened to the Neanderthals?

  • died off 40,000-27,000 years ago from the East to the West

  • anatomically modern humans migration followed this pattern (E→W)

    → AMH outcompeted them or there was a genocide→ no other hominins can co-exist with Homo sapiens

Denisovan Man:

  • found a tooth and finger bone in a Siberian cave

  • DNA evidence shows it is a completely different species from neanderthals and sapiens

  • found another jaw bone in Tibet→ lived at high altitudes

  • discovered there was interbreeding between N, S and D

    • sapiens that went to Europe interbred with neanderthals

    • sapiens that went to the East interbred with denisovans

    • sapiens in Africa did not interbreed→ original sapien population

Homo floresiensis:

  • discovered skeleton in Flores island, Indonesia

  • was a minute hominin→ 1m tall, minute brain, small size and weight

  • used primitive tools, hunted small animals (dwarfed elephants)

  • theory of how they evolved:

    • a population of erectus got stranded and dwarfed down (insular dwarfing), evidence:

      • primitive foot is similar to Homo erectus

      • dwarfed hippos have shown a reduction in brain size

    • could have been microcephaly condition affecting Homo sapiens→ discarded theory

Evidence for the Out of Africa 2 model:

  1. Fossils

    • the date of fossils decreases along migratory tracts

  2. Molecular biology

    • Mitochondrial Eve→ mtDNA is greatest in Africans (also seen in nuclear genes and the Y chromosome)

    • joining times show evidence of timing of differences

    • neanderthal and denisovan DNA show interbreeding

    • Garden of Eden hypothesis:

Archaeology:

  • can see different tools at different times and areas:→ may have shared tools (have different terminologies for each area)