A105 Lecture Outlines: 24-25:

The origins and spread of modern humans

Models of Human Origins:

  • Multiregional model: populations of archaic Homo (e.g. Homo erectus) inhabiting different parts of Africa, Europe and Asia all evolved locally into modern humans. This model assumes alot of gene flow between regions, and implies very deep roots to regional populations. Some scientists think this model supports racist thinking because it makes modern human biological variation seem profound and deep. Milford Wolpoff is the strongest advocat of this model, based on his analysis of the similarities between fossil specimens from different regions. But many anthropologists have pointed to flaws in his interpretation of the fossil specimens.
  • Out of Africa Model or "Garden of Eden" or "African Eve" or "Single Origin" model: populations of archaics inhabited many parts of the Old World, but only evolved a modern anatomy in Africa. Originating in Africa, these populations spread out, competed with and eventually completely replaced other contemporary populations (like the neanderthals). This model implies that modern humans all share a relatively recent common ancestor, and that geographical differences in human morphology (e.g. skin color) are evolved very recently. It also suggests that little or no genetic mixing (hybridization) occurred between archaic populations and the immigrant moderns
  • Modified "Garden of Eden" Model: this is similar to the Out of Africa model, but allows for some interbreeding between archaics and early modern immigrants, with the modern morphology being dominant and ultimately more successful. This model would suggest that perhaps some neanderthal genes survive in western European populations, etc. This model is supported by some (not all) paleontologists who see evidence for modern morphology in some late neanderthals in eastern Europe, and some neanderthal traits in early modern populations.

Genetic Evidence for modern human origins:

  • mt DNA (video of Rebecca Cann) comparisons used to trace recent evolution of H. sapiens sapiens (see article in reader for examples) Basic conclusion: all living humans shared a common ancestor that lived in Africa sometime between 250,000-200,000 years ago.
  • rationale of mtDNA method:
    • mtDNA inherited maternally (in cell mitochondria)
    • mtDNA not subject to same selection pressures as DNA in cell nucleus
    • mtDNA mutation rate is known, and is faster than nuclear DNA, so can measure differences between populations within one species that have accumulated recently... good for info about population migration patterns (demography)
    • African populations with greatest genetic diversity have accumulated mtDNA mutations for longer time... are ancestral to populations in Asia and Europe, which split off more recently from African roots
  • the bulk of current genetic studies support the recent "Out of Africa" model of modern human origins

Cultural Evidence for modern human origins:

  • even the early anatomically modern populations in Africa and the Near East used a technology very similar to that used by Neanderthals in Western Europe: a Middle Paleolithic technology, using Levallois flaking techniques and producing a simple toolkit made on flakes (e.g. Mousterian culture)
    • example: Klasies River Mouth site in Southern Africa, with evidence for simple flake toolkit, opportunistic hunting and shellfish collecting, use of hearths, associated with fossils of early anatomically modern humans at 120,000-100,000 b.p.
  • the first signs of "modernity" that are easy to spot are associated with Upper Paleolithic Cultures (40,000 - 15,000 bp):
    • appear across Old World by 40,000 bp (perhaps older in Africa)
    • associated with technological innovation (new raw materials used, like bone, antler, etc; new stone flaking techniques, such as blade cores, soft hammer percussion, heat treating flint) and more deliberate control/design of artifacts
    • greater diversity of specialized tool functions (e.g. needles, harpoons, engraving tools, large bifacial points)
    • stylistic variation in material culture: distinctive styles develop in different regions, and change more frequently through time (e.g. Venus figurines across Europe)
    • ornaments and art appear for the first time in many parts of the world, including Europe, Africa, and Australia... such art seems to have symbolic/ritual value that we can only guess at
  • Cultural variation (e.g. in art styles) suggests that fully modern language had developed by the U.P. times, as people were using material culture to communicate with each other (e.g. symbols of identity, ethnicity?)
  • U.P. folks in different parts of the world became ecologically sophisticated and very successful, e.g. at hunting migratory herd animals like reindeer and fishing for seasonal salmon . .. to the point where U.P. hunting success may have helped drive many large animals common in Ice Age Europe (and Australia, Africa and North America) to extinction (see article in reader)
  • Social cooperation evident in such hunting tactics... such as the collaborative effort needed to build Mammoth Bone houses in Ukraine (e.g. site of Mezhirich)... some have suggested that key cave art sites, like Chauvet or Lascaux in France, or AltaMira in Spain, would have been ritual sites associated with social cooperation... a way of coping with survival in ice age Europe.
  • folks invaded new lands with new skills: Australia by 50,000 years ago (via boat); Siberia by 30,000 years ago; North America by 18,000 years ago (via Bering Land Bridge)


Paleolithic Art links:

 

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