The Living World 8th Edition by George Johnson

تمرين 9

Genomic evidence supports the view that modern humans migrated from Africa and spread throughout the globe, not once but several times, each time adapting to local environmental challenges. To what degree does the fossil evidence support this view? Explain.
Once common in Australia, a huge flightless bird called Genyornis newtoni is now extinct. Isotopic dating of its fossilized eggshells indicate that no Genyornis eggs are younger than 50,000 years old. Humans colonized Australia 50,000 years ago. What types of evidence would be needed to support the hypothesis that humans hunted this flightless bird to extinction?
Mitochondrial DNA (from mitochondria in the egg and so not subject to recombination) is passed, essentially unchanged, from a mother to all her children through the generations. Likewise, the genes on the Y chromosome (also not subject to recombination) are passed from father to son. Would you expect studies of mitochondrial DNA variation and of Y chromosome variation to both yield the same result when researchers attempt to assess the hypothesis that all human species evolved in Africa?