The forces of natural selection that led to the evolution of bipedality would be the environment. Ardipithecus was a forest dweller and may have evolved walking on two legs to be able to carry food. The other benefit of bipedality is it freed up the hands for use of tools. They were not a aggressive creature (found potentially by the smaller canines which are used in other primates for aggressive interactions). They may have had to reach up into the trees for their nutrition as well. Their hands were not made for walking on, but for grasping.
Brain size may well have evolved if the social groups were gettting more and more complex. The ability to store information of past meetings to remember for future encounters, and problem solving.
Wednesday, November 18, 2009
ancestor's tale
In the Ancestor's Tale Chapter 1 Dawkins warns the reader to avoid looking for repeating patterns in nature's past. Dawkins also warns of the assumption that we are the ultimate creation, that all other species that have ever lived monumentally lead to us and that was their purpose. Patterns of course do exist, however they are generally patterns in random. As for the thought that all species ultimately having us as the end result is thrown off by evolution and the fact that things are ever changing.
To look at history out of Africa Dawkins states that one must look at haplotypes, or the long lasting tightly bound parts of DNA that survive over many generations. Y chromosomes only pass through the male line, and contain the material to switch an embryo into male pattern development. On the other hand, Mitochondrial DNA is passed exclusively down the female line. Y chromosomes are useful in studying recent populations, while mtDNA are more effective for studying ancient patterns. Not as easy to use Y-chromosomes for that purpose. This is not the whole story because you cannot rely solely on a single gene. The out of Africa story holds that all people outside of Africa descend from a single exodus around a hundred thousand years ago. Each gene tells a different story so could be several stories.
To look at history out of Africa Dawkins states that one must look at haplotypes, or the long lasting tightly bound parts of DNA that survive over many generations. Y chromosomes only pass through the male line, and contain the material to switch an embryo into male pattern development. On the other hand, Mitochondrial DNA is passed exclusively down the female line. Y chromosomes are useful in studying recent populations, while mtDNA are more effective for studying ancient patterns. Not as easy to use Y-chromosomes for that purpose. This is not the whole story because you cannot rely solely on a single gene. The out of Africa story holds that all people outside of Africa descend from a single exodus around a hundred thousand years ago. Each gene tells a different story so could be several stories.
Subscribe to:
Comments (Atom)