BIOL 102 Chapter Notes - Chapter 20: Rickets, Preterm Birth, Multiple Sclerosis
Document Summary
Humans are 99. 9% genetically identical to one another regardless of geographic origin. All humans are members of a single biological species, homo sapiens, which evolved about 200,000 years ago. Physical features shared between people from the same population show environmental adaptations for that specific region. Alleles can be harmful, beneficial or neutral in their effect for survival and reproduction. Skin color evolved in response to environmental uv levels through natural selection. Alleles for darker skin color conferred an advantage in sunnier environments while alleles for lighter skin color conferred an advantage in regions that receive weak sunlight. Fossil evidence shows that apes and humans did descend from a common ancestor and walking upright preceded the development of a larger brain. Fossil and dna evidence shows that anatomically modern humans first emerged in. Modern humans emerged about 200,000 years ago in africa and then spread to other continents.