Cultural development, a continuum of evolution
Oct 6, 2001, In biologicalEvolution forum.
Dov: I suggest that the following observation, presented more than once by LucasPA, might draw some further comments :
LucasPA, end of message #229: >As I said, diversification and allopatric speciation in H. sapiens did begin, but transportation and increased gene flow seems to have aborted it. H. sapiens remains one species but, like all species with a large geographical range, it has several arieties or populations.<
Dov: I repeat here a thought that I posted earlier, that the initiation of development of Human Culture (I include "civilization" in culture) has marked a revolutionary turn in evolution, replacing adaptation to environmental parameters with modification and control of environmental parameters. True, evolutionary "adaptation" has sometimes included also "modification", but with Humans the physiological adaptation has been decreasing drastically and the cultural modification+control of survival parameters have taken over the struggle for survival and proliferation.
LucasPA: This is probably true. The phenomenon we are dealing with is disruptive selection. This occurs when a species has a geographical range such that the environment in part of the range is different than the environment in another part or the rest of the range. The different environments mean different selection pressures which mean different adaptations being selected. If the disruptive selection is large enough and gene flow between the populations in the different geographical regions is low enough, you get divergence of the populations to the point of new species. Disruptive selection is responsible for "ring species" such as the Arctic Gull and the California salamander. Although populations can interbreed around the "ring", the two populations that meet on the opposite side of the ring cannot interbreed. If the ring is ever disrupted because of extinction of one of the populations, the two "end" populations would be different species. As I say, since I have not seen whether !Kung can interbreed with Australian aborigines or Patagonian Indians, it may be that H. sapiens is a ring species.
Henisdov's point becomes pertinent when we consider that humans modify their environments by their technology. Thus disruptive selection is weakened because humans don't receive the full brunt of different environments. This, together with technology that allows world-wide travel, is likely to stop the disruptive selection of H.sapiens, increase gene flow, and stop the formation of new species from H. sapiens by allopatric or ecological speciation.