Posted by Skeptic [Skeptic] on November 28, 1999 at 08:13:20 {hcnmikA.FkUIzFICAknMQ0vvLkUBWM}:
In Reply to: *Evolutin Phase III posted by AF on November 27, 1999 at 18:31:59:
:When the environment settles down to a steady state, it appears that life also settles down and does not change over long periods of time. But when the environment changes drastically, due to local phenomena that isolates a small population or due to global phenomena such as a massive asteroid strike, evolution can occur surprisingly rapidly. Why this should be I have no idea, but it's an observation from the fossil record.
AF,
Excellent post...I admit to being puzzled by the above statement, simply because I thought the answer was known. I thought it depended on how effectively natural selection can cull the population.
I was under the impression that evolution proceeds quickly when the "disadvantaged" got killed off quickly, leaving only the ones with an advantage. Hence, in a few generations, everyone has this advantage.
For example, 4% (I think) of humans are immune to the AIDS virus. If everyone on earth got AIDS - say if an air-borne version of AIDS developed, then within a few years 96% of all humans would be dead, leaving only the 4% who are immune to AIDS. Since this gives a pool of 100% AIDS-immune parents, much - but not all - of the succeeding generations would be AIDS immune. And if everyone kept getting AIDS, then within a few generations everyone would be AIDS immune. The human race would have evolved, simply because everyone who was not AIDS immune gets culled out.
I have to look this up, but I recall an island where food suddenly became quite scarce. Within a few generations, the size of horses on that island dropped dramatically. This is because a small horse needs less food than a large one. The larger horses were gradually culled out, leaving less of the large horses to have children and more of the smaller ones to have children.
I thought evolution proceeds more slowly when the disadvantaged are not killed off quickly. Hmmm...I guess in that case "disadvantaged" would not be the correct term here, but you get my meaning.
For example, because the human race takes care of its own, medical advances plus our need to take care of those who cannot take care of themselves, keep people alive who would otherwise be dead. This keeps their genes in the gene pool, and slows down evolution of humans. This would apply mostly in the case of genetically induced diseases in children.
Adult problems such as MS will be here for a long time simply because MS often does its harm after the victum is well into childbearing age. The gene is passed on to the next generation.
Of course, the need in us to keep all people alive is good for the human race as a whole.
My point is being that if "nothing is killing us off" then our evolution slows down.
Skeptic