On Mon August 7 2006 5:24 pm, ashok wrote: > maybe i am wrong....but i was always under the impression that significant > natural evolution requires > small isolated communities / populations of the said organ
No. Evolution is changes in genes. "genes" can be as small as a single DNA code for one body protein, or they can be a large "functional combination" of DNA units that work together to produce some characteristic - like a bulbous nose with hairs sticking out (or an even more critical characteristic). Some gene changes make no difference. Some may make a difference later. Let me build a hypothetical scenario to show how humans may be evolving. I forget the actual statistic but a large number of pregnancies do not occur at all despite fertilisation, but the fertilised embryo just dies because of a fatal mutation/genetic defect and comes out as the next period. Less immediately fatal mutations last for a while and result in abortions later in pregnancy. Some mutations are born as kids with no head/no limbs. They die early and do not have children. Some mutations produce early severe diabetes or defective chambered hearts. Medical science keeps these people alive till they have children and any gene they carry is being propagated among humans. But let me hypothesise on mutations that may be useful to man that we do not know about. For example - environmental poisons can harm us - and the unborn fetus more so than adults. These fetuses would be aborted early. Now supposing there was random genetic mutation that allowed fetuses to survive higher levels of toxins. This fetus would survive and in the absence of any other indicator would grow up to be a normal human who would pass his genes on. Over the course of many generations this mutation, by allowing children to be born despite high levels of toxins would serve as a genetic advantage - with children carrying these genes more likely to survive than other "normal" genes that we carry. This would be an example of human evolution in progress. shiv
