I caught some of an interview on RN yesterday morning with an erudite bioscience type, who made some very nice distinctions about what does and does not constitute evolution, including the provocative statement that in the West, humans have virtually stopped evolving as the term is normally understood (there are caveats and clarifications).
He mentioned something that he tells his new uni students on the first day of class (paraphrase):
Look to your left. Now look to your right. 2 out the 3 of you will end up dying due to inherited genetic factors. (Students look sombre) But cheer up – if this was Shakespearean times, 9 out of 10 of you would be dead already!
His point is that before the improved hygiene and medical science of the Victorian era onwards (the age of great public engineering projects including crucial complex city sewerage construction), most people born died before they reached the age of reproduction. That’s natural selection.
He continued: nowadays, in those parts of the West that are peaceful and affluent, most people live well past the prime biological age for reproduction. The constraints on our reproduction are driven by factors other than sheer survival instinct and appalling infant mortality: essentially, humans are now an artificially selected species, which to some people means that we have stopped evolving.
Of course, it’s not as simple as that – evolution in its purest sense merely means “change”, so any changes in a population’s characteristics that derive from artificial selection are still evolutionary changes, they’re just not naturally selected evolutionary changes.
I had to get out of the car and go to a meeting (and it’s weesmallhours o’clock right now, so I’m not going to search for a transcript on RN), so I don’t know whether the program went on to discuss the parts of the world where there is still appalling infant mortality and violence/war that results in many people dying before they get the chance to reproduce: by the terms he was using, those populations would still be being naturally selected so that poor populations in war-torn regions are evolving while those populations where people can read this blog are not.
Now, I’m sure that he is the source of many a quibble from the evolutionary biologist fraternity, but it’s certainly an interesting way of framing exactly what does or does not constitute evolution and the differences between natural and artificial selection of populations.