auntblabby wrote:
how does one know that we are constantly evolving? might we have stopped evolving but nobody noticed? might we actually be DE-volving with nobody the wiser?
Actually, until recently it was assumed that we were NOT still evolving.
Humans reached their present form 100 thousand years ago in southern Africa. We moved out of Africa, and drove the other human variants (Neanderthals, Denisovians) to extinction, and populated the globe. Our competition disappeared, but we didnt change.
Out culture, and technology changed rapidly, and diversified alot, and with ever increasing speed during those 100k years. But scientists assumed that we as animals had not changed at all.
And you even heard the canard that "mankind is now free of evolution" because we had supposedly shielded ourselves from natural selection.
But with the recent genome project they are finding evidence of genes becoming more frequent, or less frequent, even in the last few thousand years of historic time. The very factors like agriculture and civilization that supposedly shield us from natural selection seem to have exerted selective pressures of their own.
But organisms dont necessarily "evolve constantly". The norm seems to be "punctuated equilibrium":a brief period of fast change followed by a long period when the organism stays the same because it has become adapted to its environment.