Originally posted by 25cents
if we evolve at all (there's really no need - we have no natural predators outside of viruses)...
There's no 'if' about it. We are certainly evolving and shall continue to do so until our species becomes extinct or evolves into something else
altogether. Evolution is a permanent fact of life for all species. Human beings are not exempt.
Evolution is the result of varying environmental effects on different members of a given species. As a result of these effects some members thrive
and reproduce, while others are short-lived or sickly and fail to reproduce. The difference is based on how conducive an individual's physical or
behavioural characteristics are to survival in that particular environment. This is called natural selection.
Over time, members of the species which have characteristics well suited to survival in a particular environment will become dominant in that
environment. Eventually, most or all members of the species will come to share those characteristics or traits. In the same way, traits not well
suited to survival in that environment will wither away. This is what we call evolution.
The environment in which human beings live nowadays is largely created by human beings; and because of the complex and technologically advanced
societies we have created, even people with handicaps so severe they would not last a day in the wild can still live out their normal span and -- in
theory, at least -- reproduce. These two facts have made a great many people believe, as you do, that evolution has come to a halt.
They could not be more wrong.
Consider the following facts:
1. The environment in which we live is largely man-made, but it still suits some people better than others, so some individuals will thrive in it
while others struggle (this is not hard to see; just look about you). The ones who thrive will naturally be in a better position to contribute to the
gene pool than those who struggle.
2. There are in fact any number of different largely man-made environments. Ivy League Bostonians and Afghan refugees experience completely different
environmental influences. This ensures that different traits are selected for in different parts of the world. This increases the genetic variation on
which evolutions depends.
Now combine those facts with a third:
3. Survival is only half the story. For an individual to make its mark on the genome, it must reproduce -- which means having viable grandchildren.
Not everybody achieves this. People with inherited physical or mental handicaps rarely do, for a start -- in fact, many are warned by their physicians
not to have children. But it's not just the Huntingdon's choriacs and Down's-syndrome sufferers who fail to reproduce. What about all the men and
women who, because they're ugly or stupid or smelly or bad-tempered or cripplingly shy or whatever, simply cannot find a mate? What about the
crack-dealing kid who gets a cap busted in his butt before he gets his first girl knocked up? What about his sister, who aborts her child because she
cannot afford to bring it up? What about the cannon-fodder -- young, low-status males with low IQs and minimal life skills who die in droves in war
after war, while their stronger, smarter, better-looking officers survive? None of these people gets to have grandchildren. Their genes are flushed
out of the pool.
I think these points should suffice to show that differential selective pressure (the force that drives evolution) has not been removed from the human
equation -- and therefore, neither has evolution.
Now a word about predators and parasites. You're right to say we have no natural predators. But we do indeed have parasites, which are a much more
potent threat. Did you know that most evolutionary biologists nowadays believe that sexual (as opposed to asexual) reproduction originally evolved as
a defence against parasites? Look it up; it's called the Red Queen hypothesis. Parasites are still with us, and will always be, and as long as they
are with us, we will continue to evolve. We'll have to, because they are evolving too.
So will we evolve into skinny, floppy, alien-like creatures like the one shown in the Sky report? Or will our race split in two, as the BBC piece
suggests? Frankly, I haven't the foggiest idea. But it seems to me that the two-species scenario, horrible as it sounds, may actually come to be
realized. Looking at some of the people I see around me, I often wonder if it hasn't happened already...
[edit on 18-10-2006 by Astyanax]