Friday, 21 December, 2001

Are We Still Evolving?

In its simplest form, evolution theory states that environmental factors 'select' stronger organisms by killing off the weak before they can reproduce.  The result is that the strong survive to procreate, and random beneficial mutations advance the species.  There can be an end, though.  Sharks, for example, are so perfectly adapted to their environment that they haven't changed in hundreds of millions of years.  Some organisms adapt too well.  The stromatolites of prehistory, for example, were by some accounts so successful that they poisoned themselves with their own waste (oxygen).

What happens, though, when a species gains control over its environment, or adapts to the point where environment exerts no selective evolutionary pressures?  Sharks are perfectly adapted to the ocean, but environmental factors (predators, etc.) still play a part in killing off the weak before they can reproduce.  The environment exerts no such pressures on humans--especially those living in industrialized countries.  We have reduced infant mortality to less than 1 percent (down from over 10% 100 years ago).  Childhood mortality, too, has been reduced.  The chance for a US-born person to live long enough to reproduce is easily 90%.  Environment just doesn't exert any selective pressures. 

This is perhaps not a good thing.  Evolution strengthens a species by removing undesirable traits from the gene pool.  We've done just the opposite.  By minimizing the effects of undesirable traits--making it possible for 'weaker' people to live and reproduce--we allow those traits to spread.  We have adapted too well and are in essence poisoning ourselves with bad genes.  Maybe.  I'm certainly not suggesting that we prevent people with cystic fibrosis from reproducing.

I've been chewing on this one for a couple of days and don't quite know what to think.  I just come up with more questions.  For example, is is possible that industrial nations' mastery of environmental factors will result in an overall weaker people who can be conquered by less industrially advanced people from areas of the world where external evolutionary pressures still exist?  Could the difference in living conditions and available medical care result in speciation (the formation of a new species)?  It fairly boggles the mind, the possibilities.