The End of Human Evolution?--Not!

by Tina Blue
July 30, 2002

          According to some biologists, human evolution has come to an end, at least in the Western world, because "a Western lifestyle now protects humanity from the forces that used to shape Homo sapiens" (The Observer 3 Feb. 2002:1).  But such a conclusion rests on a pretty skewed notion of how evolution works.

          Let's leave aside the obvious fact that not all of humanity enjoys the benefits of a Western lifestyle, and those that do not are therefore not protected from evolutionary pressures, even if the Western lifestyle does defang the mechanisms for evolution, if only for the present.

          Those, like Professor Steve Jones of University College London, who propound this theory apparently forget that evolutionary forces operate over very long periods of time.  The Western lifestyle that makes it possible for "virtually everybody's genes to make it into the next generation, not only those who are best adapted to their environments" (The Observer 1) is a fairly recent development.  Even a century and a half ago in Victorian England, Jones acknowledges, "half of all children died before adolescence." Now we immunize children against formerly deadly diseases, and diseases and infections we can't vaccinate against are treated with powerful antibiotics.  Improved medical care means also that people survive accidents that once would have been fatal, and many kinds of accidents have become less common because of improved safety practices at home, in the workplace, and in public spaces.

          So pretty much everyone gets to live, even if they have genetic predispositions that a few generations ago might have carried them off before they got to reproduce, and nowadays pretty much everyone has a chance to reproduce.

          Voila!  The end of evolution.

          But wait a minute.   A period of one hundred fifty, two hundred, even several hundred years is really just a blink of an eye in evolutionary terms.  Whole populations can easily remain stable over even longer periods if their environment doesn't change too much.  But how long is the cozy environment of the advanced industrialized West going to remain unchanged?  Our economy is notoriously precarious, built as it is on the cancerous consumption of nonrenewable resources.  And if the economy really tanks, then people might show themselves to be decidedly less generous and accommodating to those whose physical or mental traits render them unproductive and an obvious drain on resources.  Throughout human existence, human infants and children considered defective have been killed or left to die.  It probably wouldn't take that much to return supposedly civilized human beings to a state where such things could happen again.

          If civilization as we know it comes crashing down about our ears, as well it might in the next century or so, then all of the aspects of civilization that seem for the moment to have halted human evolution will also come to an end.  If, as is likely under such circumstances, quick, easy, safe travel is no longer possible, then populations will become isolated and significant divergence, even speciation, will probably occur over time.

          Once our physical and social infrastructure crumbles, then we will no longer be able to immunize most children, so those with natural resistance against diseases will have an evolutionary advantage, especially if antibiotics are no longer widely available or if they lose their efficacy, which many of them are already doing at an alarming rate.

          If we revert to a wild, uncivilized state--and there are many plausible scenarios that lead to such a conclusion--then females who mate with larger, stronger males will have an evolutionary advantage, because their mates will be better able to provide for and protect them and their offspring, as well as being better able to defeat sexual rivals in physical combat.  Under such conditions, evolution favors larger, stronger males.  That is no advantage when laws protect smaller males from assault and any pipsqueak can get a gun. But given enough time, we might well end up in something of a "state of nature" unmediated by civil law, and eventually even our extraordinary arsenals will be depleted, so that the big guys will regain their natural advantage over the little guys.

          Such sexual competition in our evolutionary past is the reason why men are in general larger and stronger than women.  If it had gone on much longer without the impact of innovative weapons technology during human prehistory, then we would have become more like gorillas in the degree of our species' sexual dichotomy.  But there's still plenty of time, and we could still evolve in that direction once the accoutrements of civilization have fallen away.

          There are so many ways that our social, technological, and natural environment can change, even in the next few decades, much less over centuries and millennia.  In fact, if there is one thing we can be certain of, it is that it will change. 

          Another thing we can be certain of is that we do not have the resource reserves to maintain our current level of consumption.  At some point the luxury we in the West have enjoyed for so long will not be available, just as it was not available to our ancestors.  Our descendants are likely to face their world without the mediation of advanced medicine, modern technology, or even a hospitable environment, since we are doing our benighted best to throw earth's climate regulation systems out of whack.

          And once the mediating and mitigating effects of modern technological civilization are removed, the effects of evolutionary change in humans will become evident. Of course, you and I won't be around to see it.  Evolution seldom works fast enough for us to catch it in the act, unless--as with dogbreeding--we deliberately intervene to speed it up.  Or--as with the development of antibiotic-resistant bacteria--we inadvertently do so.

          And probably we will do a certain amount of deliberate intervening before the new Dark Ages begin, so that the results of our interventions will introduce even more variables into the evolutionary process.

          No, human evolution has not come to an end.  There will always be mutations, and some of those mutations are bound to be adaptive in the environments of the future, so that they will be selected for. The engines that propel evolution--mutation, adaptation, natural selection--are always at work, even on our own species.  It just takes a while sometimes for their effects to become apparent.

          But don't forget, evolution has all the time in the world.

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