Prefacing disclaimer: obviously, I’m not a geneticist, biologist, or any other expert qualified to speak authoritatively about evolution.
My attention was caught by the title of a recent lecture from University College of London Professor of Genetics Steve Jones: Human Evolution is Over (here and here), which I first found via Digg. I was disappointed by the lecture, or at any rate by summaries of the lecture in the news, since I can’t find the text of the actual lecture; but it caught my attention because I’d actually been thinking for a while about human evolution, and the rather unique spot we find ourselves in now.
According to the articles, the lecture essentially makes the argument that human evolution is at a near-standstill, because natural selection pressures are low, and because older fathers aren’t as commonplace as they once were (older fathers’ sperm-manufacturing cells being the product of more cell divisions, giving greater opportunity for genetic mutation).
I’m baffled by the argument that the pressures of natural selection from extremes of heat and cold, or famine, are nullified by modern heating and air conditioning, and food plentifulness. Current heating and AC technologies are not so perfect as to effectively nullify the selective effects of environmental extremes (and anyway not everyone in the world has access to these technologies), and food is far from universally “plentiful”. Even ignoring those, there is plenty of opportunity for competition and natural selection, through population growth pressures present in many areas, and epidemics of disease in many corners of the world.
Meanwhile, the argument that younger fathers have eradicated the opportunity for genetic mutation rather ignores how we got where we are, and the fact that a 35-year-old father has more years than the entire lifespan of the bulk of our ancestors; in many cases by a huge margin. Though it is true that our cells’ mechanisms for guarding against infidelity in genetic copying have become more advanced now.
And yet, despite these flaws in the arguments (at least as represented in news sources), I wonder whether there’s still some (limited) truth to the conclusion?
We’re in a weird place in evolutionary history—really, completely-uncharted territory. We are the first creatures to have become aware of the underlying mechanisms of our evolution, the first to be in a position to actually manipulate genetic material directly—both our own material and that of other plants and creatures. I wonder whether natural selection will soon be made irrelevant through our own increased powers of artificial auto-selection.
Even aside from our fledgeling ability to govern our own genetics, our modern medical technology is already starting to turn the tide of natural selection through artificial compensations. I suspect penecillin, which might at first glance seem to be a good example, is actually a poor one: it’s not an example of our ability to conquer natural selection, but only our latest short-term triumph against it in our perpetual battle with disease. After all, it’s only been around for eighty years, and there are already plenty of examples of diseases that have evolved immunities to it. Before too long, we’ll have to invent it all over again. And again.
On the other hand, in a world where prosthetic legs are available, the effects of natural selection on a “clumsiness” gene that makes people more apt to lose a leg is diminished (though not if the “clumsiness” also produces greater risk of direct loss of life 🙂 ). Genes that would otherwise have become extinct due to unpleasant aesthetic effects (lessening sexual desirability) are given a reprieve by cosmetics and (in more extreme cases) cosmetic surgery.
We already screen fetuses for common genetic diseases; how long before we start ensuring their absence through direct manipulation, a lá Gattaca? I don’t really think we’ll ever find ourselves in a world where, as in the movie, genetic discrimination ensures that unmanipulated individuals cannot obtain white-collar jobs or decent girlfriends; but I do think it’s likely that at some point, it will become somewhat routine for parents to screen their children’s genes, or the genes that they contribute toward child-bearing.
And that, in itself, disturbs me. Not because it’s unethical or somehow violates the sanctity of natural human reproduction, but because, from an evolutionary standpoint, it’s probably a really bad idea. The genes that we would tend to filter out because they’re responsible for sickle-cell anaemia or cystic fibrosis, when we are unlucky enough to obtain that gene from both of our parents, provide protection against malaria and cholera when we obtain just one copy of the gene. In our zeal to weed out genes that confer confirmed negative effects, we are very likely to strain out genes whose undiscovered positive effects actually outweigh their known negative effects in some environments.
The problem is that artificial selection is guesswork: we presume to be able to deduce when our manipulations are for the best, but we rely on faulty human reason and incomplete understanding to make these decisions. Natural selection, on the other hand, has complete understanding and flawless, unconscious reason, in that it always guarantees that the surviving genes (over sufficient spans of time) are those that confer the greatest advantages
Of course, natural selection’s perfect ability to decide which genes should be eliminated and which survive, comes at a price. For one thing, it’s awfully slow, and the knowledge that natural selection will provide us with an immunity to such-and-such a disease over the course of a number of generations is small consolation when we’re dying from it now. For another thing, it comes at the cold and calloused cost of human lives. Natural selection depends on death, in combination with reproduction and variation, to achieve its ends. There is no selection, natural or artificial, if some things aren’t dying while others survive.
Human sensibilities, meanwhile, demand that all human life is sacred, and not just those that nature would select. So of course we will continue to intervene on individuals’ behalfs—we must. To not do so would be unfeeling, uncaring, and more than a little reminiscent of Nazi eugenics.
And yet, interference comes with a price of its own. As we relieve the effects of natural selection on individuals through our efforts to use technology to cure humankind’s ills, we condemn ourselves to evolve dependencies on those same technologies. Preventing natural selection from filtering out weak genes through quicker death to the possessors or, alternatively, taking nature’s responsibilities on ourselves and doing a lesser job of filtering out weak genes before birth, ensures that weak genes will proliferate where they otherwise would not. This in turn forces us to continue to use our medical technologies perpetually, lest we suffer nature’s belated compensation for our weakened genetic resilience.
Meanwhile, natural selection will continue to have its way with those peoples for whom the wonders of modern technology are out of reach. After all, all these arguments from modern medical and genetics technology suffer the same flaws I noted for Jones’ arguments from central heating and plentiful food: they can’t completely eliminate natural selection, and (more importantly) not everyone has them. While the middle- and upper-classes of the affluent nations of the world develop a dependence on their savior technologies, those who can’t afford these miracles will continue to depend on nature to provide them with the protections they need, the hard way. But, interbreeding between the privileged and unprivileged will help reintroduce healthy genes to the “privileged” who otherwise might find themselves in an ever-escalating battle against their own degrading DNA, and beginning to dwindle in numbers in comparison to the healthier “unprivileged”.
Whether or not human evolution has effectively ceased (cough), our tools have certainly been evolving lately at a much higher rate than we ourselves have been. Perhaps the tools we have created will increasingly exert selective pressures of their own on human survival statistics, resulting in an accidental artificial selection. There are those that suggest that this has already played a large role in guiding our evolution to the current state; we start using a tool that benefits us, and suddenly the people best equipped to be using these tools have the best chances for survival.
In our current digital age, more and more professionals are finding themselves having to think about multiple tasks simultaneously (or as nearly so as we are currently capable), and of dealing with multiple channels of information. These are both things that we are currently fairly poor at handling, as a species; but perhaps evolution will produce people with true multitasking capabilities, handling multiple simultaneous conscious thoughts, or at least able to take better advantage of what multitasking capabilities the subconscious mind already posseses. Could the human brain eventually become “multicore”? 🙂
As our tools continue to evolve, I expect we’ll eventually do away with such impediments as keyboards, and be capable of communicating thoughts much closer to the speed at which we actually think them. In that event I imagine that rapid thought might become an evolutionarily favored trait. That might in turn result in an eventual (very eventual) reduction in the complexity of our vocal capabilities, as they fall out of necessity, much in the same way that we lost our (external) tails, or that whales lost their legs.
…I worry that, contrary to popular belief, human powers of reason may not be especially favored by evolution. A lot of people believe that humans are more intelligent because we are “more evolved”; but of course on reflection that’s simply not the case. We are not “more evolved” than chimpanzees, because we did not evolve from chimpanzees; chimpanzees and ourselves both evolved from some common ancestor, which means that we have had precisely as much time to evolve from that point as chimpanzees have had. We are both the result of generations of adaptations to become quite well-suited to our respective, different environments. Ours just so happened to favor greater intelligence. It doesn’t follow that we’re “more evolved”, just because the thing we’re most proud of happened to be favored (after all, it’s what we’re most proud of because it’s what natural selection favored).
And humans are not especially logical. We may be much more so than our evolutionary cousins, but we’re still not especially bright. Evolution appears to have favored quite a few mental aberrations over and above any favor given to logic and reason. Our brains are built to strongly prefer
- conclusions that align well with beliefs we already hold
- conclusions that facilitate a positive self-image
- conclusions that facilitate our desires
- conclusions that align with our emotional reactions to things
- conclusions that provide us with hope and a positive outlook, even when such an outlook is unrealistic
All of these, over conclusions that arise logically from the available facts. If the available facts are in conflict with any of these—especially the top couple—it may be a minor miracle when we actually manage to arrive at the truth. Add to these a propensity for finding patterns, that is so strong that we regularly find them where they don’t actually exist (number “patterns” in sequences of random numbers, faces of religious figures in food items, tree knots, and whatnot…), and tendencies for weighting some data far too greatly, and other data too lightly (“Counting the hits but not the misses”, leading to convinctions of prophetic truths, or miraculous answers to prayer, etc).
The way I see it, the human race has finally become just intelligent enough to begun to realize just how unintelligent we really are.
And many of these impediments to intelligence and reason appear to be the result of natural selection, indicating that these are flaws in human reason that tend to increase chances of survival, in which case there’s small hope to reach higher levels of reason until whatever selective pressures produced these flaws cease (or are overruled by still greater selective pressures, and perhaps that is already the case).