The end of evolution? (yes and no – mostly no)
I occasionally hear people talk about what humans will look and be like in the future. They hypothesize about what the next steps in human evolution will be. Will we continue to become more intelligent, taller, or more able to manipulate things with our hands etc., according to the previous trends in our evolution. However, let us really think about this. In our society today (and I'm mainly referring to the developed countries) we have amazing health care and it is fairly certain that our ability to fight and control disease externally through drugs and treatments will only get better. Soon even those with severe genetic diseases that would have eliminated them from the gene pool before adolescence a century ago will now be able to live relatively long lives. Essentially, we no longer have any reproduction of the fittest - everyone is about as able to produce offspring and pass on their genes as everyone else, as a broad generalization with some exceptions. Of course I realize that at a micro-level some evolution will continue to occur. It is not really correct to say that Darwinian evolution no longer applies to human populations. As I said there will still be some survival (and more importantly, reproduction) of the fittest, but only at a micro-level – mostly at the level of eliminating disease. The diseases that completely prevent reproduction (such as down syndrome) will always be weeded out of the gene pool because the down syndrome traits (an extra 21st chromosome) cannot be passed down to the next generation (or they are passed down at a much reduced rate). Also, certain genes may fluctuate in abundance throughout the population due to environmental and cultural factors. For instance the percentage of brown eyes will probably increase in the US as the Hispanic populations increase and disperse their traits through the gene pool (this is just a random possible example that may or may not happen). This process is more akin to genetic drift than to actual trait selection.
Evolutionarily speaking, no new or novel traits that appear will have any reproductive advantage, because everyone is already able to reproduce as much as the next guy, in general. Before long most countries will have mandatory family size limits to control the world's overpopulation. Many people can't see this occurring in the near future, but in a century or two we will have no choice. In the past, one of the main factors leading to evolution was a genetic change allowing individuals to reproduce more children or to reproduce more efficiently, consequently leading to a proliferation of those traits within the gene pool. Assuming only natural selection as the force of evolution, population control will eliminate this selection. No one will produce more offspring, thus no specific traits will be able to propagate faster than any others. Furthermore, since everyone is basically equal in reproduction, we will not "evolve" new and better genes that make us smarter or stronger (such genes would not be selected for and would not propagate through the population). In fact, it seems more likely that we will accumulate more defective genes that arise due to normal DNA replication errors and environmental mutagens and pollutants, and we will simply treat these problems with pharmaceuticals or therapy. Unless these mutations are so bad that they prevent reproduction, they will continue to be passed down.
Of course, you can probably see where this argument is going. This lack of evolution and accumulation of faulty genes will probably not happen. Not only has technology virtually eliminated any natural selection, with a few exceptions, it has created the new prospect of artificial selection. The human race WILL evolve, but it will be according to an actual plan, as opposed to the random forces of natural selection. Alternatively, a culture of breeding only with the most genetically fit might arise, a la “GATTACA,” however we see even today that it is the poorest of the poor and the most uneducated that actually has the highest birth rates (no offense intended to these populations). Honestly, if we want our lineage to continue and evolve (I hesitate to say race - race is too static of a term for a changing species), we have no choice but to actively evolve. Now don't misunderstand me and think that I'm saying we should go ahead now. Far from it! We are still in the infancy of understanding human genetics and development. We are still far from understanding exactly how the brain works and gives us self-consciousness, imagination, creativity, empathy, love, hate, and all the other nuances of human consciousness. However, that doesn't mean that we will not figure it all out eventually. We will, assuming we don't annihilate ourselves first. There are also many ethical problems with this that will have to be resolved within the population and I'm not sure how this is could work, under our current culture. However, we are already seeing the beginnings of this movement in the genetic screening of embryos for implantations. The number one thing that will have to happen is complete public education on the issues, the technologies, and the implications that go with them. Many people feel that there is something inherently wrong and sinful in "playing" God. I can see why some folks would feel that way, but I also believe that many those feelings stem from ignorance of the facts. Assuming we can overcome our fears and our ignorance, we may well be able to evolve consciously and designedly. No one is really in a position to say exactly what traits we will choose to develop - that prospect is still too far off. It certainly will not create a "perfect" human race as many people fear. That term really has no meaning. Imagine, just for fun, the human race actively developing traits that increase the sense of compassion and empathy, increasing our intelligence, giving a population of humans external gills and leathery skin to colonize the other three-quarters of the earth. Of course, these are far out ideas and have a ring of fantasy and science fiction in our ears. But these types of things are conceivably possible in the not-too-distant-future. We are learning more about how organisms develop and how the genes and environment direct this development every day.
Thus, technology hasn't really stripped us of our ability to evolve. It has simply made it so that relatively minor accidental mutations do not have the pressures to give any individuals a better chance of surviving and reproducing. Honestly, which sounds better and safer to you: waiting around for something to damage our DNA in just the right way to confer some sort of survival or reproductive advantage, or actively and carefully designing and developing these mutations and additions in order to further our long-term survival and potential?
Something one must keep in mind is that if any major catastrophe were to occur and cripple our civilization and society as we know it, the old method of natural selection would most likely resume. However, we may even be able to prevent this from occurring using our abilities of genetic manipulation. I can easily foresee us colonizing space, Mars, and, perhaps far in the future, other solar systems (assuming interstellar space travel or suspended animation are ever figured out or even possible). Regardless of how many of these ideas we as a species bring to fruition, you can be guaranteed that the human race is not truly in a state of evolutionary suspended animation, though it may appear so during our short technological adolescence. Remember the time spans involved in Darwinian evolution. If Earth history were compressed into a single year, humans would not have arrived until 2PM on December 31st.
We have not yet even been able to look at ourselves in the mirror long enough to determine if we are really evolving or not.