The Future of Human Evolution
The fossil records tell us that modern humans evolved from ape-like predecessors. While we do not know the full story of that process (and probably never will), recent advances the analysis of mitochondrial DNA show that all humans alive today trace their ancestry back to a single female who lived in Africa some 190,000 years agoa true biological Eve. Which brings us to the current topic: where will human evolution go from here?
First, though, let's be clear about what biological evolution is. There are many types of evolution associated with human beings. Our social systems have evolved from simple hunter-gatherer societies to the complex industrial cultures of today. Technology, once limited to stone and wood tools, now reaches into space and into the innermost recesses of the human genome. Biological evolution is strictly defined: there must be a change in the genetic makeup of a species. If that DNA "blueprint" remains unchanged, biological evolution has not occurred, no matter what other changes may take place. For example, we know people today are taller, on average, than in centuries past. However, this change is known to be due to better nutrition (and thus a consequence of our evolving social structure and technology), and not to genetic change.
We can't know the direction the future evolution of human beings will take. We can be sure it will happen, to be sure. By definition that depends on changes in the human genomeand all it takes to introduce a change is something as minor as a stray bit of radiation altering the makeup of a single gene. So, while this is inevitable, it is an essentially random process. As an asidethat is all science can tell us; many people (including myself) see a purposive pattern in the development of lifeevidence of a Designer at work. But that is a philosophical position. Contrary to some, there is simply no way to demonstrate that belief using the tools science is limited to.
We can, however, make some educated guesses as to what sorts of changes might become widespread and permanent. That is because, once a change has occurred the process known as natural selection kicks in. Natural selection isn't mysteriousthough it is often misunderstood. The concept is quite straightforward, though. On average, those members of a species that are best adapted (fitted) to their environment will survive and reproduce. So, if a mutation (change in the DNA) results in n individual better adapted to the environment it lives in than other members of the species, it will be more likely to survive and reproduce and so pass on the change.
So we can make a good estimate of what sorts of changes will survive, if they occur, by looking at the environment humans are likely to live in the future. And this is where the discussion gets really interesting, because humans, unlike any other species, have a growing ability to shape their environment to suit themselves. One consequence of this is that it's hard to define our environment precisely, because we keep changing it! However, we can discern some general patterns. One example is that a genetic propensity for overly aggressive behavior is contra-survival; other humans are apt to lock such individuals up. That may not kill them, but it certainly reduces their opportunity to reproduce and so pass on the genetic trait. Another factor in our technological environment is that strong analytical ability confers a major competitive advantage, which in turn tends to increase opportunities to reproduce. Such trends do not introduce major changes in the short-term. In the long term, though, any genetic change that made the individual better adapted in these respects will tend to survive and spread. On the other hand, some changes could be negative. For instancee, within a few generations, virtually all humans will have access to the means to control reproduction. In that case, we can individuals who have a genetic predisposition for responsible behavior and long-term planning to reproduce less than those who do not. These are traits that are positive for the survival and success of the individual, but they are not conducive to passing along such traits to future generations.
But there is another, truly mind-boggling aspect of humanity's ability to control its environment. That is that, through genetic science and technology, we are well on the way to being able to control our own genetic material. This is already beginning to happen with genetic screening to eliminate birth defects. Anyone who follows the news knows that actual manipulation of the human genome is n longer science fictionit is a technological revolution that is happening today.
So, in addition to natural evolution, we have the soon-to-be-real possibility of becoming a species capable of self-directed and purposive evolution! This raises a lot of questions, to put it mildly. First, there are ethical and moral questions about how this will affect individual rights, about what types of genetic manipulation are desirable and acceptable, and so on. But there are also other issues. In the process of using such technology on ourselves, would we eliminate genetic diversity, and so diminish the vast potential which is one of the things that give humans their amazing ability to adapt to new and changing situations? As it stands, the core question is, are we wise enough to take this power into our hands and use it in beneficial ways? And if the answer to that question is nowill we then be wise enough not to?