There is a rather popular conception that modern technology will result in the end or drastic curtailment of human evolution. With the advent of various medical improvements, those with conditions that would otherwise result in high morbidity prior to adolescence are now much more likely to survive to a reproductive age, and thereby will not be bred out of the gene pool. The result, it is argued, is that we will evolve into an increasingly weakened population, exhibiting a rapid increase in the severity and number of serious genetic conditions.
To counter this argument, we need to recall the unique nature of the human organism. Our primary survival skill is our rational faculty, and its ability to create increasingly advanced understanding of the Universe. This in turn allows the development of a steadily advancing technology. By “technology” is meant a set of tools allowing the modification of our physical world to better suit our needs and desires. While other animals can, in a very limited sense, alter their immediate environment to increase their likelihood of survival through the instinctive actions that they have evolved to exhibit, humans have a much more comprehensive ability to modify their survival environment. The beaver builds a dam to slow the flow of water, allowing the beaver to live in calmer waters. Man builds a hydroelectric power plant to provide electricity to thousands of homes, allowing a city to exist in a sub-freezing climate. Key to the human condition is the ability to pass acquired knowledge from generation to generation, allowing a continually accelerating advancement of knowledge, and commensurate with this rise in understanding, a continually rising level of technology.
Technology allows adaptation of the environment such that the average fitness of the individual in that environment is improved. Acting at a pace relative to which biological evolution is stationary, technology dramatically improves the likelihood of species survival, as it enables rapid adaptive change of the effective environment as the underlying environment changes. As an example, consider the advent of a lethal virus – for concreteness, say the “bird flu” did, as the media scaremongers are suggesting, turn into a human pandemic. When such events occurred in the pre-industrial period (e.g. the bubonic plague), huge segments of population were lost, and it can be envisioned that such an event could lead to rapid extinction, in a time period far too short to allow biological evolution to save the species. In the presence of modern technology, a vaccine can be expected to be developed in a matter of years, resulting in the preservation of a large, perhaps majority, segment of the human species. The effective environment for humans would thereby be modified to neutralize the effect of the bird flu virus.
This observation, however, does not nullify the process of evolution. Rather, it makes humans less dependent on it for survival, specifically with respect to events occuring much faster than evolutionary time scales.
To further illustrate the permanent presence of evolutionary processes, let us consider another (possibly fictional) concrete example. I will conjecture that in the 1800s, the occurence rate of dangerously high blood pressure, caused by genetic defects, in teenagers was much lower than at the present time. My hypothesis is based upon current medical practice, which includes early screening for high blood pressure, and available medication for its treatment. In the 1800s, with these practices not in place, morbidity rates for such a condition prior to reproductive age would have resulted in those genetic conditions being virtually eliminated from the gene pool. Today, the effective environment has changed to neutralize the effects of such a condition, and evolution has been “allowed” to produce an increasing population of individuals with adolescent high blood pressure.
Let us also suppose that at some date in the future, a societal collapse occurs, in which medical technology is no longer available for the treatment of this condition. The effective environment has now changed to put those with high blood pressure at much higher survival risk. In this event, the process of evolution will continue, and will rapidly remove the genetic variation that results in adolescent high blood pressure from the gene pool.