A common riff on the role of medical and technological advances is that they have somehow insulated humanity from evolution, or the ordinary course of evolution. This is an old canard - it goes back to the days before Darwin, and is a basic justification of eugenics programs (not just the Nazi horrors, but the more “positive” programs of encouraging the “better” kind of humans to interbreed).
It is thought that if medicine has interfered with the selective pressures we faced in the past, we will face degeneration, or be in control of our own evolution, or something, that will interfere with the “normal” course of evolution.
A [url = http://www.prospect-magazine.co.uk/ArticleView.asp?P_Article=12713]very nice article[/url] by Gabrielle Walker in Prospect Magazine, a UK publication of The Independent, discusses this in some detail.
You’d think that after we encountered AIDS, MRSA (methicillin resistant Staphylococcus aureus), bird flu, swine flu, West Nile virus, and the host of new and altered diseases that occur to us annually, we would not be so sure. But there is more.
It is often overlooked, in part because we think of what we humans do as being not a part of Nature, but of Art (the division is as old as Greek philosophy - Art is techne in Greek), that our own cultural activities both construct a niche to which we will eventually become adapted, if it persisted long enough, and also provide new selective pressures.
For a start, there has been extensive selection against diseases that only get a purchase in urban environments in Europe. Alleles that confer resistance to bubonic plague are widespread - I wonder why? Is there any reason to think that if a disease hit us today, our allele frequencies would not change so that resistant alleles became widespread, to the point where the disease was unable to spread further, vaccines and antibiotics notwithstanding?
Moreover, there is selection against (for example) lactose-intolerance that has been applied in a very brief period, in evolutionary terms. All through Asia now, this selection pressure is being applied. You don’t need to die for selection to apply, just do slightly worse at raising children and grandchildren and greatgrandchildren, etc., than those who do not have the gene you do.
Even if we can manage to modify genes directly, this does not stop evolution. One of two things can be true, or both. The genes we use will have been “tested” elsewhere before we use them, in other humans or other organisms, in which case this is still just a spread of gene alleles through selection - the fact that scientists rather than gametes spread the genes is largely irrelevant, as what happens after those genes are introduced will be independent of the scientists anyway - they are, evolutionarily speaking, a blip on the radar.
The other is that introducing these genes individually into a complex developmental program will have massive unlooked-for effects - the Pandora Principle. Biology is replete with things that are massively interlinked - if you, for example, reactivated the fossil gene for the production of Vitamin C, it may turn out that in certain environments this caused liver failure. These things are not easily predictable, if at all. And no matter how much is predictable, some outcomes will always not be.
So have we stopped evolving? We have not! Evolution is affected by behavior, this is the principle of the Baldwin Effect. It is time to lay this mistake to rest once and for all.
Emerging infectious diseases, which have shaped the course of humanity and caused incalculable suffering and death, will continue to confront society in unpredictable ways as long as humans and microbes co-exist, write authors from the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health in a review article published in the July 8 issue of the journal Nature.
The article itself discusses the evolution of pathogens and what we can do about it.