Are humans really not under natural selection?

I constantly hear the phrase “We (humans) are not under selective pressure”. This at first seems logical. We are not anymore in the open being eaten by lions, we might not die because of cold, we might be protected by walls from the elements or any other danger that other species face, which may impose a high selective pressure. We like to think of ourselves as the ones doing the selection mainly because we now have the understanding of heredity and we are starting to tap into the secrets of nature that no other species have right now, at least at a molecular level. Also, it is because of our actions and growth we are in fact imposing an extreme pressure on other species, although not on a directed and ordered way.

However, in our case that force is not something that most people accept or can see. Instead, part of this selective force has been longer than us on earth. As you might have guessed if you are reading this, this selective force that acts on the species that can go into space,  that can potentially direct the destiny of all other species, are infectious diseases. Infectious diseases come from organisms that we cannot see, and that we cannot yet fully control. An example of a selective sweep on humans made by infectious agents is the black plague in the 1800’s. An estimated 30-60% of Europe’s population was wiped out. Granted that the population then was smaller than now, however this is more evidence since the smaller the population the higher the effect of the gene pool that will be available for the next generation. We can think then that the surviving population had the set of genes that allowed successive generations to flourish. In our species selection doesn’t affect only the gene pool, but the mental power and potential that each human harbors.

This might be true for pre-antibiotic generations and two or more generations forward. I myself and most of the people I know are in this category, however this might not be true for people who will be born starting in the next 20 years. This is not to say that we must select only people with “good” genes. I develop this argument to show how important research in infectious diseases. We felt great about penicillin, we even thought that we had conquered microbes. And we were so drunk in our success, that antibiotics were being given almost in the water. However, our generation and the generations to come will have to see the effects of the increasing resistance that microbes are obtaining. We will have to be witnesses to this invisible selective force that will sweep again on our kind unless we do something about it. And we will do something about it.

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2 Responses to Are humans really not under natural selection?

  1. Michael says:

    To suggest humans are not under natural selection seems bizarre and very short sighted. Who suggests otherwise?

    I agree with your post, but natural selection continues beyond just infection. Some pressures may be relaxed or changed but human and natural history spans much further than a few generations. We might not be able to predict what these will be but they could be caused by competion for resources or even natural environmental phenomena beyond our control, for example.

    Also: gene pool = mental power and potential. Without the genes the others cannot exist, even if mental power and potential are much more than just genetic.

  2. jraygozak says:

    I agree, it is true that there are other mechanisms by which the gene pool is modified, such as people not wanting to have kids, and so on. I just wanted to make a point that we should not feel free from what other species are experiencing. And that our predators nowadays are not big lions but small beings. It is true that at the species level genes do matter for mental power, however within humans (unless there is a severe genetic or molecular handicap) the capability to achieve what any other human can achieve is not outside any genotype’s capability. Some of us have to work harder but that’s different.

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