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Genetics

Genetics

The Theme of Evolution in Genetics

 Genetics are an essential element in the process of evolution. Many of the differences within and between species are the results of differences in the genes they carry – consequence of the evolutionary processes directly affecting genes: mutation, recombination, and selection. These processes affect all living organisms, including humans.

You might think that because of advances in fields such as medicine and technology, humans are not evolving any longer. Sure, its not the same situation as in early human history. Now that the human population is so large, most of us don't have to worry about getting preyed upon by wild animals or deadly diseases such as the bubonic plague ravaging whole towns, so it is possible that selection processes are somewhat relaxed (although it is worthwhile remembering that many of the people alive today are descended from the ones who survived the Spanish influenza outbreak of 1918). But as long as not everyone reproduces equally, it is likely that our gene pool is changing over time, and thus humans are technically evolving. While frequencies of different alleles might vary, such changes might not bring about particularly drastic changes in how we look or behave.

Could humans evolve into a superhuman species further down the road? It's rather unlikely. First of all, evolutionary processes have no directionality, and no progression towards a perceived "better" stage. Also, while there is plenty of genetic variation in humans, the large population size, coupled with the lack of evidence for strong selection of particular genotypes, suggests the human species is likely to stay about the same for the time being. Some studies, however, have found the signature of selection at particular loci in human studies. A fragment of chromosome 17 is commonly "flipped backwards" or inverted. The frequency of this inversion varies in different human populations. A study in Iceland, where the inversion is common, found that women carrying this chromosome have about 3.5% more children than women who do not (Stefansson, et al., 2005).

Some people, on the contrary, think we might actually be evolving towards a more "simple" human, rather than a superhuman. Just as evolution might give rise to new traits, it might also lead to a loss of traits. This is the case for cavefish – fish species or populations that inhabit caves and live in complete darkness. As they no longer have any real need for their eyes, they have simply lost them. So could humans potentially lose body parts because we don't need them? Even if technological advances might allow us to never leave the house or decrease the need to move around, it is rather unlikely that our body will change much. Otherwise, we would have probably already lost our appendix! Medicine so far has not found much of a use for this tiny pouch attached to the large intestine. On the contrary, its inflammation, known as appendicitis, is potentially lethal.

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