Q&A on NATURAL vs. ARTIFICIAL SELECTION

This post is dedicated to my present, future & former students in BIO 140 (Evolutionary Biology) in UPLB and has been posted on my fb page about a year ago or earlier.

A student asked me:

“Is the evolution of resistance to antibiotic drugs and pesticides artificial selection?” The student added that a senior biologist he/she talked with reasoned that: “because humans invented drugs and pesticides and released them to the environment and, therefore, are not natural, the development of resistance to them qualifies as part of artificial selection.”

My answer:

The main difference between natural and artificial selection is that, in natural selection, it is nature or the environment that “blindly” (as against consciously, because nature has no consciousness) selects from among choices or variants – products of genetic processes; whereas in artificial selection, humans “consciously” or deliberately chooses organisms (plants, animals, etc.) which possess desirable (or beneficial, to humans, of course) traits. In the latest edition of the book “Evolution” (Futuyma & Kirkpatrick, 2017), natural selection is defined as: “The differential survival and/or reproduction of classes of entities” (i.e., alleles, genotypes (or their subsets), populations, species) “that differ in one or more characteristics.” The difference in survival and/or reproduction is “not due to chance” and has “the potential consequence of altering the proportions of the different entities” (~genotypic/gene frequencies). Such differences are usually inherited. On the other hand, artificial selection is defined as: “Selection by humans of a deliberately chosen trait or combination of traits in a (usualy captive) population; differing from natural selection in that the criterion for survival and reproduction is the trait chosen, rather than fitness as determined by the entire genotype.” (Futuyma & Kirkpatrick, ibid).

In the development of resistance to antibiotics among pathogenic microorganisms, or to pesticides among insect pests, plant pathogens and weeds, humans do not deliberately or “consciously” choose a trait or combination of traits, and the populations of organisms that develop resistance are definitely not captive. The same is true for the inevitable development of resistance to pest-protected GM crops, the changes in the behavior and other traits of native species as challenged by alien invasive species, and the various adaptations of organisms to all forms of pollution (that are all products of human activities). In all these cases, it is still nature that selects and one may surmise, a way through which “Nature fights back.” Possible exceptions to natural selection in a human-made environment maybe resistance to antibiotics or pesticides that had been induced in the laboratory for experimental purposes (but for which biosafety regulations have set safeguards and requires destruction of all experimental material after the conduct of studies). On the other hand, the deliberate moves toward insect resistance management or IRM with the objective of delaying the development of resistance to Bt crops may be tantamount to humans assisting nature in order to prolong the benefits to farmers that this technology provides.

No. The evolution of resistance to antibiotic drugs and pesticides does not constitute artificial selection. It is still natural selection.

As contestants in pageants say: “Thank you for that wonderful question . . .”  🙂🙂🙂

 

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