It has been known for quite some time that genetically modified bacteria, which have lost their ability to produce certain amino acids and retrieve these nutrients from their environment grow better than bacteria, which produce all nutrients themselves. This led researchers to inquire whether natural selection would favor the loss of abilities, thus making bacteria more dependent on their environment.
Of course it did or they wouldn’t be writing about it but this has nothing to do with “natural” selection. The researchers had produced the bacteria themselves.
A similar loss of traits has been observed not only in bacteria, but also in other groups of organisms. Many animals, including humans, are not able to produce vitamins themselves — they depend on their food or on vitamin-producing bacteria in their gut. Many pathogens need substances produced by their hosts in order to proliferate. Until now, it has been unclear why organisms would give up their autonomy and become dependent on others. This study now shows that the loss of capabilities may be evolutionarily advantageous and thus drive adaptation.
This trend is called devolution. It subtracts features rather than adding them. An obvious problem is that the dependent organism is apt to die when the provider of the needed substance is not available.
“There were further results we had not expected at all: When we studied the genome of the dependent bacteria, we found mutation not only in genes that are directly involved in the biosynthesis of amino acids, but also in genes, which regulate proteins that are involved in activating or inhibiting metabolic processes,” Christian Kost reports. This means that the adaptation of a bacterial population can be achieved in different ways. In the current study, this adaptation occurred only in one direction: One group of bacteria became dependent on the other. However, the researchers are convinced that a longer testing period would have eventually resulted in mutual and more complex dependencies. Therefore, they plan to extend the duration of their experiment. Natural selection depends not only on the genetic endowment of a population, but also on its size. Depending on their lifestyle, natural bacterial populations differ considerably in size. Hence, the scientists want to find out how the size of bacterial populations affects the development of dependencies and the changes in the bacterial genomes. Paper. (public access) – Glen D’Souza, Christian Kost. Experimental Evolution of Metabolic Dependency in Bacteria. PLOS Genetics, 2016; 12 (11): e1006364 DOI: 10.1371/journal.pgen.1006364 More.
Is there anything that can’t be an “evolutionary advantage”? That’s the trouble with the Darwinian model of evolution. Explaining everything means explaining nothing. Devolution happens but it is an “advantage” that leaves the life form hostage to the fate of others.
See also: [news] Royal Society evolution meeting cautioned against cheers and boos Klinghoffer describes the meeting as tense. How about “tense but timid”? We’ve all been through that at some time in our lives. No one wants to be the one to say: Yes, but it doesn’t make any sense to do things the way we are doing them any more. Our ship’s foundering.
Devolution: Getting back to the simple life
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