The Absolute Minimum Rate of Evolution

My personal favorite form of evolution. No, this has absolutely nothing to do with this article.

A recent headline from Salon.com proclaimed the following, “In experiment scientists watched evolution happen.”

Well, no shit, Sherlock.

Scientists have been witnessing evolution in action for hundreds – if not thousands – of years. How do you think a flu virus suddenly stars infecting people instead of pigs? Evolution. How is it that there are so many different breeds of dogs with such distinct qualities? Evolution. How did ancient farmers take the same plant and slowly produce different kinds of cabbages, including Brussels sprouts, broccoli and collard greens?

Evolution!

Salon.com really needs somebody equipped to handle scientific stories. How about we take a look at what a recent paper actually tells us about the world in which we live?

Yes, evolution happens all around us. And yes, scientists have seen it in action the world over, likely in hundreds of thousands of different experiments. However, that certainly does not mean that we have a great grasp of exactly how it all works and the mechanisms that drive the slow accumulation of changes. For example, random mutations occur all the time to the genome of living organisms. If that random mutation gives that organism a competitive edge, it might flourish and eventually catch on throughout the species.

But it might not do anything.

There’s a greater chance that the mutation won’t do a damn thing. It won’t give any sort of edge, and it also won’t kill the creature wielding it. So how often do these sorts of mutations occur, and how can we separate the ones that spread through a population but do nothing from those that give competitive advantages and drive evolutionary change?

That, my friends, is the question that Indiana University’s Patricia Foster, professor of biology, set out to answer in her paper recently published in the Proceedings of the National Academy of Sciences.

To do this, Foster took Escherichia coli – a simple, single-celled organism without a separate cellular nucleus that scientists often use for studies – and bred them in complete isolation. Not only were they isolated, they were kept in an environment completely devoid of selective pressures – no changes in temperatures, no new predators, no change in nutrients, no change in moisture levels, no nothing.

Then she waited.

Specifically, Foster waited for 200,000 generations to pass. In humans, this would take at least three million years. But single-celled E. coli did it in just two years.

Throughout the process, Foster looked to see what random mutations occurred and how many spread throughout the population. As it turns out, the number and rate at which they occurred turned out to be about three times lower than expected. Understanding the rate at which this happens devoid of any natural selection pressures gives a baseline for which scientists can better understand evolution. If researchers want to know whether specific patterns of evolutionary change are driven by selection or not, knowledge of the expected pattern without any selective pressures is a necessity.

“By establishing baseline parameters for the molecular nature of spontaneous mutational change unbiased by selection, we can begin to achieve a deeper understanding of the factors that determine mutation rates, the mutational spectra, genomic base composition, how these may differ among organisms and how they may be shaped by environmental conditions,” Foster said. “Since mutations are the source of variation upon which natural selection acts, understanding the rate at which mutations occur and the molecular nature of spontaneous mutational changes leads us to a fuller understanding of evolution.”

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About bigkingken

A science writer dedicated to proving that the Big Ten - or the Committee on Institutional Cooperation, if you will - is more than athletics.
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