#139 – The Long-Term Evolution Experiment – not “just breaking genes”

Two very different interpretations of the same set of data: one from Creationists and ID proponents, and the other from the scientists actually doing the work. Here, we talk to one of the latter.

A frequent talking point for creationists and Intelligent Design proponents in their anti-evolution rhetoric is a ground-breaking scientific project referred to as “the Long-Term Evolution Experiment.” Almost forty years ago, Dr. Richard Lenski began studying bacteria competing for limited energy resources (sugars) — generation after generation — looking for any genetic changes which gave any kind of advantage in that competition. His group have recently reached 76,000 generations, and documented many dozens of genetic mutations: rearrangements of regulatory pathways, elimination of genes which were no longer needed, introduction of new metabolic functions, shuffling of genetic information. In the process, there has been an incredible increase in fitness. This is much like someone deciding to train for a marathon — losing layers of fat, toning up muscles, revising their diet, replacing their normal wardrobe with ultra-light clothes and expensive runners, shaving seconds off of their run-time, increasing their stamina — and in the process, becoming a lean, mean running machine.

Nonetheless, creationists and ID proponents persist in diminishing the LTEE findings to just “breaking genes” and losing information.

After a brief introduction to the LTEE and the primary variables that they were monitoring (oxygen; fuel sources), we then talked to Dr. Zachary Blount, a member of the LTEE team who is continuing and broadening that research program, building on the findings and strategies of the LTEE. Points that we discussed included:

• the history of the LTEE: its founder, leaders, goals, and basic methodology
• twelve different “test tubes” of populations were kept separate, in order to see how the ancestral populations might try different evolutionary strategies
• they’ve now reached 76,000 generations; every 500 generations, they’ve frozen samples of the bugs so they can do follow-up experiments and/or recover from technical mistakes without having to start all over at the beginning …. they refer to this collection of samples as their “frozen fossil record”
• aerobic versus anaerobic metabolism (meaning with versus without oxygen) of glucose and another fuel source called citrate
• why did the experimenters add citrate to the medium in the first place?
• years later, the cells suddenly acquired a new ability to grow on the citrate in the presence of oxygen, something that their original bacterial ancestors were unable to do
• exactly how/why does metabolism of citrate change in the presence/absence of oxygen
• what were the “stressors” being imposed on the cells … answer: no “stress” or “stressor,” but rather simple competition for limited resources (fuel sources)
• what were the original goals of the LTEE project?
• the “randomness” of genetic variation
• mutations are not just simply individual “point-changes” in the base sequence of the DNA base, or individual amino-acids in the whole protein sequence; they can also include movements/insertions/deletions of whole segments of the DNA (thousands of bases at a time), duplication of large segments, and other forms of gene rearrangements
• the 12 separate populations of the ancestral bugs mutated in different directions and in somewhat different ways, but often landed on the same gene targets (although changing those genes in different ways)
• the mutated cells are much larger than the original ancestor (the researchers had expected a progressive reduction in size)
• the LTEE team found 57 different genetic changes …. and these were NOT simply just “breaking genes” or losing information, as creationists and ID proponents will so often say
• Dr. Blount then got into a very detailed and technical description of the whole citrate story, which is the one detail that creationists and ID proponents will particularly dwell upon, but we’re saving that part of the conversation for next week

Scott and Luke then reflected a bit on what Zachary told us so far, and how that relates to the on-going discussion going on between creationists and anti-evolutionists:

• how it’s okay to be skeptical about scientific claims … to ask questions, and put the claims to the test … this is part of the Scientific Method and something that scientists do all the time; however, once those follow-up questions and tests have been answered and the claim still stands, a good and unbiased scientist accepts the claim and moves on. But creationists and ID proponents keep circling around the same inaccurate counterarguments
• the LTEE’s finding that 12 different populations set out on 12 different evolutionary journeys and yet often arrived at similar endpoints sounds an awful lot like life’s common ancestor spreading out to several different geographically isolated parts of the globe, exploring different evolutionary pathways and often coming up with very similar and yet fundamentally different answers (comparisons between mammals and marsupials were the specific example here)
• once again, the frustrating tendency of creationists and ID proponents to focus on just “breaking genes” and degradation of information; cells have a genetic toolkit which enables them to shuffle parts of genes or whole sections of DNA around; perhaps the best and most complicated example of this genetic shuffling is our immune system
• some might think that an evolutionary advantage of “only a couple percent” is too small to realistically provide a driving force on evolution; however, say that to an athlete who’s just trying to shave a few seconds off of an event that lasts minutes or hours … or to an investor who’s comparing stocks that make either 4% or 6% gains, or the manager’s expense fees being raised to 3% from 2.5%
• Luke’s intense frustration with the leaders and scholars of creationist and Intelligent Design worldviews, who are educated and smart enough to understand the science here, but who persist in misrepresenting and distorting that science (possibly intentionally so!?)

As always, tell us your thoughts on this topic …

Find more information about our guest, Dr. Zachary Blount at his university profile page and his own lab’s web-site. Learn more about the LTEE itself, including descriptions of the team members and lists of their publications, at their webpage. You can also watch a video in which Dr. Blount regales Dr. Richard Lenski on the latter’s 60th birthday, and recounts the whole history of the LTEE.

If you enjoyed this episode, you may also like the mini-series of episodes we did focusing on Intelligent Design and its misrepresentation of science.

Episode image by WikiImages from Pixabay.

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