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| Nosil Lab of Evolutionary Biology, University of Sheffield, UK |
Here's one of those nice little pieces of scientific research that so infuriates creationist loons and sends them into deep denialism or a frenzied casting around for a way to dismiss it because it doesn't support their sacred conclusions.
One of the interesting questions in evolution is, just how predictable is it? Could we rewind the clock say ten million years and get the same result we have today? Or is there so much randomness in the process that small random differences both in the environment and the evolving individual species would add up eventually to major differences? And this of course is assuming that the main or only component of evolutionary change is natural selection and all change is adaptive. But, if random genetic drift is as important as some people think, then evolution could not be predictable except perhaps in conditions of intense selection pressure.
To help understand this a little better, a group from the Nosil Lab for Evolutionary Biology, University of Sheffield, UK, examined the differences in the DNA of a widespread species of Californian stick insect, Timema cristinae. This species has evolved two ecotypes adapted to living on different hillside plants. One with a broad body which lives on broad-leaved plants and one with a long, thin body with a central stripe, adapted to narrow-leaved plants. Although the same species, these can be seen as a species in the process of diverging into two daughter species.
Abstract
Natural selection can drive the repeated evolution of reproductive isolation, but the genomic basis of parallel speciation remains poorly understood. We analyzed whole-genome divergence between replicate pairs of stick insect populations that are adapted to different host plants and undergoing parallel speciation. We found thousands of modest-sized genomic regions of accentuated divergence between populations, most of which are unique to individual population pairs. We also detected parallel genomic divergence across population pairs involving an excess of coding genes with specific molecular functions. Regions of parallel genomic divergence in nature exhibited exceptional allele frequency changes between hosts in a field transplant experiment. The results advance understanding of biological diversification by providing convergent observational and experimental evidence for selection’s role in driving repeatable genomic divergence.
Víctor Soria-Carrasco, Zachariah Gompert, et al;
Stick Insect Genomes Reveal Natural Selection’s Role in Parallel Speciation;
Science 16 May 2014: Vol. 344 no. 6185 pp. 738-742 DOI: 10.1126/science.1252136
I think it says that repeatability of evolution is very low.
As expected, they found many genetic differences between the two ecotypes, but they also found a wide difference between what appeared to be the the same ecotype collected from different hillsides. Only 17 percent of their DNA had changed in the same way. This indicates that a lot of the change is initially random and then selection works on that randomness to arrive at the same adaptive change, but by different routes and with different genes.Andrew Hendry, evolutionary biologist, McGill University, Montreal, Canada
They've actually been able to dig down into the genome and find out a little bit more about [parallel evolution]. [The work] is really starting to give us some mechanistic understanding of the molecular basis of evolution.
So the team then transferred members of each ecotype onto the 'wrong' plant and analysed the DNA of their offspring to see how the frequency of different alleles had changed from those in their parents. These shifts would be due to selection pressure with those more advantageous to the parents making them more likely to breed and so increasing in frequency in the offspring with a corresponding decrease in their less-favourable counterparts. The result was a significant increase in those genes associated with differences in the two ecotypes. In other words, in a single generation, selection pressure had pushed the species towards the ecotype normally living on the host plant onto which they had been transferred.Tim Coulson, population biologist, Oxford University, UK
These results indicate that divergent selection plays a role in repeated genomic divergence between ecotypes. Furthermore, our results suggest that, although repeated evolutionary scenarios (i.e., replaying the tape of life) would likely result in idiosyncratic outcomes, there may be a repeatable component driven by selection that can be detected, even at the genome-wide level and during the complex process of speciation.
Víctor Soria-Carrasco, Zachariah Gompert, et al; op cit
It would be interesting to hear what one of the loons at the Discovery Institute or the Institute for Creation Research has to says on this subject. Here we see not only environmentally-driven speciation in progress but we can see significant change in the frequency allele of key genes involved in this divergence being measurable in a single generation. If this does not constitute experimental evidence for evolution and an observed instance of speciation in progress so far as they are concerned, then it's probable that there is no evidence that they would accept. It's the equivalent of watching a stone fall to Earth while denying that gravity exists.
The only way this can be dismissed as evidence for evolution is simply to ignore it altogether, or to redefine evolution as something other than the standard scientific description of ".. any change in the frequency of alleles within a gene pool from one generation to the nex" (Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989 Worth Publishers, p.974).
Any creationist up for trying for an explanation? If so, please try to spell correctly and use proper English grammar.
Thank you, Rosa, once more for spreading your knowledge! I agree with you completely when I read this: "It would be interesting to hear what one of the loons at the Discovery Institute or the Institute for Creation Research has to says on this subject."
ReplyDeleteBut IF they'll give you an answer - which I doubt they'll do - be sure that comment then will be full of insulting ad hominem arguments and so on.
Creationists usually cling to the brain's fast emotional information processing system, relying on so-called intuitive "gut-feeling" thinking (= what feels good for me must be the objectively right standpoint to have, i.e. must be the truth). See: http://en.wikipedia.org/wiki/Thinking,_Fast_and_Slow#Two_systems . That's why creationists and other woos can't use critical thinking (because that sort of rational and logical reasoning belongs to information processing system #2 ad modum Kahneman).
Since creationists and other woos are not accustomed to use logic and rationality ( = the slow system #2) in their reasoning - instead they prefer to trust their own emotions and wishful thinking - they will have to dismiss or completely ignore the facts and information you present, Rosa.
I also recommend, especially, creationists to read this article: How to spot pseudoscience - this 15-point checklist will help you tell science from pseudoscience; see: http://skeptoid.com/episodes/4037 .
Let me quote some sentences from point #15 in that article: "In some cases, such as Young Earth Creationism, proponents use the court system to force schools to teach their claims as fact. Generally, when a theory is scientifically sound, even if it's brand new it will eventually find its way into the educational curriculum. Good science is done in the lab — not in the courts, not in protest marches, not in blogs, and not in church. A political or cultural campaign to legalize or promote some product or claim is a major indicator that it's bogus."
MY COMMENT TO THAT: I doubt creationist will ever understand that argument against their own conventional bullshit thinking/reasoning. Do you agree with me, Rosa?
BTW: You also try to give creationists/woos a good advice: "...please try to spell correctly and use proper English grammar."
No, Rosa, you demand too much there. I think that creationists and other woowoos must have some disorder in their brains giving them great difficulties/problems using verbal expressions, especially reading and writing (i.e. understanding written words and sentences). In short: They are often dyslectics and dyscalculectics. By using Kahneman's system #1 (= thinking in images) instead of the verbal system #2 they have enormous difficulties understanding critical arguments. System #1 is the way of thinking and reasoning children use before their brain is mature enough to understand, use and process verbal information (i.e. using a language to communicate).
Like children creationists and woowos hardly understand what it means using logical arguments and reasoning. That's why they normally are so immune to rational arguments and logic.
What creationists doubt is not adaptation, but speciation. They know that breeds of dog or cattle can be effected by selective breeding, they just don't think a dog species could ever become a non-dog species or a cow species could ever become a non-cow species. What they would doubt here is the assessment of "speciation in progress", not the adaptation.
ReplyDeleteIt always amuses me how creationists pretend to believe that when humans classify a population as a distinct species and not a subspecies or variety that somehow that decision changes the evolutionary history of the species so it now becomes impossible whereas it was entirely possible before the change. I wonder how they think human decisions change biological history.
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