Butchering science

Creationists hate science. They hate its conclusions, they hate its methods, they hate that it doesn’t support their silly beliefs. It’s that hatred that motivates them to butcher scientific articles and papers.

One recent butchering comes from Jack Hudson. I’m sure regulars here remember him. If not, it isn’t important. He’s a creationist with a background in introductory biology courses from 20 years ago. It’s doubtful he has much experience reading scientific papers, but that doesn’t stop him from trying.

In his post he butchers two articles. I’m going to focus on the first one, but I’ll briefly mention the second one. In that one researchers found that some negative mutations don’t change the protein sequence yet they are still negative. This one is simple. The entire sequence of a gene is not devoted to just the protein sequence. A mutation can therefore change one aspect of a gene without changing another – but it can still change another process that is important in forming proteins. Alter shape in one place and you have a good chance of seeing change somewhere else as a result. Biology is still all about shape.

The second paper, though. Woo. What a doozy of a butchering. First let me summarize the paper.

In asexual populations alleles can become fixed rather quickly. Their evolution is more straight forward because they aren’t mixing and matching genes. They produce offspring with the exact same genome, less there be a mutation. If there is a mutation, it can become fixed because things are generally less complicated with asexual populations and thus more black and white. Is this mutation good or bad? As the paper says and as Jack repeats upon hearing the term for the first time, alleles sweep through a population.

But when it comes to sexually reproducing populations, things become more complicated. And this is what the paper is about. The question is, do alleles sweep through populations in sexually reproducing populations like they do in asexual populations? The answer is no.

Now, if we’re to believe Jack, this means that evolution has failed because, why, evolution predicts an advantageous allele to reach 100% fixation, of course. Except it isn’t so black and white with sexually reproducing populations. (Nor does evolution predict that anyway.)

What the researchers did was study over 600 generations of fruit flies. They let them breed naturally, but then selected out the eggs which were produced the most quickly. This led to significantly faster reproducing populations. They then tracked specific alleles to see if they would become fixed. What they found was that they don’t.

Signatures of selection are qualitatively different than what has been observed in asexual species; in our sexual populations, adaptation is not associated with ‘classic’ sweeps whereby newly arising, unconditionally advantageous mutations become fixed. More parsimonious explanations include ‘incomplete’ sweep models, in which mutations have not had enough time to fix, and ‘soft’ sweep models, in which selection acts on pre-existing, common genetic variants. We conclude that, at least for life history characters such as development time, unconditionally advantageous alleles rarely arise, are associated with small net fitness gains or cannot fix because selection coefficients change over time.

The conclusion here is that selection for a particular trait in sexually reproducing populations acts upon many different aspects and genetic variants within the genome, not merely a single gene or SNP.

This suggests that selection does not readily expunge genetic variation in sexual populations, a finding which in turn should motivate efforts to discover why this is seemingly the case.

This is the actual conclusion of the paper. To put it another way (and to repeat myself), advantageous variants do not wipe out other genetic variants in a sexually reproducing population, instead acting on variation in a more subtle and complicated way. The big conclusion here is that there is a difference in how genes become fixed (or not fixed) in asexual populations versus sexually reproducing populations.

And Jack’s conclusion?

In short, if the activity failed to occur in the lab under optimal conditions, it is unlikely that traits are going to be transmitted this way in nature.

The traits are still being transmitted through natural selection working on variation. Jack’s conclusion has little to no connection to anything from the paper. In fact, it is abundantly clear that he read an article somewhere, figured out how to butcher it, and then went and read a few lines from the original paper.

I’ve said in the past that what takes a creationist 30 seconds to say takes an educated person 3 hours to correct. This post and the research required for it didn’t take that long, but the sentiment remains true – it’s a real hassle to untangle the carelessly mushed writings of a creationist.

Ancestral environments and reverse evolution

There’s been a long debate regarding whether evolution can be reversed or not. The general trend has been that it can not. The idea goes that once one evolutionary pathway has been crossed, it cannot be retraced back to its origins. It turns out that is not entirely true.

Says [researcher] Henrique, ‘In 2001 we showed that evolution is reversible in as far as phenotypes are concerned, but even then, only to a point. Indeed, not all the characteristics evolved back to the ancestral state. Furthermore, some characteristics reverse-evolved rapidly, while others took longer. Reverse evolution seems to stop when the populations of flies achieve adaptation to the ancestral environment, which may not coincide with the ancestral state.

What the researchers did was subject fruit flies to various selection pressure for multiple decades, i.e., they changed their environment over and over. The ‘end’ result was fruit flies that were markedly different in their traits as compared to the original specimens. That’s evolution. Children should understand that. What happened next was the researchers mimicked the original environment of the fruit flies from decades gone by. In response, the fruit flies adapted to those environments, possessing many of the same allele frequencies they originally had. What I find particularly interesting is that they did not evolve exactly the same, but they still evolved in a way that was similar to the original phenotypes. This helps to explain why sharks and horseshoe crabs remain so similar for so long: the gene pool of the population centers around certain allele frequencies because, well, they work. Change may happen – in fact, it certainly does – but ancestral pheno- and genotypes can evolve to such similar future counterparts as to make little difference in show, even though we know there to actually be differences, at least in contigency. It’s a bit like how two people of very different backgrounds and even different alleles can come to have the similar tones to their skin. Their evolutionary contigency, or histories, are different, but the result is virtually the same.

Another point of note here is that evolution can produce similar things, but it will almost never produce the exact same thing. The history of life, if rerun, would be much, much different in all likelihood. When exolife is discovered, we’ll have indirect confirmation of this. Until then, it should be important for people to realize that nothing in biology is inevitable – including humans.