Over at his blog, Why Evolution Is True, the eminent evolutionary biologist Jerry Coyne seems unwisely to be relying for his information about Darwin Devolves on one of the fellows who authored the mind-bogglingly shoddy review in Science. Coyne paraphrases some of his and another guy’s claims about my discussion of the polar bear thus:
Behe claims that this is true for the polar bear: that the genes that turned the ancestral coat white and changed the fat metabolism were broken genes. But when you examine the paper supposedly supporting Behe’s claim, you find, argue Lents and Hunt, that about half of them don’t seem to have any damaging mutations, and that perhaps “none of the 17 most positively selected genes in polar bears are ‘damaged’.”
In fact, we can even grant Behe a figure of 50% of genes involved in adaptation being broken, and it still doesn’t matter. For if just half of genes involved in new adaptations do new or different things and are not damaged, then his thesis doesn’t work: evolution doesn’t grind to a halt. And, as I’ve said, there are lots of genetic changes that don’t involve broken genes, including duplications, mutations that affect gene regulation, and so on.
Okay, hold that in your head.
The Relevant Paragraphs
Here are the relevant paragraphs from my book: (pp. 16-17)
But what precisely did the changes in polar bear APOB do to it compared to that of other mammals? When the same gene is mutated in humans or mice, studies show it frequently leads to high levels of cholesterol and heart disease. The scientists who studied the polar bear’s genome detected multiple mutations in APOB. Since few experiments can be done with grumpy polar bears, they analyzed the changes by computer. They determined that the mutations were very likely to be damaging — that is, likely to degrade or destroy the function of the protein that the gene codes for.
A second highly-selected gene, LYST, is associated with pigmentation, and changes in it are probably responsible for the blanching of the ancestor’s brown fur. Computer analysis of the multiple mutations of the gene showed that they, too, were almost certainly damaging to its function. In fact, of all the mutations in the 17 genes that were most highly selected, about half were predicted to damage the function of the respective coded proteins. Furthermore, since most altered genes bore several mutations, only 3 to 6 (depending on the method of estimation) out of 17 genes were free of degrading changes. Put differently, 65%-83% of helpful, positively-selected genes are estimated to have suffered at least one damaging mutation.
It seems, then, that the magnificent Ursus maritimus has adjusted to its harsh environment mainly by degrading genes that its ancestors already possessed. Despite its impressive abilities, rather than e-volving, it has adapted predominantly by de-volving. What that portends for our conception of evolution is the principal topic of this book.
A Reasonable Vocabulary
Notice that I use derivatives of the word “damage,” not “broken.” Throughout the book I am quite careful to use both terms when the situation is uncertain. For example, when discussing Richard Lenski’s long-term evolution experiment I write, “It’s very likely that all of the identified beneficial mutations worked by degrading or outright breaking the respective ancestor genes.” (p. 179) Readers who have a reasonable vocabulary will recognize that damaged and broken have distinct meanings. (Degraded is a synonym of damaged.) If your car has been in a fender-bender, it has been damaged but may not be completely broken. And of course a car or a protein can accumulate greater and greater amounts of damage before being completely broken.
The point was hardly obscure. Here’s the very epigraph of my book, right up front: “The First Rule of Adaptive Evolution: Break or blunt any gene whose loss would increase the number of offspring.” Notice again that “break” and “blunt” have distinct meanings. The relevant definition of blunt is: To make less effective; weaken. Is that really so hard to understand?
Behold the Bizarre Absolute
It has been my experience that one very common way for opponents to try to discredit an argument is to exaggerate it, to ignore distinctions an author makes, and/or to change carefully qualified claims into bizarre absolutes. Why, here’s an example right here:
What Behe is saying is that harming genes is the only way that unguided mutations can ever help an organism.
Behold the bizarre absolute. Now all a devoted Darwinist has to do in order to knock down the strawman he set up is to, say, point to some duplicated gene or other that helps with something, and he no longer has to worry his little head about the argument.
I would advise readers who actually want to understand the argument to read it with attention; there are lots of distinctions made in the book. And I would advise Professor Coyne either to find a more reliable informant or to wait two weeks and read the book himself.
Below is the relevant information from Liu et al.’s Table S7. Those who can understand the table will see that it supports every actual, undistorted claim I made about the polar bear.
|Gene||Protein position||Ancestral AA||Polar bear AA||HDivPred|
Source: Liu, S., et al. 2014. Population genomics reveal recent speciation and rapid evolutionary adaptation in polar bears. Cell 157:785-794, Table S7.