Pharyngula

I was just catching up on a few blogs, and noticed all this stuff I missed about Jonathan Wells’ visit to Oklahoma. And then I read Wells’ version of the event, and just about choked on my sweet mint tea.

The next person–apparently a professor of developmental biology–objected that the film ignored facts showing the unity of life, especially the universality of the genetic code, the remarkable similarity of about 500 housekeeping genes in all living things, the role of HOX genes in building animal body plans, and the similarity of HOX genes in all animal phyla, including sponges. 1Steve began by pointing out that the genetic code is not universal, but the questioner loudly complained that 2he was not answering her questions. I stepped up and pointed out that housekeeping genes are similar in all living things because without them life is not possible. I acknowledged that HOX gene mutations can be quite dramatic (causing a fly to sprout legs from its head in place of antennae, for example), but 3HOX genes become active midway through development, 4long after the body plan is already established. 5They are also remarkably non-specific; for example, if a fly lacks a particular HOX gene and a comparable mouse HOX gene is inserted in its place, the fly develops normal fly parts, not mouse parts. Furthermore, 6the similarity of HOX genes in so many animal phyla is actually a problem for neo-Darwinism: 7If evolutionary changes in body plans are due to changes in genes, and flies have HOX genes similar to those in a horse, why is a fly not a horse? Finally, 8the presence of HOX genes in sponges (which, everyone agrees, appeared in the pre-Cambrian) still leaves unanswered the question of how such complex specified genes evolved in the first place.

The questioner became agitated and shouted out something to the effect that HOX gene duplication explained the increase in information needed for the diversification of animal body plans. 9I replied that duplicating a gene doesn’t increase information content any more than photocopying a paper increases its information content. She obviously wanted to continue the argument, but the moderator took the microphone to someone else.

It blows my mind, man, it blows my freakin’ mind. How can this guy really be this stupid? He has a Ph.D. from UC Berkeley in developmental biology, and he either really doesn’t understand basic ideas in the field, or he’s maliciously misrepresenting them…he’s lying to the audience. He’s describing how he so adroitly fielded questions from the audience, including this one from a professor of developmental biology, who was no doubt agitated by the fact that Wells was feeding the audience steaming balls of rancid horseshit. I can’t blame her. That was an awesomely dishonest/ignorant performance, and Wells is proud of himself. People should be angry at that fraud.

I’ve just pulled out this small, two-paragraph fragment from his longer post, because it’s about all I can bear. I’ve flagged a few things that I’ll explain — the Meyer/Wells tag team really is a pair of smug incompetents.

1The genetic code is universal, and is one of the pieces of evidence for common descent. There are a few variants in the natural world, but they are the exceptions that prove the rule: they are slightly modified versions of the original code that are derived by evolutionary processes. For instance, we can find examples of stop codons in mitochondria that have acquired an amino acid translation. You can read more about natural variation in the genetic code here.

2That’s right, he wasn’t answering her questions. Meyer was apparently bidding for time until the big fat liar next to him could get up a good head of steam.

3This implication that Hox gene expression is irrelevant because it is “late” was a staple of Wells’ book, Icons of Evolution and the Politically Incorrect Guide to Darwinism and Intelligent Design. It’s a sham. The phylotypic stage, when the Hox genes are exhibiting their standard patterns of expression, of humans is at 4-5 weeks (out of 40 weeks), and in zebrafish it’s at 18-24 hours. These are relatively early events. The major landmarks before this period are gastrulation, when major tissue layers are established, and neurulation, when the neural tube forms. Embryos are like elongate slugs with the beginnings of a few tissues before this time.

4What? Patterned Hox gene expression is associated with the establishment of the body plan. Prior to this time, all the embryonic chordate has of a body plan is a couple of specified axes, a notochord, and a dorsal nerve tube. The pharyngula stage/phylotypic stage is the time when Hox gene expression is ordered and active, when organogenesis is ongoing, and when the hallmarks of chordate embryology, like segmental myotomes, a tailbud, and branchial arches are forming.

5Hox genes are not non-specific. They have very specific patterning roles; you can’t substitute abdominal-B for labial, for instance. They can be artificially swapped between individuals of different phyla and still function, which ought, to a rational person, be regarded as evidence of common origin, but they definitely do instigate the assembly of different structures in different species, which is not at all surprising. When you put a mouse gene in a fly, you are transplanting one gene out of the many hundreds of developmental genes needed to build an eye; the eye that is assembled is built of 99% fly genes and 1% (and a very early, general 1%) mouse genes. If it did build a mouse eye in a fly, we’d have to throw out a lot of our understanding of molecular genetics and become Intelligent Design creationists.

Hox genes are initiators or selectors; they are not the embryonic structure itself. Think of it this way: the Hox genes just mark a region of the embryo and tell other genes to get to work. It’s as if you are contracting out the building of a house, and you stand before your subcontractors and tell them to build a wall at some particular place. If you’ve got a team of carpenters, they’ll build one kind of wall; masons will build a different kind.

6No, the similarity of Hox genes is not a problem. It’s an indicator of common descent. It’s evidence for evolution.

7Good god.

Why is a fly not a horse? Because Hox genes are not the blueprint, they are not the totality of developmental events that lead to the development of an organism. You might as well complain that the people building a tarpaper shack down by the railroad tracks are using hammers and nails, while the people building a MacMansion on the lakefront are also using hammers and nails, so shouldn’t their buildings come out the same? Somebody who said that would be universally regarded as a clueless moron. Ditto for a supposed developmental biologist who thinks horses and flies should come out the same because they both have Hox genes.

8You can find homeobox-containing genes in plants. All that sequence is is a common motif that has the property of binding DNA at particular nucleotide sequences. What makes for a Hox gene, specifically, is its organization into a regulated cluster. How such genes and gene clusters could arise is simply trivial in principle, although working out the specific historical details of how it happened is more complex and interesting.

The case of sponges is enlightening, because they show us an early step in the formation of the Hox cluster. Current thinking is that sponges don’t actually have a Hox cluster (the first true Hox genes evolved in cnidarians), they have a Hox-like cluster of what are called NK genes. Apparently, grouping a set of transcription factors into a complex isn’t that uncommon in evolution.

9If you photocopy a paper, the paper doesn’t acquire more information. But if you’ve got two identical twins, A who is holding one copy of the paper, and B who is holding two copies of the same paper, B has somewhat more information. Wells’ analogy is a patent red herring.

The ancestral cnidarian proto-Hox cluster is thought to have contained four Hox genes. Humans have 39 Hox genes organized into four clusters. Which taxon contains more information in its Hox clusters? This is a trick question for Wells; people with normal intelligence, like most of you readers, would have no problem recognizing that 39 is a bigger number than 4. Jonathan Wells seems to have missed that day in his first grade arithmetic class.

It’s appalling, but this is the Discovery Institute’s style: to trot out a couple of crackpots with nice degrees, who then proceed to make crap up while pretending to be all sincere and informed and authoritative. It’s an annoying trick, and I can understand entirely why a few intelligent people with actual knowledge in the audience might find the performance infuriating. I do, too.