Tuesday, December 4, 2007

Problems for Evo-Devo

A couple of weeks ago, I mentioned the new book by William Dembski and Jonathan Wells, The Design of Life. Its subtitle is Discovering Signs of Intelligence in Biological Systems, and it is the clearest, most comprehensive book to date dealing with the evidences that make neo-Darwinian theory inadequate for explaining what we now know about living things.

What I want to share today comes from chapter 2, "Genetics and Macroevolution," and has to do with the relatively new field (in biology) known as "evo-devo."

For a long time now, neo-Darwinism has postulated that microevolutionary changes (small changes that occur within a species, like bacterial resistance to antibiotics and variation in the beak size of finches) somehow help to explain macroevolution (the origin of entirely new body plans, of new families and orders). In other words, macroevolution is (for them) a logical extrapolation of microevolution, and both must rely on the same mechanisms--natural selection acting on random gene mutations. The problem is that no evidence exists to suggest that macroevolution really can be accounted for by the steady accumulation of microevolutionary changes, and there is a great deal of evidence contrary to this traditional view.

Enter evolutionary developmental biology, evo-devo. Evo-devo merges the disciplines of evolutionary biology and developmental biology, the latter being the study of the development of an organism from embryo to adult. The idea is that perhaps it's not just any genes that account for changes among species but those particular genes that control development. If one of these genes is changed (early in the embryo), perhaps the change in the adult would be significant. According to Dembski and Wells,
The promise of evo-devo is that genetically-induced changes early in development, though small and easily attainable in themselves, might nonetheless lead to macroevolutionary changes. In this way evo-devo seeks to do an end-run around the more traditional neo-Darwinian approach... Evo-devo, by contrast, promises rapid evolutionary change at a small cost, namely, the cost of mutating a few key genes that control early development.
Thus, the existence of evo-devo as a field of research represents a tacit admission on the part of biologists that the traditional evolutionary explanation is inadequate. Unfortunately (for the materialist), so is evo-devo:
Yet, despite this initial promise, evo-devo is now in a state of crisis.... William Jeffrey, an evolutionary developmental biologist at the University of Maryland, concedes that evo-devo's attempt to understand how developmental genes induce macroevolutionary change is "at a dead end."
This section is well worth your read if you're at all interested, but here's the skinny... the mounting evidence from this field indicates that genetic programs do not control development (though they do play a role in development). And this presents a big problem for neo-Darwinism.
...if development is controlled by something other than genes, then evolution must be due to something other than genetic mutations and changes in gene frequencies. Consequently, if the notion that genetic programs control development is false, then so is neo-Darwinism. Neo-Darwinism logically entails the control of development by genetic programs.

1 comment:

Stephen Matheson said...

You wrote: "...here's the skinny... the mounting evidence from this field indicates that genetic programs do not control development (though they do play a role in development). And this presents a big problem for neo-Darwinism."

You self-identify as a biologist, so you should be well qualified to read the actual scientific literature by and about evo-devo. If you do this, you will discover that Dembski and Wells aren't telling you the truth.

Whatever it is you mean by "control" (vs. "play a role"), I'm sure that the editors, associate editors, and hundreds of authors of Development, Genes & Development, Genetics, and dozens of other scientific journals and societies will laugh at the suggestion that "genes do not control development."

I suggest you find different sources, and reconsider linking the gospel to nonsense and duplicity.