Despite its early potential, evolutionary developmental biology — evo devo for short — has yet to make good on its promise.
In his review of Endless Forms Most Beautiful Sean Carroll’s new book on evo devo, Michael Ruse faults intelligent design (ID) for harping on evolution’s unsolved problems. Moreover, Carroll as well as Ruse suggest that evo devo has now resolved one of the major problems on which design theorists have been harping.
Wrong on both counts. Intelligent design does not have a problem with problems. It has a problem with bogus solutions that Darwinists like Ruse and Carroll dress up as real solutions to the problems of biological origins.
Evo devo is a case in point. This term, coined in the mid 1990s, attempts to merge two sub-disciplines of biology: evolutionary biology, which studies the mechanisms by which populations of organisms change over generations, and developmental biology, which studies the mechanisms by which individual organisms grow from conception to mature form.
Evo devo takes as its starting point that genetic mechanisms are the key to both evolutionary and developmental biology. The merger of evolutionary and developmental biology, therefore, looks to key genes that influence development and could in principle also influence changes in development and, thereby, lead to macroevolutionary change.
What if, for instance, a gene that controls development could somehow induce a change early in development? Even a small change early in development might have huge consequences for the organism’s anatomy and physiology. Think of an arrow aimed accurately at a target. Left to fly unperturbed, the arrow will land in the target’s bull’s-eye. Yet the earlier in flight that the arrow is diverted from its trajectory, the wider it will be off the mark when it lands.
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 other words, just as the arrow diverted early from its course will land wide of the mark, so development diverted early from its course might lead to significant evolutionary change. In this way evo devo seeks to do an end-run around the more traditional neo-Darwinian approach to macroevolution, with its steady accumulation of microevolutionary changes leading to macroevolution. 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.
To be sure, evo devo’s study of genes that control development continues apace. And the field is making some progress in understanding how genetic developmental mechanisms assist in microevolutionary change — such as changes in butterfly eyespots. The problem is that evo devo looks to conserved genes, which are genes that are essentially the same across widely different organisms, to study how macroevolutionary change might have occurred.
But that raises a fundamental problem. Elizabeth Pennisi, in a report about evo devo for the journal Science, dated Nov. 1, 2002, stated the problem this way: “The lists [of conserved genes give] no insight into how, in the end, organisms with the same genes came to be so different.”
The very universality of these genes invalidates the grand claims that are made for them. Here’s why: if biological structures are determined by their genes, then different structures must be determined by different genes. If the same gene can determine structures as radically different as a fruit fly’s leg and a mouse’s brain, or an insect’s eyes and the eyes of humans and squids, then that gene really isn’t determining much of anything at all.
My colleague, the biologist Jonathan Wells, put it this way in my book, Signs of Intelligence
Consider the analogy of an ignition switch in a vehicle. One might find similar ignition switches in vehicles such as automobiles, boats, and airplanes — vehicles which are otherwise very different from each other. Perhaps, in some sense, an ignition switch can be called a “master control”; but except for telling us that a vehicle can be started by turning on an electrical current, it tells us nothing about that vehicle’s structure and function. Similarly, except for telling us how an embryo directs its cells into one of several built-in developmental pathways, homeotic genes tell us nothing about how biological structures are formed. As homeotic genes turn out to be more and more universal, the “control” they exercise in development turns out to be less and less specific.To sum up, developmental geneticists have found that the genes that seem to be most important in development are remarkably similar in many different types of animals, from worms to fruit flies to mammals.
Initially, this was regarded as evidence for genetic programs controlling development. But biologists are now realizing that it actually constitutes a paradox: if genes control development, why do similar genes produce such different animals? Why does a caterpillar turn into a butterfly instead of a barracuda?
If evo devo actually resolved the problems raised by these questions, then more power to it. Yet the real problem here is that Darwinian biologists like Carroll and Darwinian philosophers of biology like Ruse are pretending that evo devo has resolved fundamental problems of evolutionary biology when in fact it hasn’t.
Regardless of whether such failures provide an opening for ID, they must be honestly admitted. Certainly, they must not be swept under the rug for fear that they might open the door to ID. Ironically, by overselling evolution, misleading reviews and interviews like those here are hastening the reception of ID among many thoughtful scholars.
William A. Dembski is the Carl F. H. Henry Professor of Theology and Science at Southern Baptist Theological Seminary, where he heads its new Center for Science and Theology. He is also a senior fellow with Discovery Institute’s Center for Science and Culture in Seattle.