Archive Classic: The Factor Darwin (and Malthus) Didn’t Consider
This entry from March 17, 2003 became inaccessible from the archives, but needs to be posted again because of its importance.
This entry and tomorrow’s were posted 16-17 years ago, but are just as significant to the origins debate now as they were then. Unfortunately, evolutionists have ignored the implications of these papers published in PNAS. It’s time to put out the word again that neo-Darwinism has been falsified and must be discarded into the waste bin of untenable ideas. Note that the papers were written by evolutionists, for evolutionists! —Ed.
Evolution is onward and upward, right? Competition between individuals leads to the fittest surviving, right? Not so fast, says Jason B. Wolf of the Department of Ecology and Evolutionary Biology at the University of Tennessee in Knoxville, writing in the Proceedings of the National Academy of Sciences. There’s an influence that puts the brakes on this “traditional paradigm”, and that is the influence of indirect genetic effects (IGEs). Most evolutionary biologists focus on the direct genetic effects (DGEs): i.e., how an organism’s body (phenotype) is the direct result of its genes (genotype). But that cannot be the whole picture, because social interactions and even the environment can cause phenotypic effects that are heritable. Thus, they can influence evolution.
Wolf studied the pupa size of fruit flies as a measure of fitness. His results supported a model that took IGEs into account, and found that IGEs fight against the effects of DGEs; that is, “competition enforces the negative covariance between IGEs and DGEs.” He explains:
For example, if we were to select the largest individuals in a generation, they would on average also be the most competitive individuals. These individuals would have a set of genotypes that, under the current social conditions, make individuals large, and selection would therefore produce a genetic change in the population. However, the progeny of these individuals would find themselves in a more competitive environment, because they all inherited genes from the most competitive individuals in the previous generation. Thus, this new generation would not be as large as we would have expected based on the size of their parents, because they are experiencing a different social environment.
As an analogy, we can view body size evolving on a treadmill, where every step forward is accompanied by movement backward due to the associated negative changes in the environment. The result is that, depending on the speed of the treadmill, the trait either remains where it started or does not move as far as expected [Dickerson (48) referred to this as “slippage” on the treadmill]. When describing his fundamental theorem of natural selection, Fisher (47) recognized this process as the critical reason why populations do not continue to evolve to higher states of fitness (or character values) despite widespread recurrent directional selection. However, his intuition that these effects would exist and be potentially important had not been previously demonstrated.
From his experiments watching pupa size evolve with and without indirect genetic effects, he found that IGEs cancel out about half the fitness gains of the direct genetic effects. This is in addition to the constraint due to antagonistic pleiotropy, where genes on the same chromosome must evolve together or else no net evolution occurs. But IGEs are expected to put more brakes on selection the more competition increases. The effect is more severe when the individuals are related. “The diminished response to selection caused by the antagonistic counterevolution of IGEs,” he summarizes, “and the further diminution expected when interactions are among relatives can be viewed as a constraint on phenotypic evolution.” How widespread is this braking effect? He notes in conclusion (emphasis added):
Because interactions between individuals are ubiquitous, the opportunity for phenotypic effects of these interactions, and thus IGEs, is considerable…. Thus, the data presented here from Drosophila are expected to have significant implications for genetic analysis of a variety of traits in a diversity of taxa. These data suggest that the traditional paradigm, focused exclusively on direct effects of genes, is inadequate. To develop an accurate picture of genetic architecture that describes how genetic variation leads to phenotypic variation in a population, information on both direct and indirect effects of genes will be required whenever individuals interact.
In the early 1800’s, Thomas Malthus proposed the principle that fecundity outpaces food supply, so that there is always competition for resources. Charles Darwin was deeply influenced by this idea. It contributed to his theory of natural selection: competition leads to the survival of the fittest. A great deal of intellectual, political and philosophical baggage soon became attached to this assumed law of nature: competition drives the fittest to bigger and better things. Wolf now seems to be saying that competition actually inhibits increases in fitness from becoming established in a population. His paper is entitled, “Genetic architecture and evolutionary constraint when the environment contains genes.”
Update 04/07/2003: In a PNAS Commentary dated April 15, James M. Cheverud of Washington University School of Medicine in St. Louis agrees that quantitative genetic kin selection models such as Wolf’s are superior to the traditional kin selection model of group selection developed by W. D. Hamilton in 1964. (Hamilton was the one who sparked an interest in social evolution, claiming that Darwinian natural selection could explain puzzling traits like altruism.) Cheverud does not claim sociobiologists have arrived at a comprehensive model, but agrees that Wolf’s is probably the best so far.
We hate to be the bearers of bad tidings to evolutionists so often. It’s getting downright depressing. Here they had pinned their eternal hopes on the picture of competition driving evolution, and now they find out instead that it puts the brakes on it. It’s like finding out your ally was a double agent all along. Now what? It was tough enough getting evolution to work with enough speed to get a Cambrian explosion, and to get birds from dinosaurs, but now the very selection pressures that are supposed to drive these transformations are seen to be like governors on the engine or brakes applied by the instructor in the passenger seat. They’ll never get anywhere at this rate.
We have no reason to believe Jason doubts evolutionary theory, because he published this paper in a very pro-evolutionary, anti-creationist, peer-reviewed journal, and teaches evolution at a state university. But in the end, he gives no alternative explanation for how this negative effect can be overcome, to allow cells to evolve molecular machines, and plants photosynthesis, and humans bigger brains. His paper leaves you hanging for the “Yeah, but…” that never comes. So how does evolution make progress against this “negative covariation”? Wolf essentially says, “Don’t ask me. I’m just the inspector to point out the leak, not the plumber to fix it.”
Let’s try another metaphor to illustrate the problem this paper presents. The pressure has been increasing on evolutionary theory to drive a more complex race in less time. Imagine the consternation of the gamblers when they overhear the test report on their prize race car that contains a much-hyped transmission, natural selection, on which they have wagered everything: “Uh oh, the drive gear on this contraption slips and only inches forward, if at all. But the neutral and reverse gears are working just fine, so at least I can rock back and forth.”
Maybe it’s time to revive the pre-Darwinian view of Edward Blyth that nature is a conservative process. Instead of generating novel phenotypes and new species, it appears to maintain a dynamic status quo and buffer against major change. This would fit in with the creationist view that God designed flexibility and adaptability into dynamic systems that were fully operational from the start, not evolving into something better. When you are on a treadmill, there is a lot of activity, but you get off where you got on.
If you are an evolutionist, we’re sorry your theory has been taking such a beating lately. Please accept this sympathy card with our sincerest best wishes.