This morning my wife left me a surprise on the computer screen; a four-legged duck named Stumpy (seen below in an AP photo)
According to the story, Stumpy was born at the Warrawee Duck Farm, about 95 miles south of London, this being the first instance of this particular phenomenon at the Farm. Apparently extra legs among ducks is fairly common, other recent cases involving a duck named Jake in Australia and this waterfowl in China. As can be imagined, ducks with extra limbs would not do well in the wild, some (like Jake) dying soon after birth. The new legs are not replacing anything, and no mention has been made as to their being functional (I assume they’re not, or at least not to the same degree), so I think what Stumpy is exhibiting can be safely said to be a deleterious change.
Note: PZ writes that Stumpy is likely the result of a change during development, likely the fusion of two embryos. I’ve tried to edit out my referring to this phenomenon as a mutation (or at least qualify it).
As cute as Stumpy may be, his picture did get me thinking; this is what most people think about when the word “mutation” comes up. There certainly seems to be at least two definitions of the term, one dealing with changes in genotype (which may or may not be expressed in the phenotype) and then the public conception of the idea, usually in the context of movie monsters and ninja turtles. In post WWII films, radiation from nuclear tests produced giant ants (THEM!), Japanese metaphors for the destruction they suffered as a result of the two A-bombs (Godzilla), and any number of other killer puppets, men-in-suits, or bugs shot on miniature sets. After the radiation scare got old, films started to turn to chemical, biological, or genetic causes for mutations, resulting in bear/salami hybrids (The Prophecy), super-sized normal creatures (Alligator), military-funded killing machines (Piranha), and even some super heroes of varying description (Teenage Mutant Ninja Turtles, The Toxic Avenger, etc.). It seems that in the public arena at least, mutation=saltation (I’m not even going to get into the bogus “organism+radiation=big angry monster” storyline), whatever unfortunate create suffering the mutation either becoming a monster or gaining powers. Even the recent Spider-Man films, as good as they are, further muddy the waters in terms of mutation, putting forth the idea that you can somehow trade-out bits of your DNA with an animal just by it biting you. Some might call this nitpicking and say “It’s just a fun movie,” and while it would be lovely if America wasn’t enamored with pseudoscience or take genetics lessons from popular cinema and TV, this is not the case.
Although the idea of a “Hopeful Monster” as conceived by Richard Goldschmidt is somewhat appealing to my imagination (it makes me think of Where the Wild Things Are), it does not provide an accurate view of evolutionary change. While Eldredge’s and Gould’s idea of punctuated equilibrium attempted to explain the seeming lack of transitional fossils through a logical and (I believe) accurate and observable model and should not be confused with the hopeful monster hypothesis, Goldschmidt wanted to explain the “gaps” of the fossil record with an idea that suddenly creatures exhibiting major change could arise, essentially causing speciation in one generation. While plants are generally unfairly ignored in the evolution debate (I wish I had more of an aptitude for them), and polyploid plants may give credence to saltation in plants, “monsters” like Stumpy do not have much reason to hope.
Let’s use Stumpy as an example of why a saltation such as an extra pair of legs would not lead to evolutionary change in a population over time. Assuming Stumpy would even be able to survive in the wild, the saltation is absolutely worthless in evolutionary terms unless he passes it on, and while I am not an expert on duck mating behavior I have to wonder if being a “Freak of Nature” if females would be less likely to mate with him or he would be otherwise impaired in seeking a mate. (Once again, if this phenomena is caused by developmental changes, then I can’t say I know its heritability if not caused by mutation.) Even if successful, such a disadvantageous genotype would not spread very far or exist for very long, predators most likely picking off the impaired ducklings if they did not die prematurely to begin with. Rather than working on variations within a given population (whether slowly or more quickly), changes like the one Stumpy exhibits do not do any good for the organism, and even if such a change occurred and was not deleterious, there is no guarantee that the trait will be passed on as it may reproductively isolate (via behavior or mechanics) the organism from others of its own kind.
While the damage is most likely unintentional, popular media has done much to misconstrue science and issues important to the understanding of evolution. As Ken Miller said in a video I saw at the newly re-opened hall dealing with human evolution at the AMNH, without evolution biology is little more than “stamp collecting” (I’ll write about my trip in a separate post). Pseudoscience is so prevalent in our society today it is maddening, astrologers spurting out idiotic claims in nearly every newspaper, celebrities like Oprah, Tom Cruise, and others signing up for metaphysical nonsense, and movies still enamored with the two most familiar manifestations of scientists in the media; the spurned nut working at a genetics lab who will “show them all” or the smart, handsome, altruistic hero who seems more like an athlete than a PhD holder.