A couple of weeks ago a friend forwarded me a link to this recent article about “ongoing research to record the interaction of environment and evolution” by University of California, Riverside biologist David Reznick. Reznick’s team has been studying adaptive changes in guppies. Reznick’s work focuses on tracking what happens in real-world situations in the wild, rather than the somewhat artificial environments in the lab. As a result, Reznick has gathered some of the more trustworthy and definitive data about changes over time in a real-world environment, largely free from the intervention and interference of the coated lab worker.
The article states:
The new work is part of research that Reznick has been doing since 1978. It involved transplanting guppies from a river with a diverse community of predators into a river with no predators – except for one other fish species, an occasional predator – to record how the guppies would evolve and how they might impact their environment.
In the recent follow-up research, Reznick’s team studied “how male color pattern affected” their differential survival in the environment. Significantly, the team even gathered DNA from the guppies over time to track who their parents were and reconstruct a guppie pedigree to help determine the reproductive success. Without going into all the details, which are interesting in their own right, the key point for my purposes today is that this adaptive change occurred extremely quickly.
Graduate student, Swanne Gordon, noted,
Our research shows that these fish adapted to their new habitats in less than one year, or three to four generations, which is even faster than we previously thought.
Reznick adds,
People think of evolution as historical. They don’t think of it as something that’s happening under our nose. It is a contemporary process. People are skeptical; they don’t believe in evolution because they can’t see it. Here, we see it. We can see if something makes you better able to make babies and live longer.
What Really Happened?
Now normally when my friend forwards a link, I will just review the article, realize it is making claims beyond the data, and move on. But coincidentally, just days earlier I had been reading Chapter 7 of Lee Spetner’s 1998 book, Not by Chance!
Part of Spetner’s argument is that many adaptive changes we see in nature are in fact not examples of a Darwinian process of chance changes + natural selection, but instead the result of specific programming capabilities in the organism to allow it to respond to changes in the environment. Indeed, what caught my eye about the article my friend forwarded is that Spetner had discussed Reznick’s earlier experiments in that very context.
After describing two different predators of the guppies: (i) the cichlid, which prey on large mature guppies; and (ii) the killfish, which prey on small immature guppies, Spetner continues:
Reznick and his team took 200 guppies from the Aripo [river in Trinidad] and put them in a tributary of the river that is home to the killfish but has no cichlids and had no guppies. Changes soon appeared in the newly introduced guppies. The fish population soon changed to what would normally be found in the presence of the killfish, and Reznick found the changes to be heritable.
The full change in the guppy population was observed as soon as the first samples were drawn, which was after only two years. One trait studied, the age of males at maturity, achieved its terminal value in only four years. The evolutionary rate calculated from this observation is some ten million times the rate of evolution induced from observations of the fossil record [Reznick et al. 1997].
Reznick interpreted these changes as the result of natural selection acting on variation already in the population. Could natural selection have acted so fast as to change the entire population in only two years?
Spetner goes on to argue that the adaptive change observed in the guppies is more likely the result of a programmed response to environmental change, and provides several examples of such changes in other species.
Where is the Darwinian Evolution?
Darwinian evolution, as we know, is supposed to work by natural selection weeding out random variation. The Neo-Darwinian model has traditionally gone a step further, suggesting that those random variations are genetic in nature — taking place in the DNA as a copying error here, a misplaced sequence there, an accidental cut-and-paste elsewhere . . .
So the question arises: do the kinds of rapid, adaptive, reversible changes Reznick observed owe their existence to this kind of Darwinian process, or are they the result of a pre-programmed genetic response to environmental changes?
Spetner makes a good argument that we are observing the latter. He goes on to show that even many of the classical examples of Darwinian evolution — you know, the examples of random mutation + natural selection that even most evolutionary skeptics have tended to accept: convergent “evolution” of plants in similar environments, the “evolution” of bacteria to live on lactose or salicin — are not good examples of Darwinian evolution at all. Even that icon of icons, finch beaks in the Galapagos, is likely not a good example of the alleged Neo-Darwinian mechanism of random mutation + natural selection.
All of this prompts me to ask a simple, but pointed, question:
How many good examples are there of Darwinian evolution?
The more research I do the more I come to the same conclusion Spetner did, namely that most adaptive changes are not the result of the random, purposeless changes Darwinian evolution posits as the engine of biological novelty.
Even skeptics of the grand evolutionary claims tend to accept, either specifically or implicitly, that Darwinian evolution can produce all kinds of minor adaptive changes, the so-called microevolutionary changes: variations in finch beaks, insect resistance to insecticides, coloration of peppered moths, and so on. And indeed, the “selection” side of the formula seems to work well, which is simply the somewhat pedestrian observation that if an organism is poorly adapted to its environment it has a poor chance of surviving.
Yet the engine of the novelty, the alleged random variation that is supposed to provide all this adaptive variability on which selection can work its magic, seems stubbornly absent. Even these most common of examples, on closer inspection, do not support the Darwinian claim. Thus the doubts multiply. If Darwinian evolution cannot even claim explanatory credit for things like bacteria being able to metabolize lactose, what can it explain? The more closely we look, the more anemic the Darwinian claim becomes.
Now we could be intellectually lazy and call every adaptive change we observe an example of “evolution.” But the problem with observing a change and claiming that we have observed “evolution” is that (i) we rob the word of explanatory value if it is applied indiscriminately, and (ii) we trick ourselves into thinking we have an explanation for what occurred, when in fact we have have no idea what is happening at the molecular level or the organismal level to produce the change. Claiming that we are witnessing “evolution” in such circumstances becomes then not so much an explanation as a confession of ignorance.
Real Darwinian Evolution
There are no doubt quite a number of legitimate, confirmed examples of random mutation + natural selection producing an important biological effect. For example, I think Behe’s review of malaria/sickle cell trait is a legitimate example of Darwinian evolution in action. And the circumstances of that example are rather telling: (a) large population size, (b) meaningful amount of time, (c) very strong selection pressure, (d) and change that can be caused by one or two single-point mutations.
If we see adaptive change outside of these parameters — small population, short timeframe, an adaptation that requires significant genetic change — we might be better served to suspect that we are witnessing a programmed adaptive response, rather than Darwinian evolution. And rather than being naively impressed with the great power of Darwinian evolution to act more rapidly than anticipated, we should be prompted to look deeper to find what is actually taking place.
Your Turn
In addition to the malaria/sickle cell example, what other examples of legitimate, confirmed Darwinian evolution can you think of?