In his latest work, The Greatest Show on Earth, Oxford biologist Richard Dawkins compares evolutionary biologists to detectives investigating a crime scene. They gather clues and by inference piece together a scenario for what might have happened. Detectives almost never have the luxury of being an eyewitness to the crime. This, Dawkins maintains, is where the analogy breaks down because biologists are direct witnesses to evolution happening in real time right before their eyes. For Dawkins, the direct observations of real-time evolutionary changes provide powerful evidence that evolution is, indeed, a fact.
I am currently working on a chapter-by-chapter response to the case Dawkins presents for biological evolution in The Greatest Show on Earth. (Go here, here, and here for comments on chapter one, chapters two and three, and chapter four, respectively.) This week I continue my critique, focusing on chapter five and Dawkins’ assertion that the evolutionary paradigm must be valid because we can see evolution in action.
Observations of real-time evolution occurring in the course of a human lifetime are rare. Dawkins acknowledges this, but points out that more and more examples are surfacing. And some of these instances are quite dramatic, indicating that microevolutionary changes and speciation (or at least reproductive isolation) can happen rapidly. Dawkins focuses on three examples of evolution in action: the evolution of lizards on the island of Pod Mrcaru, Richard Lenski’s Long-term Evolution Experiment, and the evolution of guppies in the mountain streams of Trinidad, Tobago, and Venezuela.
I have previously discussed the lizards of Pod Mrcaru on an episode of our podcast Science News Flash (go here to listen) and wrote about the Long-term Evolution Experiment in a series of Today’s New Reason to Believe articles (go here, here and here). In this article, I will examine the evolution of wild guppies studied by John Endler.
Endler noticed that local populations of male guppies in the mountain streams of Trinidad, Tobago, and Venezuela could be either brightly colored with large spots or drab. Endler reasoned that in streams with no threat from predators, females preferred brightly colored males. But in streams where predators were present, drab males were more likely to survive. In other words, Endler guessed that the effects of sexual and natural selection were competing with each other. Natural selection, he thought, won out when predatory fish shared the mountain streams with guppies but mate preference carried the day in the absence of predators.
To test his hypothesis, Endler built ponds in a greenhouse and filled them with guppies. Some ponds were lined with large, course pebbles and the others with fine, sandy gravel. Within a few months the male guppies in both types of ponds were covered with large spots presumably because females preferred mating with males that stood out. Endler then added predatory fish to some of the ponds. Those without predators continued to harbor guppies with large colorful spots. But those with predators quickly became populated with guppies that blended into the background. Guppy populations exposed to predators were characterized by males with fewer spots. Interestingly, the spots sizes also changed. Males in ponds with large pebbles had larger spots and those with fine gravel had smaller spots.
Endler then repeated the experiment in the wild transferring guppies from streams with predators into mountain streams that previously had no guppies and no predators. Male guppies that were drab in the presence of predators rapidly transformed into brightly colored fish with large spots in the absence of any predatory threat. This work is a marvelous illustration of evolution in action and evolution acting in a hurry. But does it mean that the evolutionary paradigm is a fact?
The examples of evolution in action cited by Dawkins are impressive, but they all involve microevolutionary changes or the evolution of microbes. Just because scientists have observed microevolution, speciation, and microbial evolution doesn’t mean that macroevolution is necessarily valid. The scale of the biological changes that take place in microevolution and speciation are radically different from the presumed changes that take place for macroevolution. As is true in other areas of science, processes happening at one level can’t automatically be extrapolated to other levels without proper validation. In my opinion, this validation doesn’t exist for macroevolutionary changes. (I will discuss this lack of support in more detail in the weeks to come as I continue to respond to Dawkins case for biological evolution.) But for now I refer the reader to the article I posted previously where I pointed out that there appears to be real boundaries that species can’t traverse.
As for the evolution of microbes, given their large population sizes, rapid generation times, and capability for horizontal gene transfer, it is not surprising that they evolve.
On the other hand, the capability of organisms to experience microevolutionary changes and undergo speciation can be understood as an elegant design feature and part of God’s providence. The ability of organisms to adapt to changes in the environment makes them robust, ensuring their survival. If species were truly immutable, they would quickly go extinct as environmental and predatory pressures intensified or changed. The ability to adapt also allows species to migrate from one region to another and in the process take advantage of new niches and habitats.
Even though evolutionary biologists claim that directly observing evolution in action provides proof positive that evolution is a fact, from a creation model perspective, when we happen to be eyewitnesses to microevolutionary changes and speciation we are seeing direct evidence for the Creator’s fingerprints in nature.
Just recently, scientists witnessed another instance of evolution in action: The emergence of a new finch species on the Galapagos Island. Go here to listen to the Science News Flash episode in which I described this observation and its implications. Finches provide another example of microevolutionary changes and speciation having limited creative potential.
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