Now that’s a provocative title coming from an evolutionary biologist, isn’t it? Well, it’s meant to be.
I am continually amazed by both creationists and evolutionary biologists alike in the ongoing “debate” about the validity of evolution. Many creationists feel that if they can find a single instance in which Charles Darwin was wrong about the workings of evolution, the entire idea that biological evolution shapes the biota of the world around us will be shown to be a complete fraud. Moreover, many evolutionary biologists fall to an extremely defensive position because of this.
Darwin and Alfred Wallace were right about their fundamental idea – that the process of natural selection alters populations and species because of interactions with their ecological environment. Those individuals that are better at interacting with their environment will leave more offspring to the next generation, and if offspring resemble their parents in the traits that make the parents more or less successful, natural selection will make those traits more frequent in the population and species. Since the publication of Darwin and Wallace’s joint paper to the Linnean Society describing natural selection in 1858, natural selection has been the organizing idea and theory for biology.
In addition, we have studied literally thousands of examples of natural selection in the laboratory and in the field. The studies of David Lack and Peter and Rosemary Grant and their students provide probably the best known and most charismatic examples of natural selection in the wild. However, examples of studies where natural selection is measured in the wild now fill the scientific literature. Soapberry bugs adapting to a diversity of host plants throughout their range is a solid example. One of the most detailed studies of natural selection involved the coevolution of rabbits to the virus that causes rabbit pox (Myxoma) in Australia in the 1950’s. I could go on, but I think you get the picture. In fact, measuring natural selection in the wild has become a small cottage industry within evolutionary biology.
As with anyone who’s made a new, path breaking discovery, some of his original ideas turned out to be wrong. The foremost thing that Darwin got wrong was in the process by which offspring resemble their parents. Darwin knew that his theory of natural selection required offspring to have features that resemble their parents, and he did marshal a mountain of data showing such a relationship for many different types of traits.
However, Darwin had no understanding of genetics or the true mechanisms by which this relationship holds. Like most biologists of his generation, blending inheritance was thought to explain the resemblance of parents and their offspring. Gregor Mendel was conducting his experiments on inheritance in peas at the same time that Darwin and Wallace were developing their ideas on natural selection, but the implications of Mendel’s work for understanding genetic inheritance would not enter the scientific community until 1900. There’s a big one that Darwin got wrong.
Biological evolution is also not just about natural selection. Darwin and Wallace focused on natural selection, the demographic process that makes populations more adapted to their environment. However, a number of other processes also cause evolution to happen, namely mutation, gene flow between populations, and genetic drift. Darwin did not think of these processes because on needs a fairly deep understanding of Mendelian genetics and the correct mode of inheritance to understand them or even imagine that they might exist.
The fact that Darwin got something wrong or didn’t think of something is not evidence against evolution. It is evidence that Darwin was a practicing scientist, who struggled to understand the world around him. Scientists work on what we don’t understand, and we often get things wrong. However, science is a self-correcting endeavor, that has mechanisms to put itself back on the right path.
Science progresses by discovering new questions to ask, and by finding answers to those questions, which typically raise new questions. It also replaces poorer understanding with better understanding. Darwin was one of the absolute best at asking new questions, and finding answers to those questions. And so was Wallace. Darwin and Wallace opened a new direction of inquiry about the world around us. The fact that they didn’t get everything absolutely correct says nothing about whether evolution occurs. Scientists have amassed a huge body of data that allows us to understand the workings of evolution in the wild. And we are learning new things every day. Having just passed the 150th anniversary of the publication of Darwin and Wallace’s first ideas about natural selection, scientists should be proud that we are still discovering new processes that further our understanding of the causes of evolution far beyond what Charles Darwin and Alfred Wallace imagined.