Darwin Day Brings out Evolution’s Friends and Foes

As we celebrate another Charles Darwin birthday on February 12, friends of Darwinian evolution will pick up on things he got right, and enemies on what he didn’t. Darwin was a prolific, wide-ranging thinker and writer, so it’s no surprise that a few things he wrote don’t ring true a century and a half later.

We have a recent New York Times story “Darwin was Wrong about Dating”, berating Darwin for saying that women were less enterprising or ambitious than were men but more nurturing. On the other hand we have psychologist Allen Frances writing in the Huffington Post that Darwin was the greatest psychologist of all time because, among other things, he realized humans were animals and driven by animal instincts.

Darwin surely wasn’t the first to recognize that we bear a relationship to other animals – Carl Linnaeus even categorized us as mammals in the previous century. It couldn’t have escaped notice that we humans share behaviors such as sex and breast feeding with our mammalian relatives.

People can praise or dispute the peripheral aspects of Darwin’s writings for years to come. What’s unlikely to change is the understanding that he made a giant leap for science when it came to understanding why evolution better described the natural world than a creationist picture. And Darwin came up with a plausible mechanism in natural selection.

Several readers posting comments on a previous Lightning Rod entry questioned whether Darwin was first to think of natural selection. It’s likely that others considered the idea, and it’s known that natural selection was discovered independently by Alfred Russell Wallace. But Darwin was first to state the idea clearly and make a solid case for it from hundreds of observations of the natural world. His book, On the Origin of Species was groundbreaking.

It’s written for regular people and therefore well worth reading. I’m also grateful to the person who sent me a copy of Darwin’s Century by Loren Eiseley. Eiesley was a beautiful writer and conveyed the context of Darwin’s idea.

Eiseley dispels one misconception that’s rampant among scientists, which concerns how Darwin’s picture of evolution differed from that of his French predecessor Jean-Baptist Lamarck. Biologists often refer to Lamarckian evolution as a process by which living things can evolve by passing on acquired traits – say, a giraffe having longer-necked offspring as a result of a lifetime of neck-stretching toward higher leaves.

But according to Eiseley and historians of science I’ve interviewed, the question of passing on acquired traits was still in debate in Darwin’s time. Nobody, even Darwin, knew for sure what kinds of traits could be passed down. That would have to wait for Mendel’s laws of genetics to become widely known, and even now the understanding of inheritance is changing.

Lately, scientists have been finding a number of special cases in which acquired traits can be passed down through epigenetics – a process by which chemical “tags” stick to DNA and influence its function. In lab rats, the effects of certain kinds of environmental chemicals can show up two or more generations down the line.

None of which reflects badly on Darwin, because his version of evolution was vast leap beyond Lamarck’s for a reason that has nothing to do with giraffes or acquired traits. Lamarck saw evolution as a ladder, with humans at the top – actually Frenchmen were at the top. Every species of creature had sprung from a different origin of life at a different time. Monkeys, for example, got a later start than we did, so they’re still monkeys now, but they are on the road to becoming Frenchmen.

Darwin’s extensive observations of nature and his ability to put humanity into a natural context brought us a different vision, with a common origin of life from which the various plants, animals and other living things branched out. This view has been backed by DNA, which shows we’re related to everything from mushrooms to bacteria.

And so it seems unlikely we’ll ever see a revival of Lamarck’s hierarchical version of life – or a creationist version, for that matter. But neither does Darwin have the final word. He should be appreciated for making an enormous scientific advance, but the state of our knowledge is still evolving.