Devolution isn’t a thing


Yesterday I volunteered as a Meeting Mentor at the AbSciCon meeting. It’s not a big commitment; essentially all you have to do is hang out with a high school student for half a day, going to talks and enjoying the meeting as you normally would.

During a break, I was chatting with my mentee about Betül Kaçar’s research, and he surprised me by pointing out that (as he put it), “Devolution isn’t a thing.” The student I was paired with is interested in physics and space exploration, but his comment showed an insight that not even all professional biologists really own. From what I’ve seen, it’s an insight that very few creationists own.

William Dembski, for example, says

Functioning eyes turning into functionless eye nubs is a devolution from complexity to simplicity.

Michael Behe dismisses the evolution of antibiotic resistance (which I wrote about here) as devolution. Denyse O’Leary says

Most of the time, when we think of evolution, we mean mechanisms for the growth of complex new information.

Maybe that’s what she means. It’s not what biologists mean. She continues,

Yet, in the history of life, some forms survive while — or even by — losing information (devolution).

Casey Luskin says

A scientific study published a few months ago reports that the marine stickleback (the ones with the armor plates) came before freshwater sticklebacks (the ones without armor-plating), meaning that this is not an example of the evolution of a new function, but an example of loss-of-function, or what one might term devolution.

One might, if one didn’t know what one was talking about.

The idea of devolution betrays a widely-held misconception about how evolution works. If devolution is evolution in the ‘wrong’ direction, then there must be a ‘right’ direction. There isn’t. Evolution is heritable change over time; it doesn’t have an inevitable, built-in direction. It does what works at the time. If that means getting bigger, or smarter, or more complex (in a particular population in a particular environment), that’s the direction the population will evolve. Sometimes it means getting smaller, or dumber, or less complex. That’s evolution, too. Parasites often evolve reduced complexity. Animals that live in caves sometimes lose eyes and pigments. Birds on islands sometimes lose the ability to fly. These are all examples of evolution. Devolution is not a thing.

Why don’t the cdesign proponentsists share my mentee’s understanding? It’s not that they haven’t been told; in the same post by Denyse O’Leary I quoted above, she quotes a Scientific American article by Michael J. Dougherty:

From a biological perspective, there is no such thing as devolution. All changes in the gene frequencies of populations — and quite often in the traits those genes influence — are by definition evolutionary changes.

Another misconception is that increasing complexity is the necessary outcome of evolution. In fact, decreasing complexity is common in the record of evolution. For example, the lower jaw in vertebrates shows decreasing complexity, as measured by the numbers of bones, from fish to reptiles to mammals. (Evolution adapted the extra jaw bones into ear bones.) Likewise, ancestral horses had several toes on each foot; modern horses have a single toe with a hoof.

Although she calls this ‘obfuscation’, it’s exactly right. Evolution toward reduced complexity is no less evolution. Insisting that only increases in complexity count as evolution allows creationists to dismiss any example of evolution that involves loss of function as ‘devolution’. Coupled with their refusal to admit evidence of gains of function, it allows them to dismiss pretty much everything: if it’s clear evidence of a gain of function, we need to define gain of function more narrowly. If it’s not, then it’s just devolution.

But devolution isn’t a thing.



  1. usagichan says

    Devolution is a thing , just not the thing that Dembski, Behe and Liskin think it is.
    I remember a lot of talk about devolution as a compromise when the Scots were asking for independance. Nothing to do with biology though!

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