No, we don’t assume that evolution must increase complexity

Ryan Gregory at Genomicron mocks an inane press release about a supposedly new evolutionary theory – the idea that endosymbionts will lose genes when their hosts or other microbes in their community can provide the functions of those genes. This is an old and widely established idea, so why anyone with any knowledge of recent evolutionary biology would play up this idea as novel is beyond me.

Sadly, the ignorance isn’t limited to whatever flack wrote the press release – at least one of the scientists involved is portrayed as the same misunderstanding of evolution that many creationists have:

“A common assumption about evolution is that it is directed toward increasing complexity,” said Erik Zinser, associate professor of microbiology. “But we know from analysis of microbial genomes that some lineages trend toward decreasing complexity, exhibiting a net loss of genes relative to their ancestor.”

Okay kids, repeat after me: evolution is not based on an assumption of increasing complexity. Increasing complexity (leaving aside the fact that the word complexity is terribly vague and non-quantitative) often happens in evolution, but we don’t assume that this is what should happen.

UPDATE: It could be that I’m being unfair to Dr. Zinser, that he’s being selectively quoted in a bad way by the same person who wrote the rest of the misguided press release. If that’s true, then all of my disdain is reserved for the anonymous press release writer.

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