Efficiency is not what matters most in evolution

In animals, saving energy when moving around is favored by natural selection. An evolutionary biologist and two anthropologists have now found that the stealthy gait of cats is energetically costly, concluding that there are other aspects of locomotion than saving energy that are under selection.

From an MSNBC report on a an article about the walking mechanisms in cats:

"It is usually assumed that efficiency is what matters in evolution," Daniel Schmitt, an evolutionary anthropologist at Duke University, said in a news release about the latest dog vs. cat research. "We've found that's too simple a way of looking at evolution, because there are some animals that need to operate at high energy cost and low efficiency."

No. That's not what is usually assumed to matter in evolution. Yes, it is one of many things that matter, but to say it like this is like saying "It is usually assumed that size is what matters in evolution. We've found that's too simple a way of looking at evolution, because there are some animals that need to be quite small." Or, "It is usually assumed that vision is what matters in evolution. We've found that's too simple a way of looking at evolution, because there are some animals that do not have vision at all."

What do the researchers say in the paper itself? From the article in PLoS ONE: Whole Body Mechanics of Stealthy Walking in Cats.

The assumption that energetic economy is the most important target of natural selection underlies many analyses of steady animal locomotion, leading to the prediction that animals will choose gaits and postures that maximize energetic efficiency.

Well, if you say so. Then I say you need to reexamine your assumptions...

.. which is in fact what they are doing exactly. In other words, I don't have any problems with this paper. On the contrary, they argue against what is apparently a common assumption. However, I do think it should be obvious that energetic cost is not the most important target of natural selection. Good thing that they have now shown that it isn't alyways so.

Kristin L. Bishop, Anita K. Pai, Daniel Schmitt (2008). Whole Body Mechanics of Stealthy Walking in Cats PLoS ONE, 3 (11) DOI: 10.1371/journal.pone.0003808