This Week in Evolution

This week’s paper, “Evolvability and hierarchy in rewired bacterial gene networks”, was suggested by Joel Lopez.

Randomly changing parts in a machine often breaks it. “Intelligent design” nuts claim this is also true of living things and that this is somehow evidence for design. The argument is nonsense – just because we had distant ancestors small enough that they didn’t need lungs doesn’t mean we can survive without them -- but is the claim even true? If a genetic change is big enough to have some effect, is it likely to be lethal? Or do many mutations preserve basic functions, just increasing or decreasing fitness (survival and reproduction) under particular circumstances?

Continue reading "Gene networks: evolved not designed" »

Posted by R. Ford Denison at 02:48 PM | Permalink | Comments (2)

Each generation tends to resemble the previous one, so evolution of whales from land animals, for example, took many generations. One limitation on the power of natural selection is that each generation must be viable. Some creationist suggested that the problem is analogous to "evolving" a sentence one letter at a time to make a substantially different sentence, while requiring that each intermediate step be a valid sentence. The Mosquito Eater has solved this challenge. Cool!

But we no longer need to rely on imperfect analogies to biological evolution. Molecular tools now make it possible to explore multistep evolution experimentally, as I discussed in an early post.

Posted by R. Ford Denison at 05:09 PM | Permalink | Comments (0)

This week’s paper, "Emergence of novel color vision in mice engineered to express human cone pigment", by Gerald Jacobs and colleagues at UC Santa Barbara and Johns Hopkins Medical School (Science 315:1723), is yet another experimental study that increases our understanding of how repeated cycles of natural selection, each producing a fairly small change, can lead to adaptations that may seem irreducibly complex.

Most humans have three different photopigment color sensors, as do our closest relatives. Many other mammals, including mice, have only two. Three-color vision is useful for many purposes, from identifying higher-protein leaves to eat (Nature 410:363) to telling which wire to cut to disarm the nuclear bomb buried under the stadium. But eventual usefulness isn’t enough for a trait to evolve. If a series of steps is required, each step must be beneficial, or at least not lethal. Such a series of steps has been worked out for the evolution of optically sophisticated eyes from light-sensitive spots (Proc. Roy. Soc. B 256:53), but what about color vision?

Continue reading "Evolution of color vision: transgenic mice see red" »

Posted by R. Ford Denison at 04:15 AM | Permalink | Comments (7)

A reader asked an interesting question about the difficulty of coordinated evolution of groups of genes. Although I welcome comments and questions, I won't usually have time for detailed responses. and I'd already discussed one paper this week. But then Huxley brought in a recent issue of Nature he'd been chewing on, and there it was: "Empirical fitness landscapes reveal accessible evolutionary paths" (Nature 445: 383-386). So I guess I should take this dog-given opportunity to talk about the evolution of multiple interacting genes. The Nature paper is a review article with no original data, so isn't eligible for my regular weekly paper discussion, but maybe it's OK as a bonus paper, especially since the most interesting papers it discusses were published within the last year and they do contain original data.

The exciting thing about these papers is that people are starting to use molecular methods in experiments that solve "you can't get there from here" problems in evolutionary biology.

Continue reading "Experiments with "fitness landscapes" explain evolution of interacting genes" »

Posted by R. Ford Denison at 03:57 PM | Permalink | Comments (9)