Friday, December 26, 2008

Connecting North American newts and Australian dolphins through mediocrity

Two interesting posts from Not Exactly Rocket Science: one on the evolutionary arms race between sometimes-poisonous newts and sometimes-immune garter snakes here on the West Coast, and another on how the recently-discovered tool use by Australian dolphins seems to be learned along matrilineal lines and also a recent invention by dolphins.

In the first post, newts in some areas of the West Coast have evolved poisonous skins as deterrent to predators like garter snakes, and snakes have evolved immunity that sometimes completely defeats the poison. Interestingly, in some places there's no poison and no immunity. One possible explanation for this is that we're at a special moment in time where the evolutionary arms race hasn't yet started in all geographic areas, but I doubt it. My speculation is that the time period the two species have coexisted is far longer than the period needed to go through the arms race (or even more likely than independent evolution, that genetic diffusion from areas further along in the arms race would spread quickly to new areas).

If we apply the Mediocrity Principle and assume we're not seeing a special moment in time for newts and snakes, then something else must explain the geographic difference. Time for more speculation!

I wonder if there's an alternative cyle: 1. newts develop toxicity. 2. snakes develop overwhelming immunity. 3. newts completely lose their now-useless toxicity. 4. snakes completely lose their now-useless immunity, and the cycle starts over.

Instead of the British Columbia newts evolving behind the rest, they may just be at a different point in the cycle.

Total guessing, but fun in a geeky way.

And then there's the second link, about dolphins who use marine sponges to protect their snouts while digging out hidden fish from the muddy sub-surface (one of the full articles is here). One in nine dolphins use sponges, although one in two dolphins use them in the deeper waters. The dolphins only appear to learn from their mothers, and males rarely stay with their mothers long enough to learn the technique. Finally, genetic analysis suggests that a recent "Sponging Eve" invented the technique and passed it on to her descendants now using it.

That only 11% of the females in the area use the technique doesn't sound all that impressive, until you consider that half use it in the deep water, that Sponging Eve was a recent ancestor, and that a lot of the male descendant dolphins are also indirect beneficiaries. Researchers observed 41 dolphins using the techniques, so Sponging Eve seems to have done pretty well.

But how does this successful technique relate to the Mediocrity Principle? Dolphins have been big-brained for millions of years longer than hominids, yet we just happen to observe the technique within a few decades of when it was first invented?

I speculated at some other science blog that the technique was only marginally useful, but this information suggests otherwise. The Mediocrity Principle isn't absolute, and sometimes weird things happen.

On the other hand, something else might keep the sponging technique from persisting over the long term. Maybe the dolphins get too good at exposing the fish, or use up too many of the sponges that are suitable tools. Instead of a steady-state equilibrium, it's more like the newts and snakes. The dolphins over-exploit their environment and either the tools or the fish disappear from accessible habitats, and then the dolphins forget the technique until it's reinvented.

It's all guessing, but it satisfies the Mediocrity Principle. Fortunately, it's also easily tested - just wait a century or so and see if the dolphins over-exploit the environment.

(And with that, I may be offline for awhile, so Happy New Year everyone.)

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