Every now any then, evolutionary science gives you a good kick in the obvious.
Normally in the animal kingdom, the bigger you are, the better chance you have of reproducing. If you’re a big snow crab or a large lobster, you’ve got a better chance of fighting your way to finding a successful mate.
If you’re a really huge cod and lay hundreds of thousands of eggs, there’s a better chance some of your progeny might actually live to adulthood.
But what if the tables are turned? What if you actually ended up having a better chance of success if you were physically smaller?
Here’s a snippet from a news release sent out by the Smithsonian Tropical Research Institute — and, while you may not be even in the least interested in the fighting conch, Strombus puglis, it’s worth considering. (And stay with me here: it’s easier reading than other articles from the journal “Proceedings from the Royal Society B.” I might have gone on about “Annual reversible plasticity of feeding structures: cyclical changes of jaw allometry in a sea urchin” or “Static antennae act as locomotory guides that compensate for visual motion blur in a diurnal, keen-eyed predator” instead. So think yourselves lucky.)
“The first humans to pluck a Caribbean fighting conch from the shallow lagoons of Panama's Bocas del Toro were in for a good meal. Smithsonian scientists found that 7,000 years ago, this common marine shellfish contained 66 per cent more meat than its descendants do today. Because of persistent harvesting of the largest conchs, it became advantageous for the animal to mature at a smaller size, resulting in evolutionary change,” the release says.
The concept is called “unnatural selection,” and often is connected to species that are the subject of high-intensity, size-based fishing.
There have been other studies that have suggested that size-based harvesting can skew populations. Years ago, work on dungeness crab indicated that smaller males were becoming sexually mature faster, and were becoming more successful than their larger, trappable brothers — primarily because they were too small to be legally retained.
That’s where the kick in the obvious comes in: if being big becomes an evolutionary handicap (because larger members of a species are trapped, collected and removed from the ecosystem as that thing we call “dinner,” sooner or later, smaller members of a species are going to become successful. Something along the lines of Erasmus’ “in the land of the blind, the one-eyed man is king.”
And it only makes sense that such unnatural selection can become a sort of self-fulfilling prophecy.
After all, if you’re a small male snow crab and you successfully reproduce, you’re more likely to be passing on genetic information that small is good.
The interesting thing that the researchers pointed out about the Panamanian conch is that, in the case of that shellfish, the fishing was not intensive: all of the large conch were not specifically targetted and harvested in a short-term fishery. Instead, the larger conch were filtered out in a fishery that spanned some 1,500 years: it was a far more gradual change, but a significant, specific man-made change just the same.
It’s a clear argument for an entirely different kind of scientific theory: Newton’s third law of motion — “for every action, there is an equal and opposite reaction.”
The interconnectivity of ecosystems is something we like to claim we understand when we make all sorts of broad-brushstroke decisions about harvesting wild species. Problem is, the changes crop up after the fact — even when they are penetratingly obvious from the outset.
Russell Wangersky is The Telegram’s
news editor. He can be reached by email at firstname.lastname@example.org.