Why are we trying to “demonstrate” microevolution?
|November 26, 2015||Posted by News under Evolution, Intelligent Design|
From Science Daily:
A new study shows that larger eye size is the source of a sizable reproductive advantage for a tiny freshwater crustacean, Daphnia obtusa. The research provides hard data for eye microevolution that, until now, were lacking.
Huh? Hard data were lacking, for something as obvious as microevolution? It gets better:
The focus of the research team was a tiny freshwater crustacean, Daphnia obtusa Kurz. Just 1 to 2 millimeters long, Daphnia would be hard to spot except for one distinguishing feature: its black eye, which is large for its body size.
“A big eye is costly to maintain, because any kind of neurological tissue, including retinal tissue, is energetically demanding relative to other kinds of tissue,” Dudycha says. “And we also know there are organisms, like blind cave fish, that once had eyes and have moved into environments without any light at all, and they lose their eyes, which wouldn’t happen unless there was a cost to having an eye. So if there is a cost to keep having eyes, there needs to be some kind of benefit, and we were wondering if we could measure that benefit.”
The correlation was clear: an increase in eye diameter of 20 micrometers, which is about one standard deviation of the mean diameter, translated into about one more egg beyond the average of about six.
More generally, doesn’t everyone take microevolution for granted? It’s not clear that it is even a “thing,” that is, something to think about …
In a constantly changing world, it must occur. But when does it make much difference in the long run?
Remember Darwin’s finches’ beaks? The famous changes that were supposed to add up to a new species every two hundred years turned out to be caused by hybridization. They tended to reverse themselves when the ecology altered. We should regard such changes and changes back as normal within a species.
Yes, Darwin’s “fittest” survive (that’s a tautology; it’s simply what “fittest” means). But if the conditions that make a given life form more fit than others are constantly changing, the fittest may be least likely to undergo an irreversible evolution in one direction, not the most likely to do so.
Question: Has microevolution via Darwinism (natural selection acting on random mutation) ever been shown to result in complex, co-ordinated changes across a number of systems in an organism, changes that result in major new capabilities? Let’s hear a demonstrated example.
No, macroevolution is asserted, not demonstrated. Because, as Richard Dawkins said, Darwinism is the only known theory that is in principle capable of explaining certain aspects of life. (p. 287, Blind Watchmaker, 1986).
As it happens, that is no longer true. A number of non-Darwinian mechanisms can account for significant change.
Law prof Phillip Johnson, as so often, has it right about why Bimbette’s vast TV audience “believes in” “evolution” (Darwin-style):
To make the story look better, the National Academy of Sciences improved on some the facts in its 1998 booklet on “Teaching about Evolution and the Nature of Science.” This version of the story omits the beaks’ return to normal and encourages teachers to speculate that a “new species of finch” might arise in 200 years if the initial trend towards increased beak size continued indefinitely. When our leading scientists have to resort to the sort of distortion that would land a stock promoter in court, you know they are having trouble fitting their evidence to the theory they want to support.
Or, rendered in the vernacular, shuddup, cringe, and listen to Bimbette. And many will. A few continue to subscribe to critical thinking.
Here’s the abstract:
Several studies of eye morphology have analysed macroevolutionary patterns in the diversity of eyes, and although these studies are often linked to environment or behaviour, they provide only indirect evidence of selection. Specific data to show the microevolutionary potential for adaptation by natural selection in eye morphology have been lacking. We document directional selection on eye size, an important determinant of visual capabilities, in a wild population of the freshwater microcrustacean Daphnia. We show that even slight changes in eye size may have major consequences for fitness. An increase in eye diameter of 19.9 μm – slightly more than one standard deviation – is associated with an increase in clutch size of one egg, or an increase of nearly 20% of the mean clutch size. Furthermore, relative eye size is genetically variable and thus could evolve in response to the observed selective pressure. We conclude that selection on incremental variation in eye size may have led to differences observed on broader taxonomic scales. (paywall) – C. S. Brandon, T. James, J. L. Dudycha. Selection on incremental variation of eye size in a wild population of Daphnia. Journal of Evolutionary Biology, 2015; 28 (11): 2112 DOI: 10.1111/jeb.12711
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