Darwinism vs. convergence: Another round to convergence
|April 3, 2011||Posted by O'Leary under Evolution, Darwinism|
Why doesn’t this The Scientist feature, with Richard P. Grant interviewing Yale Passamaneck (March 31, 2011) fill me with confidence about the long slow march of Darwinian evolution?:
What can a clam-like creature tell us about eye evolution? Quite a bit, as it turns out. We ran a news article at the beginning of the month, on the finding that brachiopod, or lamp shell, embryos have eyes that are more closely related to those of vertebrates, than of their spineless cousins.
Here’s the original article, where Amy Maxmen explains “Eye evolution questioned: Invertebrates with vertebrate-like vision challenge the idea that the two groups of organisms have distinctly different visual receptors” (1st March 2011):
In 2004, biologists hypothesized that an ancestor of both invertebrates and vertebrates sensed light with rhabdomeric receptors — but also had ciliary receptors embedded deep within their brains, where they have been found in marine worms and bees, and might have sensed patterns, such as the lunar cycle. As vertebrates evolved, ciliary receptors theoretically migrated towards the body surface and became the primary tools for sight.But the new results challenge this scenario with the discovery of surface ciliary photoreceptors in the larvae of marine invertebrates called brachiopods (Terebratalia transversa), shelled creatures that have been around for 540 million years. Passamaneck and his colleagues identified the expression of a gene characteristic of ciliary receptors, ciliary-opsin, in cells in the light-sensing “eyespot” of larval brachiopods.
Is “diverged from a common ancestor” more plausible than “aiming at a common target”? Why?
Why is it beginning to seem more and more like the real story is Darwinism vs. evolution?