Evolution: neutral theory (Evolution)

by dhw, Wednesday, December 09, 2020, 14:15 (1443 days ago) @ David Turell

QUOTE: Kimura posited that most of the variation between organisms is neither advantageous nor disadvantageous. Consequently, most of the variety we see isn’t a product of the hidden hand of selection but rather of luck.

QUOTE: "This kind of chance evolution is the purview of neutral theory, the historically controversial idea that “survival of the fittest” isn’t the only, or even the most common, way that species change, split or disappear.”

DAVID: It seems to me since natural selection acts only on what it is given to act upon that the theories are compatible. It doesn't explain speciation but it dos explain variations that can appear.

The first quote only mentions variations, but the whole article lays emphasis on luck and randomness, and the second quote simply creates a false dichotomy, which can be applied to speciation as well as variation. Randomness creates different conditions (unless you believe your God organizes every change), but the process of adaptation is not random and is geared to the ability (or inability) to survive in those conditions! In my own theory, this also encompasses IMPROVING the ability to survive (innovation). And so random conditions and “survival of the fittest” are partners in the process, not alternatives, and variations survive because they are advantageous in whatever conditions have randomly arisen. The interplay is well illustrated if we slightly change this example:

QUOTE: "Imagine a population of 10 birds: one red, one green and all the rest brown. These colors aren’t harmful or helpful, so all the birds have the same chance of reproducing. Then a tornado kills six of the brown birds, purely by chance. Now half the population is brown, a quarter is red and a quarter is green. A random event caused a major shift in diversity. That’s genetic drift.

This is a special instance of variation, but a far more likely example would be an environment in which brown provides better camouflage against predators. The conditions may be a matter of luck, but the survival of the brown birds is not random. The “hidden hand of selection” is completely out in the open: the colour improves (is advantageous for) the brown birds’ chances of survival. Again, we have luck, advantage and the survival principle working together.