What, the “single best idea anyone ever had” (philosopher Daniel Dennett on Darwin ) is now comparable to gravity? Experimental physicist Rob Sheldon would take issue with that.
Yes, a psychologist seems to think Darwinian natural selection is indeed a force of nature like gravity:
Natural selection, one of the fundamental processes of evolution, has something in common with gravity: A public relations problem. At one level of analysis, natural selection, like gravity, looks like a chump. When you’re looking up close at the tiny bits of stuff that go into making humans—the sequences of DNA that constitute the human genome—and how they came to be arranged in the manner that they are, natural selection doesn’t seem to have done very much. Other evolutionary processes, such as mutation, migration, and drift, seem to have exerted far more powerful influences on our genomes. For that matter, distinctly non-evolutionary events—one-off famines, freezes, floods, and fires—can exert a far more powerful influence on the fate of a species at any given point in time than natural selection can. However, when you zoom out and look at evolution from a high-altitude vantage point, natural selection is the only evolutionary force that matters at all. Michael McCullough, “Evolution’s Gravity: A Paean to Natural Selection” at Nautilus
A perfect item for Nautilus! Rob Sheldon replies:
Michael McCullough, a psychologist, seems to be in a state of what psychiatrists refer to as “physics envy” (a desire to pretend that what they do is some kind of physics). He tries to tell us that Darwinian evolution (aka natural selection) is a force of nature just like the other four elementary forces (strong force, weak force, electromagnetism, and gravity). Not only does he get the physics wrong, he gets the biology wrong. And to top it off, he also gets the physics-biology analogy completely upside-down! It is a good thing he’s an evolutionary psychologist writing for a mainstream blog.
Physics: It is true that the four elementary forces have a wide range of strengths, though Michael would be advised to learn the beauties of scientific notation. It is not true, however, that 100Mass => 10Force, as he states. The equation is F = GMm/r^2, so the force is directly proportional to the mass, not proportional to the square-root of the mass.
And biology? It is true that natural selection will remove non-viable mutations. It is not true, however, that natural selection will provide the slightest help in improving the genome. This job is traditionally assigned to random mutation, which unfortunately, has proven unequal to the task. (See, for example, Edge of Evolution.) So McCullough really should have entitled this piece “A Paeon to Random Mutation.”
Analogy: After these slight mistakes (which nonetheless typefy the carelessness characteristic of profession) we get the really big error. McCullough points out that on small scales, gravity is weak, but on large spatial scales, gravity is large.
He doesn’t know why, he just sees it as a symbolic relationship that can apply to evolution: On short timescales, evolution is weak, but on large timescales it is strong—like gravity. This is a mistake for several major reasons.
a) space is not time. (No, I don’t want to read McCullough’s take on Special Relativity, he’s already bombed his freshman class on Newtonian gravity.)
b) The reason gravity is weak at small scales and big at big scales, is that it can never be shielded. The first three forces (weak and strong forces, electromagnetism) are always shielded. We won’t get into the strong force and asymptotic freedom but electricity has + and – charges, so negative charges balance out the positive charges or “shield” them. Some would say it “must be shielded” because electrons on the other side of the galaxy would arrive to do the job if our local solar system didn’t have enough.
But gravity doesn’t have any “negative” mass particles; there is nothing known that can shield it. That means its strength just grows and grows as you add more mass. There is nothing magic or symbolic about gravity, it is the simple fact that anti-gravity (peace, cosmologists), doesn’t exist.
c) Evolution is supposedly a progressive ratchet that operates in only one direction in time. RM creates novelty, NS filters out the bad stuff, leaving only the good novelty. Rinse and repeat. Isn’t this a good analogy to gravity?
Actually, no. First, RM doesn’t produce any good novelty, only bad novelty. The ratchet does operate, but only downward. Admittedly, there is a lot of hairy math involved but “random” to a physicist means “entropy” and entropy can never produce progress. Never. (Granville Sewell offers mathematical analyses of this point.)
“Mutation,” to a biologist, means a nucleotide substitution in DNA or a peptide substitution in a protein. And given the 64 different possible 3-nucleotide DNA codons with 22 different meanings in protein production, mutations must explore a phase space of a trillion trillion trillion trillion trillion trillion options before finding a useful one (see Douglas Axe’s papers). Failure isn’t just an option, it’s guaranteed.
Given that mutations can be both good and bad, we are back to electricity with its positive and negative charges. Unlike gravity, where every step is positive, evolution is like electricity with an average over good and bad steps. But unlike electricity, the bad steps outnumber the good steps by a large margin. So rather than being the weakling on Particle Beach that becomes the Atlas of the solar system, evolution is the bully on Cellular Beach that becomes extinct in the ecosystem.
But don’t archaeology and geology demonstrate that evolution doesn’t become extinct?
No, archaeology demonstrates that life doesn’t become extinct, which proves that evolution cannot explain it. McCullough’s title should have been, “A Eulogy for Random Mutation.”
Rob Sheldon is the author of Genesis: The Long Ascent.
See also: A physicist looks at biology’s problem of “speciation” in humans
At Nautilus: Psychology needs evolutionary psychology
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