After Bret Weinstein and Heather Heying resigned from The Evergreen State College under trying circumstances, Bret started a Patreon site and a YouTube channel in which he discusses evolutionary biology. As I mentioned in a post yesterday, Weinstein has been claiming in some of his onstage conversations that modern evolutionary theory has made no progress since the publication of Richard Dawkins’s book The Selfish Gene in 1976. And I discussed why I didn’t think that was a fair criticism, suggesting that Weinstein might be unaware of the progress that’s been made in the three areas he singled out as stagnant: speciation, sexual selection, and the correlation of diversity with latitude.
In this 9-minute video, Bret argues not only that evolutionary biology is stagnant, but its central paradigm—evolution via natural selection—is lacking a very important part.
As he argues, “The most important unanswered question, at least in evolutionary biology, has to do with where the power of evolution comes from.” He claims that the standard story that random mutations (mostly bad but occasionally good), winnowed by selection, doesn’t come “anywhere close to explaining how a shrewlike animal becomes a batlike animal by having membranes and bones extended in its hands, that become wings”. He says that “There’s a flaw in the story that surrounds the question, ‘How do mutations alter the morphology of one creature so that it can take on a different ecological role?'”
Listen to Bret’s answer.
Bret’s answer to the question that he sees as heretofore unanswered is the evolution of “explorer modes,” which he defines as “mechanisms in which an evolved clade [related group of organisms] explores design space, so they can discover opportunities that it would not find by accident.”
What does this mean? He argues that an “explorer mode” gives natural selection a way to create new types of organisms in a way “that would not be discovered by accident”. I presume he means here that there are many organisms in which a combination geographic isolation “by accident”—e.g., via haphazard colonization of a new area such as an island, or separation of populations by geographic barriers or continental drift—followed by random mutation and selection, is a combination simply inadequate to explain evolution.
But why not? Bret argues that mutation and selection are “not powerful enough to account for the vast array of niches that have been discovered by species over the history of life.” But he gives no calculations to show this; he’s merely hazarding a guess, a guess without any empirical support. In other words, he’s making up a problem that hasn’t been shown to be a problem.
So what Weinstein is positing is not that animals invade new niches by accident and then evolved new species and morphologies, but that there are evolved “explorer modes” built into organisms by natural selection that help them find new niches.
He gives two examples of this. The first is Pacific salmon, which home to their natal streams, returning to fresh water from the sea every couple of years to breed. Very rarely, a salmon might invade a new stream, and, if that stream was devoid of other salmon, it would find a bonanza: lots of food and empty space. The descendants of that first explorer would thrive, and eventually, perhaps, become sufficiently genetically different that they’d constitute a new species.
The invasion of a new stream by a few stray individuals surely must have happened in evolution, but Weinstein insists that this is not an accident—a case of wayward salmon losing their way—but that they have evolved to explore. And that evolution was prompted by a form of selection that, while risky, has big payoffs: finding a new stream. He sees this form of selection as general, and essential to account for Earth’s diversity.
But there are big problems with this scenario. First, it applies only to changes in behavior: migration or wandering behavior. It does not and cannot explain the difference in morphology between a bat and its ancestor, or any differences between species in morphology, physiology, and so on. Those still require random mutation and selection. Even if his mechanism operates—and I don’t think it does in the way he posits—it only explains how an animal finds a new habitat in which garden-variety mutation and selection then proceed to work, and to create new morphology. The morphological differences evolve by same-old same-old.
But are “explorer modules” even plausible? Perhaps occasionally, but surely the cost of leaving your habitat and finding another one must frequently exceed the chance of finding a new, open niche in which you can thrive. At present, for instance, Pacific streams are pretty much tapped out for salmon residents, so invading a new stream would have no payoff. In other words, even if “explorer modules” were advantageous, they are self-defeating. Selection would favor not exploring.
Weinstein, then, hasn’t shown that the payoff from an explorer mode would generally exceed the costs. Yes, an individual could hit the jackpot, but what about all those individuals that don’t? If the average cost of exploring exceeds the benefit of a rare payoff, then exploring won’t evolve.
Further, and importantly, if these modules were favored by selection, you would see many more animals exhibiting them than do. If all salmon had evolved explorer modes, then you’d see many, many salmon leaving their streams and trying to find new ones. You don’t see that: migration is rare. This supports the idea that, in salmon, colonization of new streams is an accident: a bug rather than a feature. Weinstein has failed to explain the infrequency of exploring.
It’s clear that Bret thinks that “explorer mode” is something that is selected for. As he says, “It stands to reason, then, that selection would discover a mechanism that searched design space, rather than finding opportunities in design space haphazardly.” That’s clearly a claim that exploring is somehow built into an organism’s genes. Further, he says, it creates new morphologies faster than the conventional scenario. But we don’t know that the conventional scenario—wandering followed by the conventional mutation + selection—is too slow to create life’s diversity.
Now there are animals in which “exploration” is ubiquitous and a general phenomenon. One is the ballooning of spiders, in which spiderlings, when hatched, throw out a thread of silk to waft them away on the wind. Another is, of course, the dispersal of dandelion seeds via their fluff. Still another is the migration of young male lions away from their pride.
But these phenomena aren’t what Bret means by “explorer mode”, as they are ubiquitous in the species, and have evolved because finding a new habitat is essential if you are to avoid competition and thus leave your genes. And even in these cases, the difference between species in morphology—why a tiger is striped but leopards are spotted—evolves by conventional natural selection. Yes, a different habitat may be involved in creating that selection, but there are many ways that animals can find themselves in different geographic areas by accident. I don’t think that finches colonized the Galápagos island because they were showing their evolved tendency to explore. Most finches heading out over the Pacific, or blown over the ocean, would perish.
The other example Bret uses is human consciousness. We evolved consciousness, he says, so we can explore new ways of life. But this is not at all analogous to a salmon evolving “wandering behavior” because that kind of behavior helps you invade an empty niche. True, consciousness helped us invade a “cognitive niche”, and that may have had ramifications for the evolution of other parts of our body, like our brains or our hands, but you don’t need to invoke a new type of evolution to see how consciousness (or big brains) might have evolved. They could have evolved simply because they give individuals a reproductive advantage. There was no real “exploring” here analogous to Weinstein’s scenario of salmon taking risks because they could have big payoffs, as there was no risk involved in acquiring a mutation that made you more conscious. So I’ll ignore that scenario.
In general, I think Bret advances a thesis here that a.) isn’t needed, because there isn’t really a question that needs answering (nobody is worrying, “Hey, evolution was faster than mutation and selection could create”), b.) has its own problems, as payoffs have to be greater on average than the costs of exploring, c.) fails to explain why exploring is so infrequent, and d.) completely fails to account for the morphological differences between species that, he says, prompted this theory.
I think Weinstein’s explanation, then, is misleading: certainly so if it’s a general one intended to fill an important lacuna in evolutionary theory. Weinstein hasn’t shown that such a lacuna exists. And if there’s no need for such a theory because neo-Darwinism hasn’t been shown to be insufficient to explain diversity, then invoking “explorer modes” is an exercise without a motivation.