Sunday, November 11, 2012

"What Darwin Got Wrong" Got Wrong

(I've already written about this.)

I really wanted to like "What Darwin Got Wrong." I am skeptical of many commonly-heard versions of natural selection, especially regarding evolutionary psychology, and Fodor is a giant in his field. However, the book is deeply flawed. The critics may be right on this one.

To recap one of the major arguments in the book, it makes the distinction between frogs "snapping at flies" and "snapping at Ambient Black Nuisances (ABNs)." The two concepts are coextensive, i.e., overlap - all flies are ABNs and vice versa, so indeed as Fodor and Piattelli-Palmarini say, there can be no causal process that discriminates between them. So we can't say "natural selection selected for" one or the other. But this is misleading.

First, these two concepts are not related in the same way that arches and spandrels are, even though the book assumes they are parallel. Arches and spandrels are not coextensive, they are different things. The property of having arches or having spandrels are coextensive, though. But we can still see a very concrete difference between arches and spandrels in the actual world. We cannot see such a difference between flies and ABNs, there is no physical difference to see.

The concepts of flies and ABNs are different of course. But does that matter? Perhaps all we need is to say that evolution selected for flies or ABNs or in general the intersection of all relevant descriptions (or perhaps say: "ABN is shorthand for fly, currently"). Descriptions matter, but not here - at least until the concepts do diverge in the actual world, for example if an ABN shows up that is not a fly. Then we can reassess.

We can, however, reassess even earlier. A major flaw in the book is the "magical power" it assumes mental processes to have, that nothing else does: intentionality, the ability to consider counterfactuals, etc. But a naturalistic, computational view of cognition avoids the problems with that. So, even in the current world where ABNs and flies are coextensive, we can look at the processes taking place in the frog's head. If we see that the representations there pick out flies very specifically, or if they look just for the properties of an ABN, we can say something about that.

And we can apply the same to the mental processes of the architect designing for arches but not spandrels. Investigation of the causal cognitive processes taking place will show that arches are being designed for, not spandrels. Architect brains are just physical systems, in a naturalistic/computational world view.

In short, we can - in principle - find out what causal processes take place, and see what is being selected for. If it is hard to find that information out, we may never know (I suspect that is the case for at least some of the evolution of human psychology), but there is still a fact of the matter. Minds can take counterfactuals into account, but when they do so, there is a causal process at work.

And it isn't just minds that can take into account counterfactuals. A chess-playing machine takes counterfactuals into account, and we might not want to say it has a mind. It doesn't matter if it does or not - what matters is what computation it does. A computation on counterfactuals can be done in a mind, or in a mindless (sophisticated-enough) machine.

Which brings us to selection in general. Natural selection for Darwin was not the only mechanism of evolution, another crucial one was sexual selection. Sexual selection happens when one organism chooses another to mate with. The best strategy is to pick the mate that increases the fitness of your potential offspring, and a good estimate of that is to consider the potential mate's fitness. This is exactly a case where counterfactuals can happen: When an organism considers who to mate with, it can run scenarios in its mind such as "X's fast running is a useful trait, our children will evade predators more easily" or even "the weather is getting warmer and warmer, Y's shorter fur will be useful to our children to not overheat." In other words, sexual selection does allow for counterfactuals to be taken into account, and it is surprising to me that this point was not made in the book, which did try to anticipate responses to its arguments. Even if natural selection falls (although as I said, I do not believe it does), sexual selection can remain, and it can have effects that mirror those that natural selection can, see the second example before - it can lead to shorter fur being selected for, which an adaptationist view would argue natural selection could account for. And it does so using the minds of the organisms, which even the authors will grant intentionality to.

Of course sexual selection is not special here. Any sufficiently sophisticated system can take into account counterfactuals in its computations, as mentioned before. In principle it could happen not just in brains but in ant colonies or entire ecosystems. (Perhaps we can define "Mother Nature" using that?) But we don't need to go to such speculative lengths, for even in plain old brains the ability to consider counterfactuals can affect not just sexual selection but other kinds of selection as well: for example, similar things can happen when choosing friends/coalition-members/etc. ("I should work together with Z, his superior strength will be useful", and this improves Z's fitness since Z can now choose from more potential collaborators).

Finally, regarding "Sobel's Sieve", where red large balls remain on top while small blue ones are let through the holes, and the question is, was color selected for or size. First, it is clear as the authors admit that size is being selected for: we can see the causal processes in play. But the point is that the causal processes are there, not if we can see them. It might be hard to see them, but that doesn't mean something was not selected for as a matter of fact. Second, the authors claim a fatal flaw in the analogy is that it is not clear what is "better" - to remain on top (prospector filtering out debris) or fall out the bottom (someone trying to filter out large undesirable objects). This supposedly shows that we do need intentionality in order to know what is being selected for. But it does nothing of the sort. The analogy is only half-done: To make it a proper analogy to natural selection, it would need to continue with our taking the ones that remained on top, mixing up their "genes" to create another generation, and repeating the process on that. In that complete analogy, it is clear that the ones on top are selected for, because the ones that fell through were discarded (and if we completed the analogy the other way, the fact of the matter would be vice versa of course). In natural selection, after all, we do see which ones are actually kept and which are discarded.

Sunday, October 28, 2012

On Sexual Dimorphism in Humans

On common evolutionary argument about humans is that we have a tendency to polygamy. The degree of the tendency is debated, but factors like sexual dimorphism - that males are larger than females - is seen as supporting polygamy, since species with larger males typically are ones in which males compete for females, and that competition favors larger males.

For humans specifically though, there is at least one other explanation. Different gender roles are posited in our ancestors, where men hunt and women gather. This is an oversimplification of present-day hunter-gatherers, and we do not have conclusive evidence of our ancestor hunter-gatherers, but assuming this is the case, male size could be favored because of the different work they do: hunting large animals benefits from greater physical strength. A related argument could be made about tool-making: If men build shelter or craft weapons, physical strength is useful.

Which evolutionary theory, if any, is the right one? I don't think we have a good guess.

Saturday, October 27, 2012

Brotherly-, Sisterly-, and Siblingly- Love

Reading Steven Pinker, we get a fairly rosy picture of evolutionary theories about human beings: They don't say anything terribly bad, and when they do surprise us, we just need to adjust a little, but even then we don't need to compromise on our moral principles. I find this a little too optimistic: it seems like evolutionary theories about humans are typically chosen when they are in fact not terribly controversial. The exceptions - the book "A Natural History of Rape", for example - are rare.

Here is one evolutionary theory that seems quite natural and simple in the context of the approach taken by Dawkins, Pinker, etc.: Siblings share 50% of their genes, and this is one explanation for altruism, specifically altruism towards one's siblings, a form of kin selection. Now, the 50% number (which is just of non-fixed genes, and all the usual caveats) is only an average, of course, some siblings are more related than others. Kin selection would favor being more altruistic towards siblings that share more of your genes. Do people make such calculations, estimating how related they are to their siblings, and be nice to them in proportion? Perhaps it is just too hard to do so with any precision, and there is nothing to say about this.

However, there is one notable exception: brothers are more related to male siblings and sisters to female siblings than siblings of different genders are related. This is simply because brothers must share their Y chromosome, and sisters must share an X chromosome (that they both received from their father). Gender is an extremely noticeable fact about human beings, so kin selection would appear to suggest that we should care somewhat more for siblings of the same sex.

Technically, this could occur if a gene on the Y chromosome caused altruism towards brothers but not sisters, such a gene would spread since, if done in the right proportion, the cost of the altruism is balanced by a gain in fitness of the brother who has that same gene, a classic selfish gene situation. A similar story could be told about the X chromosome for sisters, however there things are more complicated - that same chromosome will sometimes appear in male organisms too. It is possible that this form of kin selection would be less reasonable for sisters, then.

Are we to conclude that evolutionary theory predicts brothers love each other (on average and all the usual caveats) more than sisters or either loves a sibling of the other gender? This sounds quite unpalatable, but does seem to follow from the theory of kin selection. The only possibility that could prevent it is if genes for helping brothers cannot occur in general or cannot occur on the Y chromosome for some technical reason. Neither seems plausible if kin selection is true. Hence this appears to me to be an example of a quite reasonable and natural evolutionary explanation about humans, assuming we follow that approach, but I have not seen it presented, and I suspect it is because of its unpleasantness.

(Note that Dawkins does speak of a "bluebeard gene", an implausible situation where a gene codes for both blue beards and for altruism towards blue-beared people. The example is presented to show that such a thing is extremely unlikely. However, a gene for brotherly love is not similar in any substantial respect: First, it is not a single gene that codes for both the visible trait and the altruism, it is just for the latter, and second, it picks who to be altruistic towards based on one of the most prominent features that humans notice about each other, their gender.)

Sunday, July 29, 2012

Evolutionary Explanations

It seems common these days to try to explain everything through evolutionary theory. For example, supposedly art exists because it makes us more likely to survive for some reason. There are at least 2 major problems with such thinking.

  • First, an important fact about evolution is that it uses what it has to work with. Organisms do not evolve through careful planning, instead the traits that exist and show up are then selected. Consider, then, a trait A that shows up and becomes popular at some point in some organism, for reasons that we will discuss later. It may be that using some aspect of trait A is of benefit to survival, and the entirety of trait A is retained for that benefit. It is valid to say that part of trait A is useful for reproduction, but it is not quite valid to say that "trait A is explained by its reproductive benefit". A may contain many other aspects that are not directly of practical benefit, but perhaps more importantly, A did not arise due to a need to maximize fitness. We purposefully did not mention the original reason for it showing up: Perhaps it was chance, or perhaps something else.

    Regarding such "something else", we can imagine that art arose through some intentional act at some point in time - a great leader used it to justify his rule, for example, or it was derived from religious visions seen under the influence of some drug. Art may have remained relevant later on due to some reproductive benefit, but that is just why it persists, not why it arose, in this story.

    If you are tempted to say that the origin matters less than what sustained it later on, then that is of course a fair position. But here is a counter-argument: Imagine that a particular problem faced a species. There are various ways to work around that problem; whichever is implemented first is the one that will become useful and persist for a very long time. So that the first solution to appear is of reproductive benefit is true and important, but which solution actually appeared and became part of the species became such because of specific "origin" reasons: Why that solution showed up when it did, and why others did not do so earlier. So a lot of the information about the species is lost by considering just the retention of the trait and not the specifics of the trait's appearance. To make this vivid, consider that the possible solutions can be very different from each other: The species becomes quite different depending on which solution is kept.
  • Second, evolutionary selection is a very dull blade. It selects an entire organism at a time, in effect, not for each trait separately. And the reasons an individual survives, especially among species like humanity, can involve to large degree factors like culture, intelligence, and so forth. But even in "less" sophisticated creatures non-immediate effects can be crucial: Such is sexual selection. With humans we have sexual selection as well as cultural selection and many other factors. The amount of "noise" between actual reproduction and survival and between those factors is tremendous. It is far from clear that reproductive fitness is a major factor in the actual traits we see day to day (art, personality, religion, etc.), even if it does "back" things in an important sense. We are also "backed" by particle physics (without which we would not exist), but we do not say that it determines specifically properties of our species like art or religion or poetry.

Future generations will laugh at our present time and its morbid fascination with using evolutionary theory to explain everything.

(Background: Adam Kirsch on Boyd, Pagel, and Kandel)

Sunday, January 8, 2012

Wieseltier on Rosenberg

The best article so far of 2012, about the "worst book of 2011." Remarkably concise, correct, and amusing at the same time. Link.