Most Models Aren't Even Useful

But Female Domestication at Least Makes Testable Predictions

It’s often said that “All models are wrong; some are useful.” But the corollary is that many models are both wrong and useless.

For thousands of years, Aristotelian philosophy explained why rain falls down and fire burned up, and convinced people not to worry too much about the occasional retrograde motion of Jupiter and Mars. Aristotelean physics was useful enough most of the time that it was able to hinder progress toward a better way of compressing information for quite some time. But there were a few small problems which Galileo brought to light—large spheres roll down inclines no faster than smaller spheres, there are moons orbiting around Jupiter, and so on. These were small problems that most ordinary people never even encountered, but they were enough to reveal the inherent weakness in classical conceptions of the physical universe.

The point is that science often depends on these little details to falsify a model that isn’t true.

And while people like to think that we now live in a scientific era, this is a panglossian assumption. Modern people are quite satisfied to propose a ideas that only work most of the time, like, “you should reduce salt intake to lower your blood pressure.” (This isn’t usually bad advice, but actually the ratio of potassium to sodium is what needs to be in balance.¹) And sometimes modern people are happy to propose ideas that only work a little bit of the time, like, “The Earth is Flat.” And sometimes otherwise intelligent people are quite happy to propose ideas which are completely and totally at variance with reality, like “Utilitarianism is slave morality for nerds,” as we’ve looked at previously.

At the time I debunked that, I was trying to be polite, thinking the original author would read what I had to say. Now that I’m confident he isn’t around anymore, I’ll be more candid: I was profoundly disappointed with his idea. When I first saw his post I was enchanted by the bold title, and but the nature of the argument, which criticized Effective Altruism through a Nietzschean lens. It was so captivating! So clever! So sensational!

So immediately, so easily disproven by eight minutes on Google Scholar.

Yes, I gave the idea much more time than that, looking at the angle from a variety of directions, but if the author had been skeptical, reflective, or humble enough to understand how important it is to make an effort to falsify ideas—to realize that all models are wrong, and most aren’t even useful—he would have shrugged and done something else.

This is the way I feel about the issue of hominin domestication.

Chimps, Bonobos, and Humans

Richard Wrangham and others² have argued that bonobos and humans are domesticated relative to chimpanzees. Their reasoning is maybe somewhat complicated—but never mind the reasoning. Reasoning is a great way of generating a hypothesis, but unless you want to forget about science and live in an Aristotelean bubble, it’s kindof important to test the hypothesis. So, do humans look like domesticated chimpanzees? Do bonobos?

Well I’ve written previously about domestication syndrome, which is described as a set of characteristics

known to include: increased docility and tameness, coat color changes, reductions in tooth size, changes in craniofacial morphology, alterations in ear and tail form (e.g., floppy ears), more frequent and nonseasonal estrus cycles, alterations in adrenocorticotropic hormone levels, changed concentrations of several neurotransmitters, prolongations in juvenile behavior, and reductions in both total brain size and of particular brain regions. The consistency of this extremely diverse set of phenotypic changes in domesticated mammals presents a major puzzle…³

Another trait in domesticated mammals they don’t mention here is shortened limb length; wild animals have longer legs than their domesticated cousins.⁴ And incidentally, another trait in domestication syndrome is increased affiliative vocalization; think about how domesticated dogs will often bark at strangers to alert their owners, rather than growling, silently attacking, or running away. Vocalization is an important trait, and frequency of verbalizations has been linked to white patches in monkeys’ faces, signs either of self-domestication or of the developmental pathways that produce domestication syndrome in mammals.⁵ Vocalization has also been looked at as a possible sign of self domestication in unrelated species like elephants.⁶ I’ll say more on this later; for now I just want to look at whether humans and bonobos look more domesticated than chimpanzees.

So do they? Do bonobos and humans show more domesticated characteristics than chimps?

Well the answer is that they don’t—not unambiguously. Bonobos have longer limbs and darker pigmentation, while you may have noticed that humans have (much) larger brains.

Now, maybe this isn’t devastating for the idea. After all, we can absolutely say that the idea of humans and bonobos self-domesticating is useful, or at least interesting. And maybe we can even explain the traits that don’t fit by pointing to some complicating factors, like selection for heightened intelligence in humans, or whatever it is that might make bonobos need to be dark and long-limbed.

But adding complications to save an idea doesn’t help make it more likely, any more than explaining away the retrograde motion of the superior planets using epicycles makes Aristotelian physics any more likely.

These are epicycles: Planetary motion “around the Earth” looks like this under Aristotelian physics. Image from Wikipedia.

If we’re going to take ideas seriously, really seriously, shouldn’t we take their failed predictions seriously? From where I sit, I find it hard to seriously entertain the idea that humans are a self-domesticated species. If we want to say that humans just made themselves more docile, and that’s all we mean when we speak of humans being self-domesticated, well fine, OK, that may still be true. But the strength of science as a discipline lies in its ability to save us from pitfalls, and it can’t do that if we just shrug whenever a model generates a prediction that fails.

What About Human Female Domestication, Then?

Last time I wrote about this subject, I mentioned an idea I had myself: Maybe, throughout prehistory, human males domesticated females through the process of bride capture.

Is this true? I’m not going to say that. But I can at least say that my model predicts women should have, relative to men, shorter limbs, less pigmentation, less reactive aggression, and so on. Critically, women ought to be at least as far in the direction of domestication vs men, as female chimps are vs male chimps.

After a week or two of looking, I haven’t been able to find clear data for many traits on which male and female chimps might differ. But there is one trait I have been able to identify in which male and female chimps show a difference, and that is vocalization. That characteristic chimp noise is called the pant-hoot, and while there are some dominance aspects of it, it’s mostly described as communicative and affiliative—a way of bonding between members of a band.

Humans don’t really pant-hoot; they talk. But what’s the sex difference? In humans, obviously, women use more affiliative speech.⁷

At least these models are useful for illustrating a specific point I’m trying to make. Image courtesy of Christina Morillo

But in chimpanzees, males pant-hoot more:

Males and females had equal rates of call production for all signals except pant–hoots and buttress-drumming, with males producing these significantly more often.⁸

Another report roughly corroborates (going into more detail):

individual attributes such as age and sex also influenced loud call production rates, with adults vocalising at higher rates than juveniles, and males vocalising more than females.⁹

None of this proves my idea is correct. It just shows that the idea is still in the running—at least, for now. Who knows? There may be a slew of traits I haven’t considered which will make women look less domesticated than men, and if they turn up, that’ll be it for this idea.

But until that happens, well… I like to think that, while he was alive, Aristotle was at least entertaining to his friends.

1. Perez, V., & Chang, E. T. (2014). Sodium-to-potassium ratio and blood pressure, hypertension, and related factors. Advances in nutrition, 5(6), 712-741.

2. Hare, B., Wobber, V., & Wrangham, R. (2012). The self-domestication hypothesis: evolution of bonobo psychology is due to selection against aggression. Animal Behaviour, 83(3), 573-585.

3. Wilkins, A. S., Wrangham, R. W., & Fitch, W. T. (2014). The “domestication syndrome” in mammals: a unified explanation based on neural crest cell behavior and genetics. Genetics, 197(3), 795-808.

4. Sánchez-Villagra, M. R., Geiger, M., & Schneider, R. A. (2016). The taming of the neural crest: a developmental perspective on the origins of morphological covariation in domesticated mammals. Royal Society open science, 3(6), 160107.

5. Ghazanfar, A. A., Kelly, L. M., Takahashi, D. Y., Winters, S., Terrett, R., & Higham, J. P. (2020). Domestication phenotype linked to vocal behavior in marmoset monkeys. Current Biology, 30(24), 5026-5032.

6. Raviv, L., Jacobson, S. L., Plotnik, J. M., Bowman, J., Lynch, V., & Benítez-Burraco, A. (2023). Elephants as an animal model for self-domestication. Proceedings of the National Academy of Sciences, 120(15), e2208607120.

7. Leaper, C., & Robnett, R. D. (2011). Women are more likely than men to use tentative language, aren’t they? A meta-analysis testing for gender differences and moderators. Psychology of women quarterly, 35(1), 129-142.

8. Kalan, A. K. (2019). Evidence for sexual dimorphism in chimpanzee vocalisations: A comparison of male and female call production and acoustic parameters. In The chimpanzees of the Taï forest: 40 years of research (pp. 410-421). Cambridge University Press.

9. Slocombe, K. E., Lahiff, N. J., Wilke, C., & Townsend, S. W. (2022). Chimpanzee vocal communication: what we know from the wild. Current opinion in behavioral sciences, 46, 101171.