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Snakes, Spiders, and Just-so stories

1550 words

Evolutionary psychology (EP) purports to explain how and why humans act the way they do today. It is a framework that assumes that certain mental/psychological traits were useful in the EEA (Environment of Evolutionary Adaptedness) and thusly were selected for over time. It assumes that traits are adaptations then “works backward” by reverse engineering. Reverse engineering is the process of figuring out the design of the mechanism based on its function. (Many problems exist there which will be covered in the future; see also Evolutionary Psychology: The Burdens of Proof by Lloyd, 1999). But let’s discuss snakes and other animals that we have fears of today; is there an evolutionary basis for said behavior and can we really know if there was?

Fear of snakes and spiders

Ohman (2009: 543) writes that “Snakes … have a history measured in many millions of years of shaping mammalian and primate evolution in important respects” and that “snakes … are promising tools for probing the emotional ramifications of deep evolutionary heritages and their interaction with the current environment.” Are they promising tools, though? Were there that many snakes in our EEA that made it possible for us to ‘evolve’ these types of ‘fear modules’ (Ohman and Mineka, 2001)? No, it is impossible for our responses to snakes—along with some other animals—to be an evolved response to what occurred in our EEA because the number of venomous, dangerous snakes to humans and our ancestors was, in reality, not all that high.

Ohman and Mineka (2003: 5-6) also write that “the human dislike of snakes and the common appearances of reptiles as the embodiment of evil in myths and art might reflect an evolutionary heritage” and “fear and respect for reptiles is a likely core mammalian heritage. From this perspective, snakes and other reptiles may continue to have a special psychological significance even for humans, and considerable evidence suggests this is indeed true. Furthermore, the pattern of findings appears consistent with the evolutionary premise.

Even the APA says that an evolutionary predisposition to fear snakes—but not spiders—exists in primates (citing research from Kawai and Koda, 2016). Conclusions such as this—and there are many others—arise from the ‘fact’ that, in our EEA, these animals were harmful to us and, over time, we evolved to fear snakes (and spiders), but there are some pretty big problems with this view.

Jankowitsch (2009) writes that “Fear of snakes and spiders, which are both considered to be common threats to survival in early human history, are not thought to be innate characteristics in human and nonhuman primates, learned.” For this to be the case, however, there would need to be many spiders and snakes in our EEA.

Philosopher of science Robert C. Richardson, in his book Evolutionary Psychology and Maladapted Psychology (Richardson, 2007) concludes that EP explanations are speculation disguised as results. He says that the stories that state that we evolved to evolved to fear snakes and spiders lack evidence. Most spiders aren’t venomous and pose no risk to humans. In the case of snakes, one quarter are poisonous to humans and we’d have to expect this ‘module’ to evolved on the basis of a minority of snakes that are poisonous to humans:

On this view, at least some human fears (but not all) are given explanations in evolutionary terms. So a fear of snakes or spiders, like our fear of strangers and heights, serves to protect us from dangers. Having observed that snakes and spiders are always scary, and not only to humans, but other primates, Steven Pinker (1997: 386) says “The common thread is obvious. These are the situations that put our evolutionary ancestors in danger. Spiders and snakes are often venomous, especially in Africa…. Fear is the emotion that motivated our ancestors to cope with the dangers they were likely to face” (cf. Nesse 1990). This is a curious view, actually. Spiders offer very little risk to humans, aside from annoyance. Most are not even venomous. There are perhaps eight species of black widow, one of the Sydney funnel web, six cases of brown recluses in North and South America, and one of the red banana spider in Latin America. These do present varying amounts of risk to humans. They are not ancestrally in Africa, our continent of origin. Given that there are over 37,000 known species of spiders, that’s a small percentage. The risk from spiders is exaggerated. The “fact” that they are “always scary” and the explanation of this fact in terms of the threat they posed to our ancestors is nonetheless one piece of lore of evolutionary psychology. Likeways, snakes have a reputation among evolutionary psychologists that is hardly deserved. In Africa, some are truly dangerous, but by no means most. About one quarter of species in Uganda pose a threat to humans, though there is geographic variability. It’s only in Australia—hardly our point of origin—that the majority of snakes are venomous. Any case for an evolved fear of snakes would need to be based on the threat from a minority. In this case too, the threat seems exaggerated. There is a good deal of mythology in the anecdotes we are offered. It is not altogether clear how the mythology gets established, but it is often repeated, with scant evidence. (pg. 28)

The important point to note here, of course, is the assumption that we have an evolved response to fear snakes (and spiders) based on a minority of actually dangerous species to humans.

Just-so stories

The EP enterprise is built on what Gould (1978) termed “just-so stories”, borrowed from Rudyard Kipling’s (1902) book of stories called “Just So Stories” (which he told to his daughter) where he imagined ways that in which certain animals look the way they do today. These stories needed to be told “just so” or she would complain.

And the Camel said ‘Humph!’ again; but no sooner had he said it than he saw his back, that he was so proud of, puffing up and puffing up into a great big lolloping humph.

‘Do you see that?’ said the Djinn. ‘That’s your very own humph that you’ve brought upon your very own self by not working. To-day is Thursday, and you’ve done no work since Monday, when the work began. Now you are going to work.’

‘How can I,’ said the Camel, ‘with this humph on my back?’

‘That’s made a-purpose,’ said the Djinn, ‘all because you missed those three days. You will be able to work now for three days without eating, because you can live on your humph; and don’t you ever say I never did anything for you. Come out of the Desert and go to the Three, and behave. Humph yourself!’ (How the Camel got His Hump)

These stories “sound good” but is there any way to verify these nice-sounding stories? One can then make the same argument for EP hypotheses: can they be independently verified? The thing about functional verification is that we cannot possibly know the EEA of humans—or other animals—and thusly any explanation for the functionality of a certain trait are nothing but just-so stories.

Kaplan (2002: S302) argues that:

Evolutionary psychology has not yet developed the tools necessary to uncover our “shared human nature” (if such there is—see Dupre 1998) any more than physical anthropology has been able to uncover the specifics even of such clear human adaptations as our bipedalism. It is obvious that our brains were subject to selective pressures during our evolutionary history; it is not at all obvious what those pressures were.

I don’t deny that we are the products (partly, natural selection isn’t the only mode of evolution) of evolution; I do deny that these fantasy stories can tell us anything about how and why we evolved though. I don’t see how EP can develop such tools to uncover our “shared human nature”—or any other “nature” for that matter—unless time machines are developed and we can directly observe the evolution of trait X that is being discussed.

A simple argument to show that EP hypotheses are just-so stories:

P1) A just-so story is an ad-hoc hypothesis

P2) A hypothesis is ad-hoc if it’s not independently verified (verified independently of the data the hypothesis purports to explain)

P3) EP hypotheses cannot be independently verified

C) Therefore EP hypotheses are just-so stories

This simple argument shows that all EP hypotheses are just-so stories since they cannot be independently verified of the data they attempt to explain. Stories can “sound good”, they can “sound logical”, they can even be “parsimonious” and they can even be the “inference to the best explanation“, (how do you but just because these stories are “parsimonious”, “sound logical” and are the “inference to best explanation” doesn’t make the stories true. The above argument holds for one of HBD’s pet theories, too, the cold winter theory (CWT). It cannot be independently verified either, and it was formulated after national IQ differences were known; therefore CWT is a just-so story.

(I will cover this more in the future.)


Stories about snakes and spiders in our evolutionary history are likely wrong—especially if they derive from what supposedly occurred in our EEA, an environment we know almost nothing about. The fact of the matter is, regarding snakes and spiders, there is no evidence that our fear of them is an adaptive response to what occurred in our EEA. That is a just-so story. Just-so stories are ad-hoc hypotheses that cannot be independently verified, therefore EP hypotheses are just-so stories.