Snake detection theory
There is a ‘strong’ and a ‘weak’ version of ‘snake detection theory’.
The basic idea is that, over the course of human evolutionary history—including among various ancestral primate (particularly catarrhine) lineages more generally—venomous snakes exhibited a powerful mortal threat, which selected for a kind of snake detection mechanism in our visual system.
The ‘weaker’ version might be summed up as the idea that, “evolutionary exposure to snakes contributed significantly to the evolution of neural structures in mammals for detecting and avoiding snakes.” While this detection bias may facilitate faster and more automatic fear responses to snakes, it does not necessitate them. Primatologist Lynne Isbell lays out some core hypotheses for her version of the snake detection hypothesis: note the focus tends to be on rapid visual detection rather than innate fear.
In How The Mind Works (1997) cognitive scientist Steven Pinker provides what I would call the ‘stronger’ version, tying this notion of rapid detection of snakes to a corresponding innate fear. Pinker says that, “Snakes and spiders are always scary [emphasis added],” and approvingly quotes Irven DeVore’s generalization claiming that, “Hunter-gatherers will not suffer a snake to live”.
That generalization is certainly false in a cross-cultural context. Among Okiek hunter-gatherers of East Africa, anthropologist G. W. B. Huntingford writes that,
When a snake comes into a hut at night, it is not killed, but some honey is offered to it with the words: Ui, Anum, i oiindet, “Go away, So-and-so, for you are a spirit”. A man who kills a snake at night in his hut need not necessarily become ill as a result (as the Nandi believe he will), but the ancestor whose spirit was in the snake will show his anger by never going to see the man again and transferring his attentions to some other member of the family.
Anthropologist Herbert Basedow offers a particularly powerful account among the Arunta of Central Australia,
The “totem” is very dear and sacred to the native, and is religiously protected by him. I well remember on one occasion on the Alberga River I discovered a small black and yellow banded snake which I killed. An Aluridja man who was attached to the party at the time was greatly shocked at this, and, with genuine sorrow, told me that I had killed his “brother.” Turning to an Arunita he lamented aloud: “Kornye! Nanni kallye nuka kalla ilium” which literally translated means: “Oh dear! This brother of mine is dead.”
We are given a more mixed description among the Yuki of California by anthropologist George Foster, who writes that,
Rattlesnakes were an ever-present menace, and hence it is not surprising to find doctors who specialized in curing their bites. When a rattler gave warning, he was considered to be a good snake and was left unmolested; if he did not rattle he was a bad snake and should be killed. This was the attitude described by informants. Actually, if the snake was found sleeping in the sun on a rock pile, where opportunity favored the Indian, it was promptly dispatched. If found in the brush, where movements were uncertain, it was safest to pass around the snake.
Among the Hadza of East Africa, however, we have an account much closer to the generalizations of Pinker and DeVore. Anthropologist Frank Marlowe says that,
When the Hadza see a snake, they usually promptly kill it and throw it away. It appears that their healthy fear of snakebite (there are several species that are quite dangerous in Hadzaland) may lead them to rule out eating snakes, which would require them to learn how to distinguish the poisonous from the nonpoisonous snakes. When I ask the Hadza if the species we just saw is poisonous, the answer is yes about 90% of the time, which leads me to believe that they consider almost all snakes poisonous.
Even this account raises further questions though, as Marlowe notes that the Hadza have several plant medicines used in case of snake bite, writing that, “Every adult Hadza knows about the various medicinal plants and practices. It is usually men who keep the snake medicine with them.”
As this knowledge of the dangers of snake poison and the use of medical remedies are widespread, I think this raises questions about the need for an automatic snake → fear response explanation even in contexts where snakes are ubiquitously feared. I don’t see why these kind of associations cannot be quickly and recurrently learned across societies—through observation, social learning, or cultural inheritance—even without a preferential detection bias.
Pinker endorses the notion that, “phobias are innate fears that have never been unlearned,” and adding that, these “Fears develop spontaneously in children.” He also favorably cites the claim that “fears can be easily conditioned only when the animal is evolutionarily prepared to make the association [emphasis added].” Accepting this as true, one must wonder what sort of havoc and mayhem clowns wrecked on our ancestors!
Similarly, what about cynophobia? Did we have rapid selection for fear of dogs after domestication? Or maybe domesticated dogs traveled back in time to strike fear into the hearts of the first Homo sapiens before they left Africa?
Of course, there is a sense in which all fears, thoughts, behaviors, etc are ‘evolutionary’, and can only be the result of what we are ‘evolutionarily prepared for’, but this foundational insight becomes vacuous and misleading when it is simply assumed to apply to the specific content of any and all beliefs and behaviors, rather than recognizing their clear plasticity and the paramount importance of socioecology.
Social learning of even arbitrary, non-fitness related behaviors is already well-attested in quite a few other species, making it even more dubious to reduce so many behaviors of the most cultural species of all to a bunch of discrete innate adaptive heuristics. I think it is often rather as Linnaeus said—“Man…is a mimic animal,” for better and for worse.
See my pieces on the ‘mate-killing module’ and the ‘behavioral immune system’ for some related points on these kind of issues.
I think the ‘strong’ view of the snake detection hypothesis is pretty clearly wrong, but the ‘weaker’ version seems to me more of an open question.