Social Spiders, Mole Rats, Incentives

Apparently, there are social spiders. I lived on this planet for 25 years without knowing that.

I discovered this in Bostrom’s Vulnerable World Hypothesis. It’s a generally cheerful read about the likely ends for a technological civilization.




According to Wikipedia,

Several social spiders including Parasteatoda wau and Anelosimus eximius also swarm in an analogous way to the eusocial ants, bees and wasps.[5]These species disperse and establish new colonies by means of synchronized emigrations of adult and sub-adult females.

I’ll try not to think that image at night.

Source: Wikipedia

More to the point, high levels of inbreeding seem like a stable in some of these species:

After courtship and copulation, but prior to oviposition, many females will emigrate to a new nesting site and deposit their eggs, forming a new colony. In this way social spiders are also extremely inbred, as there is limited migration of males or juveniles to different colonies, forcing the offspring to mate with one another decreasing genetic variation within the colonies.

This is really weird, because inbreeding is widely considered to be an unstable dead end – your species is going to end up with a bunch of recessive alleles and wind up being poorly adapted to its niche.

Why does inbreeding appear to survive in these spiders on a relatively long timescale? I dug up the original paper. To my delight, the authors climbed up the beauty ladder and took lessons from… mole rats!

Someone thought that “sand puppy” was a good name for these

(Speaking of naked mole rats, they are extreme outliers in longevity relative to their size. They’re also extremely immune to cancer. That said, I wouldn’t pick them as the first choice of inspiration for bioengineering, if possible.)


Either way, naked mole rats “form long-lived stable colonies with typically a single breeding female and nonbreeding colony members” – think of them as mammal ants.

They show an interesting pattern:

In the case of the mole rats, it is interesting that the highly inbred naked mole rat is the sole representative of its genus Heterocephalus, while its sister group, which includes the genus Cryptomys to which the Damaraland and other outbred social mole rats belong, is a species-rich clade of at least 14 species (Faulkes et al., 1997)

Bostrom cites this inbreeding as an example of an auto-destructive “invention” (in this case, evolutionary innovation), that drove these species into a niche sufficiently weird and specialized that they can occupy it for a while, even if the innovation is detrimental to some more general notion of fitness (okay, that’s my interpretation of Bostrom’s interpretation).

I’m not sure to what extent this is actually the case on the species scale but I do think that it is a good way to think about the economic incentives for narrow specialization. You will be economically rewarded for performing a narrow set of task and not thinking about them very much, but you also lose adaptability to other economic niches and probably sacrifice a lot of valuable things like transfer learning.


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