The notion (still popular even in the 1980s) was that creatures in general behaved in the interests of the flock, tribe, or species.
Leftists looking for proof of collectivistic behavior in nature leaped on behavior such as nit-picking, and declared that collectivism was not only good for humans, but was the natural order of living things.
Nit-picking is the odd behavior that is observed in some species of bird. Birds pick nits (parasites) out of their feathers with their beaks. However they can't reach is the top of their own head - but other birds in the flock can. We see other birds picking the nits out for them. We see cooperation.
The leftist-naturalist sees this behavior, and observes that the nit picking is in the collective interest (no birds have nits), but is against the interests of each individual bird to pick nits (the bird might get nits themselves). Hence collectivism was declared to be natural and right. Particularly when similar behavior was seen in many other species.
This scientific fallacy was allowed to stand for some time before it was more closely observed. What is actually going on is that individual birds are forming relationships with other individual birds ('you pick my nits and I'll pick yours'). Birds can cheat (defect), but doing so results in the others refusing to nit-pick for you, and that is a lonely (and itchy) road. Rather than each bird working for the good of the collective, it was working for its own long term selfishness. The mathematics is the same as for iterated prisoners dilemma.
Further, this kind of cooperation has only been seen in animals with the ability to recognize individuals in the species. So they can recognize who their trusted friends are, and punish cheaters by refusing to engage with them.
Genes are actually selfish. Collectivists were able to expound the myth that selfishness could never result in cooperation for many decades, but the jury is back with respect to Selfish Gene Theory.
Group selection is just a collectivist fantasy.
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