Eusociality, is the most sophisticated level of organization of sociality, is defined by the following characteristics: cooperative brood care, overlapping generations within a colony of adults, and a division of labor into reproductive and non-reproductive groups.

Eusociality is an incredibly successful evolutionary strategy; the Hymenoptera family is one of the most species abundant and one of the largest by biomass on the planet.

But Eusocial animals are small in size. The largest of the eusocial animals are the mole rats, which of course have exponentially smaller colony sizes than ants for example.

The reason for this is rather apparent in that a larger body mass necessitates more resources, but we do have a multitude of megafauna that’s lived in massive groups, just none of them eusocial.

I want to know if it would be possible to have megafauna exhibit eusocial traits, whether it is a roving herd that protects a central queen as it crosses grasslands or some sort of predatory fish school, I just want to know if you could ever get a decently sized eusocial animal.

  • $\begingroup$ Nice question but could you put in a one sentence definition of eusocial? I had to look it up and I might not be the only one. $\endgroup$
    – quarague
    Commented Mar 4, 2020 at 11:40
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    $\begingroup$ Eusocial: certain components of the species specialize in a given area, losing an ability in the trade off. $\endgroup$ Commented Mar 4, 2020 at 14:29
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    $\begingroup$ American Bison *are 'pretty good sized' * So are Wolves. I feel as if you've answered your own question. $\endgroup$
    – Joe
    Commented Mar 4, 2020 at 15:01
  • $\begingroup$ @Joe They are not eusocial though. But these animals existing is why I have this idea in the first place $\endgroup$
    – user71781
    Commented Mar 5, 2020 at 2:13
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    $\begingroup$ How do humans not qualify? The only box I don't see obviously ticked is "a division of labor into reproductive and non-reproductive groups", but I bet there are some cultures (especially historic and/or smaller tribal cultures) where that happened. $\endgroup$
    – Matthew
    Commented Mar 5, 2020 at 21:22

1 Answer 1


Humans would seem to be a strong argument at least for the plausibility. While typical western culture doesn't exactly fit the bill, there have been arguments that some human cultures qualify.

The catch is that humans don't have morphological role segregation; the "division of labor into reproductive and non-reproductive groups" bit is merely a social construct, and individuals might migrate between divisions during their lifetime. We also don't, typically, centralize reproduction with a single 'queen'.

Still, when you consider how close humans come to fitting the bill, it's not hard to imagine us still thriving if somehow we took the next step to having a small number of individuals responsible for mothering all offspring. At this point, we're talking more a question of biological design than environment sustainability; after all, if you take an existing human community and just tweak it so that everyone has the same (biological) mother, I don't see any obvious problems arising from that.

And... we do have some history with biological role segregation, in the form of eunuchs.

In any case, it's plausible enough that fictional examples abound. Four that come to mind off hand are Xenomorphs, Formics, Bugs, and Zerg, and there have been plenty more. (It is probably not surprising that many such examples are based on insects.)


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