The evolution of expendability: Why some ants traded armor for numbers

Lexus Lunar Lorry

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obligatory Pluribus mention

We're social, but not biologically eusocial. It's not unique to insects though, there's naked mole rats. And shrimp!
I wonder what the dividing line is between kin selection and eusociality - or is there even a clear boundary? For example, if we pick on hominids, there's the hypothesis that homosexuality/asexuality/childfree behavior massively reduces the reproductive fitness of the individual, they still have utility for the tribe by providing members that aren't directly occupied by childrearing roles (plus bisexuality can be used to help cement social bonds if you're a bonobo).

The obvious line that people point at would be differences in body morphology, but the eusocial shrimp that you link don't have huge differences between fertile and infertile females - only the fact that the former can be seen carrying eggs around.
 
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Troper1138

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"Their study reveals that, as ant societies grew in complexity and numbers, they didn’t just make their workers smaller—they also made them cheaper."

Well, I guess Capitalism is well aligned with Nature and Biology!



/s
Capitalism really is well aligned with nature and biology--no sarcasm tags required.

We should, of course, always beware of the Naturalistic Fallacy. Just because something is "natural" (or "well aligned with Nature and Biology") does not necessarily mean it is good, or that we should wholeheartedly support it.

There's probably an "Inverse Naturalistic Fallacy" too--just because something is "natural" doesn't mean it's bad, either. ("We must overcome our sinful natures to achieve salvation!")
 
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Troper1138

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So, the termites are not closely related to the ants (although the ants are fairly closely related to the wasps and bees); turns out termites are basically cockroaches (which I learned about 90 seconds ago*). I wonder if someone will apply this sort of analysis to the termites and see how well it fits with them as well?

*I mean, I knew the termites aren't closely related to the ants; I didn't know they are closely related to the cockroaches. Gives a whole new wrinkle to the old "the cockroaches will be the only things to survive World War III and will inherit the Earth" meme. And then, they will build mighty cities, and great plantations of fungi, and so forth!
 
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Veritas super omens

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Capitalism really is well aligned with nature and biology--no sarcasm tags required.

We should, of course, always beware of the Naturalistic Fallacy. Just because something is "natural" (or "well aligned with Nature and Biology") does not necessarily mean it is good, or that we should wholeheartedly support it.

There's probably an "Inverse Naturalistic Fallacy" too--just because something is "natural" doesn't mean it's bad, either. ("We must overcome our sinful natures to achieve salvation!")
Meta parasitical creatures come to mind, eh?

https://www.science.org/content/article/how-one-parasitic-wasp-becomes-victim-another-parasitic-wasp
 
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Veritas super omens

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Worker bees and worker ants are like cells of a superorganism. They are all clones so no genetic diversity is lost when one clone dies, just as no diversity dies when you slough off skin cells. The superorganism saves resources by optimizing the clones for the environment it exists in. Those resources can then be used to create more genetically distinct offspring. Some of which may have an even more optimized body plan for its worker units.
 
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Lil' ol' me

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as ant societies grew in complexity and numbers, they didn’t just make their workers smaller—they also made them cheaper.
Who's "they"?

It's not "ant societies", as societies of any kind have no influence on natural selection.

And we wonder why non-scientists are confused about evolution. It's terminology like this. Yes, it's a handy shortcut for a complex topic, but it's so misleading.

What this research shows is that natural selection, in ants' current physical environment (temperature, humidity, water & nutrient availability, etc.), with ants' current set of predators, favors quantity (more workers per unit of nutrient) over quality (better equipped workers).

Change any of the conditions (predators, nutrients, etc.) and natural selection may work differently.

This just sounds like a super-creepy justification for some future "leader" to get rid of robust competition by killing off the strongest competitors. This is basically how animal & plant (seedless fruits, oversized veggies that can't survive without human intervention) domestication works.
 
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matheme

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Worker bees and worker ants are like cells of a superorganism. They are all clones so no genetic diversity is lost when one clone dies, just as no diversity dies when you slough off skin cells. The superorganism saves resources by optimizing the clones for the environment it exists in. Those resources can then be used to create more genetically distinct offspring. Some of which may have an even more optimized body plan for its worker units.
Worker bees are in fact half-sisters, their mother is the Queen bee who mated with 10-20 drones before retreating into the hive to lay eggs for the rest of her live (or until she leaves the hive with about half the swarm to settle somewhere less busy). One of the remaining fertilized eggs can then become a new queen (Unfertilized eggs become drones). So in the end not so much cloning but regular genetics, just with an unusual number of sisters... The general idea of shared genetics within a colony is correct though.
 
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Bill T.

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Who's "they"?

It's not "ant societies", as societies of any kind have no influence on natural selection.

And we wonder why non-scientists are confused about evolution. It's terminology like this. Yes, it's a handy shortcut for a complex topic, but it's so misleading.

What this research shows is that natural selection, in ants' current physical environment (temperature, humidity, water & nutrient availability, etc.), with ants' current set of predators, favors quantity (more workers per unit of nutrient) over quality (better equipped workers).

Change any of the conditions (predators, nutrients, etc.) and natural selection may work differently.

This just sounds like a super-creepy justification for some future "leader" to get rid of robust competition by killing off the strongest competitors. This is basically how animal & plant (seedless fruits, oversized veggies that can't survive without human intervention) domestication works.
With apologies to Hillary Clinton: It takes a colony to raise a larva.

The physical characteristics of an ant are not solely the result of its parents, but also of the workers that raise them. By moving larvae around, or feeding them different diets, the behavior of worker ants affects the ultimate form an adult ant eventually takes. In the extreme case, consider colonies with multiple castes, where the workers can vary in size by an order of magnitude, despite them being (half-) siblings.

And yes, sure, the workers' behavior is controlled by natural selection, but it natural selection at two levels: The phenotype resulting from each ant's genes, and the emergent phenotype of the colony as a whole, ultimately determine the reproductive success of the colony's genotype.
 
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The Lurker Beneath

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This is interesting and maybe there is a parallel in hominin evolution. H. sapiens tends to have gracile bodies and, even in distant pre-history, have larger family groups than the heavily built H. neanderthals.

I thought of a different and more recent parallel - the move from hunting-gathering to farming, on the order of ten thousand years ago. I don't know if it is a hundred percent authenticated, but it seems to be often said that nutrition quality and health took a step down, in the interest of larger populations and civilisational development.
 
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Chuckstar

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Worker bees are in fact half-sisters, their mother is the Queen bee who mated with 10-20 drones before retreating into the hive to lay eggs for the rest of her live (or until she leaves the hive with about half the swarm to settle somewhere less busy). One of the remaining fertilized eggs can then become a new queen (Unfertilized eggs become drones). So in the end not so much cloning but regular genetics, just with an unusual number of sisters... The general idea of shared genetics within a colony is correct though.
Not all workers are half sisters. If the queen successfully mates with 10 drones, then there will be ten sets within which all are of full sisters, while being half-sisters to the workers in the other sets.

And it isn’t quite “regular” genetics between the full sisters. Males are haploid, so full sisters average 75% of the same genetics, instead of the “regular” 50%.
 
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Chuckstar

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So, the termites are not closely related to the ants (although the ants are fairly closely related to the wasps and bees); turns out termites are basically cockroaches (which I learned about 90 seconds ago*). I wonder if someone will apply this sort of analysis to the termites and see how well it fits with them as well?

*I mean, I knew the termites aren't closely related to the ants; I didn't know they are closely related to the cockroaches. Gives a whole new wrinkle to the old "the cockroaches will be the only things to survive World War III and will inherit the Earth" meme. And then, they will build mighty cities, and great plantations of fungi, and so forth!
Bees, wasps and ants are more closely related than they are to termites, but I would point out for clarification that near as we can tell eusociality evolved separately in all four lineages.

The current best understanding is that wasps, bees and ants diverged somewhat over a hundred million years ago, with bees evolving from wasps that started eating flower pollen (flowers being relatively new at the time) and ants evolving from wasps that became ground predators. Evidence of separate evolution of eusociality includes facts such as genetic studies showing that ants are more closely related to non-social wasps than social wasps as well as lack of fossil evidence of colonies/hives in any of the lineages during the early eras after they split.

And just to fill out the data, beetles and wasps diverged more like three hundred million years ago.
 
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JoHBE

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Capitalism really is well aligned with nature and biology--no sarcasm tags required.

We should, of course, always beware of the Naturalistic Fallacy. Just because something is "natural" (or "well aligned with Nature and Biology") does not necessarily mean it is good, or that we should wholeheartedly support it.

There's probably an "Inverse Naturalistic Fallacy" too--just because something is "natural" doesn't mean it's bad, either. ("We must overcome our sinful natures to achieve salvation!")

The is/ought problem.

I used to frequent a forum focussed on evolution vs religion 2 decades ago (I believe it still exists!) . Lots of interesting discussion, because it was strictly moderated. One of the most insightful posts that I still remember, was someone pointing out that the theory of Evolution was DEscriptive, not PREscriptive. That captured the essence of why quite a few well-meaning religious people could be so passionately opposed. If you grow up guided by a text that tells you in absolute terms how things SHOULD be (PREscriptive), you tend to view anything that challenges or contradicts it, from that same perspective. Not just a bunch of (DEscriptive) neutral objective observations and facts, but as a competing moral guideline.
 
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Uncivil Servant

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I wonder what the dividing line is between kin selection and eusociality - or is there even a clear boundary? For example, if we pick on hominids, there's the hypothesis that homosexuality/asexuality/childfree behavior massively reduces the reproductive fitness of the individual, they still have utility for the tribe by providing members that aren't directly occupied by childrearing roles (plus bisexuality can be used to help cement social bonds if you're a bonobo).

The obvious line that people point at would be differences in body morphology, but the eusocial shrimp that you link don't have huge differences between fertile and infertile females - only the fact that the former can be seen carrying eggs around.

No, it would require significant changes to human reproduction. Reproductive medicine is already a politically charged topic, I just can't see it happening*.

There are practical implications as well: I'm not sure that you can get there from an XY sex system. XX individuals who self-fertilize can only have daughters, but eusociality generally requires haploid males. Leaving aside the question of whether haploid vertebrates are even viable, you'd at least have to start with a sex system with WZ females and WW males. These animals exist, and some snakes have been documented to give birth without ever mating, but only to diploid WZ and WW snakes.

And that haplo-diplo lifestyle is also a major change, plants go through this which is why they produce pollen, tiny spores capable of hatching and growing short-lived male gametophytes, like if one's testes produced little mini-testes instead of sperm. So yeah, once you start borrowing plant-style haplo-diplo life cycles, you're pretty far removed from mammalian biology.


*It has been tried in the past with castrated slaves, but that's a bit drastic and also not an evolutionary procedure
 
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Uncivil Servant

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I thought of a different and more recent parallel - the move from hunting-gathering to farming, on the order of ten thousand years ago. I don't know if it is a hundred percent authenticated, but it seems to be often said that nutrition quality and health took a step down, in the interest of larger populations and civilisational development.

Nutrition actually likely improved, but infectious disease became a major problem. One thing to remember when comparing early civilizations to contemporary hunter-gatherers is survivorship bias. Cities could afford to keep marginally-productive individuals alive in ways that nomadic hunter-gatherers or even sedentary subsistence farmers simply cannot, regardless of morality, even as those same cities bred deadly diseases.

But yes, civilization brought with it specialization of tasks and societal strata and a number of social roles that converge on eusocial animals. This came about from the abundance of resources allowing individuals to focus on more than their own immediate survival.

If early cities began already possessing antibiotics, vaccines, clean drinking water, and contraception immediately, leading to a surplus population and the ability to control it from the get-go, perhaps we could have gone in that direct...oh wait, never mind, China tried that with One Child. As usual, that country is an invaluable source of "don't be That Guy" throughout history. Yeah, even if given the tools, humans would mismanage the transition, fail, and "natural" humans would continue to flourish.
 
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Seems to apply to intellectual effort as well. The individual intelligent thought is cast off in favor of a tribalist ideology that even the dumbest member can understand.

men-in-black-will-smith.gif
 
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Research has found that larger ant colony size also favors more worker castes. The most numerous caste is that of the mid-sized general purpose workers. By not having thick exoskeletons the individuals in this caste are faster, can forage better. They are lighter in weight and thus are better at excavating the nest. By carrying less exoskeleton weight, they need less energy to move about.

However, another caste which is present is the prominent large "soldier" size. This caste is larger than the typical worker, has a thick exoskeleton, and massive jaws.

"Eciton burchellii, an army ant of New World tropical forests, shows an extreme worker polymorphism with four recognized physical worker castes."
https://pmc.ncbi.nlm.nih.gov/articles/PMC2391184/

Larger colony sizes favoured the evolution of more worker castes in ants
https://pmc.ncbi.nlm.nih.gov/articles/PMC7616618/

Termites similarly have a dedicated soldier caste to defend the nest.
 
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D

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Ars, thanks for a very interesting article!

As for eusociality, mentioned above -- many human societies if not most have most of the requirements mentioned in the Wikipedia definition, even if it doesn't apply to every member.
Most ancient tribal societies used the experience of non-productive old people to make decisions, and grandparents assist (and still do, in most current societies) in taking care of their grandkids.
 
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Chuckstar

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No, it would require significant changes to human reproduction. Reproductive medicine is already a politically charged topic, I just can't see it happening*.

There are practical implications as well: I'm not sure that you can get there from an XY sex system. XX individuals who self-fertilize can only have daughters, but eusociality generally requires haploid males. Leaving aside the question of whether haploid vertebrates are even viable, you'd at least have to start with a sex system with WZ females and WW males. These animals exist, and some snakes have been documented to give birth without ever mating, but only to diploid WZ and WW snakes.

And that haplo-diplo lifestyle is also a major change, plants go through this which is why they produce pollen, tiny spores capable of hatching and growing short-lived male gametophytes, like if one's testes produced little mini-testes instead of sperm. So yeah, once you start borrowing plant-style haplo-diplo life cycles, you're pretty far removed from mammalian biology.


*It has been tried in the past with castrated slaves, but that's a bit drastic and also not an evolutionary procedure
This isn’t at all true. Naked mole rats are fully diploid. The worker caste is made up of males and females who are reproductivity suppressed hormonally. Haploid/diploid is just how some eusocial reproduction works. Haploid males are not “required”, by any means.

EDIT: Oh, termites and eusocial shrimps are also diploid. Really only the eusocial hymenopterans use the haploid sex determination system.
 
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