The evolution of animal societies

Scientists who are interested in the evolution of animal societies have long theorized about the origins of these societies. Up until now much of the research on this topic has been centered around bees and ants. Now a new study is looking at other animal societies with the hope of gaining new insight.

TRANSCRIPT

Scientists who are interested in the evolution of animal societies have long theorized about the origins of these societies.

Up until now, much of the research on this topic has been centered around bees and ants.

Now a new study is looking at other animal societies with the hope of gaining new insight.

With us now is Dr. Solomon Chak, a postdoctoral fellow in the department of ecology, evolution, and environmental biology at Columbia University.

Thanks for joining us.

Thank you.

Why not just ants and bees?

Don't they tell us everything we need to know?

Well, they are actually the coolest eusocial animals that scientists ever find.

And a lot of study has been done on them.

And the problem is eusociality in ants and bees, some bees, have evolved for a long time, like almost 100 million years ago.

And then, for us to really understand how simple society like Paleolithic animals or solitary animals evolve into eusocial species, we need to look at a group that are relatively closely related but express all this different variety of social system and that, also, these species will have similar ecologies so that we can compare it and see how they evolve step by step from simple society into the more complex eusocial form.

Let me just take a step back.

What's eusociality mean?

Right, so, eusociality, a lot of us would know it from ants and honeybees.

And they form these big colonies with usually a single queen and up to several thousands of workers.

And they're traditionally defined by three criterias -- having overlapping generations.

So the queen would produce different batch of offspring that all live in the same hive or in the same burrow.

And then, there's also cooperative care of the young.

And all these worker would work together and protect the young and feed them.

And finally, there's a reproductive division of labor, which means that the queen usually is the only one that reproduce in a big colony.

And these workers only work for the queen to help produce their other brothers and sisters.

And you're studying not bees or ants, but you're studying shrimp?

Right, we are studying shrimps.

And eusociality in shrimps have only been known for about 20 years.

But the genus express a wide variety of social system.

And in about nine species of snapping shrimps, they are eusocial, meaning that they live in a big colony where these shrimps are sponge dwelling shrimps.

They live only inside sponge canals, and you can't see them out open in the ocean.

They live inside this sponge.

And if you open up a sponge, you will see these canals like Swiss cheese went through, and that's where the shrimps are living inside.

Wow.

And you can see a big colony of up to several hundred, but you only see one or a few individuals that are queens.

They have eggs in their abdomens.

And all the other workers, they don't have any eggs, and they do not reproduce.

Is there a structural benefit to designing a society like that, where there's basically the queen is the only one that reproduces, and everyone else has a very designed task?

You're either a worker bee or a worker ant.

There is definitely some benefit, because all these worker would cooperate to help defend the colony or help feed the young.

And that really because they are highly genetically related.

They're basically protecting their own brother and sister and the parents in the nest.

There's also this idea of the inclusiveness theory.

What is this?

So, it's a theory that is one of Darwin's question when he look at eusocial ants and bees.

How, if these workers are not producing offspring, how can that gene be passed on?

How can workers ever evolve?

So, inclusive fitness or kin selection theory trying to explain this by that these workers, they are not producing offspring themselves, but they're helping the parents to produce their own brother and sister.

So they are strongly, highly related to each other.

So in that way, they're indirectly gaining fitness.

So the gene got passed on indirectly through the parents.

Mm-hmm.

So that's how these workers' traits can evolve.

Why do you study this?

What fascinates you about this?

Well, I'm interested in marine biology and how animal society evolved.

So shrimp is the perfect combination of both of these.

And they're unique because they're the only eusocial animal found in the ocean.

So that get us really curious of, is there going to be something different from what we've studied on land invertebrate and insects?

And it turns out that they actually are very similar in terms of the steps they took to evolve into eusocial species.

In studying eusocial species, is there anything that makes you think about how humans live?

I mean, are there any lessons that we can learn from how these societies function?

Well, these eusocial society, they cooperate because individuals are highly related.

And that would be something equivalent to us being more cooperative if we're working with relatives and such.

I mean, other than the fact that we can all reproduce -- or, I should say, females reproduce, but we're all in societies where it's not just one queen reproducing -- Is this how kind of tribal structures work, where people have a shared sense of community, and they will work to defend a center?

Yeah, yeah, exactly.

And that's where the idea of hierarchy or dominance come in.

So if you have one dominant queen, in a sense, of a eusocial species, then she can enforce that the workers be working for her for the benefit of the whole colony.

What still needs to be understood about this?

So, the field is moving towards genomics to try to understand what's the genetics or what's the difference between the DNA sequences or structure or how genes are expressed between these different species with different social structures.

And it seems like from social insects that a lot of these eusocial species evolve because they have new kind of ways to regulate the genes.

It's not changing a lot of genes, but a way to see what is really behind in these social shrimps.

Solomon Chak of Columbia University, thanks so much for joining us.

Thank you very much.