Ant Evolution

In this post will be covering how, when, why and who ants evolved. This is an exceptionally long story. The Lord of the rings is a film series that’s nine hours long. That is pretty long. How I Met your mother was nine seasons and that was just about how he met a woman. So long! For reference, I love both series. They are just very long. If you think those are long stories, you have seen nothing yet.

Studying the evolution of animals is hard. This is because it happened a very long time ago and nobody was there to see it. Not only that, some animals do not fossilise very well. Animals that fossilise well are big and have big skeletons. This is very bad news for people trying to study the evolution of insects. To study this, we must look at their physical similarities to other groups both in modern and fossil individuals. We can then try and use this to pinpoint when these animals diverged. This can be difficult but it can be done. Not only are the fossils a poorer quality, they are smaller and rarer. This means that the dates used in this article are not 100% accurate because there isn’t enough evidence to figure these things out accurately.

A Tyrannosaurus rex fossil and a Myrmecites rotundiceps Ant fossil. You can see why ants are harder to study.

Ants are often found in Amber which does make the job easier, however it favours worker ants which would have been foraging around the sap. We rarely find Queens or Males in amber and we never find ant brood.

Some preserved ants in my personal collection.

The Story of ants starts in the age of the dinosaurs. Loads of Ant species were found during the Cretaceous period at the end of the reign of the dinosaurs. This suggests that they evolved much earlier, perhaps in the Jurassic even. This means ants could have been running around the feet of Stegosaurus and Allosaurus, millions of years before T-rex even existed. This time frame is supported by fossils found dating back to 92 million years ago. They are of ants trapped in Amber that had features that that Wasps have but modern ants do not. As we’ve talked about in a previous post, ants evolved from Wasps. The fact that these ants 92 million years ago had features from both groups shows that it was a transitional phase. This begins to narrow down the origin of ants.

A rough timeline of ant evolution.

It is now thought that ants originated anywhere after 168 million years ago but this is unproven. This is around 30 million years older than Flowers! That means the Flowers and ants evolving was separated by the same amount of time between the extinction of dinosaurs and us. This is a very long time. At the beginning of their existence ants were less common and less varied than they are now. In fact, it wasn’t till around about 60 million years ago the ants started to be found in massive numbers like they are today. Off during the Cretaceous ants made up 1% for the insects. About 30 million years ago they represented up to 40% of all the insects. In 30 million years they became one of the rarest to one of the most common insects in the world. Again, the dates are very broad and don’t add up with you use them as exact dates but they help.

As we know by now ants are eusocial animals. At the moment, we don’t know which animals first lived in eusocial colonies.  However, modern science seems to believe that Eusociality originated in insects around 150 million years ago. One of the reasons we aren’t sure is that many existing groups with eusocial species also contain non-eusocial species. This makes it hard to figure out which groups evolved from a eusocial ancestor and which groups evolved eusociality independently. For example, we know all ants are eusocial so their common ancestor was too. Wasps and bees are eusocial in some species but not in others. So did they start off eusocial or not? Look at the image below. Did eusociality evolved at point A, and some species evolve to stop being eusocial? Or were the species at point A not eusocial and instead some species at point B and C start living in colonies?

Which groups all live in colonies and those that done all do so. Living in colonies may have evolved at point A or points B and C.

I’ve said eusocial too many times. It doesn’t look like a real word anymore. Anyway. These are just some of the reasons why studying ant evolution is hard. Another is to do with genetics.

In a perfect world we would break open the amber with ants in it and test their DNA to see how closely related they are to other ants. This will give us a good time frame of when they evolved and how they are exactly related to wasps and bees. It worked in Jurassic Park so why not now? I am so sad to say this: DNA wouldn’t survive in amber. The Half life of DNA is around 521 years. Using some complicated maths that means that a strand of DNA would completely disappear in no more than 6.8 million years. That is nowhere near the 90 million years we would need to test the DNA of early ants. Sadder still, as far as we know, Jurassic Park is impossible.

I REALLY hope I am wrong.

So for now, genetic testing is off the table. Who knows what we will discover in the future. Until then we will have to rely on what prehistoric ants look like.

Thank you for reading! I hope I haven’t destroyed too many dreams regarding Jurassic Park. Don’t shoot the messenger. I hope you enjoyed,

Alex.

Glossary

Diverged- Where one group of animals become two different groups. For example: Wasps and ants diverging from Wasp-like ancestors.

Sad- Me having to say Jurassic Park can’t happen.

References

Grimaldi, D. and Agosti, D., 2000. A formicine in New Jersey Cretaceous amber (Hymenoptera: Formicidae) and early evolution of the ants. Proceedings of the National Academy of Sciences, 97(25), pp.13678-13683.

Hölldobler, B. and Wilson, E.O., 1990. The ants. Harvard University Press.

Moreau, C.S., Bell, C.D., Vila, R., Archibald, S.B. and Pierce, N.E., 2006. Phylogeny of the ants: diversification in the age of angiosperms. science312(5770), pp.101-104.

Wilson, E.O., Carpenter, F.M. and Brown, W.L., 1967. The first Mesozoic ants. Science157(3792), pp.1038-1040.

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