Jurassic Sex Set in Stone
Prehistoric animals had sex. They must have. As paleontologist Derek Ager wrote in his classic Pricinples of Paleoecology, “After eating, the most widespread habits among modern animals are those concerned with sex, and there is no reason to suppose that this did not raise its allegedly ugly head millions of years before Freud.”
This truth is easy to forget. Even though reproduction is an essential act of life, mating itself is often a fleeting event. And given that the known fossil record is a fraction of a fraction of a fraction of life that once existed, what hope do we have that such ephemeral moments are preserved? Finding a complete dinosaur, pristine ammonite, or otherwise intact fossil is reason for celebration enough. We’re lucky if long-deceased creatures preserve anything relating to behavior. This is exactly why the few examples of prehistoric sex are so special.
About 320 million years ago, a pair of sharks died in a mating embrace. No one knows if they got a chance to finish their dance before they perished. Much later in time, about 47 million years ago, coupling turtles died as they sank into the toxic depths of an ancient lake. Their efforts were for naught. Then there were insects. So far, invertebrate paleontologists have found at least 33 examples of prehistoric insects caught in the act, many of these preserved in amber. Now researcher Shu Li of China’s Capital Normal University and colleagues have added another delicate example to the list – a pair of froghoppers found in the Jurassic rock of China that have been stuck in their sex position for 165 million years.
Froghoppers are still around today. They got their name, Li and coauthors write, “because the adults hop around on plants and shrubs like tiny frogs.” And the juveniles are often called spittlebugs because of their ability to cover themselves in a kind of foam. And while the fossils described in the new study belong to a new species, Anthoscytina perpetua, they are mating in a way strikingly similar to the way their living relatives do it.
Paleontologists were lucky to find the pair. Besides being a rare find – this is just one of 1,200 specimens Li and colleagues examined from the one locality – the mating froghoppers are special because they’re preserved as flattened fossils rather than being encased in amber. The fact that there was no ancient sap between researchers and the insects allowed the paleontologists to zoom in on the petrified pair to see the exact mechanics of froghopper fornication. These two were not just preserved belly-to-belly, but, in the words of the paleontologists, they’re fossilized with the “male’s aedeagus inserting into the female’s bursa copulatrix.” I think you get the picture.
The question is whether or not the froghoppers are preserved in their true mating position. Living froghoppers mate side-by-side, not belly-to-belly. Without similar fossils of copulating froghoppers, it’s currently impossible to tell whether the fossil represents the true mating position or if the intertwined insects were preserved that way after death. Nevertheless, the genitals of these ancient insects are strikingly similar to those of their modern counterparts, suggesting that froghoppers have been copulating more or less the same way through the ages. Should you ever stumble across a pair of mating froghoppers, stop and consider a scene that has been playing out since the Jurassic.
Li, S., Shih, C., Wang, C., Pang, H., Ren, D. 2013. Forever love: The hitherto earliest record of copulating insects from the Middle Jurassic of China. PLoS ONE 8, 11: e78188. doi:10.1371/journal.pone.0078188