How the dinosaurs did it

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First aired on Quirks & Quarks (17/11/12)

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If you stop to think about how we all begin our existence, you'll quickly realize that the history of sex is as old as life itself. Back in 2008, a little more light was shed on that history with the discovery of a 380-million-year-old placoderm fish fossil in Australia. It proved to contain the oldest vertebrate embryo fossil ever found, but more significantly, it was an indication of the earliest known evidence of internal fertilization. Put simply: vertebrate sex.

John Long, a professor of paleontology at Flinders University in South Australia, made that discovery. He has documented it in his new book, a provocative history of prehistoric sex called The Dawn of the Deed. Long's book includes the evolutionary history of copulation and insemination, and descriptions of bizarre mating habits and unusual sexual organs, as well as theories about how dinosaurs "did it." Long spoke about prehistoric sex with host Bob McDonald on Quirks & Quarks in a recent interview.

The history of sex is certainly a key to understanding the history of life itself, so it's somewhat surprising that no one has tackled this subject in a book until now. "There hasn't been a lot of evidence about the subject," Long said. "When we discovered the [fossilized embryo], that really opened up the first window into what sexual behaviour might have been like way back 400 million years ago, and that just got me thinking." After that major discovery, Long and his team realized that they hadn't just discovered the oldest embryo but had, in fact, stumbled upon the origins of copulation itself.

The logical next step was to go looking for the male genital organs, "to figure out how they were doing it," said Long. This research led to evidence of copulation in a large number of species of all sizes, including giant prehistoric fish. "This proved that instead of being a one-off incident, this was likely a widespread method of sexual reproduction."

But what can fossils tell us about the sexual intimacy of creatures who lived millions of years ago? "One would expect from looking at living fish that the primitive fish [would have] spawned in water — that they lay eggs and the males come and deposit sperm on them — but sharks and rays have a form of internal fertilization using rubbery claspers that the males insert into the females," Long explained. "That method was thought to be rather specialized...eventually, internal fertilization becomes the method of reproduction for the higher was kind of a shock that there was this very advanced form of reproduction at this very primitive [level]."

And the question on everyone's minds? How did those massive dinosaurs, many of whom were covered in spines and spikes, do it? "Very carefully," according to Long. He's joking, of course. "That's a very good question, and one that paleontologists have thought of all too often, I think." For a long time, it was assumed that dinosaurs had sex like birds (insemination is accomplished from cloaca opening to cloaca opening, as birds don't have penises). But recently, evidence has emerged that this isn't the case. "The primitive birds (ostriches, emus, ducks) all still retain a male reproductive organ," said Long. (There is one species of duck whose penis can extend to 42 centimetres in length.) "If we think of primitive birds mating with elaborate courtship rituals, I think it's most likely that dinosaurs did the same thing...there was probably an elaborate courtship ritual followed by vigorous sexual intercourse involving very large male organs!" Dinosaurs. They were just like us.

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