Dinosaurs evolved through sexual selection

Posted by Kate Taylor

The fossil record can show evidence of sexual selection, say researchers, revealing how members of a species attract a mate.

Many fossil animals have elaborate crests, horns, frills and other structures that appear to have been used in sexual display. It's hard, though to distinguish these structures from those involved in feeding behaviour, escaping predators, controlling body temperature and so on.

And while sexual selection has been observed in living animals, therefore, many palaeontologists have thought it impossible to establish extinct animals.

But, says Dr Darren Naish of the University of Southampton, "We see much evidence from the fossil record suggesting that sexual selection played a major role in the evolution of many extinct groups.

"Using observations of modern animal behaviour we can draw analogies with extinct animals and infer how certain features improve success during courtship and breeding."

Distinct differences between males and females of a species, called 'sexual dimorphism', can suggest the presence of sexual selection, and features observed in sexually mature adults, where absent from the young, indicate that their purpose might be linked to reproduction.

We can also make inferences from features that are 'costly' in terms of how much energy they take to maintain, if we assume that the reproductive advantages outweighed the costs.

Whilst these features might have had multiple uses, the authors conclude that sexual selection should not be ruled out, says Naish.

"Some scientists argue that many of the elaborate features on dinosaurs were not sexually selected at all," he says.

"But as observations show that sexual selection is the most common process shaping evolutionary traits in modern animals, there is every reason to assume that things were exactly the same in the distant geological past."