Survival of the prettiest: Sexual selection can be inferred from the fossil record

Jan 29, 2013

Detecting sexual selection in the fossil record is not impossible, according to scientists writing in Trends in Ecology and Evolution this month, co-authored by Dr Darren Naish of the University of Southampton.

The term "" refers to the evolutionary pressures that relate to a species' ability to repel rivals, meet mates and pass on genes. We can observe these processes happening in living animals but how do palaeontologists know that sexual selection operated in fossil ones?

Historically, palaeontologists have thought it challenging, even impossible, to recognise sexual selection in extinct animals. Many fossil animals have elaborate crests, horns, frills and other structures that look like they were used in sexual display but it can be difficult to distinguish these structures from those that might play a role in feeding behaviour, escaping predators, controlling body temperature and so on.

However in their review, the scientists argue that clues in the can indeed be used to infer sexual selection.

"We see much evidence from the fossil record suggesting that sexual selection played a major role in the evolution of many extinct groups," says Dr Naish, of the University's Vertebrate Palaeontology Research Group.

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

Modern examples of sexual selection, where species have evolved certain behaviours or ornamentation that repel rivals and attract members of the opposite sex, include the male peacock's display of feathers, and the male moose's antlers for use in clashes during .

Dr Naish and co-authors state that the fossil record holds many clues that point to the existence of sexual selection in , for example weaponry for fighting, from duels, and for display, such as fan-shaped crests on dinosaurs. Distinct differences between males and females of a species, called 'sexual dimorphism', can also 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.

"Some scientists argue that many of the elaborate features on dinosaurs were not sexually selected at all," adds Dr Naish, who is based at the National Oceanography Centre, Southampton.

"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."

Explore further: A clear, molecular view of how human color vision evolved

More information: Knell, R. et al. Sexual selection in prehistoric animals: detection and implications, Trends in Ecology & Evolution, Volume 28, Issue 1, January 2013, Pages 38-47, doi: 10.1016/j.tree.2012.07.015

Related Stories

Manipulative mothers subdue show-off sons

Sep 12, 2011

The gaudy plumage and acrobatic displays of birds of paradise are a striking example of sexual selection, Charles Darwin's second great theory of evolution. But new research shows that this powerful process may collapse when ...

'Sexual networks' reveal complex mating game

Jan 22, 2013

(Phys.org)—Social networks can be used to describe the sexual interactions in animal populations and reveal which individuals are directly competing in the 'mating game', according to new Oxford University ...

Studies suggest males have more personality

Nov 18, 2009

(PhysOrg.com) -- Males have more pronounced personalities than females across a range of species - from humans to house sparrows - according to new research. Consistent personality traits, such as aggression ...

The burly bird catches the girl

Aug 17, 2011

While the early bird might catch the worm, it's the quick bird that lands the ladies, according to new research into the running performance of an Arctic cousin of the grouse.

Brawn and speed make the grade during mate selection

Sep 12, 2011

Do more efficient and faster male birds win females over? New research from the United Kingdom suggests that the rock ptarmigan, the Arctic cousin of the grouse, does. University of Manchester researchers ...

More flight than fancy?

Apr 05, 2007

Scientists from the universities of Exeter and Cambridge have turned a textbook example of sexual selection on its head and shown that females may be more astute at choosing a mate than previously thought.

Recommended for you

Contrasting views of kin selection assessed

Dec 17, 2014

In an article to be published in the January issue of BioScience, two philosophers tackle one of the most divisive arguments in modern biology: the value of the theory of "kin selection."

Microbiome may have shaped early human populations

Dec 16, 2014

We humans have an exceptional age structure compared to other animals: Our children remain dependent on their parents for an unusually long period and our elderly live an extremely long time after they have ...

DNA sheds light on why largest lemurs disappeared

Dec 16, 2014

Ancient DNA extracted from the bones and teeth of giant lemurs that lived thousands of years ago in Madagascar may help explain why the giant lemurs went extinct. It also explains what factors make some surviving ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

gwrede
5 / 5 (2) Jan 30, 2013
It is quite possible that sexual selection has been there as long as the sexes. The whole point of having two sexes is the ability to choose the mate. And presumably already from the outset, there was pressure to find the fittest mate. But since real measurements of strength and viability were impossible, there had to be proxies for them.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.