Why are Fossils More Often Male?

Now that DNA analysis of long-dead animals is possible, scientists found that fossils of bison that have been collected turn out to be about 75% male. A majority of males has been found in fossils of mammoths and brown bears as well. Why is that? Before reading the article, I came up with two possibilities, extrapolated from what I know of humans. First, young males tend to take more risks, and would be more likely to end up as young healthy fossil specimens. Second, I don't know if osteoporosis was a thing among prehistoric animals, but if so, it could have rendered female bones less likely to be preserved. The first idea occurred to the scientists studying the anomaly.

Bison herds usually consist of one dominant male surrounded by a gaggle of females. Less dominant males leave the herd to find a herd of their own or form bachelor groups.

“A lot of those males are going to be roaming around the landscape and they're going to do silly stuff. They have on average more dangerous behaviours or they would be exposed to more predators,” says Llamas.

The upshot of these foolhardy males galumphing all over the place is that when palaeontologists come along millennia later looking for fossils, the chance of finding a male is greater.

On the other hand, when you find a female, it’s likely to be clustered with other females. The research team identified just a handful of such sites.

The research team posed other possibilities, some having to do with math, but osteoporosis is not mentioned. While there is no definitive answer yet, you can read about the research at Cosmos magazine. -via Damn Interesting

(Image credit: Stefan Didam)

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Is it possible that there were more male bisons than female ones that survived to adulthood (for example, male bison calves grew bigger faster and thus out-survived female calves?)
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