Pigmentation and aggression

Richard Macey:

Now two Sydney biologists have found evidence that redheads, in the bird world at least, may have an evolutionary advantage allowing them to rule the pecking order.

They made their discovery after observing hundreds of endangered Gouldian finches, brightly coloured birds from northern Australia that can have red, black or yellow heads.

After breeding hundreds for testing, Sarah Pryke and her University of NSW colleague, Dr Simon Griffith, put a redheaded and a blackheaded bird in a cage to see which one claimed control of the seed bowl. They repeated the test using yellowheads.

The reds controlled the bowl 74 per cent of the time against blacks and 81 per cent of the time against yellows, while blacks frightened off yellowheads 57 per cent of the time.

When redheads were dyed black, they still remained aggressive and retained control of the bowl, but the blacks challenged them more often.

And yellowheads dyed red found the previously tougher blackheads backed off. "It was as if they were saying 'we won't mess with you because you're a redhead'," Dr Pryke said.

She said a possible explanation was that genes for colour may be inherited along with genes that control hormones, including testosterone.

But while redheads ruled the roost, they were very stressed from fighting and died younger.

While reluctant to speculate on whether evolution had given humans with different coloured hair varying levels of dominance, she agreed it was hard not to wonder. "It may be why we associate red with aggression."

I wonder if there are any scientists brave enough to conduct this sort of research in humans?