How the tiger got his stripes

Posted by Emma Woollacott

As any reader of the Jungle Book knows, the tiger got his stripes when trailing creepers marked him out as a warning.

However, the great British mathematician and code-breaker  Alan Turing had other ideas - and new evidence seems to bear his theory out.

Turing suggested that regular repeating patterns in biological systems - such as the leopard's spots or the tiger's stripes - are generated by a pair of morphogens that work together as an 'activator' and 'inhibitor'.

To test the theory, researchers from King's College London, rather unbravely, we feel, examined the development of the regularly-spaced ridges found in the roof of the mouth in mice. Possibly, their cages weren't big enough for tigers.

And the team was able to identify the pair of morphogens concerned – FGF (Fibroblast Growth Factor) and Shh (Sonic Hedgehog). If you're interested in why the second of these got its name - and who wouldn't be? - it's because laboratory fruit flies that lack it have extra bristles on their bodies.

The scientists found that increasing or decreasing the activity of  these morphogens affected the pattern of the ridges in the mouth palate in just the ways predicted by Turing's equations.

"Regularly spaced structures, from vertebrae and hair follicles to the stripes on a tiger or zebrafish, are a fundamental motif in biology. There are several theories about how patterns in nature are formed, but until now there was only circumstantial evidence for Turing's mechanism," says Dr Jeremy Green from King's College London. 

"Our study provides the first experimental identification of an activator-inhibitor system at work in the generation of stripes – in this case, in the ridges of the mouth palate."