Many of us like nothing more than tucking into a fiery chicken madras or lamb bhuna, but the majority of other animals do their best to avoid hot, spicy foods such as chillies – which is precisely why such plants evolved to be hot and spicy in the first place. However, we’re not entirely alone: tree shrews (Tupaia belangeri chinensis) will also happily chow down on chilli peppers when given the chance. Now, an analysis of their genome by researchers at China’s Kunming Institute of Zoology has explained the secret of their tolerance.
Spicy foods derive most of their heat from a chemical called capsaicin. When eaten, capsaicin triggers the activation of TRPV1 – a receptor channel found on the surface of pain-sensitive cells in the tongue and elsewhere. TRPV1’s regular job is to alert animals to the presence of potentially harmful heat, which is why we experience a burning sensation and often start to perspire when eating spicy foods.
The team began their study of the tree shrew after they were shocked to see captive animals happily munching on chilli peppers. They discovered that a single mutation in the shrews’ TRPV1 gene decreases their receptors’ sensitivity to capsaicin. While chilli peppers do not grow within the shrews’ natural range, a plant called Piper boehmeriaefolium, which contains a substance similar to capsaicin called Cap2, does. It’s therefore believed that shrews with the mutation in question gained an evolutionary advantage over those without, thanks to their expanded diet.
This is an extract from issue 326 of BBC Focus magazine.
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