Carbohydrates, and especially the starches-such as cereals, beans and potatoes-may have been responsible for making us smart, says Dr Karen Hardy from the University of Barcelona. Although human brain size is believed to have increased because of meat-eating and the introduction of cooking, its growth accelerated once cooked starch was introduced into the diet.
If true, this suggests that our ancient ancestors were indeed eating food groups usually associated with farming methods, she says.
The human brain uses up to 60 per cent of the available glucose in the blood, and these high-glucose demands are unlikely to have been met on a low-carbohydrate diet, she says.
And even before farming, starches were in ready supply in the form of tubers, such as potatoes, seeds and some fruits and nuts. And once cooked, the starches would have been digestible.
Humans are among only a handful of primates that produce amylase genes from the salivary glands, and these also increase our ability to digest starch.
(Source: Quarterly Review of Biology, 2015; 90: 251)