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Mixed spice

The idea that cooks in hot countries adopted spices to help prevent food poisoning in sweltering conditions may sound logical, but new Australian research suggests spicier cuisines do not lead to healthier citizens.

The results may come as a blow for proponents of “Darwinian gastronomy”, who have theorised that a taste for spice developed in warmer climates – where food spoils more easily – because some spices can kill bacteria and fungi that attack food.

The new study in Nature Human Behaviour, led by the Australian National University (ANU), throws doubt on their conclusions.

The scientists analysed 33,750 recipes from 70 cuisines, which included a total of 93 different spices.

“We show that average number of spices per recipe is more strongly associated with socioeconomic factors than infectious disease,” says ANU’s Lindell Bromham, the lead researcher. 

“Areas with lower GDP per capita – greater poverty – have higher average number of spices per recipe.”

The study team – including biologists and mathematicians – also compiled environmental and socioeconomic data associated with each cuisine, then ran detailed statistical analyses to examine the complex interactions between these factors and food.

For instance, although the study did show that the average number of spices per recipe changes with temperatures, “that’s largely because nearby and related cultures tend to have the same environment and similar cuisines,” Bromham says.

And, in fact, “there’s no significant association between temperature and spice.”

Instead of a neat Darwinian gastronomy conclusion, the research found a broader association between spice, health, and poverty. Results showed that areas with lower average life expectancy – poorer health outcomes – have higher average number of spices per recipe.

But the relationships between these factors are tricky.

“The important thing is that life expectancy and GDP are general indicators of socioeconomic development, so they tend to be associated with a whole lot of things that all vary together,” says Bomham.

“In fact, GDP per capita is a better predictor of spice than infection risk, diversity of spices, crops or other plants, cultural diversity, climate, population density, or latitude.

“Why? It’s hard to tell.”

This study highlights just how difficult it is to study the complex patterns of human cultural evolution. Even answering a seemingly simple question is challenging because of the intertwined nature of culture, environment and socioeconomic conditions.

“We can show that GDP and life expectancy are better at predicting average number of spices per recipe than measure of infection risk, but we don’t know why,” says Bromham.

Nearly 34,000 recipes later, she says the key unanswered question is how to design studies to test such tricky cultural evolutionary questions.