Modern humans began to cook plant starches, such as those from roots and tubers, as far back as 120,000 years ago, scientists say.
The researchers discovered charred food remains from hearths found at the Klasies River Cave in South Africa's southern Cape.
They findings provide the first archaeological evidence that anatomically modern humans were roasting and eating plant starches as early as 120,000 years ago.
The study, published in the Journal of Human Evolution, supports the hypothesis that the duplication of the starch digestion genes is an adaptive response to an increased starch diet.
"The genetic and biological evidence previously suggested that early humans would have been eating starches, but this research had not been done before," said Cynthia Larbey at the University of Cambridge in the UK.
The work is part of a research into the role that plants and fire played in the lives of Middle Stone Age communities.
The team searched for and analysed undisturbed hearths at the Klasies River archaeological site.
"Our results showed that these small ashy hearths were used for cooking food and starchy roots and tubers were clearly part of their diet, from the earliest levels at around 120,000 years ago through to 65,000 years ago," said Larbey.
"Despite changes in hunting strategies and stone tool technologies, they were still cooking roots and tubers," she said.
The research shows that "early human beings followed a balanced diet and that they were ecological geniuses, able to exploit their environments intelligently for suitable foods and perhaps medicines," said Sarah Wurz from the University of the Witwatersrand in Johannesburg, South Africa.
By combining cooked roots and tubers as a staple with protein and fats from shellfish, fish, small and large fauna, these communities were able to optimally adapt to their environment, indicating great ecological intelligence as early as 120,000 years ago.
"Starch diet isn't something that happens when we started farming, but rather, is as old as humans themselves," said Larbey. Farming in Africa only started in the last 10,000 years of human existence.
Humans living in South Africa 120 000 years ago formed and lived in small bands.
"Evidence from Klasies River, where several human skull fragments and two maxillary fragments dating 120 000 years ago occur, show that humans living in that time period looked like modern humans of today. However, they were somewhat more robust," said Wurz.
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