Prehistoric Humans Began Eating Tubers 700,000 Years Before Our Teeth Evolved To Do So

[Judi Lynn]

What we lacked in teeth we made up for with smarts.

Benjamin Taub
Freelance Writer

Edited
by
Laura Simmons

Around 2.3 million years ago, ancient human species such as Homo rudolfensis and Homo erectus suddenly changed their diets. Using their large brains, these extinct hominins manufactured digging tools that they used to access carbohydrate-rich tubers, bulbs, and corms, despite the fact their teeth were unsuited to chewing these starchy plant fibers.

By analyzing the carbon and oxygen isotopes in the fossilized teeth of prehistoric humans, the authors of a new study were able to reconstruct these dietary changes, revealing that it took a further 700,000 years for our ancestors’ molars to catch up with their culinary behaviors. The findings provide concrete evidence to support the theory of behavioral drive, which holds that dietary habits and other behaviors that are beneficial for survival can trigger corresponding morphological changes.

"As anthropologists, we talk about behavioral and morphological change as evolving in lockstep,” said study author Luke Fannin in a statement. “But we found that behavior could be a force of evolution in its own right, with major repercussions for the morphological and dietary trajectory of hominins."

Based on the isotopes in the teeth of an early hominin called Australopithecus afarensis, the researchers discovered that humans began feeding on herbaceous grassy plants known as graminoids around 3.8 million years ago. However, about 1.5 million years later, the isotopic ratios in the teeth of some Homo species suddenly changed, indicating a massive increase in consumption of oxygen-depleted waters.

Tellingly, these isotopic values are indistinguishable from those of fossilized mole-rats, which fed on the bulbs and corms of certain graminoids. The study authors therefore conclude this abrupt switch reflects an increase in the consumption of underground storage organs like tubers, which reflect the oxygen-depleted waters of the surrounding soil.

More:
https://www.iflscience.com/prehistoric-humans-began-eating-tubers-700000-years-before-our-teeth-evolved-to-do-so-80249