Two sets of fossilized teeth found in the Sterkfontein Cave near Johannesburg, South Africa, were studied to understand more about how these early human ancestors responded to seasonal dietary changes.
There was also evidence of cyclical patterns of lithium in the teeth, which suggests food scarcity because it can vary in conjunction with body mass.
"For the first time, we've gained new insight into the way our ancestors raised their young, and how mothers may have adapted to seasonal food shortages with breastfeeding," said Renaud Joannes-Boyau, lead study author and head of the Geoarchaeology and Archaeometry Research Group at Southern Cross University in Australia.
"Seeing how breastfeeding has evolved over time can inform best practices for modern humans by bringing in evolutionary medicine.
Our results show this species is a little closer to humans than the other great apes which have such different nursing behaviors," said Christine Austin, study co-author and assistant professor of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai.
When Lucy, the world's most well-known fossil, was discovered sticking out of a shallow Ethiopian stream bed in 1974, she provided new insight about life for early human ancestors 3.18 million years ago.
How did Lucy, our early human ancestor, die 3 million years ago?