Dental News - Tooth analysis reveals secrets of our earliest ancestors

Dental Tribune International

Wed. 24. July 2019

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LISMORE/MELBOURNE, Australia: Extended parental care is considered one of the hallmarks of human evolution. Through tooth chemistry analysis, scientists were able to examine teeth that are more than 2 million years old. The findings allowed them to demonstrate why early human ancestors had fewer offspring and an extended parenting role.

Analysis of the teeth, from Australopithecus africanus fossils found in South Africa, has revealed that the infants were breastfed continuously from birth to about 1 year of age. Nursing appears to have continued in a cyclical pattern in the early years for the infants. Seasonal changes and food shortages caused the mother to supplement gathered foods with breast milk. An international research team, led by Dr Renaud Joannes-Boyau of Southern Cross University in Lismore, and Drs Luca Fiorenza and Justin Adams from Monash University in Melbourne, has published details of its research into the species, which lived between two to three million years ago.

“For the first time, we gained new insight into the way our ancestors raised their young, and how mothers had to supplement solid food intake with breast milk when resources were scarce,” said geochemist Joannes-Boyau from the Geoarchaeology and Archaeometry Research Group at Southern Cross University. For decades, there has been speculation about how early ancestors raised their offspring. With this study, the research team has opened a new window into our enigmatic evolutionary history.

Teeth grow similarly to trees: they form by adding layer after layer of enamel and dentine every day. Thus, teeth are particularly valuable for reconstructing the biological events occurring during the early period of life of an individual, simply because they preserve precise temporal changes and chemical records of key elements incorporated in the food eaten. By developing micro-geochemical maps, researchers can “read” successive bands of daily signal in teeth, which provide insights into food consumption and stages of life.

A) Plan view of the Sterkfontein surface excavation showing the association between the type site excavation and Member 4 deposits. B) Photograph of fossil teeth of specimen StS 28. C) Upper first molar (M1) StS 28B. D) Permanent lower first molar (M1) StS 28C, after being sectioned in two with a diamond low-speed high-precision rotary saw. E) Photograph of fossil teeth of specimen StS 51. F) Permanent premolar (P3) StS 51A. G) Permanent canine (LC) StS 51B, after being sectioned in two with a diamond low-speed high-precision rotary saw. The two teeth that are still embedded in the breccia were not sectioned. (Image and photograph: Southern Cross University and Monash University)

“We can tell from the repetitive bands that appear as the tooth developed that the fallback food was high in lithium, which is believed to be a mechanism to reduce protein deficiency in infants more prone to adverse effect during growth periods,” Joannes-Boyau explained further. He added: “This likely reduced the potential number of offspring, because of the length of time infants relied on a supply of breast milk.”

“This finding underscores the diversity, variability and flexibility in habitats and adaptive strategies these austral piths used to obtain food, avoid predators, and raise their offspring,” Adams, an expert in hominin palaeoecology and South African sites, emphasised.

It was announced in a press release that the team will now work on species that have evolved more recently, in order to develop the first comprehensive record of how infants were raised throughout history.

The study, titled “Elemental signatures of Australopithecus africanus teeth reveal seasonal dietary stress”, was published online on 15 July 2019 in Nature, ahead of inclusion in an issue.

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Analysis Ancestors Earliest Of Our Reveals Secrets Tooth

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