Fossil teeth reveal how 'Australopithecus' suckled

Fossil teeth reveal how 'Australopithecus' suckled

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Humans tend to breastfeed exclusively for six to twelve months, and you can keep breastfeeding alongside other foods in later years. Babies of the extinct Australopithecus africanus followed a similar pattern and they could even lengthen it at certain times.

An international team led by the US National Institutes of Health (NIH) has reached this conclusion. The study, published in the latest issue of the journal Nature, indicates that these hominids, who lived about three million years ago in South Africa, suckled their young to ensure food in times of scarcity.

This research is "the first indication of the duration of breastfeeding in one of our oldest ancestors," says Renaud Joannes-Boyau, a scientist at the University of Southern Cross in New South Wales, Australia and one of the authors. of the study.

To reach these conclusions, scientists analyzed the composition of five fossil Australopithecus africanus teeth, between 2.6 and 2.1 million years old and found in Sterkfontein Cave, on the outskirts of Johannesburg.

“Like trees, teeth contain growth rings that can be counted to estimate age. They have layers of enamel accumulated during development and include chemical signs that reflect the food we eat and the environments we live in, ”explains the researcher.

The scientists were able determine the diet of these Australopithecus Thanks to a method, developed by Christine Austin, a researcher at the Icahn School of Medicine in New York (USA), which uses the inductive laser ablation plasma mass spectrometer. This technique is minimally invasive, "something crucial in rare specimens like those of A. africanus," says Joannes-Boyau.

Breast milk as dietary support

The results revealed patterns of accumulation of barium, a mineral present in breast milk, which suggested that the pups were fed only milk for six and nine months, followed by a progressive introduction of solid foods. “We saw that, after one year of age, A. africanus individuals returned to consuming breast milk regularly for years after initial weaning,” he details.

According to the researcher, “current breastfeeding lasts approximately one year in industrialized countries, although it seems to be longer in less technologically developed human groups. Neanderthals show a similar pattern. On the other hand, great apes like chimpanzees nurse for much longer, around five years. With Australopithecus africanus we see a mixing pattern ”.

The authors suggest that this could be due to the seasonal food shortage suffered by A. africanus. Their diet was highly varied, as revealed by the enormous diversity of dental morphology, and included fruits, leaves, herbs, and roots. However, he lived in savannas, where winters are dry and resources are scarce.

The cyclical accumulations of lithium in the analyzed teeth reveal that the species did not always have food available during the dry season and that babies were breastfed during those periods, although they are already over a year old.

This pattern has important implications for knowledge about this species. One could know "how many children a mother could have in her life, the social interactions within the species or even the reasons why they became extinct", Joannes-Boyau emphasizes.

This research also shows that fossil teeth “at least two million years old keep a record of their first life episodes through your chemical signature. There is potential to test this method with other hominin species, ”he adds.

However, the scientist acknowledges that in the case of earlier species such as Australopithecus afarensis or Ardipithecus ramidus, the study will require more work. "We will have to make sure that these chemical signatures are preserved in teeth that are millions of years older," he concludes.

Bibliographic reference:

Joannes-Boyau, R, et al. "Elemental signatures of Australopithecus africanus teeth reveal seasonal dietary stress”. Nature (July 15, 2019). DOI: 2018-09-13492E

Video: Teeth and Human Evolution


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