Maternal Secrets of Our First Unlocked Ancestors

Increased parental care is taken into consideration one of the hallmarks of human evolution. A new and impressive research result published today in Nature reveals for the first time the breeding habits of one of our first extinct ancestors.
The analysis of fossil teeth of Australopithecus africanus found in South Africa, more than two million years ago, revealed that the babies were continuously breastfed from birth until about one year of age. Breastfeeding seems to continue in a cyclical pattern in the first years for babies; Seasonal changes and lack of food caused the mother to supplement the foods collected with breast milk. An international research team led by Dr. Renaud Joannes-Boyau from Southern Cross University, and by Dr. Luca Fiorenza and Dr. Justin W. Adams of Monash University, published the details of their research on the species in Nature today.
"For the first time, we gained new insights into how our ancestors raised their offspring, and how mothers had to supplement the intake of solid foods with breast milk when resources were scarce," said Dr. Joannes.
"These findings tell for the first time the existence of a long-term link between mother and child in Australopithecus, that makes us rethink about social organizations among our first ancestors," said Dr. Fiorenza, an expert in the evolution of human beings.
"Fundamentally, our discovery which the mothers of Australopithecus africanus rely on the provision of nutritional supplements for their offspring and the use of alternative resources highlights the survival challenges faced by the populations of the human ancestors in the past environments of South Africa, "said Dr. Adams, an expert in paleoecology of hominids and South African sites in the BDI of Monash.
For decades there has been speculation about how the first ancestors raised their descendants. With this study, the research team has opened a new window to our enigmatic evolutionary history.
Australopithecus africanus lived about two or three million years ago during a period of great climatic and ecological changes in South Africa, and the species was characterized by a combination of features similar to those of humans and those of apes. While the first fossils of Australopithecus were found nearly a century ago, scientists have only now been able to discover the secrets of how they raised their offspring, using specialized laser sampling techniques to vaporize microscopic portions on the surface of the tooth. Then, the gas in the sample is analyzed for chemical signatures with a mass spectrometer, allowing researchers to develop microscopic geochemical maps that can tell the story of a person's diet and health over time. Dr. Joannes-Boyau performed the analyzes in the Research Group in Geoarchaeology and Archeometry of the Southern Cross University in Lismore NSW and the Icahn School of Medicine in Mount Sinai in New York.
The teeth grow similar to trees; they are formed by adding layer after layer of enamel and dentin tissues every day. Therefore, teeth are particularly valuable for reconstructing the biological events that occur during the first period of an individual's life, simply because they preserve the precise temporal changes and chemical records of the key elements incorporated into the food we eat.
By developing micro-geochemical maps, we can "read" successive bands of daily signals on the teeth, which provide information on food consumption and life stages. Previously, the team had revealed the nursing behavior of our closest evolutionary relatives, the Neanderthals. With this latest study, the international team has analyzed teeth that are ten times older than those of Neanderthals.
"We can say from the repetitive bands that appear as the tooth developed that the return meal had a high lithium content, which is believed to be a mechanism to reduce protein deficiency in babies more prone to adverse effects, "said Dr. Joannes- Boyau said.
"This probably reduced the potential number of offspring, due to the amount of time that babies depended on a supply of breast milk. The strong bond between mothers and offspring for several years has implications for group dynamics, social structure of the species, the relationships "between mother and baby and the priority that had to be given to maintaining access to reliable food," he said.
"This finding underscores the diversity, variability and flexibility in the habitats and adaptation strategies that these australopit used to obtain food, avoid predators and raise their children," emphasized Dr. Adams.
"This is the first direct test of the maternal roles of one of our first ancestors and contributes to our understanding of the history of family dynamics and childhood," Dr. Fiorenza concluded.
The team will now work on species that have evolved since then, to develop the first comprehensive record of how babies were raised throughout history.
By: Preeti Narula
Content: https://www.sciencedaily.com/releases/2019/07/190715114241.htm