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Skull of Australopithecus africanus. Photo: Luca Fiorenza
How our ancestors sucked
Pre-human breastfeeding
habits unlocked.
By Dallas Bastian
O
ur two-million-year-old ancestors
continually breastfed infants from
birth until they were about one
year old, an analysis of teeth has revealed.
Led by Southern Cross University and
Monash University, the international team
behind the study looked at teeth from
Australopithecus africanus, which hailed
from what was likely a somewhat harsh
limestone landscape in South Africa.
Study contributor Professor Andy
Herries, head of La Trobe University’s
Archaeology and History Department, said
the research potentially shows that living
in these environments was difficult for our
early ancestors, particularly as the climate
began to change around two million years
ago. The species faced long alternating
periods of abundance and scarcity of
nutritious food. And it wasn’t long until
Australopithecus africanus became extinct.
It was those tough conditions that caused
mothers to supplement gathered foods
with breastmilk, explained geochemist
Dr Renaud Joannes-Boyau, from the
Geoarchaeology and Archaeometry
6
Research Group at Southern Cross
University.
As teeth are the only part of the human
skeleton that has direct contact with the
environment and form through incremental
layers of enamel and dentine, the authors
said they are particularly valuable for
reconstructing biological events from an
individual’s early life.
Chemical signatures locked in the teeth
reveal what young fossil humans were
eating from day to day, month to month,
explained Dr Alistair Evans, an expert in
hominin palaeoecology at the Monash
Biomedicine Discovery Institute (BDI).
To release the information about our
ancestor’s consumption, the researchers
used specialised laser sampling techniques
to vaporise microscopic parts of the tooth’s
surface that could be analysed for chemical
signatures.
One of the trace elements the team
zeroed in on was barium, as previous
research has shown that the levels of
barium in teeth correspond with increases
in mother’s milk intake and slowly
decreases during weaning.
Published in the journal Nature, the
study found that barium, along with lithium
and strontium, increased for the first year
after birth and then continued in a cyclical
pattern in the child’s early years.
Artist’s impression of Australopithecus africanus.
Image: Garcia and Renaud Joannes-Boyau
University of New England Professor
Stephen Wroe, a collaborator on the study,
said this switching on and off of milk supply
to sustain offspring when times were tough
reveals mothers developed strong and
persistent relationships with their children.
Dr Luca Fiorenza, an expert in the
evolution of human diet at BDI, said that
finding makes researchers rethink the social
organisations among our earliest ancestors.
The team will now turn its attention to
species that evolved after two million years
to develop the first comprehensive record
of how infants were raised throughout the
extinction of Australopithecus and the first
occurrence of Homo. ■