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By analyzing the fossilized teeth of some
of our most ancient ancestors, a team of scientists led by the universities of
Bristol (UK) and Lyon (France) have discovered that the first humans
significantly breastfed their infants (婴儿) for longer periods than their
contemporary relatives.
The results, published in the
journal Science Advances, provide a first insight into the practice of weaning
(断奶)that
remain otherwise unseen in the fossil record.
The team sampled minute amounts
from nearly 40 fossilized teeth of our South African fossil relatives, early
Homo, Paranthropus robustus and Australopithecus africanus. They measured the
proportions of their stable calcium isotopes (同位素）in the tooth enamel(牙釉质), which are a function of the mother milk intake by infants. They
show that early Homo offspring(后代) was breastfed in
significant proportions until the age of around three to four years, which
likely played a role in the apparition of traits that are specific to human
lineage(血统), such as the brain development.
In contrast, infants of
Paranthropus robustus, that became extinct around one million years ago and
were a more robust species in terms of dental anatomy, as well as infants of
Australopithecus africanus, stopped drinking sizeable proportions of mother
milk in the course of the first months of life.
These differences in nursing
behaviors likely come with major changes in the social structures of groups as
well as the time between the birth of one child and the birth of the next.
One of the study's lead
authors, Dr Theo Tacail said: "The practice of weaning -- the duration of
breastfeeding, age at non-milk food introduction and the age at cessation of
suckling -- differs among the modern members of the hominid family which
includes humans and modern great apes: orangutan, gorillas, chimpanzees and
bonobos.
The development of such
behavioral differences likely played major roles in the evolution of the
members of human lineage, being associated for instance with size and structure
of social groups, brain development.
However, getting insights into
these behavioral changes from fossils that are millions of years old is a
challenge and, so far, little evidence allow discussing nursing practices in
these fossil species.
The findings stress the need
for further exploration of calcium stables isotopes compositions in the fossil
record in order to understand the co-evolution of weaning practices with other
traits such as brain size or social behaviors."
http://www.dentaldailynews.com/first-human-ancestors-breastfed-for-longer-than-contemporary-relatives/
https://www.sciencedaily.com/releases/2019/08/190829115427.htm
