August 11, 2016
The new study that for the first
time examined the internal anatomy of a fossil human relative's heel bone, or
calcaneus, shows greater similarities with gorillas than chimpanzees.
The study, titled
"Trabecular architecture in the StW 352 fossil hominin calcaneus,"
and published in the Journal of Human Evolution, was undertaken by a team
of international researchers from the University of the Witwatersrand in South
Africa, Duke University, University of Southern California and Indiana
University in the US.
The team examined the internal
anatomy of our human relative,
the StW 352 Australopithecus africanus fossil, from South Africa's rich fossil
record in the Cradle of Humankind World Heritage Site, some 40km from
Johannesburg.
They analyzed the structure and
orientation of trabecular struts – the spongy material inside a bone – in the
fossil from Sterkfontein Member 4, demonstrating greater similarities between
it and the heel bone of gorillas rather
than humans or chimpanzees.
In doing this, the team revealed
new insights into how our ancestors moved through and interacted with their
environment approximately 2 – 2.5 million years ago. Similarities between the
fossil from Sterkfontein and gorillas indicate that Australopithecus africanus,
the species of human ancestor (or hominin) also represented by the Taung Child,
or at least this individual member of the species, exhibited gorilla-like
levels of joint mobility and structural reinforcement.
Results of the new study were
surprising because other recent studies of the australopithecine calcaneus,
focusing on its external anatomy, have emphasised similarities with chimpanzees
or humans.
However, since the organisation
of trabecular bone is determined in part by how an animal interacts with its
environment during its lifetime, the gorilla-like features observed in the
present study are particularly compelling in revising how we view behavioural
reconstructions of our australopithecine ancestors.
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