Hominids walked on modern feet 1.5 million-years ago
Footprints found at Ileret, Kenya, display anatomically modern features
Ancient footprints found at Rutgers' Koobi Fora Field School show that some
of the earliest humans walked like us and did so on anatomically modern feet 1.5
million years ago.
Published as the cover story in the Feb. 27 issue of the journal Science,
this anatomical interpretation is the conclusion of Rutgers Professor John W.K.
Harris and an international team of colleagues. Harris is a professor of
anthropology at Rutgers, The State University of New Jersey, member of the
Center for Human Evolutionary Studies and director of the Koobi Fora Field
Project.
Harris is also director of the field school which Rutgers University operates
in collaboration with the National Museums of Kenya. From 2006 to 2008, the
field school group of mostly American undergraduates, including Rutgers
students, excavated the site yielding the footprints.
The footprints were discovered in two 1.5 million-year-old sedimentary layers
near Ileret in northern Kenya. These rarest of impressions yielded information
about soft tissue form and structure not normally accessible in fossilized
bones. The Ileret footprints constitute the oldest evidence of an essentially
modern human-like foot anatomy.
To ensure that comparisons made with modern human and other fossil hominid
footprints were objective, the Ileret footprints were scanned and digitized by
the lead author, Professor Matthew Bennett of Bournemouth University in the
United Kingdom.
The authors of the Science paper reported that the upper sediment layer
contained three footprint trails: two trails of two prints each, one of seven
prints and a number of isolated prints. Five meters deeper, the other sediment
surface preserved one trail of two prints and a single isolated smaller print,
probably from a juvenile.
In these specimens, the big toe is parallel to the other toes, unlike that of
apes where it is separated in a grasping configuration useful in the trees. The
footprints show a pronounced human-like arch and short toes, typically
associated with an upright bipedal stance. The size, spacing and depth of the
impressions were the basis of estimates of weight, stride and gait, all found to
be within the range of modern humans.
Based on size of the footprints and their modern anatomical characteristics,
the authors attribute the prints to the hominid Homo ergaster, or early
Homo erectus as it is more generally known. This was the first hominid to have
had the same body proportions (longer legs and shorter arms) as modern Homo
sapiens. Various H. ergaster or H. erectus remains have been found
in Tanzania, Ethiopia, Kenya and South Africa, with dates consistent with the
Ileret footprints.
Other hominid fossil footprints dating to 3.6 million years ago had been
discovered in 1978 by Mary Leakey at Laetoli, Tanzania. These are attributed to
the less advanced Australopithecus afarensis, a possible ancestral
hominid. The smaller, older Laetoli prints show indications of upright bipedal
posture but possess a shallower arch and a more ape-like, divergent big toe.
More information:
 Other
institutions involved in this research included the George Washington
University, Liverpool John Moores University, Smithsonian Institution,
University of Cape Town and University of Nairobi.
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