Stone Age people
were extreme travellers
Gli Uomini dell' Età della Pietra erano grandi viaggiatori
Two new studies published February 27 in the Journal of
Human Evolution advance the idea that ancient people and Neandertals walked or
ran far greater distances than any human groups that followed, including more
recent hunter-gatherers and today’s long-distance runners. Fossils of humans
and their beetle-browed evolutionary cousins display signs of extremely
extended travel that occurred between roughly 120,000 and 10,000 years ago,
Colin Shaw and Jay Stock, biological anthropologists at the University of
Cambridge in England report in one of the studies.
Chemical
signatures of stone spear points from a southern African site (shown) indicate
that people there regularly obtained tool-making rock from more than 220
kilometers away [Credit: Sheila Coulson, U. of Oslo]
Shaw and Stock conclude that the Stone Age crowd moved
around considerably more than southern Africans from a few thousand years ago
who hunted over an area of 5,200 to 7,800 square kilometers. Highly trained
athletes today who run 130 to 160 kilometers every week come in third in this
mobility comparison.
Human ancestors started wandering long distances around
1.7 million years ago. The extent to which particular Stone Age species and
groups roamed the landscape has been difficult to establish.
Shaw and Stock’s findings support an argument for
extreme mobility among ancient people and Neandertals that has been championed
over the last 15 years by Erik Trinkaus of Washington University in St. Louis
and Christopher Ruff of Johns Hopkins University. Clues come from exceptionally
robust leg bones, a dearth of older individuals in fossil samples suggesting
that life spans were limited due to the rigors of constant travel, and an
absence of skeletal injuries in excavated fossils that would have prevented
vigorous movement, Trinkaus says.
Shaw and Stock used a calculation of the lower leg’s
ability to withstand twisting and other forces to compare Stone Age hominids’
leg strength with that of human groups with known activity levels: varsity
distance runners, varsity swimmers, non-athletic college students, Andaman
Island foragers from the 1800s who swam constantly in pursuit of food, and
southern African hunter-gatherers who hunted over a vast territory between
11,000 and 2,000 years ago.
Ancient human and Neandertal legs substantially overpowered
those of the hunter-gatherers, who had stronger legs than the other groups.
Regular swimmers brought up the rear, perhaps partly because swimming
emphasizes upper- over lower-body strength, the researchers suggest.
Anthropologists don’t know what kept ancient people and
Neandertals in constant motion. It could have been the hunt for spear-worthy
rock, the second new study suggests. Chemical analyses of stone spear points
from one southern African site indicate that silcrete spear points from 54,000
to 94,000 years ago chemically matched silcrete outcrops located more than 220
kilometers away, but not others situated only 70 kilometers away,
Rock reconnaissance missions began near the northwestern
shore of an inland delta in what’s now Botswana, propose physical geographer
David Nash of the University of Brighton in England and his colleagues.
Journeyers headed to several rock sources just beyond the delta’s southernmost
reaches.
Travel of that extent must have involved collecting both
rock for spear points and game and fish possibly not available in the northern
delta, Nash suggests. Or middleman groups could have collected blocks of stone
and transported them partway north for trade. “We cannot say for certain what
happened,” Nash says.
References
Source: A. Bower, from ScienceNews [March 08, 2013]
