A new analysis of European archaeological
sites containing large numbers of dead mammoths and dwellings built with
mammoth bones has led Penn State Professor Emerita Pat Shipman to formulate a
new interpretation of how these sites were formed. She suggests that their
abrupt appearance may have been due to early modern humans working with the
earliest domestic dogs to kill the now-extinct mammoth -- a now-extinct animal
distantly related to the modern-day elephant. Shipman's analysis also provides
a way to test the predictions of her new hypothesis. Advance publication of her
article "How do you kill 86 mammoths?" is available online through Quaternary
International.
Spectacular archaeological sites yielding stone tools and
extraordinary numbers of dead mammoths -- some containing the remains of
hundreds of individuals -- suddenly became common in central and eastern
Eurasia between about 45,000 and 15,000 years ago, although mammoths previously
had been hunted by humans and their extinct relatives and ancestors for at
least a million years. Some of these mysterious sites have huts built of
mammoth bones in complex, geometric patterns as well as piles of butchered
mammoth bones.
"One of the greatest puzzles about these sites is how
such large numbers of mammoths could have been killed with the weapons
available during that time," Shipman said. Many earlier studies of the age
distribution of the mammoths at these sites found similarities with modern
elephants killed by hunting or natural disasters, but Shipman's new analysis of
the earlier studies found that they lacked the statistical evaluations
necessary for concluding with any certainty how these animals were killed.
Surprisingly, Shipman said, she found that "few of the
mortality patterns from these mammoth deaths matched either those from natural
deaths among modern elephants killed by droughts or by culling operations with
modern weapons that kill entire family herds of modern elephants at once."
This discovery suggested to Shipman that a successful new technique for killing
such large animals had been developed and its repeated use over time could
explain the mysterious, massive collections of mammoth bones in Europe.
hand-drawn map
These maps show the locations of collections of mammoth
bones at the archaeological sites that Pat Shipman analyzed in her paper that
will be published in the journal Quaternary International. Credit: Jeffrey Mathison
The key to Shipman's new hypothesis is recent work by a team
led by Mietje Germonpré of the Royal Belgian Institute of Natural Sciences,
which has uncovered evidence that some of the large carnivores at these sites
were early domesticated dogs, not wolves as generally had been assumed. Then,
with this evidence as a clue, Shipman used information about how humans hunt
with dogs to formulate a series of testable predictions about these mammoth
sites.
"Dogs help hunters find prey faster and more often, and
dogs also can surround a large animal and hold it in place by growling and
charging while hunters move in. Both of these effects would increase hunting
success," Shipman said. "Furthermore, large dogs like those
identified by Germonpré either can help carry the prey home or, by guarding the
carcass from other carnivores, can make it possible for the hunters to camp at
the kill sites." Shipman said that these predictions already have been
confirmed by other analyses. In addition, she said, "if hunters working with
dogs catch more prey, have a higher intake of protein and fat, and have a lower
expenditure of energy, their reproductive rate is likely to rise."
Another unusual feature of these large mammoth kill sites is
the presence of extraordinary numbers of other predators, particularly wolves
and foxes. "Both dogs and wolves are very alert to the presence of other
related carnivores -- the canids -- and they defend their territories and food
fiercely," Shipman explained. "If humans were working and living with
domesticated dogs or even semi-domesticated wolves at these archaeological
sites, we would expect to find the new focus on killing the wild wolves that we
see there."
Two other types of studies have yielded data that support
Shipman's hypothesis. Hervé Bocherens and Dorothée Drucker of the University of
Tubingen in Germany, carried out an isotopic analysis of the ones of wolves and
purported dogs from the Czech site of Predmostí. They found that the
individuals identified as dogs had different diets from those identified as
wolves, possibly indicating feeding by humans. Also, analysis of mitochondrial
DNA by Olaf Thalmann of the University of Turku in Finland, and others, showed
that the individuals identified as dogs have a distinctive genetic signature that
is not known from any other canid. "Since mitochondrial DNA is carried
only by females, this finding may indicate that these odd canids did not give
rise to modern domesticated dogs and were simply a peculiar, extinct group of
wolves," Shipman said. "Alternatively, it may indicate that early
humans did domesticate wolves into dogs or a doglike group, but the female
canids interbred with wild wolf males and so the distinctive female
mitochondrial DNA lineage was lost."
As more information is gathered on fossil canids dated to
between 45,000 and 15,000 years ago, Shipman's hunting-dog hypothesis will be
supported "if more of these distinctive doglike canids are found at large,
long-term sites with unusually high numbers of dead mammoths and wolves; if the
canids are consistently large, strong individuals; and if their diets differ
from those of wolves," Shipman said. "Dogs may indeed be man's best
friend."
No comments:
Post a Comment