30 May 2014
Domestication of dogs may explain success of early humans
by Will Parker
A new analysis of European archaeological sites suggests that early modern humans working with the earliest domestic dogs were extremely successful at killing large animals. The success of the dog-human hunting combo could explain the mysterious, massive collections of mammoth bones found in Europe.
These spectacular archaeological sites yielding 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.
The new analysis, appearing in Quaternary International, comes from Penn State Professor Emerita Pat Shipman. "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," she explained. "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.
The key to Shipman's new hypothesis is recent work by a team led by Mietje Germonpre of the Royal Belgian Institute of Natural Sciences, which uncovered evidence that some of the large carnivores at these sites were early domesticated dogs, not wolves as generally had been assumed. 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 Germonpre 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. 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 studies have yielded data that support Shipman's hypothesis. One study found that the remains identified as dogs had different diets from those identified as wolves, possibly indicating feeding by humans. In another, analysis of mitochondrial DNA by Olaf Thalmann of the University of Turku in Finland 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."
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Source: Penn State