Dog skull found in Siberia is 33,000 years old - and hints that man's best friend didn't come from one single ancestor

Teeth and jaws show animal was domesticated
One of the oldest domesticated dogs ever found
Hints that man may have domesticated dogs in several places - all dogs
aren't evolved from one ancestor
By Rob Waugh

Last updated at 4:42 PM on 24th January 2012

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An ancient dog skull preserved in a cave in the Altai Mountains of
Siberia for 33,000 years has turned our ideas of man's relationship
with his 'best friend' on its head.

The skull is the remains of one of the oldest examples of a
domesticated dog ever found - and its sheer age, combined with equally
ancient dog remains from a cave in Belgium, hints that humans may have
domesticated dogs in several places.
Modern dogs may have more than one ancestor.
The Altai skull was particularly well preserved, and allowed
researchers to measure its teeth, jaws and snout for evidence it was
The Siberian skull is extraordinarily well-preserved. The scientists
were able to take multiple measurements of its skull, teeth and jaws.
The researchers are convinced it was domesticated - but it also
doesn't appear to be an ancestor of today's dogs.

Recent DNA research hinted that dogs all came from one single ancestor
- so everything from a bulldog to a poodle evolved from a single
wolf-like ancestor.

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This find hints that the evolution of domestic dogs might be more
complex than what scientists had thought.

‘Both the Belgian find and the Siberian find are domesticated
species,’ said Greg Hodgins, a researcher at the University of
Arizona's Accelerator Mass Spectrometry Laboratory and co-author of
the study that reports the find.
Recent DNA research hinted that all dogs came from a single wolf-like
ancestor - but the Altai find may prove that isn't so
‘Essentially, wolves have long thin snouts and their teeth are not
crowded, and domestication results in a shortening of the snout and
widening of the jaws and crowding of the teeth.’
The Altai Mountain skull is extraordinarily well preserved, said
Hodgins, enabling scientists to make multiple measurements of the
skull, teeth and mandibles that might not be possible on less
well-preserved remains.
‘The argument that it is domesticated is pretty solid,’ said Hodgins.
‘What's interesting is that it doesn't appear to be an ancestor of
modern dogs.
The UA's Accelerator Mass Spectrometry Laboratory used radiocarbon
dating to determine the age of the Siberian skull.
Radioactive carbon, or carbon-14, is one of three carbon isotopes.
Along with naturally occurring carbon dioxide, carbon-14 reaches the
surface of the Earth by atmospheric circulation, where plants absorb
it into their tissues through photosynthesis.
The researchers carbon-dated the skull to work out its age

Measurements of the Altai skull clearly show it is a domesticated
animal - and combined with similarly ancient remains from Belgium, it
hints that the history of man's best friend is more complex than

Animals and humans take in carbon-14 by ingesting plants or other
animals that have eaten plants. ‘Carbon-14 makes it into all organic
molecules,’ said Hodgins. ‘It's in all living things.’
‘We believe that carbon-14 production is essentially constant over
time,’ said Hodgins.

‘So the amount of carbon-14 present in living organisms in the past
was similar to the levels in living organisms today. When an animal or
plant dies, the amount of carbon-14 in its remains drops at a
predictable rate, called the radioactive half-life. The half-life of
radiocarbon is 5,730 years.’
‘People from all over the world send our laboratory samples of organic
material that they have dug out of the ground and we measure how much
carbon-14 is left in them.'
Based on that measurement, and knowing the radiocarbon half-life, we
calculate how much time must have passed since the samples had the
same amount of carbon-14 as plants and animals living today.’
At 33,000 years old, the Siberian skull predates a period known as the
Last Glacial Maximum, or LGM, which occurred between about 26,000 and
19,000 years ago when the ice sheets of Earth's last ice age reached
their greatest extent and severely disrupted the living patterns of
humans and animals alive during that time.

Neither the Belgian nor the Siberian domesticated lineages appear to
have survived the LGM.
However, the two skulls indicate that the domestication of dogs by
humans occurred repeatedly throughout early human history at different
geographical locations, which could mean that modern dogs have
multiple ancestors rather than a single common ancestor.
‘In terms of human history, before the last glacial maximum people
were living with wolves or canid species in widely separated
geographical areas of Euro-Asia, and had been living with them long
enough that they were actually changing evolutionarily,’ said Hodgins.
‘And then climate change happened, human habitation patterns changed
and those relationships with those particular lineages of animals
apparently didn't survive.’
‘The interesting thing is that typically we think of domestication as
being cows, sheep and goats, things that produce food through meat or
secondary agricultural products such as milk, cheese and wool and
things like that,’ said Hodgins.
‘Those are different relationships than humans may have with dogs. The
dogs are not necessarily providing products or meat. They are probably
providing protection, companionship and perhaps helping on the hunt.
And it's really interesting that this appears to have happened first
out of all human relationships with animals

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