I stumbled across this article while surfing for dog brain size info. It was originally entitled “Dogs and the Human Brain Size – Theory Suggests Greater Role for Man’s Best Friend.” It was posted to [email protected], and the credit for authorship goes to Shelly Simmonds. The article is quite fascinating, and adds an interesting twist to the Dog Intelligence question with regard to the synergistic relationship between man and dog. Let’s just call this Part 3 in our Dog Intelligence series (Parts 1 and 2 can be found here and here).
Dogs and humans have been best friends for a long time – about 100,000 years – according to the latest estimates. But one ANU anthropologist could create a new controversy with his latest hypothesis about the human-dog relationship.
According to Dr Colin Groves, Reader in the Department of Archaeology and Anthropology in the Faculty of Arts, not only did we domesticate dogs, but dogs may have domesticated us.
Dr Groves believes early humans came to rely on dogs’ keen ability to hear, smell and see – allowing certain areas of the human brain to shrink in size relative to other areas.
“Dogs acted as humans’ alarm systems, trackers and hunting aids, garbage disposal facilities, hot-water bottles and children’s guardians and playmates. Humans provided dogs with food and security. This symbiotic relationship was stable over 100,000 years and intensified in the
Holocene [Period] into mutual domestication,” said Dr Groves. “Humans domesticated dogs and dogs domesticated humans.”
In a keynote address to the Australasian Society for Human Biology in December, Dr Groves repeated an assertion made by others as early as 1914 – that humans have some of the same physical characteristics as domesticated animals, the most notable being decreased brain size.
The horse experienced a 16 per cent reduction in brain size after domestication while pigs’ brains shrank by as much as 34 per cent. The estimated brain-size reduction in domesticated dogs varies from 30 per cent to 10 per cent.
Only in the last decade have archaeologists uncovered enough fossil evidence to establish that cranial capacity in Homo sapiens declined in Europe and Africa by at least 10 per cent beginning in the Holocene Period, about 10,000 years ago.
Dr Groves believes this reduction may have taken place as the relationship between humans and dogs intensified and the animals allowed for the diminishing of certain human brain functions like smell and hearing.
Brain size is not uniformly reduced with domestication, said Dr Groves. The forebrain and the corpus callosum shrink the most while the midbrain and the medulla are least affected; in humans, however, the midbrain and the olfactory bulbs are strongly reduced.
Dogs are by far the oldest domesticated species, showing up on the archaeological record about 10,000 years ago. Until recently this was widely accepted as the date for the domestication of dogs.
However, a ground-breaking paper by a group of international geneticists last year pushed this date back by a factor of 10.
Led by Robert Wayne, at the University of California Los Angeles, the team showed that all dog breeds had only one forbear, the wolf, by analysing the mitochondrial DNA of 162 wolves from around the world and 140 domestic dogs representing 67 breeds.
“The study found that dogs have been separate from wolves for as long as different geographic groups of wolves have been separate from each other – and that is a very long time indeed,” said Dr Groves.
The present day gene pool of dogs is varied and well-mixed, according to the study. A review of the research in Science magazine noted that only one other mammal exhibits the rare combination of vast genetic diversity and widespread well-mixed gene pool – humans.
A coincidence? Dr Groves doesn’t think so.
I once watched a documentary that refuted the widely held view that wolves are “endangered.” The producers of that show instead suggested that wolves and their progeny (dogs), should be considered the most successful animal in the world besides humans. The current article suggests that our dog-buddies actually “enticed” us into a dependency on them by allowing us to rely less on certain senses. In turn, they took advantage of our superior “practical” intelligence. Hey, who’s really running the show here? (Apparently we truly are “hooked on dogs”).
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