Research by ethologists at Linköping University (LiU) in southern Sweden shows that many of these changes in size, colour, reproduction and behaviour in animals has been driven by the fact that the animal populations that humans selected to domesticate grow increasingly tame.
The study is published in Biology Letters.
The researchers used a population of red junglefowl (Gallus gallus), the wild ancestor of all domesticated fowl.
For five generations they selected animals with a congenital reduced fear of humans, and bred their offspring. For comparison, they also bred a separate line from the fowl that were most fearful of humans.
“We used a standardised behaviour test where we studied the fowl’s reaction to a human. This method resembled the conditions during the very first stage of fowl husbandry 8,000 years ago,” says Beatrix Agnvall, doctoral student in ethology and first author of the article.
After just five generations, the increasingly tame fowl had developed a higher metabolism and feed conversion rate – meaning they grew more even as they ate less than the more fearful animals in the control group.
They were also more cautious in situations where humans were not involved, and, as in previous studies of the same animals, they laid larger eggs. The levels of the hormone serotonin were higher in the tame roosters, and the researchers believe that this can be one of the mechanisms driving the results.
“The results show that it can automatically have led to many of the characteristics that we and our ancestors liked about domesticated animals,” Per Jensen, professor of ethology at LiU and head of the study, said.
“Therefore we can suppose that our ancestors didn’t necessarily select animals because they were good at producing food, but mainly because they were easy to manage,” says Prof Jensen, who believes the results could also apply to other domesticated animals like pigs, sheep and cattle.
Bill Condie is a science journalist based in Adelaide, Australia.
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