Evolution and Domestication: Human Involvement Altered Development of Some Animals

Humans began domesticating animals 8,000 years ago for purposes ranging from food production to companionship and this significantly changed the way both man and animal has lived. According to researchers from Linköping University (LiU), the characteristics of domesticated animals have developed differently humans began taming them.

Researchers have observed changes in animals related to size, color and reproductive behavior that, according to a news release, are related to reduced fear of humans and adapting to tamer lifestyles.

For their study, the researchers studied red junglefowl (Gallus gallus), which is a wild ancestor of all domesticated fowl. They bred selected animals that were fearful of humans, as well as those that had a reduced fear of humans as a way to note the differences that resulted from domestication.

"We used a standardized behavior 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," Beatrix Agnvall, first author of the study and a doctoral student in ethology, said in a statement.

After five generations, domesticated fowl grew larger and ate less than those that weren't domesticated and therefore remained more fearful of humans. Previous studies indicate that domesticated chickens also lay larger eggs.

Additionally, the researchers found that domesticated fowls take comfort from humans and actually act more cautiously when their human companions are abscent, which the researchers attributed these to higher levels of serotonin.

"The results show that it [domestication] can automatically have led to many of the characteristics that we and our ancestors liked about domesticated animals. 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," Per Jensen, a professor of ethology at LiU, explained in the release.

Their study, recently published in the journal Biology Letters, has potential implications for other domesticated animals as well, the researchers noted.

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