Gallus gallus, the undomesticated ancestor of modern chickens
Chickens, the surviving descendants of once-mighty therapod dinosaurs, have come to dominate American dinner tables, where its meat is consumed at a rate of 80 pounds per person per year. How the wild grub-eating Gallus Gallus was tamed and commodified into frozen breaded cutlets is actually quite an epic story, one that involves (possibly) saving Greek civilization from Persians, the rise and fall of the Roman Empire, and continues today with KFC’s remarkable invasion of China.
Jerry Adler and Andrew Lawler have written a cover story for Smithsonian magazine on the taming of the chicken that delivers these tidbits and gives plenty more food for thought. It was the Egyptians, for example, who first figured out how to artificially incubate eggs, so they could be hatched without the presence of hens—a method so important that their methods were kept secret for centuries:
What’s the News: As human societies adopted agriculture, their people became shorter and less healthy, according to a new review of studies focused on the health impacts of early farming. Societies around the world—in Britain and Bahrain, Thailand and Tennessee—experienced this trend regardless of when they started farming or what stapled crops they farmed, the researchers found.
This finding runs contrary to the idea that a stable source of food makes people grow bigger and healthier. The data suggest, in fact, that poor nutrition, increased disease, and other problems that plagued early farming peoples more than their hunter-gatherer predecessors outweighed any benefits from stability.
Hounds, pointers, and other dogs bred for their excellent abilities to pick up a scent tend to have longer snouts—but it’s not just that a bigger nose is a better one. Researchers have found that human domestication of dogs has shifted the structure and alignment of some dogs’ brains. And in those varieties with shorter snouts—which humans bred for other reasons, like appearance—the olfactory brain region rotated to a different part of their skull, leaving scientists to question whether we’ve crossed up their smelling abilities (and perhaps more).
Since the first wolf was domesticated an estimated 12,000 years ago, “selective breeding has produced a lot of [anatomical] variation, but probably the most dramatic is in terms of skull shape,” said study co-author Michael Valenzuela [National Geographic].
For this study, which appears in the open-access journal PLoS One, Valenzuela and colleagues examined the brains of 11 dog breeds and found great variation in the size and shape of their skulls. The breeds with shorter snouts had brains that rotated forward by as much as 15 degrees over the generations, the scientists say. That means that the olfactory lobe, as well as other parts of these dogs‘ brains, has shifted position and shape because humans guided their evolution through domestication.
At some point in evolutionary history dogs diverged from wolves thanks to domestication by humans. But just where did dogs first become man’s best friend? Robert Wayne and his team have many years invested in answering the question, and their newest findings, published this week in Nature, suggest that the answer is the Middle East.
Researchers looked at gene segments from 912 dogs, from 85 breeds, and samples of 225 grey wolves, dog’s close cousins who they evolved from in prehistory, from 11 regions [USA Today]. Dogs and wolves that come from the Middle East, Wayne says, show the most genetic similarity. The researchers propose that dogs were first domesticated there, and then spread outward.
Dogs and wolves are closely related enough that they have interbred at various times, complicating the problem of unraveling dogs’ origin. Wayne’s team suggests that after the domestication of dogs in the Middle East, they interbred with wolves when they reached East Asia, which is how dogs and wolves there came to share some of their genetics.
Scientists knew that the Aztec people of pre-Columbian Mexico had domesticated the turkey by the time Europeans arrived, and that those birds are the forebears of the giant birds Americans devour in gut-busting volume every Thanksgiving. But a new study (pdf) in the Proceedings of the National Academy of Sciences suggests that the Aztecs weren’t the only early Americans to tame the turkey: People of what is now the Southwestern United States, including the Anasazi, separately domesticated the birds.
Two teams that had been separately studying the bones and the fossilized dung of ancient turkeys joined forces for this find. Studying 38 different sites, they found that the Aztec peoples accomplished the feat first. But later, perhaps around 200 B.C., they saw that the people of the Southwest United States duplicated the achievement. The two instances of domestication appear to have been separate, based on DNA analysis of ancient turkey remains. However, the different Native American groups could have been in contact with each other, sharing turkey-raising tips [Discovery News].
It may not come as much of a surprise to dog-owners, but it seems that dogs and babies share similar logical abilities, as shown by a study published in Science.
Experimenters started out with a classic logic experiment, which goes like this: researchers hide a toy in location “A” multiple times while looking at a 10-month-old baby and talking to him (“Look, I have this nice ball!”). When asked to find the toy, the baby always goes to location “A.” The experimenter then hides the toy at location “B,” again while interacting with the baby. But this time, when asked to find the toy, the baby continues to search for it at location “A.” The findings hold, even when a team changes experimenters midtest. Researchers believe that infants make this error because they believe the adults have taught them something fundamental about the world (i.e., “Your toy will always be at location ‘A’”) [ScienceNow].
Scientists trying to determine where dogs were first domesticated have been sent back to the drawing board by a new study. Back in 2002, researchers sampled DNA from dogs around the world, and determined that dogs in East Asia had the most genetic diversity, suggesting that the species originated there and that dogs in that region have had the longest time to evolve. But the new study suggests that those earlier results were skewed, because DNA sampling of African street dogs has revealed equal genetic diversity.
The earlier findings may have been thrown off because the large-scale study included both purebred dogs, whose evolution has been closely guided by human hands, and street dogs, who have bred more autonomously and randomly, and who therefore show more genetic diversity. But the 2002 researchers drew DNA from different types of dogs in different regions. Says Adam Boyko, lead researcher of the new study: “I think it means that the conclusion that was drawn before might have been premature. It’s a consequence of having a lot of street dogs from East Asia that were sampled, compared to elsewhere” [BBC News].
On the steppes of Central Asia, researchers have found evidence of the earliest “horse farm” dating from 5,500 years ago, pushing back the known domestication of horses by 1,000 years. Those first domesticated horses were probably kept primarily for meat and milk, researchers say, but soon enough new uses emerged, and horse riding revolutionized transport, communications, trade, and warfare. Says study coauthor Sandra Olsen: “To me, the domestication of the horse was a seminal event in human history…. All the major empire builders, like Alexander the Great and Genghis Khan, would have been nothing without horses” [Los Angeles Times].
The evidence of the early farm developed by the ancient Botai people of present-day Kazakhstan includes massive deposits of horse bones, grooved horse teeth that indicate the animals wore bridles, and even the chemical traces of horse milk fats in ceramic pots, says study coauthor Alan Outram. “This is, apart from being fascinating, something of a smoking gun for domestication — would you milk a wild horse?” said Outram [AP]. The people of Kazakhstan and Mongolia still milk mares today to make a fermented, slightly alcoholic drink called “koumiss.”
Thousands of years ago a few bold wolves moved into a human encampment, and human lives have been richer ever since. But a new study shows that domesticated dogs gave something back to their wild cousins. A genetic analysis has revealed that the dark black coats common among wolves living in North America arose through wolves mating with dogs, who already had dark fur.
The finding presents a rare instance in which a genetic mutation from a domesticated animal has benefited wild animals by enriching their “genetic legacy.” … Because black wolves are more common in forested areas than on the tundra, the researchers concluded that melanism — the pigmentation that resulted from the mutation — must give those animals an adaptive advantage [The New York Times]. But what that advantage may be remains something of a mystery.