Once relegated mostly to farms and breeding facilities, chickens are now commonplace as pets.
Sure, they're not the most glamorous birds, but they have quite an interesting story, and that story begins in the dinosaur age. Curious? Here's a primer on chicken evolution and domestication.
The chicken's origins lie in a group of dinosaurs called the theropods, which evolved into two categories some 230 million years ago: the Ceratosauria and the Tetanurae. The Ceratosauria then split again into the ceratosauroids and the coelophysoids. The latter eventually resulted in the genetic line that produced the Tyrannosaurus rex.
In 2003, paleontologist Jack Horner discovered a 68-million-year-old T. rex fossil in Montana. Inside its thigh bone, scientists found a blood vessel they were able to analyze. Their phylogenetic analysis revealed that, genetically speaking, the domestic chicken is the closest living relative of T. rex.
Now, let's fast-forward a bit to examine the chicken's more recent evolutionary history.
The modern chicken, as we know it, is descended from several of four known species of wild jungle fowl (Gallus) that inhabited parts of Southeast Asia about 50 million years ago.
Scientists believe the red jungle fowl, Gallus gallus, is the most likely progenitor of the modern chicken, although research suggests that the domestic chicken's yellow skin is a trait inherited from the gray jungle fowl, Gallus sonneratii.
So, it's more than likely that today's chicken has multiple ancestors.
Chickens initially became domesticated between 8,000 and 10,000 years ago. There's also genetic evidence to suggest that there were simultaneous but independent domestication events in different parts of Asia and India.
According to computational biologist Michael Zody, it's difficult to pinpoint the domestic chicken's origins and domestication history because the long history of interbreeding between wild and domesticated birds has resulted in inconclusive DNA evidence.
Once chickens were domesticated, they were used for food, fighting, and religious purposes. Various cultures spread them around the world over the course of thousands of years via migration, trade, and territorial conquests.
The Polynesians brought chickens to the Pacific coast of South America around 1200 A.D. Over a period of several hundred years, and mostly due to the popularity of cockfighting, inhabitants of the New World became well versed in chicken care and breeding. Spanish explorers brought chickens to North America, and chickens soon became widely dispersed across the continent.
From dinosaurs to backyard pets, chickens have been around, in some form or another, for millions of years.