Domestic Chicken

The domestic chicken (Gallus gallus domesticus) is the most numerous bird on Earth, with tens of billions alive at any time. It was domesticated from the red junglefowl of Southeast Asia thousands of years ago.

🧬 Field Guide Specimen: Open Domestic Chicken in the CRV Science Field Guide to log the specimen, see its place among the Reptilia lineages in the Cladogram Explorer, and test your recall in the Red List conservation game.

The red junglefowl (Gallus gallus) is the main ancestor, but genetic work showed that the yellow skin of many chickens came from the gray junglefowl, through ancient hybridization. Chickens spread across Asia, Europe and Africa with people.

The chick embryo develops in an egg that can be opened and watched, and is a classic system for studying how limbs, hearts and nervous systems form. The staging table of Hamburger and Hamilton from 1951 remains the standard. The chicken was also the first bird and first domestic animal to have its genome sequenced, in 2004.

Birds descend from small feathered theropod dinosaurs, and experiments that turned on ancestral developmental programs have produced chicken embryos with dinosaur-like snouts and teeth-like structures. See Evolutionary developmental biology.

• Evolutionary developmental biology — chick embryos and evolution
• Embryogenesis — staging of development