Chickens Are Closest Living Relatives to T. Rex

The long-held theory that birds descended from dinosaurs was largely based on skeletal similarities, such as wishbones and three-toed feet. The "smoking gun" confirming this relationship, however, arrived in a spectacular fashion from a 68-million-year-old Tyrannosaurus rex femur. When scientists were forced to break the massive bone for transport from its remote excavation site, they discovered astonishingly well-preserved soft tissue, including blood vessels and fragments of a durable protein called collagen.

This prehistoric protein provided the first opportunity for a direct molecular comparison between a non-avian dinosaur and modern animals. After painstakingly sequencing the ancient collagen, researchers compared it to a database of living creatures. The results were conclusive and surprising: the T. rex's protein structure was most similar to that of the common chicken. The next closest match was the ostrich, further solidifying the avian link. This landmark analysis moved the bird-dinosaur connection from a strong hypothesis to a near certainty, proving that the fearsome predator (Review)'s closest living relative is a common barnyard animal.