ZMT: Daily Fact: Chickens are among the closest living relatives of the T. rex

Daily Fact: Chickens are among the closest living relatives of the T. rex

Original photo by The Len/ Shutterstock

Chickens might be among the closest living relatives of the Tyrannosaurus rex.

The end of the dinosaurs is often pictured as an apocalyptic event complete with a giant asteroid, a cataclysmic collision, and general fire and brimstone-type stuff, but the ends of biological epochs are rarely so cut-and-dried. In fact, the story of the dinosaurs didn't even end on that unfortunate spring day 65 million years ago, because dinosaurs still live among us — we just call them birds.

Today, scientists consider all birds a type of dinosaur, descendants of creatures who survived the mass extinction event at the end of the Cretaceous period. And yes, that even includes the chicken. In 2008, scientists performed a molecular analysis of a shred of 68 million-year-old Tyrannosaurus rex protein, and compared it to a variety of proteins belonging to many different animals. Although proteins from alligators were relatively close, the best match by far belonged to ostriches — the largest flightless birds on Earth — and the humble chicken.

Today's chicken is a descendant of a still-extant tropical bird known as the red junglefowl, and a member of an order of birds known as Galliformes (gallus means "rooster" in Latin). Following the initial 2008 study, further research has proved that a chicken's genetic lineage closely resembles that of its avian dinosaur ancestors. Scientists have even concluded that a reconstruction of T. rex's chromosomes would likely produce something similar to a chicken, duck, or ostrich. So the next time you eat a chicken for dinner, you might pause to consider its connection to some of the most fearsome beasts to ever stalk the planet.

Numbers Don't Lie

Length (in feet) of a T. rex's forearms

Number of chickens alive in the U.S. at any given time

1.522 billion

Estimated max number of generations of T. rex that lived on Earth, 68 million to 65 million years ago

188,000

Year the chicken became the first bird to have its entire genome sequenced

2004

The egg came before the chicken.

There's a well-known riddle that seems to present a biological paradox: What came first, the chicken or the egg? At first glance, the question may seem impossible to answer, but that actually depends on what you mean by "egg." Sexual reproduction emerged in nature some 2 billion years ago, and the ancestors of birds began laying eggs around 300 million years ago. With the modern chicken only emerging some 10,000 years ago, the egg — if we mean any kind of egg — clearly predates the chicken. When discussing specifically a chicken egg, the answer changes. Although scientists can't pinpoint the exact moment, at some point ancient landfowl breeders chose two of the tamest red junglefowls (Gallus gallus) and produced an egg with an embryo mutated just enough to be considered a modern chicken (Gallus gallus domesticus). In 2010, researchers found that chicken eggs can't be produced without a protein found in chicken ovaries called ovocledidin-17 — which suggests that the first chicken had to come before the first chicken egg, which was probably laid when that first chicken reached maturity at around 18 weeks of age.

Pages

Daily Fact: Chickens are among the closest living relatives of the T. rex