Are Chickens Our Closest Relatives to the Dinosaurs? Debunking the Myth

Introduction

From time immemorial, birds have captured the human imagination as remnants of prehistoric creatures. One common misconception is that chickens are the closest living relatives to dinosaurs, particularly Tyrannosaurus Rex (T. Rex). This article delves into the truth behind this popular belief, examining the scientific evidence and evolutionary timeline that debunk the myth.

The Evolutionary Connection

According to Matthew Haynes, all living birds are equally as closely related to T. rex. The divergence of bird lineages occurred sometime in the late Triassic or early Jurassic period. Thomas Holtz’s excellent GEOL 104 Lecture Notes, a freely available textbook-quality resource, provides a clear illustration to simplify this complex topic.

Coelurosauria: The Theropod Lineage

Birds and Tyrannosaurs are both coelurosaurs, which belong to the diverse and successful Coelurosauria lineage. While both are theropod dinosaurs, the exact branch they belong to on the evolutionary tree has implications for their degree of similarity to T. rex.

On the cladogram, birds (represented as eumaniraptora) are positioned far from Tyrannosauridae. However, they are still coelurosaurs, making them more similar to T. rex than other extinct dinosaur lineages. In terms of mammalian analogy, birds may be as distant from T. rex as mammals like cats and dogs—both predators with similar body plans but evolved independently over tens of millions of years.

Comparing Current Birds to T. Rex

Since we do not have a complete genome sequence for any tyrannosaur, and likely never will, the genetic similarity between birds and Tyrannosaurus remains a mystery. However, by looking at anatomical features, we can better understand their evolutionary relationship.

Paleognaths and Their Similarities to T. rex

Among modern birds, the most basal and anatomically closest to their distant ancestors are the paleognaths, which include ratites like ostriches, emus, rheas, and ostriches. Ostriches and rheas are particularly thought to be the closest to the last common ancestor of all paleognaths, making them likely the most similar to the last common ancestor of Tyrannosauridae and eumaniraptorans, including Tyrannosaurus.

Therefore, while domestic chickens (galliformes) are part of the family that includes all living birds, they are not the closest to T. rex. Instead, all birds are equally as related to T. rex, meaning chickens are as close as any other bird.

Conclusion

Chickens, while an observable and familiar example of birds, are not the closest cousins to Tyrannosaurus Rex. All birds are equally related to T. rex, making them the closest living relatives. The myth of chickens being specifically close to T. rex bleeds more from popular science fiction than scientific evidence. Understanding the broader picture of avian evolution helps dispel this and other misconceptions.