By Sophie Mendell
With modern day technology, scientists have successfully captured and shared what a dinosaur roar sounds like. Surprised by what you hear? Assuming that the modern technology and scientists mentioned above are just phones and farmers, then these clucking and bocking chicken noises must be dinosaur roars. How could this be? Well, the simple truth is this – chickens are dinosaurs.
By evolutionary definitions, all birds are, in fact, dinosaurs. Much like humans and Neanderthals are both mammals, a stegosaurus and a seagull are both dinosaurs. This unsettling reality is due to the fact that dinosaurs are technically an evolutionary category, or clade. Clades are defined by homologous traits, which are similar features, either anatomical, genetic, or some other similarity occurring in nature, that indicate shared ancestry. When two species fall within one evolutionary clade, they originated from a common ancestor and are therefore more similar to each other than to any species from outside the clade.
Figure 1. A cladogram showing the dinosaur family tree, including distant non-dinosaur cousins like pterosaurs (flying prehistoric creatures) and modern-day dinosaurs, like chickens. Chickens fall within the theropod subclade of the dinosaur clade, which is the same branch Tyrannosaurus rex is in!
For animals to fall within the Dinosauria evolutionary clade, there are several criteria they must display. Some of these include their radius (lower arm bone) being <80% of the humerus length and having semi-opposable thumbs with grasping ability of other digits. These features, among others, are all displayed by modern birds. While most of these defining features are related to bone structure, there’s been genetic evidence supporting birds’ descent from dinosaurs. In moments of absolute luck, some scientists have found incredibly rare protein samples, dating back 70 million years ago. These collagen proteins have been used to show amino acid sequence similarity to chickens and, more distantly, alligators (fun fact: alligators are not dinosaurs). The evidence from bones and genes has been sufficient to allow scientists to conclude that birds are indeed dinosaurs.
While this may be very hard to believe, it’s crucial to understand the impact of time on these classifications. The further a species gets from the start of a clade, the less effective the clade becomes at defining the species. This is because species adapt and change with time. Think about it this way: when you start elementary school, you become a student. When you enter college, you are still a student. However, these stages, defined by time in your life, are very different. Later in life, it may be more accurate to describe yourself as a “biology student” or a “graduate student” to display the progression that’s occurred since you first became a student. So, while chickens are dinosaurs, it might be better to use additional descriptions when discussing the mighty chicken. You wouldn’t be wrong if you said you ate dinosaur for dinner if you had dino chicken nuggets, but without additional information, you would confuse a lot of people.
