Everyone knows that about 65 million years ago, a massive asteroid hit the Earth and wiped out all the dinosaurs. Except, well, not so much. Most species of dinosaurs went extinct in the aftermath of the impact, but some survived. Those survivors continued on, breeding and evolving over the epochs. Today, there are at least 10,000 species of dinosaur that roam the planet, and they come in a huge diversity of sizes, shapes, and colors. We call them — you guessed it — birds.
Phylogenetic is a fancy word for how we classify animals based on genetic relationships between species. The goal of phylogenetics is to produce a phylogeny, a family tree of life. Scientists are finding that the most useful way to group organisms is by clade, which includes all descendants of a given common ancestor. The principles of phylogenetic analysis suggest this is the only correct way of classifying species.
The alternative is to group by class — that is, related organisms that display certain characteristics. The problem with this method is that an organism could get kicked out of a group if it evolves to no longer exhibit a distinguishing feature of its ancestors. This approach gets messy pretty quick — it would be like redrawing your whole family tree because you have blue eyes but none of your ancestors did.
So, back to dinosaurs: Dinosaurs are organisms that belong to the clade Dinosauria. Hundreds of millions of years ago, the first dinosaur was born from two not-quite-dinosaur parents. All of the descendants of this original dino are dinosaurs, no matter how varied or diverse. And birds, as it turns out, are among them. Image above shows what Tyrannosaurs Rex really looked like.
Image top of page: With thanks to HT Photo