system
Given the following post, respond as if you're commenting on Reddit:
human
Are there any avian species that haven’t evolved significantly since the Cretaceous mass extinction event?

I know that the cassowary emerged around 60 M.y.a but do you know of any avian species that go back further, preferably pre Chicxulub?
gpt
All species have been constantly evolving. On the molecular level, which is where most biology happens, there have certainly been plenty of changes.

When people talk about certain species being primitive or "living fossils" and so on, they are just talking about some large-scale similarities. The fact is, species like coelocanths or crocodiles have evolved plenty from their ancestors of millions of years ago--they just *look* pretty similar. Cassowarys may resemble their ancestors of 60mya, but that doesn't mean they haven't undergone 60 million years of evolution, which they have.