After all, at some point, one of our ancestors had to break with tradition ... a-billion-year-old fossil a the beginning of the phylum Chordata. That’s why it came as quite a surprise when ...

“We’re part of the same phylum called Chordata. We share a common ancestor. Those in Chordata have backbones. So, this will also include birds, dogs, cats, cows and many other animals.

Amphioxus is the most basal extant chordate and is thought to closely resemble the invertebrate ancestor of the vertebrates. Zebrafish, a teleost, is one of the most experimentally tractable ...