What is a Clade?
In biology and biological taxonomy, a clade is a group consisting of a single common ancestor, all the descendants of that ancestor, and nothing else. Over centuries of work, biological taxonomy has endeavored to split groups into clades, rejecting non-clade classifications, which are referred to as “paraphyletic.” True clades are “monophyletic.” An example of a true clade would be birds. Birds are believed to all descend from a common ancestor that lived about 150 million years ago. However, reptiles and apes are not clades. Reptiles aren’t a clade because birds descended from reptiles (dinosaurs), and birds aren’t considered reptiles. A group that excludes descendants of a common ancestor isn’t a clade. Apes aren’t a clade because humans descended from apes and humans generally aren’t considered apes. If you include humans and the extinct relatives of humans, like Neanderthals, to be apes, then apes are a clade, but this generally isn’t done. Simpler organisms, such as arthropods (cr
