Branching off first doesn't make a species primitive
- The idea
- Predict
- See it
- Why
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The idea
“The species that branches off first, or looks simplest, is the one the others came from.”
Lampreys have no jaws and platypuses lay eggs. Trees often draw them off to one side, like leftovers from the start.
The short version
The mistake: The species that branches off first, or looks simplest, is the one the others came from.
What's actually true: Every living species is a tip of the tree. Its lineage has evolved just as long as every other one since they split.
- Each node is a common ancestor that lived in the past. Living species sit at the tips, in the present.
- Any two living tips trace back to their shared node over the same time, so neither is more evolved.
- Some lineages changed slowly and others quickly, but all kept evolving.
- Every species mixes ancestral traits with new, derived ones. Losing a part can be derived too, like snakes losing their legs.
On the exam: The ancestor is a node, never a living tip. All living tips have evolved equally long since they split.