Your closest living relative is a cousin
- The idea
- Predict
- See it
- Why
- Check
The idea
“Of two closest living relatives, one evolved from the other, like humans from chimps.”
Chimps share most of our DNA and sit right next to us on the tree, so they look like our ancestors. They're alive today too.
The short version
The mistake: Of two closest living relatives, one evolved from the other, like humans from chimps.
What's actually true: Closest living relatives both descend from a common ancestor at the node they share. Neither is the other's ancestor.
- On a tree of living species, each tip is alive today. Each node, where branches split, is a common ancestor from the past.
- Groups that split from the same node are sister groups. Like cousins, neither descends from the other.
- Since the split, both lineages have evolved for equally long. Keeping more ancestral traits doesn't make a species older, less evolved, or an ancestor.
- The more recent the node two groups share, the closer they are. The order of the tips doesn't show who came from whom.
On the exam: Living species are tips and ancestors are nodes. Two living species are cousins, never parent and child.