Reading Kinship in DNA Bands

Each bird’s DNA can be written out as a long line of chemical letters, drawn here as coloured bands stacked in a strip. Counting how many bands differ between two species tells you which pair split from a shared ancestor most recently, even when their bodies look nothing alike.

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In the picture

The ostrich, standing along the top beside the emu and the kiwi.
The strip of coloured bands under the emu: the same stretch of DNA, read band by band.
The odd-coloured band in the ostrich’s strip, where the letter does not match the other two birds.
The high fork where the emu and kiwi lines meet: their most recent shared ancestor.
The low fork where the ostrich line joins: a far older shared ancestor.

Examples

Human and chimpanzee DNA differs at roughly one letter in a hundred, placing our shared ancestor only a few million years back.
A dog breed DNA test works the same way: the lab matches letter patterns against reference breeds instead of judging the dog by its looks.

Key takeaways

Fewer letter differences between two species means a more recent common ancestor.
Looking alike is not proof of close kinship; separate lineages can evolve similar bodies.