#1840: Genetic Testing Results

XKCD comic, described below.
Transcript

[Cueball is seated on an medical examination table while Ponytail stands dressed in a doctor's coat holding a file in her right hand.]

Ponytail: Your genetic test results are back. Apparently you're part of an unbroken lineage stretching back billions of years to the early Earth!

(Sourced from explainxkcd.com)

That's very exciting! The bad news is that it's a risk factor for a lot of things.

ExplainOriginal