10. Bonus: Shared ERVs Establish Human-Chimp Common Ancestry
Humans have a genome that is 3.2 billion base pairs. Retroviruses are viruses that insert DNA into your genome at unpredictable locations. When this happens in egg and sperm cells, every descendant inherits that DNA at the exact same spot. Most are nonfunctional.
Humans, chimps and monkeys share thousands of identical insertions at the exact same positions. EACH of these happening without common ancestry is astronomically unlikely.
Nested pattern
- oldest are shared by all three
- newer ones are shared by only humans and chimps
- the newest aren't shared
The probability of all these shared insertions arising independently at these exact same positions in this nested pattern is effectively zero without common ancestry.