CRISPR began as a bacterial immune system, not a human invention

Doudna and Sternberg trace CRISPR's origins to an obscure feature of bacterial DNA first noticed by microbiologists studying how bacteria defend themselves against viral infections. Bacteria, it turned out, store snippets of viral DNA from past infections in repeating sequences called CRISPR arrays, using this genetic memory together with a protein called Cas9 to recognize and slice apart the DNA of viruses that attack them again.

The authors emphasize that no human engineer designed this system — evolution had already solved the problem of programmable, sequence-specific DNA cutting billions of years before scientists understood what they were looking at. The breakthrough wasn't inventing a new molecular tool from scratch, but recognizing that this ancient bacterial defense mechanism could be reprogrammed with a synthetic guide sequence to target essentially any DNA of choice, human or otherwise.

Takeaway: some of biology's most powerful tools already exist in nature — the human contribution is learning to redirect them.