Secrets in your bones

The assignment of a headless skeleton to the 19th-century Irish-Australian folk hero Ned Kelly is forensic DNA's latest coup. DNA is resilient. Tiny quantities from bodily fluids, hair, skin or bone can be amplified using the polymerase chain reaction (PCR). Specific repeat patterns within DNA are unique to each of us and are readily seen after PCR. The repeats are inherited by our offspring; it was a match to Kelly's sister's great-grandson that allowed the identification.

This is nothing compared to Tutankhamun's mummified DNA, which survived more than 2,000 years. And there was the sequencing of a 38,000-year-old Neanderthal genome. Preserved microbial DNA is now tracing the historical plagues of mankind. The debate about whether medieval Europe's Black Death was a "plague" rather than an ebola-like haemorrhagic virus was resolved when bones in ancient burial pits yielded the plague bacterium's DNA.

Did Charles Darwin die of Chagas disease, a parasitic infection that's common in Latin America? During his voyage on the Beagle, Darwin was attacked by reduviid bugs that transmit the disease. The intestinal and cardiac problems that troubled him in later life are symptoms typical of Chagas. Finding parasite DNA in his bones would close the case, if only the dean of Westminster Abbey would let us investigate.