Snakes are able to convert their venom back into harmless molecules that scientists say could help find a cancer cure.
A joint British-Australian study of venom and tissue gene sequences in snakes showed that venom not only evolved from regular cells but could be turned back into harmless proteins.
Gavin Huttley, from the Australian team, said it was the first time snakes' venom had been shown to evolve back into regular tissues and was a significant finding for the development of drugs for conditions like cancer or diabetes.
Snake venom typically targets the same physiological pathways as many human diseases and Huttley said understanding how the venom molecule changed form could help scientists develop new drug cures.
Some snake venoms, for example, cause the cells that line blood vessels to separate and die, including the kinds that feed cancerous tumors, and Huttley said mapping how that worked could lead to more effective cancer treatments.
"It highlights that venom molecules, these things that actually kill us, in fact are just derivatives of normal proteins," said Huttley, from the Australian National University.
"By studying the molecular events you get an idea about what it takes to make a protein to target those specific physiological functions," he said.
Huttley described a snake's venom gland as "like a small drug company, running huge numbers of experiments on evolutionary timescales with new molecules and seeing what works".
The scientists had essentially "piggybacked" on the snake's internal research to try and map the amino acid changes involved in the evolution of regular cells into venom and back again, he said.