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Today, Bengal's crude bombs are known locally as peto.

This hypothesis starts with "Peto's paradox," Vollrath told Live Science.

In the 1970s, an epidemiologist named Richard Peto described a puzzling phenomenon: Large animals, despite having many more cells that could potentially turn into cancerous cells, don't seem to have a higher risk of developing cancer than smaller animals.

Scientists call it Peto's paradox: cancer is caused by gene mutations that accumulate in cells over time, yet long-lived animals that have lots of cells, such as elephants and whales, hardly ever get it.

But University of Oxford epidemiologist Richard Peto sees another way.