Explanation: The myth that cockroaches will inherit the Earth in the event of nuclear warfare surfaced shortly after the United States dropped atomic bombs on Hiroshima and Nagasaki in 1945. Reports later emerged that the 300 million-year-old insects were among the razed Japanese cities' only survivors. During the Cold War, anti-nuclear activists and scientists spread the myth far and wide as a cautionary tale of the atom bomb's destructive potential.
To test whether this doomsday scenario has any legs, the MythBusters subjected German cockroaches to three levels of radioactive metal cobalt 60. They started with a baseline exposure of 1,000 radon units (rads) of cobalt 60, capable of killing a person in 10 minutes, and followed it up with 10,000 and 100,000 rad exposures on separate guinea pig — er, roach — groups. (As a comparison, the bomb on Hiroshima emitted radioactive gamma rays at a strength of around 10,000 rads.)
Since radiation gradually destroys organisms on the cellular level, the MythBusters monitored the radiated roaches for 30 days. After a month, half the roaches exposed to 1,000 rads were still kicking, and a remarkable 10 percent of the 10,000 rad group was alive. The results confirmed that cockroaches can survive a nuclear explosion — but only to a point, as none of the critters in the 100,000 rad group made it through.
Cockroaches' ability to withstand extreme radiation exposure may come down to their simple bodies and slower cell cycles. Cells are said to be most sensitive to radiation when they're dividing. That's why humans are more vulnerable — they have some cells that are constantly splitting up.
Roaches, on the other hand, only molt about once a week at most, which makes radiation's window of opportunity to attack cells much narrower. But if the nuclear explosion was powerful enough, even these ancient critters couldn't continue on.