Myth: Only cockroaches would survive an extreme nuclear fallout.
You’ve probably heard that “the only living things that would survive a nuclear war would be cockroaches”. It has even be suggested that cockroaches can survive the amount of radiation at ground zero of a nuclear explosion, though of course, not the explosion itself.
In any event, more recent research has shown that, while cockroaches can withstand ionizing radiation bursts about 10 times as high as humans, they actually are relative light-weights in that arena. In fact, it only takes a burst of about 1,000 rads to significantly interfere with a cockroaches’ ability to reproduce, which would obviously be the eventual end of the cockroach. For reference, this is about the level of radiation at around only 15 miles from Hiroshima directly after the bomb was detonated (aside: the Hiroshima bomb was a 15 kiloton weapon, which is nothing next to the 20-50 megaton nuclear bombs that can be found in most nuclear stockpiles today).
Further, at levels of around just 6,400 rads, about 94% of immature cockroaches will die, and at around 10,000 rads most adult cockroaches will not survive. While this is very impressive by human standards (humans only being able to survive about 400-1000 rads before death), it’s decidedly unimpressive by insect standards; most insects can survive much higher rates than the cockroach, according to the United Nations Scientific Committee on the Effects of Atomic Radiation.
So who are the actual living creatures that would inherit the Earth after a world-wide nuclear war? Well, it has been shown that fruit flies take around 64,000 rads to kill. More impressive than that is the flour beetle which can withstand up to around 100,000 rads before dying. Even better is a type of wasp, the Habrobracon, that can survive as high as 180,000 rads! However, these all get beat by the Deinococcus radiodurans microbe. This bacteria can survive radiation levels as high as 1.5 million rads at room temperature and nearly 3 million rads when frozen.
Origins of the Myth
It isn’t entirely clear where the myth that cockroaches were impervious to ionization radiation got started, but it seems to have been largely popularized by anti-nuclear activists in the 1960s who often used the cockroach in their slogans and campaigns. For instance, in a New York Times advertisement sponsored by the National Committee for a Sane Nuclear Policy:
“A nuclear war, if it comes, will not be won by the Americans … the Russians … the Chinese. The winner of World War III will be the cockroach.”
Bonus Science Stuff:
The primary reason cockroaches and many types of insects are so resistant to ionizing radiation is that their cells don’t divide that much between molting cycles. Cells are most susceptible to damage by ionizing radiation when they are dividing. Given that a typical cockroach only molts about once a week and its cells only divide around a 48 hour period during that week, about 3/4 of the cockroaches exposed would not be particularly susceptible to damage by ionizing radiation, at least, relative to those whose cells were currently dividing.
As you might have inferred from this, this means that if the radiation experienced by these cockroaches was consistent over a long period of time, they are going to be significantly more susceptible to problems than the numbers quoted in this article. The above numbers are using specific bursts of radiation over a short span. Given that at any given moment about 75% of cockroaches aren’t experiencing cellular dividing, about 75% of them are going to be much less susceptibility to damage from these short bursts of radiation, which will drastically skew the numbers of what the species as a whole could survive when talking about a global nuclear fallout scenario. More accurate research would then have to be done to see what levels of radiation kill or otherwise will significantly harm the roaches that are currently having their cells divide. Further, ionizing radiation is cumulative, so that would have to be factored in as well.
The largest nuclear bomb ever detonated was the Tsar Bomba, detonated by the Soviet Union. This bomb was estimated at around 100 megatons of TNT or about just shy of 7000 times more powerful than the nuclear bomb dropped on Hiroshima.
The Deinococcus radiodurans microbe was first discovered growing on rotten canned meat that had been sprayed with an ionizing substance meant to preserve it. This microbe had no problems surviving such low levels of radiation.
A cell’s increased susceptibility to damage by ionizing radiation when dividing is why humans and other mammals are so susceptible to this radiation, given that we experience cellular dividing all the time. This is also why radiation is effective at such low doses at killing cancer cells, relative to what is required to damage healthy cells. Cancer cells divide much quicker than most other cells in the human body; thus, you can kill the cancer cells faster than the healthy cells and hopefully find a happy medium where all the cancer cells die, but enough of the healthy cells remain and are undamaged enough for the person to continue living on more or less as before.
While cockroaches may not be well equipped to survive nuclear fallout, relative to various microbes and most of their insect brethren, these little critters are extremely hardy with fossil records of cockroaches dating all the way back to 300 million B.C., which pre-dates dinosaurs by around 70 million years. Cockroaches have been shown to survive with their heads chopped off for nearly a month. Further, they can survive as much as 45 minutes without oxygen and can survive on very low quality of food, such as the glue on a postage stamp or cellulose.
[Reposted (with editing) from Misconception Junction]