Mythconception: Can cockroaches survive a nuclear wipeout?

Lewis Thomson has been working out who, or what, could survive a nuclear holocaust.

Lewis - Cockroaches: these creepy crawlies are incredibly hardy creatures able to survive what would kill most of us. You can squeeze a cockroach to a quarter of it’s normal height and it will crawl away unharmed. It’s even said that if there was a nuclear war, cockroaches would be the only thing left alive. But is that actually true?

Well, while cockroaches are able to tolerate high temperatures, nothing on Earth could survive the heat produced by a nuclear bomb exploding. The temperature within a ten metre radius of the explosion becomes hotter than the surface of the Sun. If the cockroaches were far enough away, they could survive the initial blast. But what about the nuclear fallout?

When a nuclear bomb explodes it releases ionising radiation, and this kind of radiation contains enough energy to break apart chemical bonds including those holding our DNA together. This means our cells stop working properly and can die causing vomiting, hemorrhage, seizures and, in many cases, death. So are cockroaches somehow immune to these problems?

Well, it’s true that cockroaches are able to tolerate much higher levels of radiation than we can. In a rather unpleasant experiment, the animals were subjected to high radiation levels for a month. Radiation is measured in a unit called Gray - 10 Gray would kill a human in a few days. But some of the cockroaches survived a months exposure to 100 Gray. So why are cockroaches better than humans when it comes to surviving radiation?

Well, DNA is most vulnerable to radiation damage when it’s dividing. This happens any time your body is making new cells, which in us is happening all the time. But cockroaches, like most insects, produce new cells at a much slower rate and so the proportion of cells in the body that will be vulnerable to radiation damage is much lower than in humans. But would this be enough to save them from nuclear war?

The nuclear bomb which was dropped in Hiroshima in 1945 is estimated to have emitted between 4 and 12 Gray of radiation in a one kilometre radius, so cockroaches would have been okay. But today’s nuclear weapons are estimated to be several thousand times more deadly so a global nuclear war today would almost certainly wipe out cockroaches.

However, there are some organisms on Earth that might survive. Thermococcus gammatolerans is a species of Archaea - a group similar to bacteria which lives in boiling hot hydrothermal vents on the ocean floor. It can tolerate 30,000 Gray - that’s over 3,000 times what humans can cope with. One species of fungus has been found growing inside the melted reactor of the Chernobyl nuclear power plant, finding a way to convert the radiation into energy for itself.

While cockroaches have a better chance than us at surviving nuclear war, they probably wouldn’t. The only things we’re pretty sure would survive are a few species of Archaea, bacteria and fungi. So let’s hope humanity has the sense to not hit that big red button.