Of so repeated the idea that, after a nuclear holocaust, the humanity would perish but the cockroaches would survive, in the end we have forgotten to explain the reason that it could happen.
First, let’s clarify: if a nuclear explosion occurs, cockroaches will not survive if they are close. For example, the 15-kiloton bomb that exploded in Hiroshima triggered a 982 ° C firestorm that incinerated everything within a radius of 1.9 km. What the cockroach would do is survive the subsequent radioactive fallout.
And is that the common cockroach can withstand no less than 6,400 rads (the standard measure of ionizing radiation). In comparison, the lethal dose for a human being is only 500 rads.
The reason for this resistance to radioactivity is only a hypothesis. In their larval period, cockroaches experience a weekly change during which their cells subdivide at half the usual frequency. Already adults, they are subdivided even less. Radiation causes the majority of mutations in replicating DNA, that is, it is more frequent in cells that are subdividing. This slowness protects the cockroaches from mutation.