The same thing that makes the patchwork colours on a tortoiseshell cat, also - according to some - is why human females live longer, see colour better, and even more often survive the coronavirus. It's all thanks to having two X chromosomes. Females compensate by switching one of them off, and the result is two distinct groups of cells in the body, each preferring one of the two X's. Welcome to the weird world of female mosaicism... Like this podcast? Please help us by supporting the Naked Scientists