One of these is about how quickly it takes biological systems to decay. It would be expected that if a particular mechanism is no longer needed, the species might get rid of it. But a new study of rare male Timema stick insects shows that this isn’t necessarily the case. “Males and females have a different number of X chromosomes; males have one (XY), and females have two (XX),” explains Dr Darren Parker, from Bangor University, in a statement. “The result of this is that gene expression needs to be balanced equally between them. Species have evolved a wide range of mechanisms known as ‘dosage compensation’ to do just this. But what happens when these mechanisms for equally sharing male and female genes are no longer needed?” “This is the precise situation found in asexually reproducing stick insects. Because the females reproduce without fertilization from males, there is no need to equalize gene expression. By investigating gene expression in rare males, our study found that rather than decaying away as we expected, dosage compensation mechanisms remained fully functional despite not being needed for over a million years.” A million years without sex It’s historically been thought that asexuality is unable...