by ooli

Hyp:

The hypothesis suggests that, as the Y chromosome is smaller than the X chromosome, and in some cases absent, it is unable to ‘hide’ an X chromosome that carries harmful mutations, which may later expose the individual to health threats.

Proof:

same pattern in the classes of animals possessing their own unique pair of sex chromosomes that are the reverse of all other animals. In birds, butterflies and moths, it is the male of the species that has the homogametic sex chromosomes (denoted by ZZ) while the female has the heterogametic chromosomes (ZW). Female birds, butterflies and moths were usually found to die earlier than their male counterparts, giving credence to the unguarded X hypothesis

But:

“In species where males are heterogametic (XY), females live almost 21 per cent longer than males. But in the species of birds, butterflies and moths, where females are heterogametic (ZW), males only outlive females by 7 per cent.”