Males of a species are keen to spread their sperm as far and as wide as possible. But why would a female wish to mate with multiple males? For the Trinidadian guppy, promiscuity brings with it the risk of nasty diseases and being eaten during the act, all for the sake of a male who doesn't lift a finger to protect or provide. In the August 29
The embryos, whose genes were altered by CRISPR, were not intended for implantation.