The Wikipedia page on the Estrous cycle says:
Humans have menstrual cycles instead of estrous cycles. They shed their endometrium instead of reabsorbing it. Unlike animals with estrous cycles, human females are sexually receptive throughout their cycles.
The page on the menstrual cycles says:
The cycle occurs only in fertile female humans and other female primates
Do we know how many million years ago that switch happened and our female ancestors got sexually receptive throughout their cycles?