I mean, if (as seems to be the case) maternal condition is at the root of swaying in order to give baby boys vs. baby girls a better chance of surviving to adulthood to pass down genes to future generations, then it is utterly ridiculous that the time of day you have intercourse would sway gender whatsoever. Boys need more nutrients. If you don't have enough nutrients, boys have a lower chance of survival and that is true whether they were conceived at 8 am or 8 pm.