I'm glad Savage mentioned science here because there is a very interesting hypothesis being developed concerning beauty among animals and humans. An anatomy and evolutionary biology lecturer at my Uni talked about how human beauty, especially female, is somewhat unusual in the animal kingdom.

As you may be aware, there is a lot of competition between members of the same gender to acquire the 'perfect mate'. Usually, it is the males that show off their physical prowess to outcompete their peers. Females do it too to some extent. However, in many species, the males also show off their virility by displaying very colourful and aesthetically pleasing signals. Think of peacocks, lion manes and deer antlers, these are all the tools of courtship for the males to attract females. The females of these species by contrast to the males seem rather plain.

Now if we look at humans, there seems to be a rather marked reversal of these roles. Females have developed permanent features like breasts and curves that attract males. While the male physique is still a means of competition, females seem to have become the 'embodiment of beauty' if you will, something that is rare if not unique among animals. So, what is the point of this female beauty?
Well, it can be attributed to the female wanting to find the perfect mate so that she doesn't waste her resources with a lesser mate (to put it bluntly). But a lot of animals also have rather temporary displays by females, like dogs and baboons that are in heat which both display their enlarged posterior. What would be the point of keeping that female beauty for the humans? It's practically a waste of resources at this point.

The hypothesis for that is that the constant tempting of the female is an advantage for keeping the male to help with child-rearing. As humans have become bipedal, their pelvis have become narrower and as they developed hunting and ate more nutrient rich food, their head got bigger. As you may imagine, the head has become hard to pass during child birth as it must go past the pelvic cavity. This leads to a high mortality rate in newborns. So, the mother must take absolute care with her child as it was a very painful and intense birth. In addition, the child is also born relatively premature when its small size is compared to other apes at birth.

With all that extra care needed, the mother's best interest is to keep the male around and other family members as well to help with raising up the child. Hence the mother develops permanent attractions and make the males somewhat confused by hiding when she actually is ovulating. This 'benefit of the doubt' makes the male less likely to kill the newborn as the male is unsure if the baby is actually his or a competitor's. In other animals, the ovulation period is very visible (see the dog and baboon above) but vanishes as soon as a the female is impregnated and thus, the male can determine if he has actually mated with that particular female. If the male finds out that someone else impregnated his mate, he will very likely kill the child of that lineage. Taking a dramatised example from The Lion King, once Mufasa was killed, Scar would take the lead of the pride and kill Mufasa's lineage. This is a somewhat sad natural trend that is seen in many species. But, it happens much less in humans thanks, in part, to female beauty.

Thanks for reading all the way if you did! The lecturer spent at least 4 hours teaching this so be glad if you could understand it in less.