The one on the left (Tina Turner, I think her name is?), her smile is much more trustworthy.

"The spotted hyena has a very big clitoris, named pseudopenis. It is by far the largest clitoris in the animal kingdom. In these hyenas, the vulva is fused, and the clitoris is used for urination, mating (it contracts for mating and the opening widens to allow the penetration by the male's penis) and giving birth. To complicate it all, the females also possess a fake scrotum made by the enlarged joined vulva and pseudo-testes filled with fatty tissue. Female spotted hyenas carry in their blood higher levels of testosterone than the males (!), and this even from embryo stage: they are bigger and more aggressive than the males and are the dominant sex in the spotted hyena society."

Seriously mouth wide open smiling is the single most hideous thing that humans do.