Originally, children were not cute. It’s not that they were ugly; it’s that they lacked a certain something that made them cute. This resulted in a lot of attrition: when the children would cry or destroy things or in general be unappealing, parents couldn’t say, “Oh, but isn’t he cute when he’s nice?” Instead they’d leave the kids by the side of the road.
Then, eureka! A child was born who was amazingly cute. Imagine the advantage this gave her in survival! Even more amazing, when she grew up and had children of her own, those children were cute. Soon the cute gene ruled supreme, with parents everywhere accosting strangers and demanding that they admire the cuteness of their child.