When a chimpanzee is born, they are able to grasp their mother’s fur with their hands and feet and cling on effectively within weeks. A human newborn is not as strong or directed in their efforts though they still retain some of the so-called primitive reflexes from our common primate ancestor which fade as a human baby gets older. Newborn humans can strongly grasp with their hands (palmar grasp reflex) and they can flex their toes (plantar reflex) but due to their foot morphology, which lacks an opposable hallux (a big toe that looks more like a thumb) they cannot grasp with their feet as they do with their hands.
This is a problem for a species of “riders“, mammals whose breastmilk composition requires them to carry their baby with them for frequent feedings, unlike “parkers” whose offspring can be left for long stretches while their mother hunts or forages (or goes to the bathroom by herself for crying out loud!) If a baby cannot cling to it’s unlikely to survive, most rider mothers cannot afford the extra energy (literally in the form of calories) to carry their infant and it would certainly slow her down in the face of danger. Even if the mother did everything in her power to carry and protect her baby, the odds are against their survival and so that babies trait, the trait for not being able to cling on, wouldn’t get passed on. Unless of course, the mother was clever enough to make a technological adaptation for easier carrying… (you see where I am going here). Continue reading