That explanation is a bit circular along the lines that kids like putting things in their mouths because they like putting things in their mouths. As to why we've evolved that way it's probably to build the immune system. It needs exposure to stuff in the environment to figure what to react to. The increase in asthma and allergies in the modern world is probably because kids don't get enough dirt exposure and then the immune system overacts later.
> That explanation is a bit circular along the lines that kids like putting things in their mouths because they like putting things in their mouths.
That's not what the article says at all. It says most of the babies sensory experiences are oral because they lack mobility to explore things with other tactile senses. Granted the article doesn't example this specifically but a lot of sensory input will be suckling (dummies, mother's nipple / bottle's teat, their own digits, etc).
By the time they're a bit more mobile and can open their hand to grasp objects (remember the ability for a baby to even open their hand takes a few weeks to learn) happens, they've often already gotten into the habit of exploring the world via their mouths.
It doesn't say it in that article I linked to, but I do vaguely recall reading elsewhere that because babies develop tactile senses on their hands later than the senses in their mouth, babies will often have more nerve endings in their mouth. However I cannot find a source for that so this might be a detail I'm miss-remembering.
