Humans understand these things because they are persons. Where did their personhood come from if not another person? How personhood can arise out of non-personhood is unexplained.
"Personhood" seems a very arbitrary (and not at all clearly defined) qualification here. "Understanding" arises from thinking, not from "personhood". And surely, there are non-person minds that understand less complex things. That they can evolve to achieve person-caliber capabilities incrementally and over long periods of time is well-accepted.
As an aside, we can't communicate very well with the smartest animals, so we don't know how much they can understand. It could be more than most of us think.
As an aside, we can't communicate very well with the smartest animals, so we don't know how much they can understand. It could be more than most of us think.