Absolutely fair point: it is an unanswerable question. It's just... Aargh: - Africa, Australia: continuous habitation; no suitable creatures. - Europe, Asia:

Absolutely fair point: it is an unanswerable question. It's just... Aargh: - Africa, Australia: continuous habitation; no suitable creatures. - Europe, Asia: continuous habitation; suitable creatures. - South America: recent habitation; no suitable creatures (discounting cameloids). - North America: recent habitation; ???. It's a tantalizing, permanent un-known that just invites speculation! Nothing wrong with indulging imagination a bit, so long as we recognize that's what we're doing.