Believing, from reasons before alluded to, that our continents have long remained in nearly the same relative position, though subjected to great oscillations of level, I am strongly inclined to extend the above view, and to infer that during some earlier and still warmer period, such as the older Pliocene period, a large number of the same plants and animals inhabited the almost continuous circumpolar land; and that these plants and animals, both in the Old and New Worlds, began slowly to migrate southwards as the climate became less warm, long before the commencement of the Glacial period.
Aurrean aipaturiko arrazoiengatik, uste izanik gure kontinenteek kokaera erlatibo bertsuan iraun dutela, nahiz eta sestra-gorabehera handien mende, oso aiher naiz aurreko hipotesia hedatu eta honako hau inferitzera, alegia, Pliozeno zaharra bezalako lehenagoko aldi beroagoan, espezie bereko landare eta animalia asko bizi zela poloinguruko ia etengabeko herrialdean, eta landare eta animaliok, hala mundu zaharrean nola berrian, hegoalderantz migratzen hasi zirela klima apur bat hozten hazi zenean, glaziaraldia baino askoz lehenago.