|
The excerpt represents the core issue or deciding factor on which you must meditate, and is drawn from On the Origin of Species by Charles Darwin: day. Hence we may suppose that the organisms now living under the climate
of latitude 60 deg, during the Pliocene period lived further north under
the Polar Circle, in latitude 66 deg-67 deg; and that the strictly arctic
productions then lived on the broken land still nearer to the pole. Now if
we look at a globe, we shall see that under the Polar Circle there is
almost continuous land from western Europe, through Siberia, to eastern
America. And to this continuity of the circumpolar land, and to the
consequent freedom for intermigration under a more favourable climate, I
attribute the necessary amount of uniformity in the sub-arctic and northern
temperate productions of the Old and New Worlds, at a period anterior to
the Glacial epoch.
On the Origin of Species |
