Posted on Sunday 31 May 2009
families mean always the newest. Now, the earliest mammals to appear onearth were creatures of distinctly marsupial type. As long ago as thetime when the red marl of Devonshire and the blue lias of Lyme Regiswere laid down on the bed of the muddy sea that once covered the surfaceof Dorset and the English Channel, a little creature like the kangaroorats of Southern Australia lived among the plains of what is now thesouth of England. In the ages succeeding the deposition of the red marlEurope seems to have been broken up into an archipelago of coral reefsand atolls; and the islands of this ancient oolitic ocean were tenantedby numbers of tiny ancestral marsupials, some of which approached inappearance the pouched ant-eaters of Western Australia, while othersresembled rather the phalangers and wombats, or turned into excellentimitation carnivores, like our modern friend the Tasmanian devil. Up tothe end of the time when the chalk deposits of Surrey, Kent, and Sussexwere laid down, indeed, there is no evidence of the existence anywherein the world of any mammals differing in type from those which nowinhabit Australia. In other words, so far as regards mammalian life, thewhole of the world had then already reached pretty nearly the same pointof evolution that poor Australia still sticks at.
About the beginning of the tertiary period, however, just after thechalk was all deposited, and just before the comparatively modern claysand sandstones of the London basin began to be laid down, an arm of thesea broke up the connection which once subsisted between Australia andthe rest of the world, probably by a land bridge, _via_ Java, Sumatra,the Malay peninsula, and Asia generally. ‘But how do you know,’ asks thecandid inquirer, ‘that such a connection ever existed at all?’ Simplythus, most laudable investigator–because there are large land mammalsin Australia. Now, large land mammals do not swim across a broad ocean.There are none in New Zealand, none in the Azores, none in Fiji, none inTahiti, none in Madeira, none in Teneriffe–none, in short, in anyoceanic island which never at any time formed part of a great continent.How could there be, indeed? The mammals must necessarily have got therefrom somewhere; and whenever we find islands like Britain, or Japan, orNewfoundland, or Sicily, possessing large and abundant indigenousquadrupeds, of the same general type as adjacent continents, we see atonce that the island must formerly have been a mere peninsula, likeItaly or Nova Scotia at the present day. The very fact that Australiaincloses a large group of biggish quadrupeds, whose congeners onceinhabited Europe and America, suffices in itself to prove beyondquestion that uninterrupted land communication must once have existedbetween Australia and those distant continents.
In fact, to this day a belt of very deep sea, known as Wallace’s Line,from the great naturalist who first pointed out its far-reachingzoological importance, separates what is called by science ‘theAustralian province’ on the southwest from ‘the Indo-Malayan province’to the north and east of it. This belt of deep sea divides off sharplythe plants and animals of the Australian type from those of the commonIndian and Burmese pattern. South of Wallace’s Line we now find several