Our assumptions are not quite so broad as this, but few of us realize that the Protestant Christian Religion stands fifth in the number of communicants, as compared with the other great religions, and that against our hundred millions of people in America, the Malay Archipelago has over two hundred millions.
Wallace found marked geological, botanical and zoological differences to denote his line. And from these things he proved that there had been great changes, through subsidence and elevation of the land. At no very remote geologic period, Asia extended clear to Borneo, and also included the Philippine Islands. This is shown by the fact that animal and vegetable life in all of these islands is almost identical with life on the mainland: the same trees, the same flowers, the same birds, the same animals.
As you go westward, however, you come to islands which have a very different flora and fauna, totally unlike that found in Asia, but very similar to that found in Australia.
Australia, be it known, is totally different in all its animal and vegetable phenomena from Asia.
In Australia, until the white man very recently carried them across, there were no monkeys, apes, cats, bears, tigers, wolves, elephants, horses, squirrels or rabbits. Instead there were found animals that are found nowhere else, and which seem to belong to a different and so-called extinct geologic age, such as the kangaroo, wombats, the platypus—which the sailors used to tell us was neither bird not beast, and yet was both. In birds, Australia has also very strange specimens, such as the ostrich which can not fly, but can outrun a horse and kills its prey by kicking forward like a man. Australia also has immense mound-making turkeys, honeysuckers and cockatoos, but no woodpeckers, quail or pheasants.
Wallace was the first to discover that there are various islands, some of them several hundred miles from Australia, where the animal life is identical with that of Australia. And then there are islands, only a comparatively few miles away, which have all the varieties of birds and beasts found in Asia.
But this line that once separated continents is in places but fifteen miles wide, and is always marked by a deep-water channel, but the seas that separate Borneo and Sumatra from Asia, although wide, are so shallow that ships can find anchorage anywhere.
The Wallace Line, proving the subsidence of the sea and upheaval of the land, has never been seriously disputed, and is to many students the one great discovery by which Wallace will be remembered.
Wallace's book on "The Geographical Distribution of Animals" sets forth in a most interesting manner, the details of how he came to discover the Line.
It was in Eighteen Hundred Fifty-five that Wallace, alone in the wilds of the Malay Archipelago, became convinced of the scientific truth that species were an evolution from a common source, and he began making notes of his observations along this particular line of thought. Some months afterward he wrote out his belief in the form of an essay, but then he had no definite intention of what he would do with the paper, beyond keeping it for future reference when he returned to England. In the Fall of Eighteen Hundred Fifty-seven, however, he decided to send it to Darwin to be read before some scientific society, if Darwin considered it worthy. And this paper was read on the evening of July First, before the Linnæus Society, with one by Darwin on the same subject, written before Wallace's paper arrived, wherein the identical views are set forth. Darwin and Wallace expressed what many other investigators had guessed or but dimly perceived.