Alfred Russel Wallace was a great traveller, observer, collector and naturalist who lived at the same time as Darwin. He sent Darwin his thoughts on evolution of species after extensive observations around the world, especially in and around Borneo. This accelarated Darwin to publish his conclusions on origin of species along with Wallace’s. What struck me was the exceptional insight with which he talks about the so-called Wallace line. This is the imaginary line that divides the Asian coast from Australian. Wallace observed a dramatic change in plant and animal lives when one goes from the Indonesian islands to the Australian.
The Australian and Indian regions of Zoology are very strongly contrasted. In one the Marsupial order constitutes the great mass of the mammalia,–in the other not a solitary marsupial animal exists. Marsupials of at least two genera (Cuscus and Belideus) are found all over the Moluccas and in Celebes; but none have [[p. 173]] been detected in the adjacent islands of Java and Borneo. Of all the varied forms of Quadrumana, Carnivora, Insectivora, and Ruminantia which abound in the western half of the Archipelago, the only genera found in the Moluccas are Paradoxurus and Cervus. The Sciuridæ, so numerous in the western islands, are represented in Celebes by only two or three species, while not one is found further east. Birds furnish equally remarkable illustrations. The Australian region is the richest in the world in Parrots; the Asiatic is (of tropical regions) the poorest. Three entire families of the Psittacine order are peculiar to the former region, and two of them, the Cockatoos and the Lories, extend up to its extreme limits, without a solitary species passing into the Indian islands of the Archipelago. The genus Palæornis is, on the other hand, confined with equal strictness to the Indian region. In the Rasorial order, the Phasianidæ are Indian, the Megapodiidæ Australian; but in this case one species of each family just passes the limits into the adjacent region. The genus Tropidorhynchus, highly characteristic of the Australian region, and everywhere abundant as well in the Moluccas and New Guinea as in Australia, is quite unknown in Java and Borneo. On the other hand, the entire families of Bucconidæ, Trogonidæ and Phyllornithidæ, and the genera Pericrocotus, Picnonotus, Trichophorus, Ixos, in fact, almost all the vast family of Thrushes and a host of other genera, cease abruptly at the eastern side of Borneo, Java, and Bali. All these groups are common birds in the great Indian islands; they abound everywhere; they are the characteristic features of the ornithology; and it is most striking to a naturalist, on passing the narrow straits of Macassar and Lombock, suddenly to miss them entirely, together with the Quadrumana and Felidæ, the Insectivora and Rodentia, whose varied species people the forests of Sumatra, Java, and Borneo. -source
Why so? This is an important question that directly leads to some of the key ideas of origin of species. And, very quickly he arrives at it:
The regular and unceasing extinction of species, and their replacement by allied forms, is now no hypothesis, but an established fact; and it necessarily produces such peculiar faunæ and floræ in all but recently formed or newly disrupted islands, subject of course to more or less modification according to the facilities for the transmission of fresh species from adjacent continents. Such phenomena therefore are far from uncommon.
On a lighter note, here’s Wallace’s love note to Bamboo:
Different species of Bamboo abound in all tropical countries, and wherever they are found the natives apply them to a great variety of uses. Their strength, lightness, smoothness, straightness, roundness, and hollowness,–the facility and regularity with which they can be split,–their different sizes, the varied distance of their joints, the ease with which they can be cut, and with which holes can be made in them,–their hardness outside, their freedom from any taste or smell, their great abundance, and the facility with which they are propagated,–all make them fitted for a hundred different purposes, to serve which other materials would require much labour and preparation. They are at once the most wonderful and the most beautiful production of the tropics, and the best gift of Nature to uncivilized man. -Source
Uh, Uncivilized man?! Uncivilized man?! You snob! While reading Wallace’s accounts, now and then, you get a taste of how culturally offensive the man sometimes is. He was, of course, conforming to his times. A great naturalist, nevertheless.
More at Alfred Russel Wallace Page.