So far, everything runs strikingly parallel with evolution on earth. It is probable that it will be found to have run parallel farther still and that animal life on both planets, too, has been similar — for at least part of the evolutionary story. But during all the years of earnest and competent research not one clear sign of manlike life on Mars has been detected. Professor Lowell's famous Martian "canals," which for a long time were considered a probable sign of the intelligent direction of water, are now believed to be wide, shallow river valleys.

This lack of manlike life is precisely what a biologist would expect. Man and man's active mind are believed to be products of the Great Ice Age, for that time of stress and competition on earth is what is supposed to have turned mankind's anthropoid ancestors into men. The period of ice and cold over wide areas of the earth was caused, at least in part, by the elevation of continents and mountain ranges. On Mars, no mountain ranges exist, and it probably never had an Ice Age.

It is on these hypotheses that science bases its assumption that there is no human intelligence on Mars, and that animal life on the planet is still in the age of instinct. The thing to expect on Mars, then, is a fish life much like that on earth, the emergence of this fish life onto the land, and the evolution of these Martian land-fishes into retilelike creatures. Finally, animals resembling the earth's present rodents like rats, squirrels, and beavers would make their appearance.

The chief reason to expect this final change of Martian retiles into primitive mammals lies in the fact that on earth this evolution seems to have been forced by changeable weather. And Mars now possesses seasonal changes like those on earth.

Pure biological reasoning makes it probable, therefore, that the evolution of warm-blooded animals may have occurred on Mars much as it did here. There seems no reason to believe that Martian life has gone farther than that. Mars is a relatively changeless planet. Biologists suppose that the rise and fall of mountains, the increase and decrease in volcanic activity, and the ebb and flow of climate forced life on earth along its upward path. Martian life of recent ages seems to have lacked these natural incentives to better things.

Now, there is one creature on earth for the development of whose counterpart the supposed Martian conditions would be ideal. That animal is the beaver. It is either land-living or water-living. It has a fur coat to protect it from the 100 degrees below zero of the Martian night.

The Martian beavers, of course, would not be exactly like those on earth. That they would be furred and water-loving is probable. Their eyes might be larger than those of the earthly beaver because the sunlight is not so strong, and their bodies might be larger because of lesser Martian gravity. Competent digging tools certainly would be provided on their claws. The chests of these Martian beavers would be larger and their breathing far more active, as there is less oxygen in the air on Mars.

Such beaver-Martians are nothing more than pure speculation, but the idea is based upon the known facts that there is plenty of water on Mars; that vegetation almost certainly exists there; that Mars has no mountains and could scarcely have had an Ice Age; and that evidences of Martian life are not accompanied by signs of intelligence.

Herds of beaver-creatures are at least a more reasonable idea than the familiar fictional one of manlike Martians digging artificial water channels with vast machines or the still more fantastic notion of octopuslike Martians sufficiently intelligent to plan the conquest of the earth.