BRAINS AND LONGEVITY IN ANIMALS.
AMONG the interesting suggestions for thought recently made in the Natural History Museum at South Ken- sington is a kind of side-note on the relative size of brain of extinct and living animals of allied kinds. The text is given by the skeleton and skull of an extinct monster resembling a rhiccceros. In the case beside the skeleton lies a cast of the brain cavity, representing the brain itself, of the creature. Beside this lies another model of the brain of a modern rhinoceros, a stupid animal enough, but the brain of which is some eight times the size, measured by cubical Contents, of that of the prehistoric beast. The immediate Inference is that this insignificant ancient brain was large enough for mere inherited capacity, but not large enough for the development of individual experience, while the madam animal corresponding has a brain capable of amassing individual experience on a certain scale. But it
may be doubted whether this is all that the difference in brain capacity suggests. May not the survival or disappear- ance of species be due very frequently to the relative amount of brain possessed by them ? And is not this quite as important a factor in the preservation of many animals
as change of environment, food supply, or climate ? There seems every reason to believe that this is the case, both from existing records of survival or loss and the evidence of the past. Though in many cases where the thinking process has been replaced by pure inherited instinct, as in the ants and bees, the life-preserving and life-propagating activities have been mechanised with excellent results, it will be found that as constant brain activity prolongs human life, so the possession and use of more than the average amount of brains helps to prolong the existence generally of certain species, and sometimes of individual animals. It is fairly certain that in many cases the stupid ones went to the wall very early. The American bison was the dullest of all the Bovidae. The herds, even when not hunted, would get into serious trouble in cross- ing a river where they had miles of bank to choose from. Catlin saw them enter the river opposite a steep perpendicular bank, swim across, and stand in rows up to their chins in water under the low cliff, apparently quite helpless and not knowing what to do next, until they were exhausted and carried down the current. They never learnt anything from experience, and just went on with their own dull, instinctive life until the last of them was shot. Something of the same kind may be noted in the history of the survival or disappearance of some of the tribes of Indians which destroyed the buffalo. When Catlin was living as an honoured guest among the then numerous and flourishing colonies of red men, these were generally at feud with one another, but the war was not carried on a outrance. It was a kind of sporting event, in which the larger tribe did not care to kill off all their enemies at once, for fear that there might be no stock left to provide scalps and amusement in the future. They were, indeed, more provident of their enemies than of their game. Catlin's pet tribe, the Mandan, seem to have been both amiable and, as Indians go, very much less crafty than their neighbours and hereditary enemies, the Sioux. When food began to grow scarce in the Mundane' camp, they used to hold buffalo dances, a ceremonial after which the herds were always confidently expected to appear within a week. In due time buffalo were seen grazing just on the sky-line of a distant hill, and the Mandan warriors jumped on their horses and went off to kill them. In twenty minutes some half of those who went out came riding breathlessly back, many of them wounded. The others had been killed and scalped by the Sioux, who having got news of the buffalo dance, had dressed some of their number up in buffalo skins about the time when the Mandan would be looking out for them, and thus baited a very effective trap. Clearly the Sioux brains, as among savage foes, were the better, and the tribe the more likely to last, as it has.
Our almost extinct wild-cat is a beast which for want of memory has not been able to hold its own. While the fox and the badger, especially the latter, are adepts at avoiding traps, the wild-cat seems quite unable to keep out of them. Yet the glutton, another carnivore of the Northern forests, without any apparent brain endowment of the positive kind, has learnt the whole art of trapping so successfully that it will follow along a whole line of forty miles of traps, break into every one from behind, and carry off the baits without being caught. In the same way the baboons of Africa, whether North or South, maintain themselves in a locality in their full numbers long after most other creatures of equal size have disappeared. The part of the Matoppo Hills in which Mr. Rhodes's tomb is cut in the rocks is deserted by the Matabele because, as they are now disarmed, the baboons carry off all their corn and pumpkins. The rat and the rabbit are not very different in point of fecundity. But while the rabbit, except on very favourable soil, disappears in a cultivated country like England, where it is not afforded any protection, the rat is practically master of the situation, so greatly does his power of individual experience, and probably also of communication, exceed that of the other rodent. It can hardly be an accident that the grey parrot, one of the cleverest and most thoughtful of birds, is by far the longest-lived. There is an undoubted instance of this bird surviving for a century, and half that time is quite a common
age. But in rile case of birds so many other considerations than those of brain intervene in determining what leads to longevity that only vague generalisations are possible. Size, food, and species all have their known results on the duration of a birds life. A gannet has been known to live for forty years, Spanish Imperial eagles to nearly that age, an Egyptian vulture to forty-two, ravens for twenty years, and swans for nearly as long. But it is a fairly safe inference that the life of birds is, in proportion to their size, longer than that of mammals. Comparing the general average of brain-power, that of birds is much higher than among the average of beasts; and it is quite probable that it is this excess of brain vitality which gives the birds an excess also in bodily vitality. The birds themselves offer some examples of failure to survive, due probably to their lack of power to record individual experience. By all accounts the great auks, besides being rather helpless, though probably not more so than penguins, were also very dull creatures. They used to sit on their islands without moving while the seamen put a plank from the rock to the ship and simply drove them like sheep into the hold of the vessel. When the penguin colonies of the South Pacific were first invaded, the birds did move off inland, apparently thinking that the sailors were seals. There are penguin colonies to- day where the birds will not move when sitting on their eggs. But these are generally in places where the birds scarcely ever see a human being, and where, if they do, they are not molested.
That creatures once little gifted with brains, and never called upon to use what they had, may become in time users of experience in a considerable degree, and thus just able to preserve the race, appears from the story of the Green- land right whales. Persecuted until they were practically driven off the seas, they took refuge furthest north along the ice-fringe. There they had a secure refuge under the ice. So well aware did they become of their danger that for hundreds of leagues the whales could only be found close to cover, under which they retired at once when boats appeared in sight. The drifting and floating ice enabled them to come up to breathe in places where boats could not row, or if they took refuge under a big stationary part of the pack, they could always venture out to the edge to spout. Fortu- nately for the Greenland right whales, they were in the habit of retiring to the ice-fringe to breed. Apparently the instinct as to the place of giving birth to the calves is stronger than any experience of danger, for the Southern right whales, which always came to the shores of Southern New Zealand to breed, continued to do so till the last was killed.
It is remarkable that among insects the races which prolong their existence through the European winter are generally those which exhibit mechanised intelligence in a very high degree. Their equivalent to brains, retaining the inherited capacity, enables them to store food, make and warm a home, and so to live through the winter while other races perish almost entirely. The difference of longevity de- pending entirely on the degree of intelligence possessed by the creatures is remarkable, even in such closely allied insects as the hive bees and the wasps. The hive bees all survive through the winter, live on their stores, and warm their hive. The wasps, which make no store because they have not the sense to do so, nearly all die, their houses rot, and only the queen, which has hibernated in a miserable make- birift kind of way, survives. Our ants hibernate in the winter; but where this is not done other species of ants duly make a store, and so survive, and de facto lead a much longer life, because it is a working and active one.