Although experiments in the training of pigs show that they have rather remarkable intellectual capacities, the most human feature in their mental organization is found in the keen sympathy which they exhibit with the sufferings of their own kind and the willingness with which they encounter danger in protecting their comrades. It usually requires close observation for the naturalist to determine the existence of this motive among the other wild or domesticated mammals. In fact, the traces of it are very slight indeed, and are generally to be attributed to the care of parents for offspring or of the males for their harem—a disposition which, though akin to the defence of the kind, is nevertheless of a special and peculiar nature. Even among our domestic dogs, whose sympathies have been developed in a remarkable degree and who will sacrifice their lives to defend or rescue the human beings with whom they are familiar, there appears to be but little disposition to support members of their species who may be assailed. With pigs, however, as is well known to all those who have observed their habits, the characteristic cry of distress of their fellows proves very exciting and stimulates all the adults, both male and female, who hear it to hasten in defence of their kinsmen. It is a noteworthy fact that while most other animals when in danger utter no distinct or continuous cry, the pig gives voice in a vociferous and insistent manner, as if he had a right to expect the sympathy and help of his species. The cry goes with the custom of defence which in this species has attained a better foundation in the sympathetic motives than in any other mammal below the level of man.
It is perhaps due to their relatively high intellectual organization that the excessively domesticated pigs are liable to suffer from attacks of mania. This is most commonly exhibited by the sows, which at times will destroy their young shortly after they are born. The sight of their progeny seems to infuriate them in a curious manner. One sow which I owned killed three successive litters; another fine animal of the Berkshire breed, a very amiable, indeed affectionate, creature, was carefully watched at the time she first bore young, precautions being taken to prevent her from harming them; she would willingly allow them to suckle, provided she did not see them, but the moment she laid her eyes upon them she was seized with the strange fury.
Although this singular perversion of the natural instincts of maternity sometimes occurs among the pigs which are allowed to roam together in herds, it seems to be far more common in those conditions where the animals are confined in pens without contact with their kind, and where they have no chance to recognize the young as members of their species or to acquire that interest in them which they would gain in the society of the herd. It is also clear that this maniacal habit is inherited; according to my observation it is common among the Berkshire, and relatively rare in other less specialized varieties.
The intelligence of the pig is also shown in the readiness with which the creature changes its habits to meet varied environments. Thus the pigs which range the woods in the western and southern parts of the United States have learned to catch the crawfish which abounds in the shallow streams in those parts of this country. They will wade up a brook, turning over the stones and driftwood as they go, catching with a quick movement the crustaceans which they have thus dislodged from their cover. Along the shores of the Bay of Fundy, the pigs, accustomed to follow the tide out, picking the chance food which is thus exposed to them, have learned carefully to avoid the risk of being caught by the returning waters. With the first splash of the turning tide they hasten inshore until they have attained safe ground.
One of the best evidences of the mental state of these animals is found in their actions when assailed by dogs or other beasts of prey. Pigs, though wary and sensible of danger, seem exempt from the extreme fear which leads to panic, and fight, even before being brought to bay by long chasing, in a discreet and valiant manner. Where a number of them are attacked by dogs or other enemies, they will form a circle with their heads out, each supporting the other in such a manner that the ring cannot readily be broken. Their thick-skinned forequarters and stout tusks provide them with excellent instruments with which to resist an assault.
The sagacity of the pigs is probably, in part at least, to be attributed to the fact that in their native state they are communal animals, all the species of their family being accustomed to live gregariously, so that for ages they have had the training which every social organization, however simple, affords. They are, moreover, omnivorous feeders, accustomed to subsist on a great variety of food—a habit which seems in all cases to promote the development of the intelligence in animals.
Although the pigs by their nature afforded the best opportunity for developing an intellectual animal which has come to us through our domesticated creatures, no effort whatever has been made by selection to develop the latent mental capacities of this species. It is perhaps the only form of those which man has subjugated which by his treatment he tends to degrade. In the time to come, when men will be held to a better accountability for the treatment of their captives, the condition of these animals will afford a fair field for the reformer's care.
The geologist who is acquainted with the mammalian life of the Middle Tertiary period readily notes the fact that the variety in genera and species appears to be much greater than it is at the present time. A great number of forms, differing somewhat widely from those now in existence, then abounded in the Americas and the Old World. It may at first sight seem unfortunate that man did not have the chance to essay his domesticative arts on that older and apparently richer life. A closer examination, however, leads us to see that the species of that time, though more numerous than those of the present, were on the whole less fitted for our use than the fewer but more completely differentiated kinds with which we have had to deal. The multitude of kinds which we find in the Mesozoic period indicates that the life was in a state more experimental than that to which it has attained. A host of forms on their way towards the specialization which has now been attained have been removed from the sphere, in the manner of a scaffolding from a completed structure. That which has been left remains because it has successfully accomplished the task of reconciliation with environment, or, in simpler phrase, because it has learned to do things which were useful and profitable in a more perfect manner.
As an illustration of the fact that the animals of to-day are better fitted to be the help-meets of man than were their ancestors of an earlier time, we may note the state of the horse at the time when that genus was undergoing its development in the region about the upper waters of the Missouri. As may be imagined, the long and difficult passage from the five-toed to the single-toed form was slowly accomplished, and to its doing went a great many temporary forms, which served, we may say, as stepping-stones for the ongoing. So far as we can judge, these intermediate forms were small, rather frail creatures, which probably could not have been made to serve any purpose useful to man. It was not until the mechanical system of the large single toe with the wonderfully developed nail, which makes up the foot and hoof of the horse, had been attained, that the creature becomes fit for the wonderful work we have persuaded him to do in our civilization.
A comparison of the skulls of the Tertiary mammals and those of our own day indicates that in certain of the important series, and presumably in them all, the brain has increased in size from the earlier to the later times. This increase in brain capacity has doubtless been attended by a decided gain in the measure of intelligence, a gain which has doubtless served to make the modern representatives of the series fitter for man's use than their ancestors were. For, while the number of our very useful domesticated forms may seem at first sight to be dull of wit, none of them are really low in the intellectual scale as we apply it to the brute; in fact, a considerable measure of intelligence is absolutely required as a condition for true subjugation. This is seen by the fact that nothing like a real adoption into our social system has ever been accomplished except with a few of the higher orders of mammals and birds, species which have an intellectual capacity that we recognize as akin to our own. Thus, so far as we can see, man's appearance on this stage was, so far as it relates to the possibility of companionship with the lower life, exceedingly well timed. He came at a period when the life was ready to give him and to receive from him a large measure of help. If his advent had been much earlier, he might have had less trouble in his contests with the larger carnivora; but if there had been a lack of beasts to obey his will, it is doubtful whether he could himself have won his way above that primitive life.