Radio Times/1923/10/12/Do We Inherit Our Habits?

A RECENT TALK BROADCAST FROM LONDON.



HE effect on the body of a persistent habit is called an "acquired character." The question is: Do we inherit such habits from our ancestors? The great brawny arm of the blacksmith is an acquired character, and so is the deep expanded chest of the professional singer. Now, everyone knows that babies are not bent with brawny arms or expanded chests; therefore the only sense in which it could be said that such bodily features are inherited would be, that the children of blacksmiths more quickly obtained huge development of the arm muscles than other people, and that the singer's children found it easy to acquire chest expansion.

Whether this really is so or not is a much disputed question.

Nowadays education is considered to be the best means of improving the condition of the submerged tenth of our population, and it would be a disheartening conclusion to have to come to that the training of one generation had no effect whatever on the capacity of the next, and that all the work would have to be done over again from the very bottom with every new crop of man.

Now, a question of this kind cannot be settled by observations on men and women. There are so many disturbing factors which enter into the calculation. A man may have a brilliant father, but at the same time he may also have a very stupid mother. A man may have brilliant gifts, but, owing to lack of opportunity, these may never have been cultivated.

It is related of James the First that he put two young children in the charge of a deaf and dumb woman and sent the party to an islet where they were periodically supplied with food, but where no one but themselves lived, as that the children grew up with no one to teach them how to speak. The object of the experiment was to discover the primitive language of mankind, and it is stated that after a residence of some years on the islet the children spoke very good Hebrew!

In the good old days a Monarch claiming his position by divine right might allow himself to try experiments with human beings, but nowadays we are not allowed to experiment with our fellow men. If, therefore, this all-important question is to be settled. it must be by other means.

About fifty years ago a German professor called Weisman took up this question. He bred large numbers of white mice and he cut off their tails as soon as they were born and raised litters from these mutilated specimens in order to sec whet her the offspring would be born without tails. When he found that generation after generation of baby mice came into the world fully provided with tails, he came to the conclusion that acquired characters could not be inherited. This conclusion he stated in a very dogmatic way; it came to be widely accepted, and soon grew into a recognized tenet of biological teaching. It may be pointed out, however, that the experiment was not well adapted to settle the question; for to lose a tail is certainly not to acquire a new habit.

About thirty years ago, when the fossiliferous rocks of America began to be thoroughly searched, most wonderful successions of animal life were found in them, and it seemed quite clear that we were dealing with the records of evolution; the animals whose remains were preserved in one stratum were just a little different from those whose remains were found in the stratum immediately below; and the animals found in the stratum next above were also slightly different, and these differences were all steps in the same direction.

A distinguished American naturalist, named Cope, pointed out that the changes in the structure of the fossil animals were just such as we would expect if they bad been caused by progressive changes in habits as the surroundings of the animals changed. Thus the early horses had teeth studded with pointed cusps—like the teeth of pigs, and fed like pigs on soft juicy plants.

But as time went on and the climate became drier, the juicy plants were replaced by harsh dry grasses, which were more difficult to chew and the cusps on the teeth became gradually connected by cross walls, so as to give rise to the complicated pattern seen on the grinding teeth of a horse to-day. Cope concluded that in this case we had an instance of acquired characters being inherited.

In the twentieth century, however, a new set of experiments has been carried out in the University of Vienna by a professor named Dr. August Kammerer, and these seem to me to have led to a definite answer to the question. The simplest of them had for its subject the black and yellow salamander which is common throughout Europe. This animal is like a large newt, but, unlike the newt, it does not lay eggs, but its young are born alive; they come into the world as little four-footed beasts provided with long feathery gills attached to their necks. They live in the water for six months and then their gills drop off and they come on dry land.

Kammerer chose almost black specimens and kept them in cages the walls of which were painted yellow, whilst the floors were covered with yellow earth. In these cages they lived for four years until they were fully grown. As they grew older, the yellow patches on their skim increased in number and size, till when the animals were fully grown, these patches united to form two bands of yellow running down the back. When two such animate produced a brood of young, these young were divided into two equal lots and one lot were reared to maturity in the same kind of cages as those in which their parents had lived; whilst the other lot grew in cages with black walls and floors covered with black garden earth. Both lots from birth were yellower than their parents had been at the corresponding age, and in both the yellow spots increased in size and number during the first six months.

Then, however, those in the yellow cages go on increasing in yellowness—till, when adult, little or no black is visible on the upper side of the animal; whereas, in the case of those kept in black cages, the yellow spots become sprinkled with minute black dots which increase more and more till the yellow patches look dusty, and at the same time they diminish in size. The young produced by two such blackened specimens, if reared to maturity in black cages, become almost entirely black, the yellow spots disappear completely.

If these young are reared in yellow cages they grow into a peculiar form very unlike any found wild—characterised by the presence of a single stripe of yellow down the back.