Man-Made Plants

At least a half dozen species of plants are man-made. They are hybrids which can transmit their basic and unique characters to future generations.

The fact that what long was considered an impossibility in the plant kingdom has been achieved is revealed by Dr. H. Bentley Glass, professor of biology at Johns Hopkins University. With newly developed techniques which make possible the doubling of chromosomes, bunches of genes which are the units of heredity, the creation of species may be just at its threshold and man may take over control of evolution.

The definition of species, after all, is the ability to produce offspring with the major characteristics of the parents. The first successful attempt, Dr. Glass says, was by a Russian geneticist about 30 years ago. He crossed a radish and a cabbage and produced a “rabage.” When two rabages were mated they produced seed which sprouted into other rabages.

Unfortunately for the man who had been the first to cross one of the great barriers in biology, the rabage was a pretty poor specimen. It had the prickly, uneatable leaves of the radish and the poor root system of the cabbage. Russian agricultural authorities had been led to expect great things. They were bitterly disappointed that the new vegetable did not fit into one of the five-year plans. The geneticist was not heard of again and it is generally believed that he was “eliminated” as a reward for one of science’s greatest achievements.

Creators of new species have fared somewhat better in other countries, especially the United States, but they have not fared too well anywhere. In practically every case the new species they have created have taken over the worst characters of the parent species. They have been of no commercial value. It is likely that about the same thing has happened in nature throughout the milleniums.

But bad may be good. It all depends on the environment into which the new species is born. Under the right circumstances, the rabage might have superseded both radish and cabbage. That is, it might have been adapted to a change in environment in which both parent species would have become extinct.

Although no new animal species has yet been man-made there seems no overwhelming reason why this should not happen with some of the new chromosome-doubling drugs. However, a new kind of man is not likely. Among higher animals the mechanism of heredity is very complex indeed. It isn’t likely to happen in nature, in the face of atomic radiation. It has been calculated that normally there is one human mutation per generation for each 50,000 individuals. The high probability is that this mutation involves a recessive, or hidden, gene. Its effects do not appear in the population until two persons carrying the same recessive are mated. About 999 out of 1,000 recessive genes are “bad” and in due course will cause the extinction of the line in which they appear. In the long history of the race it is likely that everybody has fallen heir to one lethal gene, but it may be a long time making its appearance in family lines.

Most of the genes in any given population, good or bad, are so hidden that it is practically impossible to predict what the offspring of any particular couple will be.

The recessive genes have vastly increased through the operation of human “melting pots” all over the world in the last few generations. One result is that minority races tend to become absorbed in majorities. Thus the relatively small American Negro population, without any further inter-marriage but purely through the cropping out of recessives already received from the white majority, will be entirely amalgamated in the more numerous race in approximately 2,000 years.

Genetics is getting into the hands of scientists tools which can speed up the natural process of change about 1,000-fold and this may result in either good or evil. The good side is well illustrated by hybrid corn—a plant which cannot be considered a new species. This lately has been carried to the point where corn with much more sugar in its stalks and only six instead of twelve feet high can be produced.