New paths in genetics / by J.B.S. Haldane.

  • Haldane, J. B. S. (John Burdon Sanderson), 1892-1964.
Date:
1941
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: New paths in genetics / by J.B.S. Haldane. Source: Wellcome Collection.

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    New Paths in Genetics put the matter slightly diíFerently, biologists and philoso¬ phers used to ask, Why do two rabbits produce rabbits, and not rats, roses or bicycles? The geneticist is able to answer the much simpler question, Why do two pink-eyed white rabbits give only pink-eyed whites, and not blue-eyed whites, or browns, or blacks ? The answer to this easy question throws some light on the much harder first question. If, with Darwin, we hold that varieties are incipient species, it throws a good deal. We said that genetics deals with innate differences. What do we mean by the word innate? Supposing your female cat has a long tail, but one of her kittens has a short tail. This may be because the tail has been cut short, or because the father was a short-tailed or Manx cat. In the former case we say that the difference was due to environment or nurture, in the latter we say that it is an innate difference due to nature. The tailless kitten was destined to be tailless from the moment when it started life as a single cell derived by the fusion of an egg-cell from its tailed mother and a spermatozoon from its tailless father. Nature has not quite the same meaning as heredity, for animals or plants may have a genetically determined nature different from that of any of their ancestors. For example, double stocks {Matthiola vncand) are quite sterile. All their ancestors have been single. Nevertheless we know that some singles breed true, while others throw doubles, so we can ascribe the 12