Heredity / by J.A.S. Watson.

  • James Anderson Scott Watson
Date:
[1912]
Catalogue details

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

Credit: Heredity / by J.A.S. Watson. Source: Wellcome Collection.

    41/104 page 39
    ACQmRED CHARACTERS 39 Generations of giraffes have stretched their necks to reach the foliage of trees, and the neck of the giraffe is grown to a prodigious length. The antelope has been accustomed for centuries to flee from beasts of prey, and has developed in the direction of extreme speed. Lamarck's theory of evolution was to the effect that races were developed by the accumulation of the effects of use and disuse. And certainly it seems the obvious explanation of the dwindhng of the whale's hind limbs, to say that they have become gradually smaUer through disuse, or to say that the neck of the giraffe has become long through its special use, which involves its being stretched continually. But we have no proof whatever that these explana¬ tions are the correct ones. Moreover, it is possible to explain all the instances given above without assuming the inheritance of modifications. According to Darwin's theory of Natural Selection, the giraffe's neck has be¬ come long because through generations the longer- necked specimens have been able to reach more leaves than their shorter-necked fellows, and consequently have been able to live through times of scarcity while the others starved. The longer-necked specimens have continually been preserved by nature, and the race has become long-necked. Similarly, the fleet antelope escapes from the lion, while his slightly more slow-footed brother is caught and eaten, and the race thereby becomes swifter of foot. As regards the dwindling of disused members, the ex¬ planation of the modern Darwinian is perhaps less con¬ vincing. But Darwin says that the wings of the ostrich, for instance, became useless when the ostrich took to running. Hence those individuals which wasted least food and energy in wing-building had the more for leg-building. They had thus the advantage over their stronger-winged fellows and tended to be preserved. Yet in certain cases such an explanation seems un¬ deniably far-fetched. Take the case of the eyes of cave
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