Adaptation

Abstract

NOTWITHSTANDING all the discussion that has taken place since 1859 concerning evolution, adaptation, and selection, biologists are still far from agreement, not merely concerning the explanations that have been proposed, but also concerning the things to be explained. Mr. J. B. S. Haldane (NATURE, Sept. 21, 1929) cites evidence that differential survival may be due to physiological differences associated with visible characters not themselves useful or harmful. Prof. D. M. S. Watson, in his presidential address to Section D of the British Association at the recent meeting in South Africa, suggested that structural adaptation may be in many cases imaginary, or may have been the cause of habit, not the consequence. He stated that in extreme cases it was not possible to doubt the special function to which a structure was adapted, but in others a similar habit occurred without any corresponding structural adaptation. As an example of this he referred to the paddle-like limbs of ichthyosaurus as proving that it was an aquatic animal, but stated that there was no indication in the post-cranial skeleton of hippopotamus that it also was aquatic: “its limbs show no swimming modification whatever”.