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Published online by Cambridge University Press: 14 March 2022
Biologists have recently found it useful to give a prominent place in their theories to the concept of a plant or animal population. Genetics, ecology, paleontology, and especially the theory of evolution have been able to make notable advances as a result of employing the concept in their interpretations and inferences. The concept has not, however, first been rigorously defined and then put to work. That is rarely the way fruitful scientific notions develop. On the contrary, in most discussions the term “population” has a large degree of vagueness about it. This is due in part to the fact that the term has been taken over from ordinary language and employed in a number of novel contexts. But some of the vagueness also seems to be an unavoidable consequence of the immensely intricate phenomena to which the term refers. In any case, the role played by the concept of a population in evolutionary theory makes even a brief inquiry into its meaning worthwhile. The present paper is concerned with such an inquiry. What I wish to do is, first, to review the major ways in which the concept has been used by biologists in connection with recent formulations of the theory of evolution; and secondly, to comment on a few misleading issues which may arise if care is not taken to observe certain logical and linguistic distinctions.
1 Cf. Th. Dobzhansky, Genetics and the Origin of Species, 3rd. ed. rev., (New York, 1951) pp. 260. “Individuals are combined into reproductive communities, Mendelian populations. These supraindividual entities are considered supraorganisms by some authors….”
2 W. C. Allee, A. E. Emerson, O. Park, T. Park, and K. P. Schmidt, Principles of Animal Ecology, (Philadelphia, 1949) p. 265.
3 Cf. J. B. S. Haldane, “The Statics of Evolution,” in Evolution as a Process, edited by Julian Huxley, A. C. Hardy, E. B. Ford, (London, 1954) pp. 109–121.
4 Cf. G. S. Carter, Animal Evolution, (London, 1951) p. 30; and also my paper, “The Concept of Evolution,” Mind LXIII, N.S., 249 (Jan. 1954) p. 16ff.
5 Cf. B. H. Burma, “The Species Concept: A Semantic Review,” Evolution, III, 1949, p. 369ff.
6 Cf. G. G. Simpson, The Major Features of Evolution, (New York, 1953) p. 116 ff.
7 This term was first proposed by J. L. Gilmour and J. W. Gregor in Nature, 144 (1939) p. 333, and has since then been widely used, though with considerable variation in meaning.
8 G. G. Simpson, The Major Features of Evolution, p. 380. G. S. Carter in Animal Evolution, p. 140, speaks of demes as “the basic units of animal populations.” But this phrase seems to apply more appropriately to individual organisms. Simpson's phrase seems better.
9 ibid.
10 Cf. W. C. Allee, et al., Principles of Animal Ecology, pp. 305–6.
11 The expression “open system” is used here in the sense attached to it by von Bertlanffy in his Problems of Life (New York, 1952) p. 125 ff. See his paper, “The Theory of of Open Systems in Physics and Biology,” Science, Vol. cxi, (Jan. 1950), pp. 23–29. The suggestion that biological populations are open systems is also made by Felix Mainx in his Foundations of Biology (Chicago, 1954), p. 40.
12 W. C. Allee, et al., Principles of Animal Ecology, pp. 263–65.
13 G. G. Simpson, The Major Features of Evolution, p. 291.
14 Th. Dobzhansky, Genetics and the Origin of Species, p. 15.
15 ibid.
16 E. Mayr, Systematica and the Origin of Species, (New York, 1943) p. 120.
17 Th. Dobzhansky, Genetics and the Origin of Species, p. 263.
18 G. G. Simpson, The Major Features of Evolution, p. 341.