Differences of opinion within (neo-)Darwinism: Gould’s critical appraisal of neo-Darwinism

Abstract

Die moderne biologie (sedert Darwin) word nog steeds deur talle uiteenlopende standpunte gekenmerk. Bepaalde neo-Darwinistiese aannames verraai die invloed van wysgerige sienings wat meestal onbewus op biologiese denkers inwerk. Die bestaande tipeverskeidenheid, beide in die paleontologiese rekord en die tans lewende “natuurlike sisteem” staan teenoor die funksionalisme van die neo- Darwinisme. In hierdie artikel word grootliks op die skerp kritiek wat Gould en Eldredge op die standaard neo-Darwinistiese opvattinge uitgeoefen het ingegaan. Beide die kontinuïteitspostulaat en die idee van vooruitgang staan op gespanne voet met die natuurwetenskaplike stande van sake.

The opposition between vitalism and physicalism forms an integral part of the history of biology. Before Darwin entered the scene vitalism ruled the day, coupled with the influence of Plato on idealistic morphology. But even after Darwin published his Origin of Species in 1859 we can observe a proliferation of diverging biological orientations. Nonetheless, this article mainly focuses on the contrast between gradualism and stasis with a view to the underlying philosophical assumptions surrounding this opposition. Within (neo-)Darwinism there is an a priori commitment to the slogan that nature does not make jumps. The effect of pursuing this commitment is that it gets difficult to face the discontinuities of the fossil record. Sterelny confronts the assumed “gradualness of evolutionary change” with the simultaneous appearance of most of the major animal groups in the Cambrian explosion. Recently Denton emphasized that nature is in fact “a fundamental discontinuum of distinct Types and not the functional continuum maintained by Darwinian orthodoxy”. The standard (neo- Darwinian reaction to the discontinuities in the fossil record is to argue that it is the result of the imperfection of the fossil record. However, Gould and Eldredge pointed out that the dominant pattern of the fossil record is stasis – a type appears abruptly, remains constant for millions of years (stasis) and then disappears equally abruptly. According to them stasis is data. A few textbook cases of alleged transitional forms had to save the day. But against all expectations of the gradualist faith in the presumed continuity of descent, Gould remarks that almost all these famous exemplars turned out to be false on rigorous restudy and that nearly all these classics have since been disproved. The important point made by Gould is that gradualism (the continuity postulate – nature does make jumps) “stood prior to natural selection in the core of his [Darwin’s] beliefs about the nature of things”. How these factual patterns affect the mystery regarding the origin of humans is briefly discussed and then the article is concluded with Gould’s questioning of the idea of progress.