First Debates

The proposal to treat the Natural System genealogically immediately sparks a lively debate. Many taxonomists take this proposal very enthusiastically, and the most radically minded phylogeneticists decisively break with “pre-Darwinian” systematics; this attitude will be summarized later as follows: “for phylogenetics, the centuries-old work of the natural systematics is of little value. For it, everything that had been done before Darwin needs to be redone” [Kozo-Polyansky 1922: 8]. With this, disagreements among phylogeneticists arise about how to interpret phylogeny, how to reconstruct it, and how to represent it in classifications. Thus, paleontologists object to using the phylogenetic approach in the systematics of extant organisms: in this, they refer to Haeckel’s idea that phylogenetic reconstructions must be based on paleontological data, without w'hich they remain purely speculative [Scott 1896]. Many taxonomists insist that phylogeny should not be interpreted simplistically as just a genealogy; they emphasize, with reference to Darwin, that in recognizing closely related groups, it is necessary to take into account the “internal” parallelisms between their members [Scott 1896; Engler 1898; Osborn 1902]. Devoted “Haeckelians” (such as William Scott) insist that genealogy should be reconstructed based only on the characters inherited from a common ancestor, while those inclined to natural systematics (such as Adolf Engler) believe that it should be supported by the largest number of characters. All these debates will be echoed in modern cladistics by disputes between adherents of the principles of synapomorphy and total evidence (see Section 5.7.3).

At the same time, the relation of systematic phylogeny to two other dominant approaches, namely natural systematics and typology, is hotly discussed. Early attempts to elaborate evolutionary classifications are criticized for their authors not actually reconstructing phylogenies but simply “attaching” phylogenetic interpretations to the preceding classifications without any significant changes in them [Bessey 1915; Kozo-Polyansky 1922]. For this reason, Haeckel’s systematic phylogeny is sometimes referred to as a “hidden” typology [Naef 1919; Meyer 1935] and resulting systems are estimated as “pseudo-phylogenetic” [Kozo-Polyansky 1922].

There are many who sharply criticize an equation of the natural and phylogenetic classifications. From a philosophical background, this is objected to by insisting that classifications based on similarity as such are primary, while their phylogenetic interpretations are secondary, so the latter are redundant [Gray 1876; Caruel

1883; Driesch 1899]. Proponents of the natural systematic criticize the Haeckelian approach in that it is based on analysis of only a few characters as evidence of genealogical relationships, while actually natural classifications should be based on a large number of characters. Typologically minded researchers, even admitting the evolutionary idea, consider it inapplicable in systematics because the latter must be “an exact and logical ordering of verifiable facts,” therefore the natural system should be developed without reference to unreliable genealogical schemes [Huxley 1864]. At the same time, many taxonomists remain apart from these discussions, considering the genealogical idea as just one more (along with many others) speculative and therefore redundant interpretation of the fundamental concept of affinity.

A very important consequence of mastering the evolutionary idea becomes the phylogenetic interpretation of the originally typological concept of homology: it leads to a revision of the basic criteria for distinguishing homologous and analogous structures and to the introduction of a new terminology. Thus, Haeckel calls Owen’s special homology homophyly [Haeckel 1866]. Zoologist Edward Ray Lankester suggests eliminating Owen’s notion of homology altogether as “idealistic” and replacing it with the notion of genealogical correspondence, with its two distinguishing forms [Lankester 1870]. One of these is homogeny as a correspondence of structures inherited from a single ancestral form; it is close to Haeckel’s homophyly. All other correspondences are homoplasies, in their wide understanding including parallelisms, analogies, and also serial homologies. A very detailed system of gradations between homologies and analogies is proposed by George Mivart, who includes genealogical and ontogenetic criteria in their definition [Mivart 1870]. He identifies more than two dozen variants of correspondences of anatomical structures: for example, according to Mivart, there are “homological analogy” and “analogical homology.”

At lower levels of taxonomic hierarchy, the basic idea of classification Darwinism provides a strong impetus to a nominalistic understanding of species: since species are constantly changing, they are “a human contrivance [...] made simply for convenience’s sake” [Bailey 1896: 457, 459]; “species and variety are [...] abstract concepts, they do not exist in nature” [Timiryazev 1904: 81]. However, more moderately minded taxonomists, along with rejecting species as real natural units, ascribe a real status to local geographic races. This viewpoint leads to a “species splitting”: in the second half of the 19th century, races and subspecies are frequently denoted by binomens, i.e., they are actually assigned a formal species status in classifications. In the first half of the 20th century, an emphasis on intraspecific units will be actively developed in biosystematics (see Section 5.6).

 
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