Homology and Homoplasy 4356 HOMOPLASYAnother way of comparing and classifying features among organisms ishomoplasy,
a term introduced by Lankester [1870] to incorporate an evolutionary dimension
into Owen’s definition. A pioneer of evolutionary morphology, especially analyses
of relationships between germ layers, homology and classification, Lankester is
perhaps better known for his emphasis on degeneration as an evolutionary force,
as editor, reviser and translator of Haeckel’sHistory of Creation[1876], and as the
author of a series of books of essays on science (Fireside Science; The Kingdom
of Man; Extinct Animals) aimed at the general reader. Lankester [1870a] dealt
specifically with whether Owen’s term analogy could be used for homoplasy, argued
that analogy has a wider significance than given to it by Owen and saw that the
term applied to features irrespective of whether their bearers shared a common
ancestry: “Any two organs having the same functions are analogous, whether
closely resembling each other in their structure and relation to other parts or not;
and it is well to retain the word in that wide sense” (p. 41).^14
7 HOMOGENY AND HOMOPLASYBoth Lankester and Gegenbaur placed homology into an evolutionary framework
because they were staunch Darwinians: “in [the various] kinds of animals and
plants [we see] simply the parts of one great genealogical tree, which have be-
come detached and separated from one another in a thousand different degrees,
through the operation of the great destroyer Time... ” [Lankester, 1870a, 34].
Lankester was concerned that although the majority of evolutionists would agree
that organs A and B were homologous in animalsαandβbecause a common
ancestor possessed the same organ, the term homology made no reference to evo-
lutionary lineage, indeed it was typological, referring homologues to some ideal
type. Consequently, Lankester thought it “necessary to have two terms in place
of the one ”homologue” [ibid.p. 36]. His criterion for establishing thetwo classes
of homologywas the evolutionary history of the organisms concerned. Lankester
coinedhomogenyfor similar features shared by two organisms as a consequence of
common descent:
Structures which are genetically related, in so far as they have a single
representative in a common ancestor, may be calledhomogenous.We
may trace anhomogenybetween them, and speak of one as thehomogen
of the other... details not traceable to, and inherited from the ancestor
cannot be homogenous. [Lankester, 1870a, 36, his emphases]
Lankester introducedhomoplasyfor what he considered to be a single class of
evolutionary phenomena. Homology and homoplasybothreferred to the conse-
quences of the actions of identical or nearly similar forces or environments, in the
(^14) See Rieppel [1988], Hall [1994b; 2003a], Panchen [1999] and Gould [2002] for discussions of
Lankester’s position.