Homology and Analogy: A Century After the Definitions of "Homologue" and "Analogue" of Richard Owen

Boyden, Alan

doi:10.1086/394676

Cited by 55 publications

(30 citation statements)

References 9 publications

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“…As noted by Boyden (1943) in a paper written to commemorate the 100th anniversary of Owen's formal definition of homology: new terms are not indicated here … Owen, defined the terms clearly and used them effectively. There should be no further need of discussion regarding the necessity of clarifying the meaning of the terms homology and analogy.…”

Section: Homology Analogy and Homoplasymentioning

confidence: 99%

Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolution

2003

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Homology is at the foundation of comparative studies in biology at all levels from genes to phenotypes. Homology is similarity because of common descent and ancestry, homoplasy is similarity arrived at via independent evolution. However, given that there is but one tree of life, all organisms, and therefore all features of organisms, share some degree of relationship and similarity one to another. That sharing may be similarity or even identity of structure and the sharing of a most recent common ancestor--as in the homology of the arms of humans and apes--or it may reflect some (often small) degree of similarity, such as that between the wings of insects and the wings of birds, groups whose shared ancestor lies deep within the evolutionary history of the Metazoa. It may reflect sharing of entire developmental pathways, partial sharing, or divergent pathways. This review compares features classified as homologous with the classes of features normally grouped as homoplastic, the latter being convergence, parallelism, reversals, rudiments, vestiges, and atavisms. On the one hand, developmental mechanisms may be conserved, even when a complete structure does not form (rudiments, vestiges), or when a structure appears only in some individuals (atavisms). On the other hand, different developmental mechanisms can produce similar (homologous) features. Joint examination of nearness of relationship and degree of shared development reveals a continuum within an expanded category of homology, extending from homology --> reversals --> rudiments --> vestiges --> atavisms --> parallelism, with convergence as the only class of homoplasy, an idea that turns out to be surprisingly old. This realignment provides a glimmer of a way to bridge phylogenetic and developmental approaches to homology and homoplasy, a bridge that should provide a key pillar for evolutionary developmental biology (evo-devo). It will not, and in a practical sense cannot, alter how homoplastic features are identified in phylogenetic analyses. But seeing rudiments, reversals, vestiges, atavisms and parallelism as closer to homology than to homoplasy should guide us toward searching for the common elements underlying the formation of the phenotype (what some have called the deep homology of genetic and/or cellular mechanisms), rather than discussing features in terms of shared or independent evolution.

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Section: Homology Analogy and Homoplasymentioning

confidence: 99%

Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolution

2003

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“…The opposite view, held by e.g. Remane (1952), Patterson (1982) and Boyden (1943), is well synthesized by de Beer (1971:9) when he says that "serial homology is really a misnomer, because it is not concerned with tracing organs in different organisms to their representatives in a common ancestor (.. .…”

Section: Taxic and Transformational Homologymentioning

confidence: 99%

Concepts and Tests of Homology in the Cladistic Paradigm

1991

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Abstract-Logical equivalence between the notions of homology and synapomorphy is reviewed and supported. So-called transformational homology embodies two distinct logical components, one related to comparisons among different organisms and the other restricted to comparisons within the same organism. The former is essentially hierarchical in nature, thus being in fact a less obvious form of taxic homology. The latter is logically equivalent to so-called serial homology in a broad sense (including homonomy, mass homology or iterative homology) -Of three tests of homology proposed to date (similarity, conjunction and congruence) only congruence serves as a test in the strict sense. Similarity stands at a basic level in homology propositions, being the source of the homology conjecture in the first place. Conjunction is unquestionably an indicator of non-homology, but it is not specific about the pairwise comparison where non-homology is present, and depends on a specific scheme of relationship in order to refute a hypothesis of homology. The congruence test has been previously seen as an application of compatibility analysis-However, congruence is more appropriately seen as an expression of strict parsimony analysis. A general theoretical solution is proposed to determine evolution of characters with ambiguous distributions, based on the notion of maximization of . homology propositions. According to that notion, ambiguous character-state distributions should be resolved by an optimization that maximizes reversals relative to parallelisms. Notions of homology in morphology and molecular biology are essentially the same. The present tendency to adopt different terminologies for the two sources of data should be avoided, in order not to obscure the fundamental uniformity of the concept of homology in comparative biology.

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“…Even before the molecular basis of the gene was discovered, it was clear that the sharing of genetic information is an important explanation for the sharing of traits between species, i.e., homology (e.g., Boyden 1943). However, it also has long been clear that there is not a one-to-one correspondence between individual genes and traits.…”

Section: Parent-offspring Trait Homologymentioning

confidence: 99%

Developmental causation and the problem of homology

Baum¹

2013

Philosophy and Theory in Biology

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While it is generally agreed that the concept of homology refers to individuated traits that have been inherited from common ancestry, we still lack an adequate account of trait individuation or inheritance. Here I propose that we utilize a counterfactual criterion of causation to link each trait with a developmental-causal (DC) gene. A DC gene is made up of the genetic information (which might or might not be physically contiguous in the genome) that is needed for the production of the organismic attributes that comprise the trait. I argue that individuated traits-phenes-correspond to organismic features that are caused by DC genes. Using such an approach, we can define a DC map, which shows the relations between each pair of phenes and provides a succinct summary of genotype-phenotype relationships and phenotypic complexity. Phenes in parents and offspring are judged to be homologous if their DC genes are composed of orthologous genetic factors. When comparing more distantly related organisms, traits are homologous when linked by a chain of parent-offspring homologs along the path of ancestry that links the two organisms. There are three possible ways to deal with the potential for multiple equivalent DC genes: maximal, minimal, and consensus homology. Whereas maximal homology has limited utility, the other two approaches have value and can help to guide research at the intersection of evolution and development. IntroductionThe homology relation refers to the idea that different organisms of the same or different species share the same traits. For example, it is generally agreed that my middle finger nail and your middle finger nail are homologous with one other and with the hoof of a horse. As this example shows, homology does not require that the structures in question be identical in form or function. So what notion of "sameness" is connoted by homology? Darwin and subsequent biologists have generally agreed that the concept of homology relates in some way to descent from common ancestry (e.g., Lankaster 1870). A fingernail and a hoof are homologous because the common ancestor of a human and a horse had a structure that became modified to give rise to the human middle finger nail and the horse's hoof. Philos Theor Biol (2013) While the idea is simple, nailing down (no pun intended) the concept of homology has proved challenging, to say the least. While all agree that homology depends in some way on common ancestry, the manner of this dependence is far from clear. In particular, how can homology refer to the inheritance of traits from common ancestry when phenotypic traits are not passed on from generation to generation? Thankfully, we do not pass on our fingernails to our children by direct grafting! This paper is built on the premise that in order to get traction on homology, and put the concept to work in comparative biology, we first need to solve a much less studied conceptual problem: the nature of traits. When observing an organism we get the sense that it may be atomized into parts in some objecti...

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Homology and Analogy: A Century After the Definitions of "Homologue" and "Analogue" of Richard Owen

Cited by 55 publications

References 9 publications

Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolution

Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolution

Concepts and Tests of Homology in the Cladistic Paradigm

Developmental causation and the problem of homology

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