ART & ORGANISM
DEEP ETHOLOGY
EVOLUTION
analogy and homology
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The shared past of a trait, no matter how superficially dissimilar, or the current similarities of a trait, even when there is no shared evolutionary past, can tell us much about the developmental processes, environments to which they have accommodated over their deep history, and as yet unsuspected physiological substrate.
HOMOLOGYrefers to a connectedness through shared ancestry … a deep, possibly profound relatedness between phenomena that may not be obvious as they are presently manifest.
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HOMOLOGY and ANALOGY in evolutionary theory
. the importance of homology in Art & Organism
“The present contains nothing more than the past, and what is found in the effect was already in the cause.”
(Henri Bergson —Creative Evolution)
Similarity due to Common Ancestry (homology) of trait (may inform us about control systems)
“Common ancestry is shared by two characters if in principle each can be shown to have evolved from the same character in a common ancestor.” (Hailman p183)
Similarity due to Common Functions (analogy) of trait. (generally attributed to parallel or convergent adaptation — May inform us about ecological adaptiveness of trait)
An extreme example of analogy: The ripples on the skin of a fast moving porpoise and in the endothelial lining of a blood vessel — both responses to comparable adaptive needs
Common appearance (homoplasy) of trait. (May inform us about external and internal forces “guiding” the development of the trait)
“Common appearance” is sometimes used in the sense of topographic relationships –but clearly, two traits can appear physically the same without sharing common ancestry. In fact, common appearance can be an important clue about “function.”
Because various combinations of these three kinds of commonalties is central to most arguments about evolutionary relationships, Hailman (1976) has utilized Venn diagrams in keeping them straight: the three sets– ancestry, function, appearance– can define 8 topological areas
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“A cautious man should above all be on his guard against resemblances; they are a very slippery sort of thing” (Plato, “The Sophist”)
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The use of behavioral traits to reconstruct phylogenies is controversial [more from Wells]
BEHAVIORAL HOMOLOGY.
- The concept of behavioral homology reflects the problem of treating behavior as the “function” of a structure –the two cannot be separated (Hodos, Atz). Behavior, particularly
- FAPs, can be measured (and thus compared) as minutely as morphological traits.
- The criterion “OF POSITION” for homology of morphological relationship can be applied in behavior if temporal relationship is considered.
Note 1: Plato, “The Sophist” (trans FM Cornford) Plato’s Theory of Knowledge. London 1935 ( p.180) epigraph to Malcolm S Gordon (1977) Animal Physiology: Principles and Adaptations (3rd edition)