I would like to understand better the use of the words homology, homologue homologous by anatomists. Is an anatomist always commenting on the similarity in evolutionary origin and/or embryological development as well as similar morphology when using this term? That is an anatomist may say of two (differently named/identified) body parts that they are similar in appearance, but will only say that two such parts are homologous with consideration that they have shared evolutionary/embryological origins as well? I thought this was the case, but am thrown by the following statement from a footnote in Terminologia Anatomica (A04.3.02.001, pg 36): In this sense the mm. intertransversarii anteriores, mm. posteriores laterales cervicis, and mm. intertransversarii laterales lumborum, being hypaxial muscles and homologues of mm. levatores costarum and being supplied by rami anteriores are not true back muscles. I think that because mm.levatores costarum is innervated by rami posteriores that it is an epaxial muscle (although conventionally grouped as a thoracic muscle) and therefore could not be an (evolutionary/embryological) homologue for the hypaxial intertransversarii. If this thinking is wrong please let me know, but I'm considering otherwise the fault lies in my understanding of the meaning of homologue.
I saw a couple of questions here. Let me first start by defining homology and analogy from an evolutionary perspective.
The terms homology and analogy were first used by an English anatomist, Sir Richard Owen, drawing upon his experience/influence in early 19th century German traditionalists who searched to define by searching for a common Bauplan (an idealistic morphology for organism). Homology meant an essential resemblance, kind of like Aristole’s eidos, a reflection of a common underlying structural plan and descent. Analogy refers to any other kind of resemblance – it refers to archetype, eidos or Bauplan and no shared descent. However, a reflected organism that developed under the constraints of simple convergent adaptations.
So the flipper of a whale and wing of a bat are homologous to the human hand since the skeletal elements are similar in origin. Evolution has altered the basic underlying plan of the labyrinthology ancestor. The wing of a fly and wing of a bat are analogous – though structurally different but evolved.
Let’s bring this back to anatomy and the Terminological Anatomy footnote you referenced. I do not believe that you misunderstood the definition of homology and analogy. I consulted Dorland’s Medical Directory 26th edition and they provide a definition for homology which is very different than the definition for homology: Homological, homologous organ or part; an organ similar in structure, position to another.
I believe Terminological means the other parts of levator to include longus and brevis. The definition given for Homology, matches to the one I gave above – “structural similarity due to descent from common form.”
Being trained in evolutionary biology, I personally do not like to use homology to describe structures within a single organism. Homology analogy implies a comparison between two organisms – although the same species and the comparison can come between the sexes. I like to say all the “true back” muscles are derived from epaxial muscles, thus sharing a common embryological origin. I tend to save homology and analogy for discussion regarding evolutionary origins of structures.