Theimportance of evolution cannot be gainsaid as far as explaining theorigin and development of human beings and other species isconcerned. Indeed, it is well acknowledged that human beings havebeen considerably obsessed with research pertaining to their origins,with numerous theories being crafted in this regard. It has widelybeen accepted that human beings have evolved through varied stages tobe what they are today, and are still continuing in the evolutionprocess. The comprehension of the evolution theory has necessitatedthat the body structures of varying species be examined. This isessentially what has given rise to comparative anatomy.
Comparativeanatomy underlines the comparative study pertaining to the bodystructures of varying species of animals so as to comprehend theadaptive modifications that they have experienced or undergone in thecourse of their evolution from shared or common ancestors. Ofparticular note is the fact that the field has been primarilyconfined to the examination of vertebrae animals. This science isbased on the fact that appearance has for a long time been utilizedas a sign that organisms are related. The body structure is,inexorably, connected to function, in which case it offers evidencepertaining to descent with some changes. For instance, the mammothand elephants are seen as descendants of a common ancestor as aresult of their similar anatomies and body structures (Wiens, 2004:917). This makes comparative anatomy suitable as the first line forreasoning in the determination of the inter-relatedness of species.Of particular note is the fact that it is important that evidencededuced from comparative anatomy is supported with evidence derivedfrom other scientific fields of study.
Theorigin of comparative anatomy may be traced way back to CharlesDarwin. He opined that the forelimbs of animals such as bats, whales,humans, as well as other creatures bear some striking similaritiesirrespective of the fact that their forelimbs were utilized forvarying purposes such as flying, swimming or lifting, or evenwalking. In essence, Charles Darwin suggested that the similarity offorelimbs would be an indicator of similar origins. Darwin utilizedthis evidence in indicating that modern forms had a common ancestor(SaxenaandSumitra,2008, 58). Of course, he had to offer explanations for the variationsin their usage of the forelimbs and other parts of the body. In thisregard, he opined that the varying modifications essentially amountedto adaptations of the animals or vertebrates to the particular needsthat the modern organisms had. On the same note, Darwin observed thata large number of animals incorporated structures that they neverused (TreutingandSuzanne,2012: 43). More often than not, the structures eventually degenerateand even become undersized unlike the case for similar organs inanimals that utilized them. Darwin gave these useless organs the namevestigial organs. For instance, in the case of humans, vestigialorgans may include the wisdom teeth, fused tail vertebrae, appendix,or even the muscles responsible for the movement of the nose andears. Darwin underlined the notion that vestigial organs may be arepresentation of structures that are yet to disappear completely buthave been rendered unnecessary for survival, perhaps by someenvironmental change. Eventually, the organs would becomenonfunctional, as well as reduce in size.
However,Darwin differentiated between analogous and homologous structures. Hestated that evolution through natural selection meant that, given thesame environmental demands, the unrelated species may autonomouslyevolve structures that are superficially similar in a process knownas convergent evolution (Jesse et al, 2007: 396). These body partsthat are outwardly similar in unrelated organisms are calledanalogous structures and may be extremely difficult in their internalanatomy as the parts do not emanate from similar ancestral structures(Wiens, 2004: 917). For instance, the wings of birds and those offlies are analogous structures that have emanated through convergentevolution, just as is the case for the fat insulated and streamlinedshapes of penguins (birds) and seals.
However,vestigial and homologous structures offer evidence pertaining to therelatedness of animals that have been adapted in varyingenvironments. Indeed, it is noted that modern organisms are adaptedin varying lifestyles and habitats. In spite of the diversity in thefunctioning o =f their structures, the internal anatomies pertainingto mammal forelimbs and birds bears significant similarities. Darwinnoted that via natural selection, the forelimbs of birds and mammalswere transformed to carry out specific functions (HymanandMarvalee,1992: 78). These internally similar structures are referred to ashomologous structures, which underlines the fact that they havesimilar or shared evolutionary origin in spite of the possiblevariations in functions.
However,comparative anatomy has been often ran into trouble as a result ofembryology. It has been noted that homologous structures that areabsent in adult organisms are usually present in particular embryonicdevelopment stages. In this case, the embryo comes as a microcosm ofevolution, going via numerous evolution stages so as to create thecurrent state in which the organism is. In particular, species thathave little or few similarities in their adult form may incorporatestrikingly similar stages of embryos.
Hyman,Libbie H, and Marvalee H. Wake,1992. Hyman`sComparative Vertebrate Anatomy.Chicago [u.a.: Univ. of Chicago Press
Jesse,Love Hendrikse., Trish, Elizabeth Parsons & Benedikt,Hallgrímsson, 2007. "Evolvability as the proper focus ofevolutionary developmental biology". Evolution& Development 9 (4):393–401.
Saxena,R K, and Sumitra Saxena,2008. ComparativeAnatomy of Vertebrates.Tunbridge Wells, Kent: Anshan
Treuting,Piper M, and Suzanne M. Dintzis,2012. ComparativeAnatomy and Histology: A Mouse and Human Atlas.Amsterdam: Elsevier/Academic Press
Wiens,JJ, 2004. "What is speciation and how should we studyit?". AmericanNaturalist163 (6):914–923