Everyone has heard about rudiments or vestigial organs at least once. We have an image of them like of those structures that are left within us from our distant ancestors. By definition, the vestigial organs have changed functions or none of them [1].Originally, vestigium means ‘footprint’, which fits to a conceptof the vestigial organs as evolution steps of each organism [1,2,3].
Some examples of human rudiments are quite famous: tailbone (coccyx), vermiform appendix, body hair, goose bumps, ear muscles, and wisdom teeth [1,2,3]. Also, each human embryo has branchial arches, remnant of gills; some people can have Darwin’s tubercle, which’s homologue is presented in monkeys, rhinos, horses, cows, goats, and etc.; and the human’s vomeronasal bone also does not have any function as it is not connected to any nerve [2,3]. Except the human, animalspossess atavisms too. For instance, dewclaws and ear muscle in dogs, pelvic or leg bones in whales, third eye lid’s nictitating membrane in monkeys [1,2].
It is impressive that some behavioral concepts are also claimed as vestigial. The dogs making circles before getting asleep turns out to be an action of their lost motive to tramp down grass for their own comfort. The palmar grasp reflex of the human babies originates from our ancestor’s need to hold their mother’s fur while being carried. Flightless cormorant, having no wings, holds them outstretched in the sun in order to dry them like its ancestors did, which is actually unnecessary for its own survivalnowadays [1].
After the branchial arcs of the human embryo being mentioned, now we can survey how the rudiments may draw our attention to themselves. Normally, the embryo has some features of its development that are not seem in a body of an adult organism, like the branchial arches. If development error, like an apoptosis’s dysfunction, occurs the baby is born with syndactyly (unseparated fingers or toes) or tail of the coccyx [1,3]. Notoriously known cleft palate, in its turn, is the result of a fusion error [3].
Speaking of adult organisms, the vestigial structures are exposed to changes due to various conditions. Thus, hormonal disbalance in the males results in gynaecomastia, dentistry operations can cause excessive proliferation of the debris of Malassez which can go to cysts or tumor. The latter is the remnant of a tooth root epithelial cells originated from the tooth development. However, these cells may be useful and protective when the tooth is damaged or inflamed [3]. These examples show us that the rudiments can be activated or inactivated in some way, and that such events can give us either benefit or detriment.
Such activity of the rudiments is explained by the changes on a molecular level in regulatory genes. The latter influencesstructural genes in a way of encoding or not for rudiments’ occurrence [1]. Hence, we see some vestigial structures dormant, but not forever.
In a finale, the vestiges can be called so as long as they change DNA in the way they are presented in a phenotype of the organism [1]. Indeed, the vestigial structures present telltale outcome of the evolution of plenty of animal species. They aresome kinds of retrospective of the past by which we can discuss long ago evolution processes.
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