Charles Darwin's Theory Of Natural Selection

In 1859, Charles Darwin revealed his theory of evolution by natural selection in his famous book “On the Origin of Species.” Natural selection is the process by which organisms evolve over time to allow for better adaption to its environment in order to survive and have more offspring.1

In Homo sapiens (genus and species of man), the notion of natural selection is observed in the way we perform our activities of daily living. In 2003, Davidson et al.2 presented data supporting the concept that craniofacial structural and anatomical changes took place for the development of speech and language. Unfortunately, the undesired consequence of this evolution facilitated obstructive sleep apnea (OSA) in modern humans.2

Klinorynchy is the posterior migration of the splanchnocranium (facial skeleton) under the neurocranium.3 This shift shortens the maxilla, palate, ethmoids and mandible in order to provide speech and language. These changes are seen in the evolution from Pan Troglodyte, a common chimpanzee, to the modern Homo sapien.4 According to Crelin et al., the anterior migration of the foramen magnum with pharyngeal collapse is part of the evolutionary change to facilitate speech but diminish olfaction.5 Lieberman et al. proposed that the change from an obtuse to an acute cranial base angulation seen in the modern Homo sapiens furthered the development

described that the posterior migration of the tongue into the pharynx decreased the oral cavity size to improve speech and deglutition.7 In the animal kingdom, the mechanism known as the epiglottic–soft palate lock-up, the overlapping of the epiglottis and soft palate, is prevalent. 2 Interestingly, the mechanism is present in infant Homo sapiens, but disappears as the soft palate shortens and the larynx descends in order to promote buccal speech.2 Although, these adapted anatomic features facilitate speech and the development of language, they also predispose humans to