Facial Development Clue to Evolution?
The BBC reported this week on the study of embryonic facial development providing clues to human evolution.
Dr Mosley discusses how evidence from human bodies suggests that humans may have evolved from fish. The article discusses non-facial aspects of human development that Dr Mosley hypothesises can be traced back to our ‘fishy ancestry’. Of particular interest however is his discussion around facial development in human embryos. He talks about the ‘philtrum’, the groove on your top lip that lies just beneath your nose. Although this has no obvious function, it is a side-effect of the complex process that the embryo goes through in craniofacial development.
Craniofacial development begins very early on in the embryo’s life – during its first two months of existence. Dr Mosley notes that initially the embryo has eyes on the side of the head, much like a fish. The areas that will become the nostrils and middle part of the lips also have to drop down from the top of the head. The top lip, palate (roof of the mouth) and jaw begin life as “gill-lie structures” on the neck that have to move together for successful formation.
Regardless of whether or not humans do actually share an ancestry with fish, craniofacial development in humans is an amazing process. The automatic and complex developmental process of moving towards a recognisable human face is conducted with extreme precision. Dr Mosley notes that if the movement of the jaw, palate and top lip coming together is out by as a little as an hour, then the lip and/or palate will not fuse properly. It is at this point that a cleft lip and/or palate can occur, as the unsuccessful fusion leaves a gap or cleft.
The cleft may occur solely in the lip, in the palate, or in both areas. It may also affect the soft palate, towards the back of the mouth. Depending on the site and severity of the cleft, several corrective operations may be necessary during infancy, childhood and even adolescence.
Speech development can be quite disordered for a number of reasons. In many children with a cleft, the middle ear can be affected and grommets may need to be inserted to maximise the child’s hearing abilities. If a child cannot hear properly then they may also have difficulty learning to recognise, discriminate between and use different sounds. Articulatory problems will occur as many speech sounds require successful contact between the tongue and the palate or soft palate. Compensatory articulation can also be a problem as the child attempts to compensate for the inability to produce the target sound and ends up producing an entirely different sound. Velopharyngeal inadequacy may also occur, when a cleft affecting the soft palate prevents successful closure between the throat and nasal cavity, which is necessary for the production of many speech sounds.
Speech therapy therefore plays a large part in the long-term treatment of children with a cleft lip and/or palate. If you feel that your child may benefit from speech and language therapy, I.T.S. could be of help. Contact us here: https://integratedtreatmentservices.co.uk/contact-us/enquiry/
You can read Dr Michael Mosley’s article and watch a sped-up video of facial development in a human embryo here: http://www.bbc.co.uk/news/health-13278255
Sarah Bennington May 2011
Written on behalf of Integrated Treatment Services. ITS is a private Speech and Language Therapy service based in Leicestershire and the East Midlands. It specialises in providing highly-skilled Speech and Language Therapists, but also associates with other therapeutic professionals, including Occupational Therapists, Physiotherapists, Psychologists and Arts Therapists.
