Assignment 9

Jacqueline Ottley
Assignment 9

How much of a child's intelligence is genetically determined, inherited from   his/her parents, and how much is due to his/her environment? Discuss these important factors.

No set of genes or gene markers has been conclusively linked to the development of intelligence. Specific genes that have been studied are primarily those believed to be linked to the development of brain size.
Yet no link between human brain size and intelligence has been established. Other theories have been proposed to explain how difference in brain size and structure have evolved. One such theory detailed by British neuroscientist John R Skoyles in his paper, Human Evolution Expanded Brains To Increase Expertise Capacity Not IQ, argues that size differences are related to skill development Skoyles maintains that the human brain increased in size over time due to a need for increased expertise or skill capacity associated with highly complex tasks that have varied from culture to culture.
He argues that this explains difference in brain size among groups.
Contributing evidence comes from studies on children suffering from sever epilepsy who have had a brain hemisphere removed to prevent debilitating seizures. If removed early enough half a brain seems to work nearly as well as a whole one. The remaining hemisphere often co-opts the functions previously handled by the missing portion.
Data from patients suffering from microcephaly a congenital disorder which results in reduced brain size and function, reveals that though a majority of patients score considerably below average on IQ tests, a small portion test in the normal range.
These examples challenge the notion that a person's brain size determines his or her cognitive ability.
Some genes that have been correlated to G are those associated with cathepin D (CTSD) and cholinergic muscarinic 2 receptor (GHRM2). But it remains undear what role these particular genes play in the development...