Nature vs nurture

Scientists have argued about this for years.  How much of who we are is the influence of our genes (nature) or our environment (nurture)?

It was the British scientist, Francis Galton, who in 1874 started the nature vs nurture debate.

There have been a number of studies on identical twins to determine if nature or nurture has more influence over certain physical and mental traits.  Identical twins are genetically identical and are much more similar than non identical twins, whether they were brought up together or separately.

Thomas Bouchard of the University of Minnesota did the most famous research on genetic influences in humans. He studied identical twins separated since birth.  “Bouchard did not find outstanding similarities between identical twins on such standard measures as IQ tests or standardized personality tests, but he did find striking similarities were mannerisms (such as wearing rubber bands on the wrists, or reading magazines backwards), personal choices (such as choice of names for pets or children, or choice of clothing styles), and expressive social behavior (shyness or social ease, laughter, facial expressions and posture).  Bouchard’s findings can be interpreted as strong support for genetic influences on personality.”

Professor Marcus Munafo recently reported in The Guardian that the rates of schizophrenia in people who have been adopted are related to rates in their biological relatives (not their adoptive family).  He says “Environmental factors can be divided into shared environmental factors (things that make us similar) and non-shared environmental factors (things that make us different, including chance events that may happen to one sibling but not another).

New evidence is being reported through studying our genes using genome-wide association studies (GWAS).  These studies are showing us that genes can be linked to personality traits but the environment can influence these genes. Professor Munafo says “If we had the entire genetic code for an individual we still wouldn’t be able to predict their outcomes with any certainty, even for traits with high heritability.”

As well as affecting our personality , nature and nurture also will affect our physical characteristics – for example height. We have a genetic predisposition to a certain height, influenced by the genes of our parents.  Normally tall parents will have tall children.  But how tall we become is affected by our environment. If we are undernourished, this will reduce our height.

What if we overrode the effects of our environment?  If everyone smoked or ate a high fat diet, who gets lung cancer and heart disease would be down to those who are genetically predisposition.

So it would seem that who we are is a mix of nature and nurture.  Our genes give us the building blocks to make us who we are, but the environment will have an influence on who we become.

Read More:
Bouchards research
Professor Munafos’ report in The Guardian

Image credit: http://www.slideshare.net/candipill/nature-vs-nurture-debate