Nature or Nurture? How can we test how important each is to our physical and behavioural characteristics?

Researchers from King’s College London have coordinated a multicentre study where two genetic variants have been identified which, when present together in the same individual, increase the risk of male pattern baldness (otherwise known as androgenic alopecia) seven fold. These variants are present in one in seven Caucasian men and provide novel insights into the cause of this common and sometimes distressing condition. A confidential survey has revealed that genetic factors have a substantial impact on how likely women are to cheat on their partner and how many sexual partners they will have!

Can future sports stars be predicted just by looking at the length of an individual’s fingers? According to new research, women whose ring fingers are longer than their index fingers should achieve higher levels in sports. The study, led by Professor Tim Spector from the Twin Research Unit at King’s College London, is published online today in the British Journal of Sports Medicine. A joint study from The Twin Research Unit at Guy’s and St Thomas’ NHS Foundation Trust and Newcastle University has found that genes play a significant part in determining body odour and therefore every person’s odour is completely individual to them.

Twin Studies A twin study is one of the method used. There are two types of twin: dizygotic (DZ) or fraternal twins monozygotic (MZ) which are identical twins and so have exactly the same DNA as each other, i.e. the genotypes are identical.

Adoption Studies Adoption studies involve looking at someone who has been adopted and comparing their intelligence with their biological and adoptive parents. If the IQ was more similar to their biological parents who have DNA in common, then we could conclude intelligence was as a result of nature. However, if the IQ was more similar to the adoptive parents who have the upbringing in common, it would be nurture.

The matching of parents. The authorities tend to find adoptive parents who are similar to the biological so the transition is easier for the child. For example, matching up parental occupations. Small samples; it is difficult to find people willing to come forward who also know their biological parents, this makes the results less representative. - Less reliable as the proportional impact of anomalies could be exacerbated

Results? Thus far the sum of research suggests that both factors play a role.

Rubber band hypothesis The idea used to describe it is the Rubber Band Hypothesis. It says that the potential (length of the band) is decided by genetics. However, the environment stretches this band, so that someone with a low potential could be stretched beyond someone with a high because of environmental differences. But if someone with a high and someone with a lower genetic potential had the same environment, that person with the higher genetic potential would be able to 'stretch' their intelligence to a higher level.

How much heritability? Estimates of genetic and environmental effects from recent MZ twin studies. A, additive genetic variance, or heritability; C, variance explained by shared environment; E, variance resulting from nonshared environment and errors of measurement.