Thursday 24 January 2013

Maybe she's born with it. Maybe it's a bit more complicated.


Intelligent parents often have intelligent offspring. This is a clear trend that many people are aware of. However there is much debate as to how much of this intelligence is conferred by genetics and how much is a result of upbringing and environment - most likely, it is a complicated balance of the two. Nevertheless research published this April has now identified certain genetic factors that appear to convey a higher level of intelligence.

Previous studies, looking at identical twins and children adopted into families have shown that approximately half of all intelligence is derived from genetic factors. Neurophysiological research has also shown that key differences in brain structure and function leads to differences in levels of intelligence.
slice of the brain of a 56 year old patient (male) taken with positron emission tomography (PET) ©Wikicommons; Image Credit: Jens Langner
In this study, 3511 unrelated and healthy adults were assessed for their levels of intelligence (through reasoning tests, educational level and general IQ-type tests). They were also given full genetic screening that looked at upwards of 500, 000 SNPs (common DNA mutations).

After sifting through the data, the researchers found that 40% of the variation seen in crystallized-type intelligence and 51% of the variation in fluid-type intelligence was accounted for though the SNPs - the rest of the variation most likely came through still unknown/unidentified variations in lifestyle and upbringing. Factor such as diet, obesity, smoking and drug abuse are all thought to impact on intelligence.
One key mutation was seen in the gene coding for production of a protein with the rather catchy name of FNBP1L. FNBP1L is known to influence cell signalling and movement. It is produced in large quantities in growing neurons in the brain. Certain specific mutations in this gene have been linked with significant increase in fluid intelligence.

The researchers that were performing the study found that they were able to predict the comparative intelligence of a random subject with an 8-11% (fluid vs crystallized) margin of error based around knowledge of the subject's genome and certain socioeconomic factors . Whilst this may not seem too accurate, it is in fact a huge leap forward in our understanding of the heritable traits of intelligence.

Some definitions

Fluid intelligence is the abiltiy to think logically and solve problems. It is independent of acquired knowledge.

Crystallized intelligence is the ability to use skills, knowledge, and experience. It is often increased with age

SNPs (single-nucleotide polymorphisms) are single changes in one chromosome compared to its pair.

Read the original paper here

Published in The Yorker January 10th, 2013