Nature vs. Nurture: Genetics, Environment, and Cognition

This is the title of Chapter 12 in Greenwood and Parasuman’s Nurturing the Older Brain and Mind. They begin the chapter with a quote from Rene Dubos, So Human an Animal. “Genetics and experiential factors shape the biological and behavioral manifestations of human life, but they do not suffice to account for the totatality of human nature. Man also enjoys a great degree of freedom in making decisions; he is par excellence the creature that can choose, eliminate, organize, and thereby create.”

It is unfortunate but all too often the nature vs nurture issue is regarded as a deterministic dichotomy. Behavioral geneticists have done studies, identical twins have been frequently used, to estimate topics such as how much is IQ determined by genetics and how much is determined by the environment. What these studies neglect is the interaction between genetics and the environment. Neither exists in isolation from the other. Behavior and performance are the result of the interaction between genes and the environment.

Fortunately molecular genetics provides an alternative approach to behavioral genetics. The molecular approach allows for the study of specific genes and their alleles. This research has found that a particular allele of the apolipoprotein E (APOE) gene is a major risk factor for the development of Alzheimer’s. Pay attention to the term “risk factor.” Rather than causing Alzheimer’s this particular allele increases the risk of suffering from the disease. Moreover, it is possible that age-related cognitive decline may occur only in those who possess one or two copies of this allele. It is estimated that this could include about 14% of the US population.

The weight of evidence from research on this allele suggests that this risk factor interacts with lifestyle factors. Carriers of this allele obtain a greater benefit from exercise than non-carriers for late-life cognitive functioning. This benefit is most strongly evidenced when the exercise is carried out in mid-life. Cognitive experience also confers stronger benefits on allele carriers than people who do not carrier the allele. Understand that cognitive experience benefits everyone, but it is even more beneficial for those carrying this threatening allele.

So no evidence has been found that condemns any of us to Alzheimer’s or dementia. The activities covered in Nurturing the Older Brain and Mind and the healthymemory blog should be undertaken by all of us. This advice is further underscored for those with risk factors.

© Douglas Griffith and healthymemory.wordpress.com, 2014. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

Advertisements

Tags: , , , , , , , , , , , , , ,

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: