1 February 2012
If you consumed a fair bit of popular media during the last decade, you probably heard a lot of genetic determinism, not that the term was actually used. People’s choices, it was breathlessly reported, could be explained by the fat gene, infidelity gene, religion gene, or violence gene.
It was a natural for pop science. The 1990s saw the human genome mapped, and some of that energy was bound to spill over from hypothesis to . . . hype. In those days, Nobelist Walter Gilbert, extolling the Human Genome Project, would hold up a data CD and inform his audience, “This is you.” You, a genome decoded.
But was it you? Or anybody?
Let’s think that one out: Puberty, to take an example, is controlled by hormones. So, no one wonders whether they should grow a beard or start menstruating. It just happens, and we adjust or we don’t.
But are our choices about relationships, religion, or violence really controlled by genes in the same way? If so, why do we contemplate choices, debate them, or worry whether we have done the right thing, let alone suffer agonies of guilt over past choices? Experience alone should tell us that genes don’t rule, the way some have claimed.
In recent years, scientists have established that the genome is not a master influence in the body. It is controlled by an epigenome. The epigenome has only recently been discovered and is not well understood, but we now know that it helps determine how much influence our genes have.
As Professor Thomas Woodward and cataract surgeon James Gills explain in The Mysterious Epigenome: What Lies Beyond DNA (Kregel Publications, 2011),
This built-in director, found in all our cells, sits above our DNA and carefully controls how genes are expressed. This has been compared to a skilled musical director waving a baton in front of an orchestra. This remarkable system actually has several layers, or levels, that all seem to be tightly coordinated into one smooth system.(p. 15)
In other words, our genome offers potential, but our epigenome determines how it is expressed—just as the music director may ask, at a certain point, for the brass to pipe up and the strings to subside.
According to considerable recent research, Woodward and Gills say,
Many patterns of daily living—including diet, stress, smoking and exercise—have the power to partially reprogram our epigenetic system and that of our offspring.(p. 18)
Reprogram us to what extent? In lab rat studies, stress can trigger a series of chemical reactions that dictate how active genes will be. These genes, awakened, can be inherited that way and may influence metabolism, behavior, and proneness to disease, including heart disease and diabetes. Other recent rodent studies suggest that
a parent’s exposure to drugs, alcohol, and stress can alter brain development and behavior in their offspring.[2-4]
Can humans be affected? It seems so.
In one study, not only did traumatized pregnant women who had been near 9/11 have significantly lower cortisol levels in their saliva, but so did their children, measured after birth. Researchers noted that the effect was most obvious when the exposed children were in the third trimester.
There is also some evidence that parents’ poverty can lead to children’s obesity:
DNA is “programmed” in the womb to turn certain genes up or down, and some programming that leads to obesity can continue into childhood and adulthood.
The obesity cited above is not a predetermined genetic inheritance. The parent did not have a “gene” for, say, obesity. Rather, an experience (poverty) altered the way certain genes are expressed. The alterations are passed on, at least for a generation or so, increasing the risk of obesity in children. So epigenetics is really a tool for assessing risks over time, which increases chances for prevention.
What about epigenetics’ effect on evolution? Interestingly, the epigenome is said to evolve faster than the genome, but most of its changes don’t last. That’s most likely because in later generations, earlier epigenetic changes get overwritten.
It’s good news for those who think that improving people’s lives can make a long-term difference to their families. Provided, of course, that the proposed improvement is needed.
More on that later.
Next: Why so many proposed improvements don’t really work.
See also: Is intelligence inherited? Is the race to the swift?; and
 “Traumatizing your DNA: Researcher warns that it isn’t ‘all in the genes’”, Physorg, March 23, 2011: http://tinyurl.com/4btd25s
 Amy Coghlan, “Unzipped chromosomes pass on parental stress,” New Scientist, 27 June 2011: http://tinyurl.com/44qfm5l ; See also “Chronic Stress May Cause Long-Lasting Epigenetic Changes,” Medical News Today, 17 Sep 2010: http://mnt.to/f/3JTm
 “Effects of Stress Can Be Inherited, and Here’s How,” ScienceDaily, June 24, 2011: http://tinyurl.com/5rcc5co
 “Nature and Nurture Work Together to Shape the Brain,” Society for Neuroscience, November 13, 2011: http://tinyurl.com/6n6knax
 Mo Costandi, “Pregnant 9/11 survivors transmitted trauma to their children,” The Guardian, September 12, 2011: http://tinyurl.com/3f729xj (Subsequent studies on stressed rats identified the cause as differences in DNA methylation—that is, the way that DNA is chemically modified.)
 “Poverty leaves its mark on DNA, researchers find,” CBC News, Oct 28, 2011: http://tinyurl.com/3auutwp ; “You Are What Your Father Ate, Too: Paternal Diet Affects Lipid Metabolizing Genes in Offspring, Research Suggests,” ScienceDaily, Dec. 23, 2010: http://tinyurl.com/2fznwdg
 “Are Genes Our Destiny? Scientists Discover ‘Hidden’ Code in DNA Evolves More Rapidly Than Genetic Code,” ScienceDaily, Sep. 16, 2011: http://tinyurl.com/64av75s
 “Epigenetic Changes Often Don’t Last, Probably Have Limited Effects On Long-Term Evolution, Research Finds,” ScienceDaily, Sep. 20, 2011: http://tinyurl.com/5vnp8ut