Apparently longevity is not only in your genes, but in a few particular little culprits locked up inside your DNA. That is if you believe a finding reported by Thomas Perls, head of the New England Centenarian Study. In a July 2010 Science article, Perls and his team attributed the longevity of the 100-somethings in the sample to inheritance of a distinct genetic cluster. However, several days after the study's publication critics challenged the methodology used to reach this conclusion. It turned out that the "peers" who should have peer-reviewed the article never were consulted before the article's publication.
As is the case when someone is accused of murder, fraud, or ethical violations on the front page only to be exonerated weeks or even years later in a small item on page 10, the Perls study was headline news; the critique of it buried in the backwaters. Clearly, people would much rather hear about genes as the cause of their long life or lack thereof. Everyone would much rather blame genes than the environment or personal choices when looking at health, personality, and even social attitudes. Without getting into the thorny details of the methodological question, let's get to the real reasons that people love saying that it's all in our genes.
Genetic explanations provide us with great rationales for behaviors we would rather disavow. Drive too fast? You're genetically programmed to be Type A so of course you're always in a hurry. Uncomfortable with close relationships? Well, blame it on your progenitors, especially Grandpa, who never could communicate with anyone. Finding it hard to keep your weight in check? Well, just look at some of your relatives who love to eat and hate to exercise.
Yet research evidence shows that all of these behaviors are highly modifiable. We can change them if we want to change. Other than the truly, 100% genetically determined characteristics such as those you can see (eye color, birth marks) and those you can't (blood type), many of your traits can be altered by the choices you make.
There are also surprising ways that the environment influences even those components of our body's cells that we think are subject only to genetic influence. Parts of the cell's instructions for constructing proteins (basic elements of life) can be altered by stress. While pregnant, a mother's exposure to trauma can alter the way she builds these instructions in her growing child's cells.
Many genetic proponents point out the amazing similarities between identical twins reared apart. There's the story of the male twins, separated at birth, who by midlife had married women with the same first name, held their coffee cups the same way, and even chose the same unusual brand of toothpaste. Clearly, this could not be coincidence- it had to be evidence of nature with a capital "N." Yet, these same researchers, working in the Minnesota Twin Study, ignored the ways that the twins differed such as in their weight, just to take one basic area of functioning. In other words, they looked at the "hits" and not the "misses" in calculating the genes-to-environment ratio.
There are also surprising facts about identical twins. Did you know, for instance, that there is more than one type of monozygotic (MZ) set of twins? (see the illustration here) Only 1% are completely identical meaning that they shared one placenta and one amniotic sac- the sources of nutrition while in utero. About three quarters share one placenta but mature within two separate amniotic sacs. The remaining one quarter or so do not share either a placenta or an amniotic sac. As a result, though their genes are identical, the prenatal environments of most MZ twins are not.
Another important concept in the nature-nurture debate is "niche-picking." Almost 30 years ago, developmental psychologist Sandra Scarr and colleagues set forth the notion that our genetic predispositions lead us, perhaps, to gravitate toward certain activities- sports, music, dance, math, and so on. Once we start to become involved in these activities, we develop further those qualities that led us there in the first place. The kid who loves baseball eventually perfects a mighty swing. The cartwheel-loving tot ends up winning balance beam competitions 10 years later as she develops her strength and agility. Potential abilities that were at one time influenced in some way by a particular DNA combo now flourish through training, dedication, and education.
Think about the meaning of these findings. People love to say that they got their personality from their aunt and their interest in cars from their dad. But when we start to think about nature-nurture issues in terms of more complex relationships, we start to think about our lives differently. It's unlikely that you would agree with the claim that, for example, you got your love of 90s music from your daughter or possibly your son but because development is a two-way street, you are just as likely to be influenced by a child as the other way around. The people in your life, including those who are no longer alive, have become a part of "who" you are, and they alter whatever shoe-loving or high-strung genes you inherited in many complicated ways.
It's important to keep a critical eye whenever you read a new study that claims to have solved the nature-nurture puzzle. It's just as important to be on the lookout for researchers who provide valid criticisms of such studies even though these critiques might not make the Nightly News. We can control our genetic destinies - for worse but, let's hope, for better.
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Copyright Susan Krauss Whitbourne, Ph.D. 2010