Twins and What They Tell
Us About Who We Are by Lawrence Wright
You might not know:
Identical twins separated at birth actually score more alike on personality and intelligence tests than identical twins raised together (roughly the same as the same person taking the test on separate occasions). Researchers assume this is because they feel no social pressure to differentiate.
Due to the widespread use of ultrasound, researchers now believe that the number of pregnancies that begin as twins is far greater than previously known. “The frequency of twin [embryos/fetuses] among abortions is three times higher than the frequency of twins at birth.” Many of the embryos simply vanish and are absorbed into the womb or in rarer instances into the body of the remaining twin. Extreme examples: five fetuses removed from the brain of an infant girl, a six-pound fetus discovered during the autopsy of an elderly man.
In rare instances, separate embryos merge together to create a single individual. This phenomenon only comes to light when blood donors are discovered to have two separate blood types (indicating they were merged fraternal twins). It’s probably more common than we think. You could be two.
Twin studies are clearly important indicators in the study
of the effects genes and environments play in shaping individual traits such as
intelligence, personality, happiness, and health, and in shaping larger social
conditions and outcomes. And it’s pretty
creepy to be a parent reading about study after study that point to the
ascendancy of genes (and weirdly relieving in some instances, particularly in light
of today’s occasionally holier than thou parenting culture). What’s creepier still is the desire to shape
the gene pool that seems to creep into the work of even contemporary behavioral
geneticists (did I make that up?), such as David Lykken, who, according to Wright,
believes that we should set up a licensing system for childbirth. Since illegitimate children are (on average)
10 IQ points below those born in wedlock, Lykken thinks we should prevent
unmarried children from having children. For their first offense they would be incarcerated in a maternity home
and then forced to give up the baby. For
their second offense they would be sterilized for up to five years. I’m thinking: NO. And yet, while the nurturing loving family (and
for the record, in my book, the shape that family takes should be up to you –
it’s the most profound decision you make) you create may not be able to prevent
the onset of depression, Wright reports that “happiness seems to be largely a
gift of the environment…the one thing a good family can do is make a child
happy.”