Genes load the gun, environment pulls the trigger: nature and nurture reframed
Experts on obesity, autism, individuality and hormones all describe traits as genetic predispositions that the environment either triggers or restrains, and warn that heritability is widely misunderstood. It matters because it replaces fatalism with a clearer sense of what we can and cannot change.
What does the phrase about genetics loading the gun mean? Show answer
Genes set a predisposition, and the environment determines whether and how strongly it shows up as a trait.
How heritable is body weight, according to Zachary Knight? Show answer
About 80 percent, based on twin comparisons, which is more heritable than most diseases and close to height.
How can obesity be highly heritable and still have risen so fast? Show answer
Genes mainly determine where a person sits on the weight distribution, while a changed environment shifts the whole distribution upward.
Where are most body-weight genes expressed? Show answer
In the brain, which controls food intake and energy expenditure; about 1,000 genes have been linked to body weight.
How does Karen Parker describe the genetics of autism? Show answer
As highly heritable, about 40 to 80 percent genetic with widely varying estimates, and largely an inherited polygenic condition.
What environmental risk factors for autism does Parker list? Show answer
Advanced parental age, severe prematurity and maternal illness during pregnancy, which may matter for one child and not another.
What does Parker say about vaccines and autism? Show answer
The original paper was retracted over fabricated data, and every study she is aware of shows no relationship.
Why is height less heritable in places like rural Bolivia or India? Show answer
Poor nutrition and frequent infections keep people from reaching their genetic potential, so heritability falls from about 85 to about 50 percent.
What third factor does David Linden add to genes and experience? Show answer
The randomness of development, which makes even identical twins differ and is not passed on to children.
What does Linden mean by replacing nurture with experience? Show answer
Everything that impinges on you from early fetal development to the end of life, including your mother's diet and your gut bacteria.
What does androgen insensitivity syndrome show? Show answer
A hormone must bind a working receptor to act; XY individuals who make testosterone but lack functioning receptors develop a female appearance.
Does a predisposition mean individuals can easily override it? Show answer
No. Knight says diets to keep weight off have been very unsuccessful, because rising hunger and lower energy use defend the old weight.