A "black box" is a biological mystery. It s what biologists call any human
trait they've observed, studied, and measured on the "outside" of human
beings but whose "inside" origins-- which genes formed it, which hormones
made it that way-- remain mysterious. Each aspect of the trait that
biologists establish (these are pretty standard: prevalence data (how many
people in a random population have it), twin data, correlation data (do
blacks or Asians have it more than whites, for example), pathology or not,
and so on) is a clue pointing to the solving of the mystery.
We have a long list of black boxes human traits-- and each of these traits
has a "clinical profile," the sum total of clues we have from looking at the
outside, clinical level. They are mysteries waiting to be biologically solved
on the inside, the mystery of what creates them: eye color, height, cystic
fibrosis, cancer, intelligence, Tay Sachs, baldness, athletic ability,
resistance to some viruses and susceptibility to others, skin tone and muscle
mass and allergies and sexual orientation. Some traits can be defined simply
by looking at the person, like hair color or height. Some cannot, like cancer
or blood type (A, B, or O). Some human traits are behavioral, like manual
dexterity, sexual orientation, hand-eye coordination, and schizophrenia, and
some are not, like blood type (A, B, or O), race, or the hardness of tooth
enamel. Some are disease traits: hemophilia, schizophrenia, cancer, color
blindness. Some are politically and religiously charged: skin color, sex.
Some traits are not politically and religiously charged: the hardness of the
enamel on your teeth, which is controlled by a single gene, whose location is
known, and whose functioning we understand.
Here s a mystery for you (which should be pretty easy to figure out). One
particular black box interests us here. It has been the object of decades of
empirical observation, and researchers have compiled a pretty complete
"clinical profile" for it. We know what the trait is; what we don t know is
what creates it. This is What We Know, the clinical profile:
- The trait is referred to by biologists as a "stable bimorphism, expressed behaviorally."
- Its exists in the form of two basic internal, invisible orientations, over
90% of the population accounting for the majority orientation and under 10%
(one reliable study puts the figure at 7.89%) for the minority orientation,
although there is still debate about the exact percentages.
- Only a very small number of people are truly equally oriented both ways.
- Evidence from art history suggests the incidence of the two different
orientations has been constant for five millenia.
- A person's orientation cannot be identified simply by looking at him or
her; those with the minority orientation are just as diverse in appearance,
race, religion, and all other characteristics as those with the majority
orientation.
- Since the trait itself is internal and invisible, the only way to identify
an orientation in someone else is by observing in them the behavior or reflex
that express it. However--
- The trait itself is not a "behavior." It is the neurological orientation
expressed, at times, behaviorally. A person with the minority orientation can
engage, usually due to coercion or social pressure, in behavior that seems to
express the majority orientation-- several decades ago, those with the
minority orientation were frequently forced to behave as if they had the
majority orientation-- but internally the orientation remains the same. As
social pressures have lifted, the minority orientation has become more
commonly and openly expressed in society.
- Neither orientation is a disease or mental illness. Neither is
pathological.
- Neither orientation is chosen.
- Signs of one's orientation are detectable very early in children, often,
researchers have established, by age two or three, and one's orientation has
probably been defined at the latest by age two, and quite possibly before
birth.
These first intriguing observations began to catch the attention of
researchers. The trait looked biological in origin. The data was indicating
that the trait had a genetic source:
- Adoption studies show that the orientation of adopted children is
unrelated to the orientation of their parents, demonstrating that the trait
is not environmentally rooted.
- Twin studies show that pairs of identical (monozygotic) twins, with their
identical genes, have a higher-than-average chance of sharing the same
orientation compared to pairs of randomly selected individuals; the average
(or "background") rate of the trait in any given population is just under 8%,
while the twin rate is just over 12%, over 30% higher.
- The incidence of the minority orientation is strikingly higher in the
male population-- about 27% higher-- than it is in the female population, a
piece of information that gives indications to the biological conditions
creating the trait.
- Like the trait eye color, familial studies show no direct
parent-offspring correlation for the two versions of the trait, but the
minority orientation clearly "runs in families," handed down from parent to
child in a loose but genetically characteristic pattern.
- This pattern shows a "maternal effect," a classic telltale of a
genetically-loaded trait. The minority orientation, when it is expressed in
men, appears to be passed down through the mother.
That s the clinical profile for this trait, this black box.
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