> This question is for Rees, Our resident psychologist. It is a
serious
question. It is Genealogy related, so don't everyone jump on me. I am
sending it to the group because I thought someone else might be
interested......Here goes.....
>
> Just how much of our character, good or bad, how much of our
personality
, good or bad and how much of our intelect do we inherit from our
ancestors,
seriously.....
> I have several reasons for asking...some obvious and some not so
obvious.
>
> I studied a little of it in college but not that much.
>
> "Preacher'
Preacher, cousins,
A few decades ago, I thought of becoming a psychologist AND a geneticist.
As an adolescent, I had done a research study using virusses to transport
genes from one antibiotic-resistant bacterium to another without the
resistance - primitive gene-splicing - finding genetics fascinating. And
in my clinical training I studied with brilliant British eccentric Lindon
Eaves, whose twin studies really hooked me. Here's an example of the kind
of stuff Eaves and his researchers found:
"Jim had known since he was six that he was an identical twin. He had been
separated from his brother when he was only a few weeks old, after they had
been adopted into different families. Jim desperately wanted to find his
long-lost brother." It turns out that the set of twins, that were both
named Jim, were born prematurely on August 19, 1939 at Memorial Hospital in
Pigua, Ohio. Immediately upon birth, the twins were put up for adoption,
separately. Ernest and Sarah Springer adopted one of the twin boys and named
him James. Two weeks later, Jess and Lucille Lewis adopted the second twin
and named him James also. Neither of the adopting parents knew one another.
That's not all of the bizarre coincidences that fill both of the "Jim's"
lives. These are some examples of what went on in each of their lives before
reuniting.
--Both had married a girl called Linda, divorced her, then remarried to a
woman named Betty.
--Both named their first born son James Allen.
--Both had owned a male dog and named it Toy at in one point in their lives.
--Both men worked at McDonald's; both worked part-time as Deputy-Sheriff;
and both had once been attendants in filling stations.
--Both spent their holidays at the same beach near St. Petersburg in
Florida; and both drove there and back in the same type of car, a Chevrolet.
(Watson p. 10-11).
These strange coincidences go on and on. The lives that the two men lead are
incredibly similar. These twins are not the only case of this nature. There
are hundreds of thousands of twins that have the same occurrences that take
place in both of their everyday lives. For instance, there is a set of
elderly twins that didn't meet until they were in their early forties. When
they did actually meet, they were both wearing a beige dress and a brown
velvet jacket. As they reminisced and caught up on all of the years that
they lost, they found out some bizarre coincidences of their own. They both
fell down the stairs at age fifteen and broke their ankles. That's not all,
here are the most bizarre circumstances of these particular set of twins.
--Both met their future husbands at a town hall dance when they were
sixteen.
--Both suffered miscarriages with their first pregnancies.
--Both had two boys followed by a girl.
--Both drink their coffee black and cold with no sugar.
--Both laugh more than anyone else that they know.
--Both were married in the early twenties in big autumn weddings with all of
the trimmings, including a choir.
Sounds as if who we are is predestined by genetic makeup, environmental
influences and personal experience having a minimal role. But - on the
other side of the coin: rates of concordance (the probability that a
person will have a trait or disorder if his or her twin has it) for
identical twins with schizophrenia usually average 50%, although some
studies have found 0%, and other close to 100%. But the upshot is this: if
you have an identical twin with schizophrenia, there's a chance you won't
develop the disorder; over the years, the odds have seemed to be about
50-50.
Lots of theories abound regarding the inheritability of personality traits.
My reading of them over the years has led me to conclude that who we are is
typically half genetic, half environmental. And I still doubt that there is
but one gene that determines characteristics of temperment, intelligence,
interpersonal styles, even disorders such as alcoholism. It seems to be
immensely complex, the patterns of inherited and learned qualities. I favor
a "stress-diathesis" model, which holds that "each person inherits certain
physical predispositions that leave him or her vulnerable to problems that
may or may not appear, depending on what kinds of situations that person
confronts (Durand and Barlow)."
Now - what does this mean in genealogy? How similar is my personality to
that of Thomas Chapman of Jordan's Journey 1610, alleged great grandfather
of my ancestor Isaac Chapman of Orange county VA? Well, lets assume ALL my
personality comes genetically from my parents, so I'm one half the character
my father Cecil is. His personality is thus one half of his father Byrd's,
which means I have one-quarter the personality of my grandfather. The
percentage declines exponentially because I am getting genetic
predispositions from four grandparents. So, I'm one-eighth my great
grandfather, and one sixteenth my great great grandfather. By the time we
get back to Thomas of Jordan's Journey, I share but one in two-thousand
forty-eight genetic characteristics.
Of course, there are several flaws in this exercise. If any aspect of my
personality is learned or provoked by my environment, the proportion of
qualities I share with Thomas dwindles even further. If I have only 1/4th
of my father's personality, my genetic concordance with Thomas in
infinitesimal: about 3.231700e+616. Not that there are that many variations
in human traits, personality or otherwise. If, however, a genetic trait is
Y-linked, meaning always present when there's a Y chromosome present (which
there always is in a male), it was probaly present back hundreds of
generations. And, if there's been no mutation, I have the same Y chomosome
my paternal male ancestor had thousands of years ago. (Unfortunately,
there's few genes on the Y chromosome, an argument for matrilineality which
I won't explore here). Adoptions and "back-door" contributions spoil
everything.
One final note: single genes are more likely involved in a diathesis for
physical conditions than for behavioral characteristics. So, a
vulnerability to cardiac disorder, like height and eye color, are more
likely to be inherited from a given ancestor than a tendency to act or think
or feel a certain way.
Whew. . . more than anybody probably wanted to know. But, my
great-great-great-great-great-great-great-great-great-great-great-great-grandmother
was known to ramble on and on. I obviously get it from her.
Rees