[from Mary Powers 9508.05]
[The 7/7/95 New Yorker has an article on twins, "Double Mystery",
by Lawrence Wright, that has some statements and comments about
the relationship between heredity and environment that I think
are worth quoting on this net.
First, discussing the work of a psychologist at the U. of
Virginia, Sandra Scarr. The quotes are hers, the rest is Wright]:
Over the last fifteen years, Scarr has been refining a new theory
of development, based largely on her conviction that environments
do influence the intellects of young children. At early stages
of life, she observes, enriched environments...can boost a
deprived child's achievement. Even young children, however, are
genetically programmed to create certain experiences for
themselves. For instance, a smiling, gregarious baby is more
likely to be cuddles and petted than a fussy and undemonstrative
one. If these two dissimilar infants are siblings, their
experiences of living in the same home can be quite different.
As children mature, they gain more and more control over their
environment, and actively select from the superabundance of
opportunities and experiences those which conform to their
genetic disposition. The distinction between genes and
environment become less and less clear.
"We propose that development is indeed the result of nature _and_
nurture, but that genes drive experience. Genes are components
in a system that organizes the organism to experience the world".
Identical twins who have been reared separately may live in
different families, and even different cultures, but they evoke
similar responses from their environment and are disposed by
their natures to make similar choices and build similar niches
for themselves.
...We make our environments, rather than the other way around -
that is, as long as the environment we find ourselves in is not
so impoverished or abusive that normal development cannot occur.
[Now Lindon J. Eaves, a geneticist at the Virginia Commonwealth
University School of Medicine]:
"A philosopher who was talking about twins said that maybe it's
freedom that makes identical twins different... Frankly, I don't
believe that for a minute. It could be freedom that makes them
alike...I think freedom means something about the capacity of the
human organism not to be pushed around by external
circumstances.. I would argue that...natural selection has placed
in us the capacity to stand up and transcend the limitations of
the environment."
[And Wright concludes the article]:
It may be threatening to see ourselves as victims of our genes,
but that may be preferable to being victims of our environment.
To a major extent, after all, our genes are who we are. A trait
that is genetically rooted may seem somehow more immutable than
one that may have been conditioned by the environment. This
seems to leave aside the possibility of free choice--or even
consciousness of choice at all. And yet people who are aware of
their natures are constantly struggling with tendencies they
recognize as ingrained or inborn. It makes little difference how
such tendencies were acquired--only how they are managed. If it
is true that our identical clone can sort through the world of
opportunity and adversity and arrive at a similar place, then we
may as well see that as a triumph of our genetic determination to
become the person we ought to be.
[The only thing missing from all this is a model - for example
the idea that what genes do is (maybe something like) provide
reference signals for the construction and operation of the
hierarchies of control systems that we call organisms]
Mary P.