|Our Evolutionary Inheritance
Food and Alzheimers: Closer Links Than Once Believed
The random mutations that are the source of evolution can have three kinds of consequences
for an organism:
1) the emergence of an adaptation,
meaning a structure or mechanism built through natural selection;
2) by-products or side effects (or “"exaptations"”
or “"spandrels", see links below) that accompany
such adaptations without having been selected directly;
3) “"random noise", meaning
mutations whose results do not affect natural selection and
so do not affect evolution.
Thus, the emotion associated with jealousy is an adaptation
that strengthens the tie between a child's parents, stress
is a by-product of the chronic activation of the fight-or-flight
system, and variations in individuals’ temperaments
are probably due to random noise.
The ability to ascribe beliefs, needs and desires to other
people is a very useful cognitive mechanism for an individual
to have. It lets that individual not only anticipate hostile
attacks, but also foresee other people's needs and meet them
to promote ties of attachment, or simply understand their
circumstances and actions.
This inference module (or “mind -reading”
module) seems to appear at around age 3 in all human beings,
regardless of their culture of origin. This module also seems
to be distinct from the one that deals with inanimate objects,
and a malfunction in this module results in a disturbance
that resembles autism.
Evolutionary psychology is an approach that grew out of sociobiology
in the late 1980s. Evolutionary psychology seeks to re-examine human
behaviour in light of natural selection and sexual selection.
This approach is based on the fact that the earliest ancestors of today's humans
(for instance, Homo habilis, who appeared about 2.5
million years ago) evolved for thousands of years in an environment
very different from our own. The term "environment of evolutionary adaptedness (EEA)"
is used to refer to these various constraints to which our
hunter-gatherer ancestors were subject on the savannah.
|Some of these
constraints were physical, such as the need to keep warm, to
find enough food, and to avoid disease and predators. But even
more important were the social constraints, such as the need
to maintain reciprocal relationships with other individuals,
to avoid cheaters, and to secure a good rank in the hierarchy,
as well as the need to find a partner with whom to reproduce
and to form sufficient ties with that partner to raise the
in addition to selecting the anatomical characteristics best
suited to the physical environment, evolution also selected
the psychic mechanisms that provided our ancestors with the
best pay-off in these social situations. Evolutionary psychology
thus sees the modern human brain as being composed of modules
that specialize in problem-solving and that have thus
enabled the species to optimize its reproductive success.
Thus we see that our brain was not “selected”
to live in the urban, technological environment that we know
today. For some brain functions, this does not matter.
But for others, such as the chronic activation of the brain's
alarm system, the consequences
for the organism may be disastrous. The corollary of
this might be the calming effect that city dwellers experience
when they go out into the country, an environment much
more similar to the one in which our species evolved.
With its model based on modules adapted to the problems encountered by our ancestors,
evolutionary psychology thus departs significantly from the standard
model of the mind on which the social sciences are based.
The basic reasoning
underlying evolutionary psychology is often summarized in
the following five principles.
- The human brain's circuits are subject to natural selection
(through the genes that encode for the major neural pathways)
and have evolved so as to generate behaviours that are
adapted to environmental circumstances.
- The human brain's circuits have not been selected
to solve all types of problems, but only those that have
affected our ancestors’ reproduction over millions
- Most of what happens in our brain does so without
our being aware of it, so that many things that seem
easy to us (such as recognizing someone's face, or running)
actually involve highly complex neural circuits and operations.
- Various types of neural circuits have become specialized
in solving various kinds of adaptive problems.
- The modern human brain is actually adapted to the conditions
of the Stone Age.
We perform most of our
everyday tasks mechanically, without even thinking about
them. And yet, to perform a task such as recognizing someone,
or tying our shoelaces, or simply talking, we must have highly
complex networks of neurons in our brains. One proof of this
fact is that machines assisted by tremendously powerful computers
can still manage such tasks only with some difficulty.
The hundreds of thousands of years of evolution that shaped
our brains have thus developed an unconscious mode of operation
of the brain circuits that let us solve those problems
that humans have been encountering since the days of our earliest
ancestors.One example of this unconscious operating mode is
that if you know how to type, your fingers can find the letter
G on a keyboard right away, but if someone asks you to say
where that letter is, you have to think about it for a moment.
Another example is our perception of perspective.
This perception occurs because of specialized brain circuits
that our ancestors developed to process visual information.
These circuits are the basis for many of the optical illusions
that we experience. For instance, despite what you may
think, the two white rectangles superimposed on the railroad
tracks below are actually the same length.
Source: R. L. Gregory