Transcript EATING BEHAVIOUR - Caroline Chisholm School

You will be able to:
 Understand the evolutionary explanation
of food preferences
 Evaluate the evolutionary theory of food
preferences

Outline and evaluate
evolutionary explanations of
food preference.
(4 marks + 16 marks)

Our feeding system is
designed to identify
the things we need
and to reject things
we either do not
need or that might
be dangerous such
as toxins (poisons).
During evolution we
have evolved a
digestive system suited
to breaking down
these foodstuffs into
the nutrients we need
so they can be
absorbed into the
bloodstream and
metabolised by the
body.
 Our taste sensitivities
are still influenced by
our evolutionary past:


Sweet – allows us to
identify foods rich in
carbohydrates such
as sugars – a key
source of energy

Sour – identifies food
that has gone off
and may contain
harmful bacteria

Salt – critical to the
normal functioning
of cells in the body

Bitter – associated
with plant chemicals
that might be
harmful

Umami – discovered
relatively recently
and represents a
meaty or savoury
quality indicating a
good source of
protein.

The ability to
distinguish between
these tastes is
adaptive as it is
important for
survival.

Babies and young
children show a
range of taste
preferences. In some
cases this is very
narrow.

Some of their dislikes
are understandable;
some vegetables
such as broccoli and
Brussels sprouts
contain chemicals
that can be toxic to
the very young
(Nesse and Williams,
1994).

Babies can identify
and distinguish
between foods from
an early age. They like
sweet tastes.
Furthermore, sweet
foods are effective in
reducing distress in
babies (Benton, 2002).
This suggests an innate
(genetic) preference,
possibly with adaptive
purposes.

In adults taste
preferences settle
down and stay fairly
constant with the
exception of women
in the early stages of
pregnancy.

Morning sickness is
found in at least 75%
of women and has a
convincing
evolutionary
explanation – the
embryo protection
hypothesis (Profet,
1992).

Surveys show
consistently that the
foods most avoided
by pregnant women
are coffee, tea,
meat, alcohol, eggs
and vegetables
(Buss, 2008).

Morning sickness is
most severe in the
early weeks of
pregnancy, when the
baby’s major body
organs are developing
and the baby is most
vulnerable. Usually it
then eases off and
disappears as the
baby becomes fully
formed.


Alcohol and coffee
and tea (which
contain caffeine) can
damage the baby’s
major organs. Meat
and eggs are
common sources of
toxins such as
bacteria, while some
vegetables contain
toxic chemicals
harmful to the
developing foetus.

The sickness reaction
therefore helps the
mother to avoid
foods that may be
harmful, while
vomiting prevents
any toxins entering
the mother’s
bloodstream and
affecting her baby.

Food neophobia is
another evolutionary
aspect of food
preferences.
Neophobia means
‘fear of the new’.
Animals have a
powerful tendency
to avoid foods they
have not come
across before.

Although this can lead
to a dull diet, it means
that we always eat
food that we know is
safe and avoid new
foods that may be
harmful. An aspect of
neophobia is that we
tend to show greater
liking for foods as they
become more familiar.

Food preferences in
babies, children and
non-human animals
are evidence for
neophobia and the
evolutionary
advantage of eating
food we know is
safe.

Birch (1999) notes
that neophobia is
less noticeable in
very young children
just beginning to eat
solid food.

Possibly because
food is selected by
the caregiver.

As children
become more
independent
and able to
select food,
they become
more cautious
about eating
unfamiliar
things.

We are very
quick to
learn to
avoid certain
foods once
they have
made us ill

Rusiniak and Brett
(1977) made wolves
sick with
contaminated
lamb’s meat and the
wolves then left
sheep alone.

Rats were poisoned
while eating familiar
and unfamiliar food
at the same time.
The poison could
have come from
either food, but

The rats avoided the
unfamiliar food after
the sickness episode
as previous
experience
suggested that the
familiar food was ok.

Humans are
omnivores and are
specialised to eat
meat as well as fruits,
nuts and plants.


Humans developed
to eat meat about 6
million years ago
Meat is a rich source
of protein and this
change in diet
allowed the
development of a
larger brain, basic to
the success of
humans.

The shift to meat
eating helps to
explain the selective
pressure on brain
evolution in order to
cope with new
technical and social
skills.

Fossil evidence on
changes to our
digestive system
supports hypotheses
on the evolution of
meat eating and the
shift to hunter-gatherer
society. However,
there is a limited
amount of fossil
evidence, and
evolutionary
explanations are often
speculative.


Through evolution,
other distinctive eating
behaviours have
emerged:
Spices such as onions
and garlic are used in
cooking, especially in
hot countries where
food goes off quickly.
Spices contain
chemicals that kill
bacteria, so protect
people from
poisoning.

Biological explanations
of eating behaviour
especially the
evolutionary approach
ignore the cultural and
social changes in food
availability and choice
over the years of human
evolution. Although
eating behaviour has a
biological and therefore
‘nature’ element’ it is
also heavily influenced
by environmental
‘nurture’ factors.