Download Evolutionary explanations of food preference.

Evolutionary explanations of
food preference.
We are going to look at the evolution of the human diet and how we
identify the foods that we need.
The environment in which our species first evolved is referred to as the
EEA (environment of evolutionary adaptation) and this gives us an
insight into the adaptive problems of our ancestors.
Humans first emerged as a separate species about 2 million years ago
on the Africa savannah.
Natural selection favoured those who adapted to this environment and
hunter-gatherer society. Hunter-gatherers ate mainly animals and
plants.
Preferences for fatty food may have been adaptive as they provided high energy
sources.
In the EEA calories were not as plentiful as they are today so humans seem to have
evolved a preference for food rich in calories.
Fossil evidence from early hunter-gatherers suggests that their diet consisted of
animal based foods, especially animal organs (brains, kidneys and liver) which are
high in nutrients.
It is believed that the high quantity of meat in the diet contributed to the growth of
the human brain.
Milton (2008) claims that if early humans had not eaten meat, they would not have
evolved into the active intelligent species they are now.
Hunting has also required humans to develop specialised skills such
as weapon and tool making.
It also requires social co-operation which probably put pressure on
the evolution of language and other social skills.
As the physical demands of hunting would be more suited to males,
females would be more preoccupied with child care and gathering
berries, leaves etc.
This shows that the evolution of our diet has widespread
consequences for human society.
Two mechanisms that we rely on to identify foods are smell and taste.
Our sense of smell (olfaction) is sensitive to about 10,000 smells.
The sense of taste (gustation) is critical in food choice and food avoidance
– taste receptors are replaced every 10 days or so.
The mechanism
Food dissolves in saliva into molecules that combine with the taste
receptors. This triggers the GUSTATORY nerve which takes the information
to the brain.
Taste and Smell
It is the pattern of stimulation across
thousands of taste receptors that give us
our sensation of flavour
5 key flavours
Sweet – helps us identify carbohydrate
essential for fuel
Sour – helps identify when food has
gone off –this food could contain
harmful bacteria
Salt –this is essential for cell function
Bitter –a taste associated with plant
chemicals some of which could be
poisonous to humans
Umami – recently discovered – savoury
taste which may be associated with
protein (like meat)
How can we know what our early ancestors
ate?
Investigate similar primates like the
great apes
Investigate hunter gatherer societies
which still exist
What would be the advantage of eating meat? How could
this lead to the development of human society?
Disgust
When we taste something
bitter or sour our face registers
disgust – this facial expression
is similar across all cultures, it
is seen in all babies and is also
seen in primates like
chimpanzees.
The feeling of disgust helps us
to avoid these foods in future
Other key terms include
Neophobia ‘fear of new’
Cultural
transmission
Taste Aversion
Learning
Neophobia
• Animals tend to avoid food they
haven’t come across before.
• We show a greater liking for
foods that are familiar to us.
• We also show a liking for variety
in food we know are safe –
children will eat more smarties if
they are multi-coloured than if
they are just one colour
Cultural transmission
• Spices can have anti bacteria
properties and can help prevent
food poisoning –information
about how and when to use
spices can be passed on through
cultural transmission
Aversion learning
• We avoid eating food that we believe has made us sick in the past.
• Garcia et al made wolves sick by contaminating lamb meat with
poison. When the wolves next encountered lambs they sniffed them
then left them alone.
• Do you know any other examples?
Nature-Nurture debate
• The evolutionary approach suggests that our food
preferences are mainly due to nature rather than nurture –
genetics rather than the environment.
• This ignores the cultural and social changes in food
availability over the years of human evolution.
• It is important to recognise that food choice is heavily
influenced by environmental factors