Robin Dunbar explains how the distant past underpins our current behaviour, through the groundbreaking experiments that have changed the thinking of evolutionary biologists. He explains phenomena such as why 'Dunbar's Number' (150) is the maximum number of acquaintances you can have, why all babies are born premature and the science behind lonely hearts columns. I found it a fascinating read.
Brain. The human brain is 2% of total
body weight but takes 20% of total energy intake. In primate species the neocortex correlates with the
number of females in a breeding group (social skills) while the limbic system correlates with
the number of males in a breeding group (emotional response – competition for
dominance and rank).
Theory of the mind. The
ability to understand others may not think or believe as you do emerges at
around 4 to 5 years old. There are various levels of intentionality; a
chimpanzee operates at the first three levels, a typical theatre audience can
work at five levels but Shakespeare sometimes worked at six levels. For example: (1) Intend that (2) Audience believe (3) Iago wants that
(4) Othello to suppose that (5) Desdemona loves Cassio and (6) and that
Cassio
loves Desdemona.
Colour vision. Men can
only see three colours (red, blue and green). Around one-third of women can see
4 basic colours (tetrachromic), the usual three plus either an extra shade of
green or an extra shade of red. A few women can see all five. The genes for red
and green vision are on the X chromosome so men can only inherit this from the
mother, while women have X chromosomes from both parents and the colour genes
may be different for either or both the red and green gene. The gene for blue
vision is on chromosome 7.
Lactose intolerance. Human
skin synthesises vitamin D as a reaction to UV light. A light skin allows more
UV light to penetrate in areas with weaker light levels. Calcium is involved in
this process. Post-weaning lactose tolerance is limited to Caucasians
(especially north Europeans) and cattle keeping people on the southern edge of
the Sahara.
Kissing. Probably
evolved as a way of testing the genetic make-up of prospective mates. An ideal
mate will have a complementary immune system; smell is one way of determining
this and saliva is full of chemicals. It is a myth that Eskimos ‘rub noses’ –
in fact they place their noses close together and breathe in deeply.
Monogamy and promiscuity. Some studies indicate that about one-third of men are habitually promiscuous, while about two-thirds are habitually monogamous while in a steady realtionship.
Community. Hunter/gatherer:
temporary night camps have a variable composition of 30 to 50 individuals. A
clan is typically around 153 individuals and a tribe: between 500 and 2,500 individuals.Business:
less than 150 employees – person to person oversight works well but more than
150 – formal hierarchy is needed to work efficiently.Modern
human social groups: 3 to 5 really good friends; c. 10 close friends; 12-15 sympathy
group ( a death will affect you, a typical size for a sports team or jury); c. 30
social circle; up to 150 acquaintances and 1,500 for the number of people you
can put a name to. Using
names of existing family members or deceased relatives identifies family
membership.
Language. Language is a form of social grooming; primate grooming is about commitment rather than hygiene. Women talk to service their social networks. Men talk (about themselves or things they claim to know about) to advertise themselves.
Population. Britain: population in 2009 was over 61 million. The optimum population for the country is between 17m and 27m according to the Optimum Population Trust (OPT).
Religion. Some aspects of religious belief have explicit benefits; these do not justify the truth of religions but do offer explanations of why religion evolved. They (A) provide an explanatory structure to the universe so that we feel we can control it (plausible but not true), (B) make people feel better about life (actively religious people are happier), (C) provide a moral code and social order (so help community building) and (D) provide a community and group membership (also help community building).
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