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I have an article in The Conversation, an Australian
human genome provides penetrating and unexpected insights into
human individual and collective history. Among them is the
counterintuitive idea that genes are at the mercy of experience -
that what we do in our lives affects which genes are switched on
A stressful experience, for example, can make you more
vulnerable to infection, because stress hormones indirectly alter
the switches that control the expression of genes.
So, far from genes being the cause of how we act, the new
understanding sees them as just as much a consequence of how we
act. This subtler view of genes has yet to colonise the popular
On a much longer, evolutionary timescale, the same reversal of
causation is necessary.
We now know that many genetic changes in human beings are driven
by cultural ones, at least as much as the other way round.
For example, the ability to digest lactose as adults spread
among Africans and Europeans because of dairy farming, rather than
Blue eyes may be a consequence of the invention of agriculture.
Reliance on grain in sunless northern climates led to vitamin D
deficiency because grain is lower in vitamin D compared with
traditional diets of fish, meat, berries, etc. So people eating
bread as a staple got less vitamin D in their diet.
Another source of vitamin D is sunlight. Mutations making skin
paler would enable sunshine to be more easily absorbed, making up
for the decrease of vitamin D in these northern climate diets. One
of the mutations that made skin paler had the side effect of making
eyes paler, and bluer.
This not Lamarckism; it
is Darwinism, because it still depends on selection among random
If we take this nature-via-nurture idea seriously, and put the
cultural horse before the genetic cart, then an upside-down view of
human uniqueness emerges.
Genes that facilitate language may be the consequence, as much
as the cause, of speech.
This radically alters the way we should look at the "human
revolution" - the relatively sudden transformation of African
hominid apes to fully modern human beings around 100,000 years
Instead of seeking some genetic mutation that triggered this
transformation, we should instead consider a cultural trigger.
What was the key cultural mutation?
Culture is itself dominated by the Darwinian trio of
replication, variation and selection.
The explosive take-off of human technology and prosperity over
the past 100,000 years can be traced back to a particular cultural
invention - exchange - which happened some time before 120,000
years ago (when man-made objects first started moving
long-distances through trade).
This had the same impact on cultural evolution that sex had on
Just as sex made evolution cumulative, by enabling individuals
to pass on mutations to their descendants, the invention of
exchange - swapping one thing for another - enabled people to draw
on the inventiveness of strangers.
This meant technology could begin to embody combinations of new
ideas, drawn from different places and times through the medium of
The result was a self-reinforcing cycle of exchange and
specialisation: the more people exchanged, the more they
specialised and vice versa.
As a result, the human lifestyle moved with increasing speed
away from individual self sufficiency and towards mutual
interdependence, shared innovation and collective intelligence.
Today nobody even knows how to make a pencil (the person who
mines graphite does not know how to fell trees), because the
knowledge is stored among brains rather than in them.
History plainly shows that the bigger the exchange network, the
more rapid the rate of technological change. Conversely, if people
are isolated from exchange networks, their innovation rate slows -
as happened in China under the Ming empire, for example.
If societies are completely isolated, innovation may even go
into reverse and technologies start to be discarded - as happened
in Tasmania after it became an island 10,000 years ago.
The implications of this way of seeing human society is that the
bottom-up evolution of human technology and society is inevitable,
inexorable and potentially infinite, but its rate depends on the
degree integration of human minds into a collective brain by
Or to put it another way, human prosperity depends upon ideas
having sex. The internet, by connecting human minds all over the
world, can only accelerate innovation.