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Survival of the nicest
11 November 2006
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Lee Alan Dugatkin
ALTRUISM - helping others at a cost to oneself - has been a stubborn thorn
in the side of evolutionary biologists. If natural selection favours genes
that produce traits which increase the reproductive success of the
individuals in which they reside, then altruism is precisely the sort of
behaviour that should disappear.
Darwin was acutely aware of the problem that altruism posed for his theory
of natural selection. He was particularly worried about the
self-sacrificial behaviour that social insects display: how could natural
selection explain why a worker bee will defend its hive by stinging an
intruder and dying in the process? In On the Origin of Species, he
summarised the topic of social insect altruism as "one special difficulty,
which at first appeared to me to be insuperable, and actually fatal to the
whole theory". But then he came up with an explanation.
Since worker bees were helping blood relatives - especially their queen -
Darwin hypothesised that natural selection might favour altruism at the
level of blood kin. One hundred and four years later, the biologist Bill
Hamilton would formalise Darwin's idea, but the path from Darwin to
Hamilton was not smooth. The nature of altruism and its similarities to
the human trait of goodness make it susceptible to political,
philosophical and religious subjectivity. Studying the structure of an
atom isn't personal: studying altruism can be. It certainly was for the
next two figures in the history of altruism, Thomas Huxley and Peter
Kropotkin.
Huxley, also known as "Darwin's bulldog", outlined his thoughts on this
topic in an 1888 essay entitled "The struggle for existence": "From the
point of view of the moralist, the animal world is on about the same level
as the gladiator's show... Life [for prehistoric people] was a continuous
free fight, and beyond the limited and temporary relations of the family,
the Hobbesian war of each against all was the normal state of existence."
For Huxley, altruism was rare, but when it occurred, it should be between
blood relatives.
Kropotkin, once a page to the tsar of Russia and later a naturalist who
spent five years studying natural history in Siberia, thought otherwise.
In Siberia he thought that he saw altruism divorced from kinship in every
species he came across. "Don't compete!" Kropotkin wrote in his
influential book Mutual Aid: A factor of evolution (1902). "That is the
watchword which comes to us from the bush, the forest, the river, the
ocean. Therefore combine - practice mutual aid!"
How could two respected scientists come to such radically different
conclusions? In addition to being a naturalist, Kropotkin was also the
world's most famous anarchist. He believed that if animals could partake
in altruism in the absence of government, then civilised society needed no
government either, and could live in peace, behaving altruistically.
Kropotkin was following what he saw as "the course traced by the modern
philosophy of evolution... society as an aggregation of organisms trying
to find out the best ways of combining the wants of the individuals with
those of co-operation". He saw anarchism as the next phase of evolution.
Huxley was no less affected by events around him. Shortly before he
published "The struggle for existence", his daughter, Mady, died of
complications related to a mental illness. In his despair over Mady's
passing he wrote, "You see a meadow rich in flower... and your memory
rests upon it as an image of peaceful beauty. It is a delusion... not a
bird twitters but is either slayer or slain... murder and sudden death are
the order of the day." It was in the light of nature as the embodiment of
struggle and destruction - the antithesis of altruism - that Huxley saw
the death of his daughter and it was in that mindset that he penned his
essay.
A suite of other fascinating characters would follow Huxley and Kropotkin.
In the US there was the Quaker ecologist Warder Clyde Allee, who did the
first real experiments on altruism in the 1930s and whose religious and
scientific writings on the subject were often indistinguishable; in fact,
he would often swipe text from one and add it to the other. Around the
same time in the UK, J.B.S. Haldane, one of the founders of population
genetics, was talking of altruism and kinship, and came close to
developing a mathematical theory on the subject. But he stopped short -
nobody quite knows why.
A mathematical theory for the evolution of altruism and its relation to
blood kinship would come a generation later with Bill Hamilton, who was
both a passionate naturalist and a gifted mathematician. While working on
his PhD in the early 1960s, he built a complex mathematical model to
describe blood kinship and the evolution of altruism. Fortunately, the
model boiled down to a simple equation, now known as Hamilton's rule. The
equation has only three variables: the cost of altruism to the altruist
(c), the benefit that a recipient of altruism receives (b) and their
genetic relatedness (r). Hamilton's rule states that natural selection
favours altruism when r
b > c.
Hamilton's equation amounts to this: if a gene for altruism is to evolve,
then the cost of altruism must be balanced by compensating benefits. In
his model, the benefits can be accrued by blood relatives of the altruist
because there's a chance (the probability r) that such relatives may also
carry that gene for altruism. In other words, a gene for altruism can
spread if it helps copies of itself residing in blood kin.
A generation of biologists were profoundly affected by Hamilton's rule.
One them was the population geneticist George Price, an eclectic genius
who became depressed when he came across Hamilton's work. He had hoped
that goodness was exempt from scientific analysis, but Hamilton's theory
seemed to demonstrate otherwise. Price went through the mathematics in the
model and realised that Hamilton had underestimated the power of his own
theory.
While working with Hamilton on kinship and altruism, the atheist Price
underwent a religious epiphany. In an irony that turns the debate about
religion and evolution on its head, Price believed that his findings on
altruism were the result of divine inspiration. He became a devout
Christian, donating most of his money to helping the poor. At various
times he lived as a squatter; at other times he slept on the floor at the
Galton Laboratory of University College London, where he was working.
Price lived the life of the altruists that he had modelled mathematically.
Since Hamilton published his model, thousands of experiments have directly
or indirectly tested predictions emerging from his rule, and the results
are encouraging. Hamilton's rule doesn't explain all the altruism we see
but it explains a sizeable chunk of it. With time, Hamilton himself began
to realise the power of his model, as well as its implications, and was
somewhat dismayed that altruism could be boiled down to a simple equation:
"I like always to imagine that I and we are above all that, subject to far
more mysterious laws," he noted in volume 1 of his book Narrow Roads of
Gene Land. "In this prejudice, however, I seem, rather sadly, to have been
losing more ground than I gain. The theory I outline... has turned out
very successful. It... illuminates not only animal behaviour but, to some
extent as yet unknown but actively being researched, human behaviour as
well."
Profile
Lee Alan Dugatkin is a biologist at the University of Louisville,
Kentucky. His most recent book is The Altruism Equation: Seven scientists
search for the origins of goodness (Princeton University Press, 2006).
>From issue 2577 of New Scientist magazine, 11 November 2006, page 56-57