By Bob Holmes
New Scientist, March 9, 2009
Edited by Andy Ross
According to Richard Dawkins, the genes that do the best job of passing
themselves along to the next generation are the ones that flourish. But some
evolutionary biologists argue that this view leaves us blind to crucial
evolutionary processes among groups, species, and even ecosystems.
Entire species can have traits that, over geological time, make them more
likely than others to survive. This can lead to evolutionary change that
could not be predicted from individual adaptations alone.
selection may help explain some puzzling observations. For example, larger
individuals often outcompete smaller ones, so selection at the level of
individuals would tend to favor large body size. But a larger-bodied species
has a larger requirement for food and space, and so might run greater risks.
Species selection may oppose individual selection to help keep body size
Species are stable enough over time for selection to have
some effect in shaping their characteristics. In contrast, most evolutionary
biologists have difficulty accepting that natural selection can act at an
intermediate level to select groups.
Many lab experiments have shown
that group selection can lead to evolutionary change. But in nature,
cooperative groups are vulnerable to takeover by cheaters. These selfish
invaders pay none of the costs of cooperation yet reap the benefits. David
Sloan Wilson has shown that cheaters will not prosper if groups frequently
break up and reform again with new members. Each fresh start favors the
groups with the fewest cheaters.
Evolution can make the conditions
needed for group selection more likely in the future. Group selection may
sometimes favor the interests of a group over any of its constituent
individuals, and ecosystem selection might act to shape an entire ecosystem
over the interest of its constituent species.
According to this
hypothesis, just as the cells within our bodies sometimes sacrifice
themselves to ensure the body as a whole remains healthy, so individual
species within some ecosystems may on occasion make sacrifices to ensure
that the whole ecosystem survives. Still, the mainstream view is that
individual species in an ecosystem are like cancerous cells in a body,
growing as aggressively as possible and heedless of the cost to the
Genes operate as part of networks of interacting genes, in
which multiple genes affect each trait and each gene affects multiple
traits. These networks usually have enough redundancy that deleting any one
gene has little if any impact on an animal's form or function. So it is the
network that is selected, says Eva Jablonka.
Dawkins says that only
by looking at the fitness of the genes themselves, averaged over all their
possible contexts, can one really understand evolution. Genes carry
information in a stable form from one generation to the next, usually
changing only slowly, while individuals, groups, and species come and go.
Wilson on Altruism
By Leon Neyfakh
Boston.com, April 17, 2011
Natural selection means that the fittest pass down their genes to the next
generation, and every organism would seem to have an overwhelming incentive
to survive and reproduce. Yet self-sacrifice exists in the natural world. By
identifying the mechanisms through which altruism and other advanced social
behaviors have evolved, we stand to gain a better understanding of human
The currently accepted explanation for altruism is
William Hamilton's theory of kin selection theory. It says that an organism
trying to pass its genes down to future generations can do so indirectly, by
helping a relative to survive and procreate. Acting altruistically toward
someone with whom you share genes is just a different way of promoting your
Harvard biologist Edward O. Wilson argued in a paper in
Nature last August that kin selection theory doesn't explain altruism. That
paper, co-written with Harvard mathematicians Martin Nowak and Corina
Tarnita, is now being challenged in letters, blog posts, and rebuttals in
other journals. Richard Dawkins: "It's almost universally regarded as a
disgrace that Nature published it."
Wilson made Hamilton's theory the
basis of his work in sociobiology. But over decades he came across evidence
that made him doubt the connection between genetic relatedness and altruism.
His alternative theory holds that the origins of altruism and teamwork have
nothing to do with kinship. Under certain circumstances, groups of
cooperators can out-compete groups of non-cooperators. This group selection
is the basis for a variety of advanced social behaviors linked to altruism,
teamwork, and tribalism.
Many biologists are baffled by the attack on
the mathematical equation underlying Hamilton's theory. According to Nowak,
the critics don't understand the math. The equations underlying kin
selection theory can't be used to explain the natural world. Nowak believes
that many of the people disputing his paper have never actually done the
Critics feel Wilson and his coauthors are wrong to treat kin
selection as something separate from natural selection. As Dawkins explains
it, kin selection is not a distinct process but a necessary consequence of
neo-Darwinian natural selection.
Wilson argues that advanced social
behaviors like altruism are evolutionarily advantageous on a group level.
That socially advanced organisms end up favoring their kin is a byproduct of
their group membership, not the cause. Wilson plans to extend his new ideas
about the evolution of social behavior to humans in a book next year.
AR Interesting topic, and relevant to
my argument in G.O.D. Is Great.