快猫短视频

NOT until February last year did Lee Klinger find what he鈥檇 been looking
for鈥攁 peat bog in Africa. 鈥淚鈥檇 been tromping around the world for more
than a decade, looking for peat bogs,鈥� says Klinger of the National Center for
Atmospheric Research, in Boulder, Colorado. 鈥淚鈥檇 found them in the United
States, of course, my own back yard; I鈥檇 found them in Canada, in Costa Rica, in
Sumatra, in Northern Europe; but I couldn鈥檛 rest until I鈥檇 found one in Africa.鈥�
Forays into a dozen African countries had proved fruitless. It was only when
Klinger and a team of African botanists ventured into the remote Ndoki region of
the northern Congo that he saw African peatland at last.

Trudging through the world鈥檚 peat bogs in rubber boots might sound like a
bizarre pastime for an atmospheric chemist. But Klinger is also part biologist
and, to him, peat bogs are far more than the desolate landscapes they often
appear to the untutored eye, or even to the eye of the average ecologist.
Instead, he sees them as the ultimate destination of most of the world鈥檚
ecosystems. Given enough time, Klinger believes, ecosystems from woodland to
marsh follow a seemingly inexorable series of habitat transformations until they
become peat.

This process of succession to a climax might take a few thousands of years.
But once established, peat bogs are incredibly stable, persisting for perhaps
tens of thousands of years. You might even call peat bogs a kind of
superorganism, not least because the biophysical interactions that go on in the
succession appear to be enhanced by the ecosystem itself. For instance, plants
that thrive early in the succession acidify the soil and so encourage the
establishment of late-successional species, including sphagnum mosses.

Klinger鈥檚 peat bogs figure in the current revival of the idea of 鈥渢he
superorganism鈥�. Many biologists react to this idea by recoiling as if faced with
something repellent. And for good reason, because the concept of the
superorganism is usually associated with a quaint, thoroughly wrong-headed view
of the world.

Brave souls

Nevertheless, a few brave souls are daring to utter the word again, linking
it not just to peatland but also to the communities of mites on the backs of
insects, ant colonies, many kinds of ecosystems and, its ultimate expression,
Gaia. This last theory, the thirty-year-old brainchild of Jim Lovelock, revolves
round the idea that the Earth鈥檚 biological and physical components interact in a
way that is self-sustaining. It is as if the Earth鈥檚 biota nurtures its own
existence, but only in a non-purposeful way. Once dismissed as little more
than New Age mysticism, Gaia theory is now taken seriously by scientists,
although in a different incarnation. Today, researchers are viewing Gaia and the
whole notion of the superorganism in the light of the modern mathematical theory
of complexity.

Although a precise definition is elusive, a superorganism can be thought of
as a group of individual organisms whose collective behaviour leads to
group-level functions that resemble the behaviour of a single organism. Take an
ant colony, for example, where internal climate is kept within narrow limits by
the activity of its teeming members, even though no single ant can be seen
seeking this goal. The finely regulated temperature is necessary to safeguard
the brood and the future of the colony. And the myriad plants that play a part
in the peatland succession appear to create the physiological conditions that
promote the succession.

The superorganism idea has its roots in the Aristotelian notion of nature as
an organic whole, imbued with cooperation for the good of all individuals. In
the early decades of this century, the Harvard University biologist William
Morton Wheeler developed the superorganism idea further, from a metaphor into an
explicit description of a colony of social insects. Wheeler was reacting against
the Darwinian notion that natural selection worked only at the level of the
individual. 鈥淭he struggle for existence is not more than half the truth,鈥� he
wrote. 鈥淭o us it is clear that an equally pervasive and fundamental innate
peculiarity of organisms is their tendency to cooperation.鈥� Wheeler did not
reject Darwinism but tried to include perspectives other than that of the
individual.

The advent of modern evolutionary theory in the 1940s, and the reductionist
thinking that grew out of molecular biology in the 1960s, buried Wheeler鈥檚 idea.
Modern biology taught that organisms and their behaviour could be discerned only
through their molecules, and how they evolved could be revealed by uncovering
the results of competition between individuals. Richard Dawkins鈥檚 concept of the
selfish gene is the ultimate expression of this last idea.

Meanwhile, a few biologists independently began plotting to pry the lid off
the superorganism鈥檚 coffin. For instance, a decade ago the Harvard biologist
Edward Wilson wrote that 鈥渢he time may be at hand for a revival of the
superorganism concept鈥�. His interest was in how social insect colonies operate.
鈥淐olonies do more jobs than individual ants do,鈥� he says. 鈥淔or instance,
leaf-cutter ants are the only organisms other than humans that engage in food
production.鈥� In other words, the interaction of individuals in a coherent group
performed functions beyond the scope of a single individual.

Focusing more on the evolution of superorganisms than on their behaviour,
American geneticist David Sloan Wilson at the State University of New York at
Binghamton and philosopher Elliott Sober of the University of Wisconsin
published a paper in 1989 entitled 鈥淩eviving the superorganism鈥�. In it, they
wrote that 鈥渞eviving the superorganism concept might seem like bringing back Dr
Frankenstein鈥檚 well-intentioned monster鈥�. It was a self-deprecating statement
that many evolutionary biologists heartily agreed with.

The reason for this reaction was that Wilson and Sober were trying to
reinstate the idea of group selection as an important force in evolution (see
鈥淕roup Therapy鈥�), which was anathema to the prevailing view. 鈥淭hey apparently do
not understand the fundamental mechanisms of natural selection,鈥� was how Dawkins
greeted Wilson and Sober鈥檚 mission. Nothing daunted, the Americans persisted and
are beginning to have some success.

Thomas Seeley of Cornell University, for instance, believes you can invoke
group-level selection in bee hives, because like ants they display apparently
organised, group-level behaviours such as brood rearing, inner-climate control,
and hive defence. He applies the term superorganism to hives, saying that it
describes 鈥渁 functionally integrated group of organisms鈥�. But the word
superorganism is conspicuously absent from his new book on bee colonies The
Wisdom of the Hive. Its omission was a 鈥渢actical decision鈥�, Seeley says,
because 鈥渋t has often been used carelessly [and] has acquired pejorative
connotations鈥�. Once people have embraced his approach, says Seeley, 鈥淚 will
start using the term superorganism again, and carefully.鈥�

Here, Seeley touches on a key issue: semantics. What exactly is meant by
superorganism? For Wheeler, it was a real entity, an organism in its own right.
For others, it is a metaphor, 鈥渁 very respectable scientific metaphor鈥�, as
Edward Wilson puts it. 鈥淚ts usefulness is that it describes something
intermediate between fully integrated, unmistakable organisms on one side and a
group of loosely organised, interacting organisms on the other.鈥� The metaphor
prompts 鈥渁 cascade of interesting questions鈥� about what are undoubtedly
important phenomena in the natural world, he says. The question then becomes,
what kind of phenomena are we dealing with? And here, compared with even a few
years ago, the framework for answering that question has shifted
dramatically.

Rhythmic patterns

Sandra Mitchell, a philosopher at the University of California, San Diego,
argues that the functional organisation and self-regulation that
characterises superorganisms are best viewed in the context of complexity
theory. This theory deals with the spontaneous emergence of order from the
internal dynamics of complex systems. Where traditional evolutionary biology
explains order in nature as the outcome of adaptation through natural selection,
for instance, complexity theory suggests that much of this order springs from
within the system itself, with natural selection playing second fiddle.

For example, ant species of the genus Lepthothorax live in small
colonies, in which they raise their broods. When the ants are few in number,
they move about randomly, displaying a chaotic pattern of care for the brood. As
the number of ants increases and crosses a critical value, they suddenly start
moving in concert in a rhythmic pattern, with 25-minute cycles of tending the
brood interspersed with periods of rest. This looks like a cooperative effort at
brood care which, notes Brian Goodwin of the Open University, 鈥渉as been
suggested as the outcome of natural selection鈥�. However, in a computer
simulation of an ant colony, in which the ants obey a few very simple rules of
interaction, the same rhythmic pattern emerges. 鈥淪o you see,鈥� says Goodwin,
鈥渟election is not the explanation of the coordinated activity. The pattern
emerges as a property of the system itself.鈥� Natural selection, he says, simply
fine tunes the order emerging from the system.

Similarly, Mitchell, working with entomologist Robert Page from the
University of California, Davis, simulated a honey bee colony. Again, built-in
interactions between individuals were few and simple, yet complex behaviours
such as patterns of working and resting emerged. For Goodwin and Mitchell, the
emergence of such regularities is what characterises a superorganism, rather
than its being like an organism.

In this interpretation, superorganisms are simply part of the spectrum of
complex systems, which also includes non-living systems. As an enthusiastic
proponent of complexity theory, Goodwin can be expected to embrace such a view.
But he is not alone: Mitchell and Edward Wilson accept the complex systems
approach as valid, as do Lovelock, Seeley and Klinger. Others differ. For
instance, John Maynard Smith, the prominent evolutionary biologist at the
University of Sussex, thinks complexity theorists are misguided. 鈥淭he attempt to
escape the effect of evolution is wrong,鈥� he states strongly. 鈥淩emember the
phrase that says `Nothing in biology makes sense except in the light of
evolution鈥�? Well, nothing in evolution makes sense except in the light of
natural selection.鈥� David Wilson takes this position, too. 鈥淐omplexity by itself
cannot create functional organisation,鈥� he says.

Nevertheless, there is growing interest in at least considering higher levels
of selection, such as species selection, in the natural world, and this is what
complexity theory promotes. If superorganisms (in the metaphorical sense)
represent the biological section of the spectrum of complex systems, would
social insect colonies be included? Most would answer, yes. What of ecosystems?
There is more equivocation here, particularly regarding the global ecosystem, or
Gaia.

Klinger strongly believes that the robust dynamics of succession towards
peatland display the characteristics of a complex system, partly because they
promote their own formation but also because they are so similar in fundamental
structure. 鈥淚 could show you a handful of vegetation from a peat bog and
challenge you to tell me whether it came from the Congo or northern Minnesota,鈥�
says Klinger. 鈥淵ou couldn鈥檛 say, and that鈥檚 because, structurally, they are all
the same. Yes, the species may be different in different parts of the world, but
often the genera are the same. And in terms of physical form鈥攖he shape of
the mosses, the sedges, and other bog species鈥攖hey are the same the world
辞惫别谤.鈥�

Powerful attractor

In other words, no matter what kind of ecosystem a particular peatland might
have derived from, or where it is located, it converges on the same physical
form as all others. The emergence of the same patterns of order is exactly what
is expected from similar complex systems: it is as if all peatlands are pulled
to the same so-called attractor. 鈥淭hat鈥檚 how powerful it is,鈥� says Klinger, with
the enthusiasm of a proud parent.

Other properties of ecosystems can also be seen from the perspective of
complexity鈥攆oodwebs for example. 鈥淵ou can view foodwebs as an emergent
property of complex systems,鈥� says Stuart Pimm, an ecologist at the University
of Tennessee. They emerge as stable, repeated patterns in different ecosystems.
These patterns include the length of a food chain鈥攖he progression of who
eats whom, from the bottom of the foodweb to the top鈥攁nd the ratio of
predator species to prey species.

Another such property of ecosystems is called persistence, which includes the
ability to keep out potential invader species. Pimm and others have simulated
ecosystems in computers, adding species at random one at a time from a pool of
about a hundred. Each additional species enters the ecosystem easily when the
number in the ecosystem is low. But when that number approaches 15 or so, entry
becomes increasingly difficult. And entry at this numerical level becomes
increasingly difficult as the ecosystem matures over time, even if the potential
invader is competitively superior to species within the ecosystem. That
resistance to invasion can be seen as an emergent property of a complex
system.

Collapse of the biota

So, it appears legitimate to consider ecosystems as complex systems. But what
of Gaia? 鈥淭he serious Gaia theory of today concerns the interactions of a large
complex system from which emerge certain properties that we can observe, such as
the maintenance of global temperature and cycling of gases,鈥� says Lovelock.
Nevertheless, there is still a broad spectrum of opinion on Gaia. Although
Maynard Smith accepts that 鈥渋t is a healthy way to look at a two-way interaction
between organisms and their physical environment . . . the analogy of Earth with
an organism is misleading.鈥� One reason, he says, is that the planet is not the
product of evolution in the way that a true organism is, another is that it does
not reproduce. Neither of these criteria is a problem for Goodwin, who focuses
on the emergent properties of the system, which include not only homeostasis but
other properties as well.

For instance, in the history of the Earth since complex forms of life evolved
500 million years ago, the biota has collapsed five times in mass extinctions
involving the loss of at least 50 per cent of species and sometimes as much as
95 per cent. After each extinction the biota bounced back in diversity, usually
with different players on the stage, but with the pattern of
interaction鈥攖he pattern of niches鈥攔emaining the same. Reptiles were
the major carnivores before the extinction at the end of the Cretaceous 65
million years ago, and mammals filled that role afterwards, for instance.

So Gaia can be seen as fragile, in that the biosphere can be tipped into
catastrophic collapse through some perturbation. But it is also resilient,
because recovery is always fast and complete. This is certainly a property of a
complex dynamical system. But can Gaia be classified as a superorganism? It
depends what you mean by superorganism, and who you ask.

鈥淲henever there is semantic confusion like this, it indicates one of two
things,鈥� observes Edward Wilson, referring not just to Gaia but to all levels of
complexity in the biological world and how it is described. 鈥淔irst, either the
philosophers have got involved,鈥� he says. 鈥淥r, second, we are on the edge of a
large, important, and relatively unexplored area of the natural sciences. Or
maybe both. But I certainly believe the second to be true.鈥�

* * *

GROUP THERAPY

THE Harvard biologist Edward Wilson stated two decades ago that altruism is
鈥渢he central theoretical problem of sociobiology鈥�. It was perceived as a problem
because according to Darwinian principles, organisms pursue purely selfish
interests. They maximise their own opportunities to breed, and do not surrender
them so that others may breed in their place.

By contrast, anyone who has logged onto the Human Behavior and Evolution
Society (HBES) network on the Internet recently will have read that altruism is
not a problem at all. According to the swelling voice of the 鈥淕roup Selection
Squad鈥� on the network, a generation of evolutionary biologists has mistakenly
believed that natural selection works only at the level of the individual. The
Squad seeks to assert group-level selection as an equally important phenomenon,
perhaps even more so. Will the Squad succeed?

First, some history. Before the early 1960s, evolutionary theory viewed
nature through a lens of harmony and benevolence. Individuals in social groups
were held to act for the good of their group, and hence their species, ensuring
its survival. But this concept, known as group selection, was very soon
recognised as naive in terms of Darwinian theory, and the focus of attention
shifted towards individual-level selection.

In tandem with this shift came the development of mathematical models of
altruism and cooperative behaviour. In both cases, individuals were seen as
acting in their own interests or in the interest of their genes. Yet ultimately,
the models showed that the group could benefit too (鈥淏orn to trade鈥�, New
快猫短视频, 26 October, p 34). As Mark Pagel of the University of Oxford put
it last year: 鈥淥ne of the greatest triumphs of evolutionary thinking has been to
show how selfish interests of individuals coincide with those of the group.鈥�

Ethologists found these ideas acted out in the field. For instance, in
chimpanzee society, brothers band together to try to monopolise breeding
opportunities in their territory and among baboons, unrelated males form
alliances for the same purpose. Nevertheless, some researchers felt uneasy about
abandoning the idea of group selection, notably because social groups often act
as if they are superorganisms. But, says Frans de Waal, of the Yerkes Primate
Center in Atlanta, the strength of prevailing theory meant that 鈥渨e weren鈥檛
allowed to talk like that鈥�.

Not so for David Sloan Wilson from the State University of New York at
Binghamton, leader of the Group Selection Squad. Since the mid-1970s he has
developed a theory of group selection that, he believes, avoids the pitfalls of
earlier theory. He argues that the fundamental issue is the 鈥渧ehicle of
selection鈥�, which he says is a group with a common fate in an evolutionary
sense. The individuals in a social group fall into this category, for instance,
if through their relationships or common defence they serve the group鈥檚 interest
as well as their own. So natural selection will favour the genes for behaviours
in individuals that promote group welfare.

In lion prides, for instance, when females cooperate to repel danger they
ensure not only their own survival but also the group鈥檚. Given this concept,
says David Wilson, group selection works when there is competition between
groups of the same species. In the case of lions, groups with females that are
better at repelling attackers will thrive better than those with less skilled
females.

David Wilson is certain of his position, and frequently claims in his writing
that he has the support of two of his archcritics, the pioneers of 1960s鈥�
evolutionary thinking, George Williams of the State University of New York at
Stony Brook and William Hamilton of the University of Oxford. There is a grain
of truth to this, but the grain is minute. Williams concedes that group
selection is possible in theory, but the circumstances that favour it are so
rare that the phenomenon plays an insignificant part in the spectrum of
evolution.

Williams has become irritated that no matter how many times he states his
position, David Wilson ignores it. Williams refused to comment on a paper by
Wilson published in December 1994. 鈥淭here鈥檚 no point,鈥� he told a colleague.
鈥淭hese people can鈥檛 hear what I鈥檓 saying.鈥� Richard Dawkins did comment. 鈥淭hey
are zealots, baffled by the failure of the rest of us to agree with them,鈥� he
wrote of Wilson and his colleague Elliott Sober. 鈥淚 remain reciprocally baffled
by what I see as the sheer, wanton, head-in-bag perversity of the position they
肠丑补尘辫颈辞苍.鈥�

Although most evolutionary biologists still see individual-level selection as
the driving force of natural selection, some are beginning to be sympathetic to
David Wilson鈥檚 effort. 鈥淭here is probably an interplay of individual selection
and group selection in social animals,鈥� says de Waal. Many ethologists agree.
And many entomologists see group selection as valid for discussing colonies of
social insects.

So, do the growing rumblings on the HBES network portend a revolution? The
established figures in the field do not think so, but you would hardly expect
them to do so. While he criticises David Wilson for causing confusion by using
the term group selection in many different ways, John Maynard Smith of the
University of Sussex also praises him for making it a legitimate topic of
discussion again.