From bird nests and beaver dams to spider webs and the display arenas of
bowerbirds, the architecture of animals has fascinated our species from the
dawn of history. The order and regularity of honey bee comb has inspired
human builders and philosophers alike. Paper-making wasps and adobe-using
birds may have opened our eyes to important technological innovations, and
the relentless works of coral colonies dwarf human achievements. How do
animals manage their feats of engineering, and what does it tell us about
their minds?
Mike Hansell, an emeritus professor at the University of Glasgow, has written
extensively on the building behaviour of caddis-fly larvae, wasps and birds.
Two of his previous books, Animal Architecture and Building Behaviour (1984)
and Bird Nests and Construction Behaviour (2000) are classics: wonderfully
detailed and extensively illustrated. They focus on how structures are
built, and discuss with great insight the physical and chemical constraints
imposed by natural materials.
Built by Animals represents a complete change of pace. Hansell’s focus here is
far more on the mental processes behind the behaviour. The style could
hardly be more different: Hansell writes entirely in the first person, as
though he is reminiscing. The result is a highly personal narrative, which
may strike the audience as warm and friendly, or disconcertingly informal.
Certain termites, for instance, build “rather charming little nests of mud
that look like fat-stemmed toadstools about 35cm high that, if painted red
and yellow would look just right alongside some plastic gnomes in an English
suburban garden”. He also opines that few crickets sing “in the fitted
kitchens of the smart bungalows now populating the land”.
Although Hansell brings a wealth of personal observations to his discussion,
some readers may find him distractingly discursive. In the chapter on the
evolution of swallow and martin nests, the narrative wanders somehow to
hummingbirds, spiders, garden peas, mice, parasitic wasps, grasshoppers,
hairworms, the development of Victorian greenhouses and railway stations,
yellow-jackets, termites and ants. There are also descriptions of Buffon,
Lamarck (particularly his statue in the Jardin des Plantes), and Mendel
(with a few pages on genotypes, phenotypes and dominance). I lost the
thread. In the chapter on traps we are told a great deal about amino acids,
proteoglycans, aerodynamic damping and hysteresis, but the original story
(about caddis-fly traps, which are fascinating) somehow gets forgotten in
the process.
Alas, the reader is not similarly distracted by diagrams and photos: there are
fewer than two dozen illustrations in the book. The audience must depend on
the author’s powers of description. Thus we are forced to imagine the
internal structure of a beaver dam, the elaborate stepwise building of
weaverbird nests, the remarkable repetitive structure of wasp nests, the
intricate design of caddis-fly traps, and so on. But then the object of
Hansell’s book is not so much to describe and explain as to argue that
building behaviour in animals is innate and unintelligent; for this,
illustrations might be counterproductive.
Hansell’s primary target is cognitive ethology, and in particular the late
Donald Griffin. He takes umbrage at the title of an uncited article:
“Thinking about thinking”. Even as loosely defined as Griffin had in mind,
apparently “thought” should be a forbidden term. Hansell’s strategy for
arguing that animals are intellectually dead is three-pronged. The first
step is to discount the abilities of animals on the basis of brain volume.
The second is to invoke Occam’s razor (the simplest possible explanation is
likely to be – or for some, is inevitably – the correct one). The last step
is to describe animals that fit the mindless-builder model.
Brain size, Hansell tells us, should lead “to certain expectations” – namely,
that smaller animals are simple and have limited, stereotyped repertoires.
Using this simple rule of thumb, we can apparently conclude thats ince
female humans have, on average, significantly smaller brain volumes than
males, their behaviour should be simpler and more stereotyped – one of
Darwin’s few mistaken inferences. Humans, by the same token, should be less
behaviourally elaborate than whales and elephants. In fact, it is relative
brain volume that seems to matter. When researchers plot brain mass against
weight for warm-blooded animals, the points cluster rather tightly around an
upward-slanting line. On average, an animal weighing ten times as much has a
brain about five times as heavy. All other things being equal, brain mass
scales with the number of sensory receptors and muscles the animal
possesses, and these increase more slowly than weight. (Cold-blooded animals
generate a line of the precisely same slope, though they are able to make do
with one-tenth the number of neurones. Insects, because so much of their
nervous system is in ganglia outside the head, fall on a different line.)
This brain-to-mass relationship is the biological reason that female brains
are smaller, while at least as intellectually potent as those of males. The
generally accepted measure (one Hansell even cites when discussing
bowerbirds) is the scaled ratio of brain volume to body weight. By this
measure, animals with more brain mass than is predicted by the general trend
(eg humans, porpoises and crows) stand out, as do those with a shortfall
(opossums, for instance). Birds with the most elaborate bowers do indeed
have the largest brain-to-body ratios.
Hansell is particularly unimpressed with social insects, including that
epitome of all-round complexity, the honey bee. Bees may have astonishing
memory, navigational abilities, the capacity to form concepts and cognitive
maps, and the planet’s second most complex language, but we can ignore them
because their brains are small. Their building behaviour is trivial, we are
told: they build repetitive cells (except when they don’t) and use their own
bodies to measure size (as, however, do almost all species, birds most
especially). Spiders able to plan circuitous routes to prey, or others that
make and carry portable trap nets to ambush their victims, suffer from the
same disqualifier: small body size, and thus small brains. By this measure,
a book on animal building could be restricted to elephants and aquatic
mammals – except that these creatures do not build anything.
Occam’s razor can be a useful check on any tendency to formulate overly
elaborate explanations of phenomena, but its utility in ethology has proved
rather mixed. The behaviourist school of psychology, which held stultifying
sway over the study of behaviour in the first six or seven decades of the
twentieth century, “simplified” the analysis of humans and animals by
eliminating any role for instinct and insight, instead explaining everything
on the basis of learned associations – even the circulation of the blood.
One of Griffin’s main arguments was that a mindless devotion to Occam’s razor
blinds us to unusual abilities in animals. The history of ethology is in
large part a series of surprises, showing animals to be cleverer and better
equipped than human imagination was prepared for. Fettered by the
restrictive razor, who could have discovered that animals can have language,
cognitive maps, echolocation, UV and polarized-light orientation, magnetic
field navigation, social cognition, innovation, concept formation,
self-awareness and even practise deceit?
A better measure of animal intelligence ought perhaps to be found in the
behaviour that brains generate. Instances of apparently foolish builders are
common (and not unknown even among humans), as are cases in which creatures
simply follow a set of rote instructions. This is typical of animals living
in predictable or unchallenging niches. Neurones are expensive to build and
very costly to operate; selection will work to keep brain size to a minimum.
But the more complex animals seem to have built on their inborn repertoires.
The extra layers of cognitive flexibility involve learning, an ability to
reorder and reorient innate components, and a capacity to innovate in what
seem to be sensible ways.
Consider the beaver, a species with iconic status among animal builders.
Hansell, armed with his sharp, ever-ready razor, dismisses them summarily.
Being impressed by beaver achievements, we are told, depends on careless,
uncritical anthropomorphism, an emotional response to plush fur and
human-like behaviour. And yet why should human-like behaviour not be based
on human-like creativity in some species? Surely some analysis of the
building activities should precede dismissal of the species into cognitive
outer darkness. Beavers, for instance, seem to have at least six alternative
internal designs for dams (and, given how little this has been studied,
probably many more); is Occam best served by assuming that there are at
least six alternative programmes, or is it simpler to suppose that there is
some element of evaluation and decision-making here, based on context and
the availability of materials?
When beavers incorporate novel elements such as plywood sheets and plastic
tarpaulins into dams, are their innate circuits misfiring or is there some
basic level of understanding of the goal they are working towards that
encourages flexibility? It seems worthwhile at least to explore these
possibilities rather than dismiss outright Darwin’s suggestion of
evolutionary continuity in mental processing. Alas, Occam’s razor has
relentlessly sliced these paragraphs and pages from Mike Hansell’s book; the
animals we read about are the helpless, hapless pawns of their instincts,
blindly bumbling their way through life, incredibly lucky that the world is
simple and unvarying enough to accommodate so many races of robots. How odd
that natural selection has never worked to favour the sorts of cognitive
prowess so evident in nearly all other classes of behaviour.
Mike Hansell
BUILT BY ANIMALS
The natural history of animal architecture
268pp. Oxford University Press. £16.99 (US $29.95).
978 0 19 920556 1
James Gould is Professor of Ecology at Princeton University. He is the
author of Ethology: The mechanisms and evolution of behavior, 1982.
