| Culture in the Animal Kingdom |
| Sunday, 01 May 2005 | |
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Mark Harrison explores the evidence for cultural behaviour in animals. Culture has historically been thought of as a uniquely human characteristic: the Oxford English Dictionary defines culture as “the civilization, customs, and artistic achievements of a people, especially at a certain stage of its development or history”. However, recent discoveries have confirmed that, like the use of tools and a highly developed brain, culture is fairly common in the animal kingdom. Yet studies reveal that it is not just restricted to our closest relatives. Culture is important to biologists —
anthropologists in particular — because in order to exhibit culture an animal
must be capable of socially transmitted learning, traditionally considered a
hallmark of high intelligence. Revealing the extent of culture in the animal
kingdom, especially in the primate lineage, may help us to understand how and
why human culture and intelligence evolved. The If an animal is capable of social learning,
once discovered, a useful behaviour will spread through the population until it
reaches an unsurpassable geographical barrier, such as an ocean or mountain
range. Behaviour seen on one side of the barrier will therefore differ from
that on the other side. But just observing differences in behaviour between
populations, not necessarily caused by differences in social learning ability,
could be due to genetic or ecological factors. For example, if a tool is only
present at the site where it is in use, it is difficult to say for certain
whether that use is cultural, or whether it would be used at both sites if it
were present. Only when ecological and genetic explanations can be discounted
can a behavioural variant confidently be considered as cultural. Hence
culture is easiest to identify when it involves non-essential behaviours, for
example grooming techniques, as these are less likely to be affected by
ecological factors. The ability to learn from others is useful because it
allows the bearer to adapt to changes more quickly than solely through genetic
adaptation or individual learning. A sensible place to start looking for culture
in the animal kingdom is in our closest living relatives, the great apes. It
has long been established that great apes in captivity are capable of learning
a wide variety of behaviours including problem-solving, tool use and even sign
language. Despite many years of debate the existence of cultural behaviour in
the wild has only really been confirmed in the past six years. Information
collected by Andrew Whiten and colleagues from seven sites, totalling 151 years
of observation, revealed that an ecological explanation could be discounted —
and hence a cultural explanation accepted — for 39 different behaviours found
to vary between the sites, including forms of tool use, grooming techniques and
courtship behaviour. This is
consistent with our genetic similarities to chimpanzees, and the numerous
observations of tool use by chimpanzees in the wild, including fishing for
termites and cracking nuts with hammers. Carel van Schaik and colleagues looked at
cultural behaviours in orangutans, which rarely use tools in the wild and are
largely solitary. Long-term observations from six research sites in Borneo and
Sumatra demonstrated a similar pattern of cultural behaviour in wild orangutans
to that seen in chimpanzees: blowing raspberries when making their nest for the
night, opening up tough foods with sticks, and building roofs on their nests to
protect themselves from the rain. With the exception of tool use during
feeding, cultural variations in great ape feeding behaviour have yet to be
documented. This is because small differences in the availability and
nutritional content of food items between sites make it difficult to preclude
ecological explanations. Current studies by the author and a number of other
researchers aim to take these small ecological differences into account and
reveal the true extent of cultural variation in orangutan feeding behaviour. Sceptics have pointed out that in virtually
all these cases it is impossible to completely discard an ecological or genetic
explanation. Much of the available evidence for culture in primates remains
based on plausibility arguments. For example, chimpanzees in one area may have
a greater supply of fruit, their preferred food, and so may not use hammers to
crack nuts even if both the nuts and hammers are available to them. This
possibility is hard to exclude, but the studies on orangutan feeding behaviour
mentioned above may go some way towards achieving this. Furthermore, the long
life span of many primates — an estimated 58 years for orangutans in the wild —
hinders the study of transmission of traditions between generations. For these
reasons, the best candidates for the demonstration of culture in animals
actually come from non-primates. Whales and dolphins also exhibit cultural
behaviour. Male humpback and bowhead whales sing to attract females, and the
songs of different males within a population at any given time are virtually
identical, despite the fact that the population of thousands may span thousands
of kilometres. These songs vary widely and continuously, both within and
between breeding seasons. The speed and geographic breadth of these changes
makes an ecological or genetic explanation highly unlikely. Off the coast of
Argentina, killer whales swim ashore to catch seals. This behaviour is very risky
as beached individuals will die if they can’t return to the ocean. Killer whale
mothers have been observed teaching their young this technique, actively
pushing juveniles up onto the beach, directing them towards prey and helping
them back into the sea afterwards. This satisfies all the conditions of
teaching and social learning and so can be considered cultural. The best evidence yet for culture comes from
studies on fish, in which one can conduct direct and rigorous experimental
tests. For example, Helfman and Schultz’s translocation experiments in the
early 1980s — on the elegantly named ‘French grunt’— showed that translocated
fish adopt the schooling and migratory behaviour of the group to which they
were introduced, rather than that from where they came. The same study also
showed that control fish translocated into the same area, but with resident
‘teacher fish’ removed, did not adopt this behaviour. These experiments
completely preclude both genetic and ecological explanations. The confirmation
of cultural behaviour in fish provides excellent support for its presence in
primates, given the latter species’ higher level of intelligence. There is also
a hint that the mechanism of cultural transmission of behaviours may be simpler
than was originally thought. It is worth noting that the definition of
culture used by biologists in such studies is much stricter than that typically
used for humans. Many examples of human behaviour would not be considered
cultural under the criteria used by biologists. The use of medicinal plants by
forest Indians, for example, can be explained on ecological grounds, as these
plants are not available to all human populations. We know that the knowledge
of which plants to use for medical treatment is passed on by social learning in
humans, but sceptics are unwilling to accept a cultural explanation for their
behaviour, even in animals such as chimpanzees, who have a proven ability for
social learning in captivity. Were animals to be judged by the same standards
used for humans, we would find animal culture to be even more widespread than
currently realised. Some might argue that the degree of complexity in human culture is so great that animal and human cultures can never be compared. In light of this, many prefer to use the term ‘tradition’ rather than ‘culture’ when discussing behavioural variants in animals. This is a little like saying that because digestion or locomotion differ in humans and chimpanzees, the two processes are not comparable. Whilst it is certainly true that the degree of cultural complexity in humans is much greater than that shown in even the most cultural animals, this raises the interesting question of whether our ancestors were also cultural. Would it be reasonable to assume that stone-age or Neanderthal man were cultural? What about Homo erectus and Australopithecus? Most would agree that these species would have been cultural to some extent, but chimpanzees — separated from us by just 5.5 million years — are considered to be our sister taxa and are almost identical to us genetically. So why not them too? An increasing number of anthropologists and biologists now believe that some animals can indeed be considered cultural and that a broader definition of culture — like that used in this article — is more useful for understanding how and why human culture evolved. It is now beyond doubt that the cultural differences between ourselves and the rest of the animal kingdom are differences of degree rather than kind, which leaves us to ponder once again, what does actually define us as human? Mark Harrison is a PhD student in the Department
of Anatomy |
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