Whale: Encyclopedia II - Whale - Whale intelligence

Whale - Whale intelligence

For more material in this area, focusing more on dolphins, see cetacean intelligence.

Many people believe that cetaceans in general, and whales in particular, are highly intelligent animals. This belief has become a central argument against whaling (killing whales for food or other commercial reasons).

There is no universally agreed definition of "intelligence." One commonly used definition is "the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience." Proponents of whale intelligence cite the social behavior of whales and their apparent capacity for language as evidence of a sophisticated intellect. Given the radically different environment of whales and humans, and the size of whales compared to (say) dolphins or chimpanzees, it is extremely difficult to test these views experimentally.

One traditional indicator of intelligence is brain capacity, since humans have bigger brains than most other animals. Whales have the largest brain of any animal. A typical sperm whale brain weighs about 7.8 kg, whereas a typical human brain weighs about 1.5 kg. While it may seem that this would indicate that five times greater intelligence, in mammals brain size is in approximate ratio to body size, and most of the extra capacity is used to manage the larger body.

A more precise indicator is the brain-body ratio: the size of the brain compared to body mass. Here humans have a decisive advantage. A human brain comprises about 2% of the human body mass, while the sperm whale's brain comprises only 0.02% of its body mass. A cow's brain is four times as large as a whale's on this measurement. On the other hand, a large proportion of a whale's body mass is blubber, which requires no brain power, and this distorts the ratio somewhat. Nevertheless, it is clear that brain size is not a decisive criterion. Hummingbirds have an even higher brain-to-body ratio than humans.

The next consideration is the structure of the brain. It is generally agreed that the growth of the neocortex, both absolutely and relative to the rest of the brain, during human evolution, has been responsible for the evolution of intelligence, however defined. In most mammals the neocortex has six layers, and its different functional areas (vision, hearing, etc) are sharply differentiated. The whale neocortex, on the other hand, has only five layers, and there is little differentiation of these layers according to function. This has led some to argue that the whale brain has not significantly evolved since the distant ancestors of the whale took to a marine lifestyle about 50 million years ago.

From an evolutionary point of view, this is consistent with the principles of natural selection. Intelligence does not arise spontaneously: like any other animal capacity, it evolves under the pressure of the animal's environment. The human brain has evolved under the pressure of natural selection in a hostile terrestrial environment. The key primate characteristics - bipedalism and the opposable thumb - gave the early hominids the ability to manipulate their environment through the use of technology (by making tools). This unique adaptation created a virtuous cycle: tool-making gave those hominids with larger brains a decisive evolutionary advantage, leading to larger and more sophisticated brains, and thus to more tool-making. This process explains the exponential growth of hominid intelligence over the past million years.

By contrast, the whale has faced no such environmental stimuli to brain evolution. Whales live in an unchanging and benign environment with few natural predators. Their sole adaptation to their marine environment has been increasing size. The whale's lifestyle consists of swimming and eating, tasks which fish perform perfectly competently with very small brains. From an evolutionary point of view, there is no reason for whales to have evolved intelligence, since their survival does not require them to perform any tasks for which intelligence is necessary.

It is certainly true that whales have a sophisticated social system, and that their communication system may contain some of the elements of true language, although our knowledge of whale communications is not very advanced. These capacities are sometimes confused with intelligence. But many other animals, including insects, have complex social systems, and many others, such as birds, have sophisticated communications. Whales also have very acute hearing, which gives them advanced echo-location capacities analogous to sonar - but so do bats. All this has led many (though far from all) zoologists to the conclusion that there is no convincing evidence for superior whale intelligence.

Adapted from the Wikipedia article "Whale intelligence", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki