Intelligence has been considered a unique feature of human beings as it gives us the ability to devise elaborate strategies for solving problems. There are three key evolutionary explanations of intelligence, which are, foraging/ecological, social and sexual selection. Foraging is when animals learn food preferences from others. This ability has clear survival advantages because the animal can learn from others rather than using trial and error process to identify which foods are harmful. The larger the range of food required, the larger the foraging area must be and the greater the requirement for more complex abilities.
Many primates have to balance their diet by selective eating through successful hunting, which requires forethought, planning, cunning and the ability to coordinate the actions of a number of individuals. Finding food over a particular area may require a cognitive map (memorized spatial knowledge).Obtaining the food requires tool use and hunting techniques, which is another indication of intelligence in both human and non-human species.
Visalberghi and Trinca (1987) did a study to look at the effects of tool use. Capuchin monkeys were given task of pushing peanut butter out of a tube. They found that the monkeys were quick at finding a suitable stick but tried out many unsuitable ones first. This suggests no understanding of causal relationships and that many animals develop the skill through trial and error rather than insight. Only the great apes show the sophisticated understanding of cause and effect so this supports the link between tool use and intelligence. The association between the growth of hunting and intelligence shows that more intelligent individuals are more intelligent than less intelligent.
However many species with very successful hunting techniques are not very intelligent and therefore it is unlikely that the benefits of hunting would account for human levels of intelligence. The efficiency in foraging of a particular animal has been shown by various psychologists. Galef (1988) did a study in which a rat was allowed to eat food with a distinctive flavour, with cocoa or cinnamon. A test rat was then put in with the demonstrator for 30 minutes, but with no food present. This test rat then had to choose between cocoa-flavoured and cinnamon-flavoured food. It was found that the test rats preferred food of the same flavour as that eaten by the demonstrator.
This was still the case 4 hours after the demonstrator had eaten and when 12 hours had elapsed before the test rat made its choice. Therefore it can be concluded that interacting with a rat after it has eaten creates a particular preference for that food. These results could be interpreted in a number of ways, in terms of the rats been neophobic, meaning unwilling to try anything new. The test rat could have picked up on the smell of the particular food on the breath of the demonstrator and will have been choosing between what was familiar and unfamiliar rather than been influenced directly by the demonstrator actually eating the food. However despite this Galef also found similar results even when the test rats were familiar with both cocoa and cinnamon flavoured food.
The social theory says that interactions with other members of a social group present an intellectual challenge and primate intelligence has been evolved in response to this challenge. It has been suggested that intelligence is an evolutionary adaptation for solving social problems. The most intelligent species are the social animals, which are bees, parrots, dolphins, elephants, wolves, monkeys, etc. The group living could have set the stage for the evolution of intelligence in two ways; sociality which increases the value of having better information, because information is one commodity that that can be given away and kept at the same time. For example a more intelligent animal within a group has the benefit of knowledge and what it can get in exchange for the knowledge.
Secondly group living itself has new cognitive challenges. Social animals send and receive signals to coordinate predation, defence, and foraging and sexual behaviour. They exchange favours, repay and enforce debts, punish cheaters and join coalitions. Machiavellian Intelligence Hypothesis came from various related hypotheses, which Bryne and Whiten (1988) brought together. This suggests that deceiving and detecting deception are the primary reason for the evolution of intelligence. Evidence supports this, as Bryne and Whiten (1992) have shown that there is a strong positive correlation between neocortex ratio and the prevalence of tactical deception in various primates and this implies that there is a clear relationship between social manipulation and intelligence. Cosmides (1989) has shown how human intelligence is specially adapted to deal with social problem solving.
Grooming is an effective mechanism, because primates such as chimpanzees spend far more time than is necessary for purely hygienic purposes in picking through each other fur and removing bits of plant material, insects and scabs. It has therefore been suggested that grooming serves social ends such as strengthening alliances between individuals and bringing about reconciliation after a dispute. The hypothesis goes beyond grooming to see what other ways, which can help the individual benefit from group living. One of these ways is Theory of Mind, which is the ability to be self-aware and to appreciate others have self-awareness too.
These can make heavy demands on cognitive skills because they have to recognize a number of other individuals, to remember who has given favours to whom, who has alliances with whom and most importantly how it would appear from someone else’s perspective. The theory would predict that there is a strong association between the time spent grooming, possession of theory of mind and intelligence. There are however difficulties with testing these ideas, which are how an animals intelligence would be measured. In human intelligence it is difficult to measure because of the controversy of whether it is possible to construct a way of measuring intelligence, which is culture fair (i.e. not biased towards a particular culture).
According the Ridley (1993) the evolution of human intelligence was the result of sexual competition between individuals of the same sex. The fact that the brain has tripled in size in three million years is very fast in evolutionary terms. One force that can bring such rapid change is sexual selection. Miller (2000) suggests that a similar process of which has left the peacock with a long tail has also shaped human brains. It has been proposed that humans will have considered cognitive abilities as well as other adaptive criteria such as health and fitness.
Females chose males who were amusing, inventive and creative brains, and this shows that art, music and literature function as a courtship display. Female brain size has increased in order to decode and appreciate the male’s new abilities. Support for the sexiness of intelligence comes from research investigating what characteristics people seek in a partner and it was found that intelligence came consistently at the top of the list.
In the EEA meat was an important source of saturated fat. Stanford believes that strategic sharing of meat paved the way for human intelligence, as it will have forged alliances, persuaded females to mate (i.e. ‘meat for sex hypothesis’). Strategic meat sharing requires considerable cognitive abilities because males would have to keep a running score of debts, credits and relationships. Evidence from the animal kingdom supports the meat for sex hypothesis, because male chimps use meat to entice females, often withholding it until mating and when begging for meat receptive females have more success than non-receptive. Evidence also comes from human societies, in terms of the Ache in Paraguay. Mitani and Watts (2001)showed that male chimps share with each other more than females due to alliances rather than sex.
It can be concluded that intelligence is a key component in the adaptability of a species. Three main theories have been proposed for the evolution of intelligence, which are, ecological, social and sexual selection. At this time the social theory provides the more plausible explanation of intelligence. However all of these ideas are continuing to be researched, so that an even more reliable explanation of the evolution of intelligence can be produced in the near future.