Human Intelligence


Human intelligence

Key Terms:

  • Evolution - the process by which the genetic composition of a population changes over successive generations through the process of natural selection.
  • Ecological demands - the features of an animal's environment providing a survival value.
  • Social complexity - the amount of organisation and order amoung animal social groupings.
  • Genetic factors - developmental influences passed through heredity.
  • Heritability - the degree to which a quality or behaviour is genetically determined.
  • Environmental factors - developmental influences aquired through experience.
  • Cultural influences - development factors originating from a cutural grouping.

Evolutionary Factors in the Development of Human Intelligence

  • Human intelligence is said to have evolved, as fossil evidence indicates that early humans did not have the brain capacity and functions of modern-day humans.
  • The evolutionary approach believes that human intelligence evolved due to the demands of an ever-changing environment, creating selective pressure for increased intelligence.
  • Humans needed to contend with the ecological challenged of foraging for food, dealing with increasing social complexity and the need to develop an more advanced brain.

Ecological Demands:

  • Intelligence is perceived as prospering within a given environment, especially by demonstrating foraging abilities.
  • Humans adapted to global cooling in Palaeolithic times by finding food and exploiting new environments, due to the development of higher mental skill, like co-operative hunting and tool use.
  • With plants only available periodically, hunting meat become a neccessity, as meat is calorie-rich and hunting was less labour-intensive than foraging for other foodstuffs.
  • Being a good forager required higher levels of intelligence, which increased survival rates, leading to individuals being naturally selected.

Foraging Hypothesis:

  • Milton (1988) argued that increased intellect occured due to demands of foraging.
  • Fruits grow seasonally and are distributed unpredictably over large areas; the development of mental maps helped fruit eaters to know when and where to look for food, and monitoring the avilability of different fruits helped to develop this ability.
  • This was achieved by natural selection acting to create advanced memory skills and foraging techniques, attainted by the development of more advanced brains.
  • Gibson (1987) proposed the food extraction hypothesis - seeing the need to find hidden foods as driving the evolution of intelligence.
  • Hidden foods, such as roots, are difficult to locate and extract, but provide rich nutrition, especially during times of scarcity.
  • The need for cognitive processing, manual dexterity and tool use created selective pressure for a larger cortex, which allowed juvenile animals to develop advanced imitative abilities.
  • Parker (1996) proposed an extension to the food extraction hypothesis, apprenticeship, where co-evolution of a set of interrelated cognitive abilites -such as imitation, intelligent tool use, self-awareness and demonstrating teaching - enabled immature hominid apes to learn tool-based extractive foraging skills and ease maternal pressures by boosting an offspring's ability to learn these talents.

Research on the Foraging Hypothesis:

  • Milton (1988) - found that fruit eating spiders have greater relative brain size, larger hime ranges and more protracted learning/dependency period, supporting the idea of greated intelligence evolving in fruit eaters.
  • Barton (1996) - found that fruit eating


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