Pheromones

• Pheromones - definition


  Are a chemical substance produced and released into the environment by an animal affecting the behaviour or physiology of others of its own species.
• pheromones effects

  • female menstrual cycle
  • olfactory recognition of new-born by its mother
  • people my give off different odours based on mood

  Although there is some evidence, nothing is conclusive on whether, or not humans have functional pheromones.
• it isn't clear yet if pheromones signal btween humans the same way as with animals, e.g. mating and aggression
• types of pheromones in animals

  1. primer pheromones
  2. signalling pheromones
• primer pheromones


  are pheromones that cause slow, long-term physiological changes such as hormonal effects.
• signalling pheromones


  are pheromones that produce rapid behavioural effects, such as mating.
• info

  • in humans, there is some evidence of primer pheromones, but there is equal amount of opposite evidence
  • no human pheromone has yet been found
  • humans lack of functional vomeronasal organ (VNO) which is essentially how one would 'smell' a pheromone. Without the anatomical ability to detect the scent of a pheromone, it is unclear how as pheromone would affect human behaviour.
• Major Histocompatibility Complex (MHC)

  • One aspect of natural selection would be to make sure that the immune system of any offspring would be as effective as possible
  • research on the MHC looks at the role of genes linked to the immune system in human attraction. MHC has influence on the human smell.
  • researchers are devided on whether MHC could be an example of a human pheromone.
• Sexual Selection in animal models

  • a female mouse chooses a mate whose major MHC genes are least similar to her owmn - same may go for human females.
  • MHC genes are co-dominant, so the more diverse the MHC genes of the parents, the stronger the immune system of the offspring.
  • it would obviously be beneficial, therefore, to have evolved systems of recognitizing individuals with different MHC genes, and preferentially selecting them as sexual partners.
• co-dominant


  means that both sets of inherited genes have an effect on the child's immune system.