The Biological Approach - Evolution

Charles Darwin proposed that all species have evolved over time from common ancestors through thr process of NATURAL SELECTION. 

Natural selection in bioloical psychology = Behaviours that help us survive are more likely to be passed on to future generations, rather than the ones that do not help is survive

Darwin also proposed that humans are a product of evolution and are closely related to other primates,such as monkeys and apes. Humans have evolved over millions of years from the same primate ancestors, just like other mammals - WHICH IS WHY BIOLOGICAL PSYCHOLOGISTS BELIEVE IT MAKES SENSE TO STUDY ANIMAL SPECIES AND MAKE GENERALISATIONS TO HUMAN BEHAVIOUR.

EVOLUTION = referrs to the change of successive generations of the characteristics of a population

In the animal kingdom male species display traits such as mating calls and colourful plummage in order to attract mates and successfully reproduce. 

It is well known that animal species defend their territory through aggression towards their own species. Territory is neccessary for survival and humans often resort to violence to defend their territrory.

Darwin provided evidence that limited number of facial expressions are shown in the same ways in different cultures. Darwin claimed that emotional expressions such as happiness (smiling), displeasment (frowning) and surprise (wide eyes) have resulted from evolution and are genetically 'wired in' humans. 

This can be seen in babies when something touches their face or mouth and they turn their heads. This can also aid breastfeeding which is needed in order to survive - hence is a behaviour of natural selection and has been passed on through generations.