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This week I have been continuing to read Carlson et al (2007)focusing on scientific methods used in psychology. I have also been reading ‘Psychology’ by Martin, Carlson and Buskist (2006) to gain an understanding of evolution, genetics, and behaviour.

The Scientific Method in Psychology
Psychologists carry out three main types of scientific research: Naturalistic or Clinical Observation, correlational studies and experiments. The latter makes things happen and allows us to observe the results.’ This allows the person carrying out the experiment to identify the relationship between cause and effect. The researcher must first understand the problem they are trying to solve and come up with a hypothesis based on information gathered through naturalistic observations and previous research/experiments. When performing an experiment Carlson et al (2007) explains how independent variables are manipulated and dependant variables measured/observed.

Psychology – Evolution, genetics, and behaviour

Biological Evolution
A key, influential figure in the theory of psychology is Charles Darwin. Following his voyage on the Beagle and his thinking and research of artificial selection, he argued that organisms adapt to their environment by biological means. Darwin was not the first person to suggest a theory of evolution but he was the first to provide evidence. He believed that ‘selection was the foundation of mans success in making useful races of animals and plants’ (Darwin, 1887). However, Darwin was unable to work out how selection could be applied to organisms living in nature. It was after his reading of Malthus’s population that Darwin suggested that ‘selection’ would result in the production of new species – this was the idea of natural selection – in any population some members of a species will produce more offspring then other members. Some animals are likely to live longer and produce more offspring if they have characteristics that help them to survive or easily adjust to alterations to the environment. There are two key ideas central to Darwin’s theory of evolution:

Adaptation – the capability of a species to adapt to changes in the environment
Natural Selection – the process where differences in some species will be transferred from one generation to the next.

Darwin’s theory has four fundamental premises:
1. Plant and animal communities change over a period of time with some becoming extinct and other new forms emerging
2. The evolutionary process is steady and continuous with new species emerging slow and steadily.
3. Organisms descend from an original and common ancestor.
4. Natural selection also aims to maintain a status quo under constant environmental conditions and not just cause alterations in populations during changing environmental conditions.

There are two aspects of natural selection that determine whether an animal will be successful in reproducing:

Variation – this includes differences in physical characteristics (i.e. size, strength) and behavioural characteristics (i.e. intelligence, sociability) between members of a species. These differences are as a result of genotypes(genetic differences) and phenotypes (produced as a result of the interaction of its genotype with the environment).

Competition – because individuals of the same species share the same environment competition for food, habitats, and mates is to be expected. For example if a bird finds a mate then that is one less mate for other birds.
So basically, it can be said that natural selection works because members of different species have different phenotypes and these are caused by different genotypes, which some successful members will pass (their genes) to the next generation. Therefore competition for resources such as food will only allow the best adapted phenotypes to survive, and hence evolutionary change.

Natural Selection and Human Evolution
Ok so from this I have gained an understanding that there are some ‘pieces of the puzzle’ that we may never be able to find, and not all our questions on the evolution of humans will be answered. Natural selection has favoured two important human characteristics:

Bipedalism – the ability to walk upright on two feet – evolved over 4million years ago and meant ancestors had more mobility and meant the hands were free for grabbing, holding and throwing objects.

Encephalisation – an increase in brain size
The combination of these two characteristics led to improvements in tool making, food gathering and hunting. It further allowed humans to make use of new environments and develop well organised communities. These advances helped humans live longer. This also meant that because people were living longer older members of communities shared their knowledge to younger members through language. It meant others could be warned of potential danger, but also used to communicate a good location for hunting.
Most importantly, it reinforced the basis upon which all human cultures are built. Cultural evolution –i.e. changes in cultures as a result of changes in the environment over a period of time, has only be made possible because humans have been genetically gifted with a capacity for learning and language.

Heredity and Genetics
Genetics – the study of ‘the structure and function of genes in the way in which genes are passed from one generation to the next.’ This also includes how genetic make up influences physical and behavioural characteristics. Also related is Heredity – ‘traits and tendencies inherited from a person’s parents and other biological ancestors.’ Basic principles of genetics:
Genes – parts of genetic material known as DNA (deoxyribonucleic acid). Our development and behaviour is only influenced through protein synthesis. Genes can be found in chromosomes which contain DNA and can be found in all cells. Every set of chromosomes contains a different combination of genes. As humans we inherit 23 individual chromosomes from our parents (i.e. thousands of genes) – so 23 pairs (46 in total). So our genetic blueprint is as a result of a combination of genetic instructions that our parents inherited from their parents previously.

Genetic diversity
Only identical twins are considered to be genetically identical. When changes in an environment occur, genetically diverse species have more of a chance of surviving and adapting to the new environment because some members of a species may have genes that will enable this survival.

The expression of a gene is affected by a person’s sex, interactions with other genes, and the conditions of the environment in which the individual lives. Mutation or chromosomal aberrations cause changes in genetic material.

Mutations – accidental changes in the DNA code, can have harmful effects or can result in characteristics that can benefit certain environments, they happen spontaneously or as a consequence of human related factors e.g. radiation.
E.g. Haemophilia – gene arose with Queen Victoria (1819-1901), more likely to bleed even from small, minor injuries.

Chromosomal aberration – alterations in the total number of chromosomes or in parts of chromosomesE.g. Down’s syndrome –have different physical characteristics such as being shorter, having a rounder face, broader skulls, and demonstrate impaired physical, psychomotor and cognitive development.

Behaviour genetics
Is the study of the effects of genetic influences on behaviour (heritability). It helps to provide reasoning for why people differ. Psychologists explore the relationship between genes and behaviour in human beings using artificial selection studies of identical twins, animals, and adoption.