H3. Evolution, Genes, Environment and Behaviour

Evolution (biological)

Gradual change over time in organic life from one form into another

Natural selection

Characteristics that increase the likelihood of survival and reproduction within a particular environment will be preserved in the population and therefore become more frequent over time

This process is based upon 3 factors:

1. Biological variation

2. High reproduction rates and the fact that not all members of a population survive

3. Competition over limited resources

Mutations

Random events and accidents in gene reproduction during the division of cells

Dominant (allele)

The particular characteristic that it controls will be displayed → standardized form of notation: represented by capital letters

Recessive (allele)

The characteristic will not show up unless the partner gene inherited from the other parent is also recessive → standardized form of notation: represented by lower case

Allele

Alternative forms of a gene that produce different characteristics

Polygenic transmission

When a number of gene pairs combine their influences to create a single phenotypic trait

Genotype

The specific and complete genetic make-up of the individual

Phenotype

The individual’s outward observable characteristics

Adaptations

Physical or behavioural changes that allow organisms to meet recurring environmental challenges to their survival, thereby increasing their reproductive ability

Genes

Functional segments of the long molecule deoxyribonucleic acid, or DNA, that code for manufacturing specific proteins

Chromosome

A single- or double-stranded structure comprising proteins and deoxyribonucleic acid (DNA)

Somatic

A somatic cell is any cell forming the body of an organism; they do not contain reproductive cells

Diploid (number of chromosomes)

The number of chromosomes carried by a cell with two complete sets of chromosomes (one from each parent) is called the diploid number of chromosomes

Gametes

Sex cells (eggs and sperm)

Haploid (number of chromosomes)

The number of chromosomes carried by a gamete cell (sex cell (eggs and sperm)), which is half the number of chromosomes carried in a typical cell, is called the haploid number of chromosomes

Zygote

A fertilized egg containing 46 pairs of chromosomes

Nucleotides

Nitrogenous base, phosphate and sugar groups

Inherited behavioural adaptations

Traits that organisms are born with that help promote their chances of survival and reproductive success

Fixed action pattern (FAP)

An unlearned response automatically triggered by a particular stimulus

Releasing stimuli

External stimuli that trigger fixed action patterns

Behavioural genetics

A field of psychological science dedicated to investigating how genes and environmental factors interact during the course of development so as to affect behaviour

Degree of relatedness

The proportion of genes we inherit from others by direct common descent (consider the degree of genetic similarity between humans within the proportion of the genome which varies between individual humans)

Shared environment

The environmental factors that certain individuals (e.g., twins) share in common (such as the same parents or physical home environment)

Non-shared environment

The environmental factors that certain individuals (e.g., twins) do not share with each other (such as specific friendship group or unique individual experiences)

Single nucleotide polymorphisms (SNPs)

The units of variation in the genetic code of our DNA

Genome-wide association (GWA) studies

Studies that scan the whole genome of many individuals in order to identify genetic markers for behavioural traits or diseases

Gene chip

A microarray that can sample DNA from an individual to identify the expression of a wide range of genes across the genome

Polygenic score

The summed effect of multiple single nucleotide polymorphisms (SNPs) on a given trait

Adoption study

Studies that make use of the fact that adopted children share a greater proportion of their genes with their biological parents and siblings than their adopted parents and siblings, to draw conclusions about the relative roles of genes and the environment in psychological and behavioural traits

Twin studies

Studies that compare trait similarities in identical and fraternal twins

Concordance rates

Statistical expression of the probability that two individuals with shared genes will share a particular trait to the same degree

Equal environments assumption

The assumption that the environments that identical and fraternal twins share are equally similar (However, there are potential problems here. For instance, because identical twins are more similar to one another in behaviour and appearance than are fraternal twins, they may be treated more alike and therefore share a more similar environment. This might lead to twin studies overestimating the heritability of behavioural or psychological traits)

Heritability coefficient

Estimates the extent to which the differences, or variation, in a specific phenotypic characteristic within a group of people can be attributed to their differing genes

The Big Five (OCEAN)

1. Openness to experience (imaginative, artistically sensitive, refined VS unreflective, crude and boorish, lacking in intellectual curiosity)

2. Conscientiousness (responsible, goal-directed, dependable VS undependable, careless, irresponsible)

3. Extraversion – introversion (sociable, outgoing, adventuresome, spontaneous VS quiet, aloof, inhibited, solitary)

4. Agreeableness (co-operative, helpful, good natured VS antagonistic, unco-operative, suspicious)

5. Neuroticism (worrying, anxious, emotionally unstable VS well adjusted, secure, calm)

Reaction range

The range of possibilities – the upper and lower limits – that the genetic code allow

Passive gene-environment correlation

An association between the child’s genetic inheritance and the environment in which they are raised (genes shared by parents and children may be expressed in the parents’ behaviours and the environment they create) (passive because this correlation does not result from any action of the individual themselves)

Example: A child born to highly intelligent parents is also likely to have good intellectual potential. If, because of their own interests in intellectual pursuits, these parents provide an intellectually stimulating environment with lots of books, educational toys, computers, and so on, this environment may help foster the development of mental skills that fall at the top of the child’s reaction range. The resulting bright child is thus a product both of the genes shared with the parents and the enriching environment they provide.

Evocative gene-environment correlation

Where a child’s genetically influenced behaviours evoke certain responses from others in their environment

Example: Some children are very cuddly, sociable and outgoing almost from birth, whereas others are more aloof, shy and do not like to be touched or approached. These characteristics are in part genetically based (Kagan, 1999; Plomin et al., 2007). Think about how you would be most likely to respond to these two types of babies. The outgoing children are likely to be cuddled by their parents and evoke lots of friendly responses from others as they mature, creating an environment that supports and strengthens their sociable and extraverted tendencies. In contrast, shy, aloof children typically evoke less positive reactions from others, and this self-created environment may strengthen their genotypically influenced tendency to withdraw from social contact. However, a behaviour pattern can also evoke an environment that counteracts the genetically favoured trait and discourages its expression. We know, for example, that activity level has moderate heritability of around .40 (Table 3.1). Thus, parents of highly active, ‘off the wall’ children may try to get them to sit still and calm down, or those of inactive children may press them into lots of physical activities designed to increase physical well-being, in both instances opposing the natural tendencies of the children. Thus, the environment may either support or discourage the expression of a person’s genotype

Active gene-environment correlation

An association between genotype and the environments that genotype leads someone to seek out

Example: A large, aggressive boy may be attracted to competitive sports with lots of physical contact, a highly intelligent child will seek out intellectually stimulating environments, and a shy, introverted child may shun social events and prefer solitary activities or a small number of friends. These varied self-selected environments may have very different effects on subsequent development.

Evolutionary psychology

A growing discipline that seeks to explain how evolution shaped modern human behaviour

Kin selection

An evolutionary strategy in which behaviours are selected that favour the reproductive success of an organism’s relatives even if that is at a cost to that organism’s own survival and reproduction

Reciprocal altruism

A behaviour in an organism that reduces its fitness to survive and reproduce while increasing another organism’s fitness; undertaken with the expectation that the favour will be returned later

Evolutionary personality theory

Looks for the origin of presumably universal personality traits in the adaptive demands of our species’ evolutionary history

Strategic pluralism

The idea that multiple – even contradictory – behavioural strategies might be adaptive in certain environments and would therefore be maintained through natural selection