Week 2

Evolution as the Scientific Foundation of Human Nature

‘Human nature’ is a term referring to what it is to be human, or the essence of humanity.
The characteristics, such ad ways of thinking, feeling, and acting, which humans are said to have naturally.
Much like ‘cat nature’ vs ‘dog nature’.

Creationism

Scientific thinking about species before Darwin was dominated by creationism - the belief that God had created different species as they appear today and that each species was immutable, their characteristics were fixed and unchangeable.
Darwin’s evolutionary theory, in contrast, was a theory of species changing over time.

Natural Selection

All species are capable of overproducing offspring.
However, environmental pressures can threaten survival.
A struggle for existence among individuals ensues and some reproduce, others do not.
Individuals differ on traits (i.e., adaptations) that enable them to survive and reproduce.
Those best suited to the prevailing environment will leave the most offspring (i.e., the “fit” to the environment).
These traits are passed on the the next generation.
The genetic make up of subsequent generations will be different to the previous generation, because the next generation only includes genes passed on from the best reproducers.
Natural selection is not random - it is this process of passing on genes that are most suited to the environment over generations.

Evolution as Adaptation

Evolution is an adaptation to the environment.
It is not a force that pushes a species towards ever-increasing levels of complexity and refinement.
However, over time new traits emerge and are passed on and this may lead to what appears to be a ‘higher’ level of evolution.
But many of the traits from previous generations, our ancestors, remain encoded within us.

Homo Delinquens

Cesare Lombroso drew on the idea of evolution as leading to a higher level to develop a theory of criminal behaviour.
He saw European adult males as the highest form of evolved life.
According to Lombroso, born criminals have certain physical characteristics or abnormalities that make them different.
These abnormalities were “atavistic” characteristics which he believed occurred because offenders were the products of an earlier stage human evolution, a stage where more primitive humans and apes existed.
Lombroso believed degeneration affected criminals especially, in particular the “born delinquent” whose development had stopped at an early stage, making them the most “atavistic” types of human being.

Gene-Based Evolutionary Theory

Darwin was able to develop a logic for evolution as a process, but he had no idea of he mechanisms that underpin evolution.
This required the discovery of genes and the study of genetics.

Evolution and Genes - Mutations

While offspring have a combination of perfect replicas of genetic material passed down from their parents, occasionally there is a genetic mutation and an individual acquires a new trait.
If the mutation results in a trait that makes the individual more successful in reproducing, the gene will be passed down and over time more and more members of the species will have that gene.
Genetic mutations are the basis of evolution.

The Selfish Gene

From an evolutionary perspective, genes are the centre of the universe.
They are immortal - so long as organisms exist and inherit them, and pass them on to the next generation.

Evolution and Behaviour

From an evolutionary perspective, all social behaviour has the ultimate aim of ensuring an organisms genes are passed on the next generation.
The logic of the ‘selfish gene’ applies to every species.
Therefore, sociobiologists are interested in the social behaviours that are common across species.

Altruism

Kin Selection:

Act altruistically in service of genetic relatives (offspring and sometimes other relatives) - referred to as ‘inclusive fitness’.

Reciprocal Altruism:

Individuals help others with the expectation of receiving help in return at a later time.
It is a form of cooperation that benefits both parties involved.

Parental Investment

Trivers’ (1972) parental investment and sexual selection theory.
Parent who invests more will be more choosy in selecting a mate.
Females look for a partner who can provide resources and be relied upon to a make long-term child rearing commitment.
Males are more indiscriminate than females in sexual selection (and are likely to select multiple partners); but must compete other males for mating rights.

Evolutionary Psychology

Central Ideas:

The original adaptive purpose of evolved psychological mechanisms need not still be valid.
Evolved psychological mechanisms do not operate at a conscious level.
Evolved psychological mechanisms do not furnish humans with a repertoire of behavioural responses that are fixed at birth and that set individuals along a predestined pathway.

Crime-Focused Evolutionary Approaches

Criminal behaviours were adaptive responses at some point in our evolutionary history.
Evolutionary origins remain encoded in human psychological make up (evolved psychological mechanisms).

Violent Offending

Evolutionary psychology does not propose human violence as a generalised aggressive impulse that is expressed indiscriminately.
The issue is whether the circumstances in which human violence occurs today indicate that the violence had its roots as an adaptive strategy that increased reproductive success.

Power and Status:

Most assaults and homicides involve male perpetrators and victims.
Male violence gives a perpetrator a competitive advantage over rival males.
Aggressive makes could take resources from weaker males, defend themselves from an attack.
This display of power and the status that arises could attract and keep more sexual partners.
Male violence today is often about asserting status or restoring honour and reputation.

Sexual Proprietariness:

Males are possessive of their mates due to uncertainty about parentage, leading to jealousy and suspicion of infidelity.
This can result in violent behaviour from males and retaliatory responses from females.

Genetic Relatedness:

Intrafamilial homicide was eleven-times more likely to involve non-genetic relatives than genetic relatives.
Adopted and step-children are often victims of abuse due to evolutionary pressures for reduced parental investment.

Rape

Prevalence and Context:

Rape is primarily committed by males and is not unique to humans; it also occurs in other species, such as orangutans.

Rape-Specific Hypothesis:

Suggests rape evolved due to differences in reproductive strategies between males and females.
Males, able to reproduce with minimal parental investment, may use rape as a strategy to increase reproductive success.
Males who rape may pass on their genes more effectively, increasing their representation in future generations.
Severe punishments are needed to prevent the spread of genes associated with rape.
Females are more selective in mates due to their limited reproductive capacity, leading to potential forced copulation by some males.

By-Product Hypothesis:

Rape is a side effect of other male sexual adaptations, such as strong sex drive or promiscuity, rather than a specific reproductive strategy.

Spousal Abuse

Spousal abuse can be seen as an evolved aggressive behaviour.
Abuse by women may have evolved to prevent abandonment and ensure continued paternal investment in offspring.
Abuse by men is often driven by sexual jealousy, particularly related to infidelity or suspected infidelity.
In ancestral environments, spousal abuse or violence may have been adaptive for men to prevent cuckoldry or losing a fertile partner.

Cuckoldry:

Males face risks from raising another man's child due to paternity uncertainty. Consequences include wasted resources, loss of potential future offspring, and damaged reputation.
To avoid cuckoldry and ensure paternity, men may exhibit extreme behaviours, including abuse.

Child Abuse and Neglect

It would seem counterproductive, from an evolutionary perspective, to harm one’s own child.
There are, however, at least four conditions under which parental abuse, parental neglect, and/or even murdering one’s own child could have evolved.

Resource Scarcity and Family Size:

Larger families with multiple children may experience higher rates of abuse and neglect.
Limited resources and caregiving capacity lead to insufficient care for each child.
Therefore, there is an increased likelihood of neglect or abuse when resources are stretched thin.

Single-Parent Households:

Abuse and neglect is more common in single-parent families.
An absence of one parent may reduce the remaining parent’s investment in the child.
Lower overall resources and care provided to the child.

Nonbiological vs. Biological Children:

Higher likelihood of abuse/neglect towards stepchildren or nonbiological children.
Harming biological children directly affects gene transmission.
Nonbiological children do not share the same evolutionary stakes, making them more vulnerable.

Children Perceived as Less Reproductively Valuable:

Increased risk of abuse or neglect for children seen as unlikely to reproduce (e.g., those with severe health issues or deformities).
Investment in less viable offspring may be perceived as less worthwhile.

Homicide

Daly and Wilson (1988) - Homicide as a By-Product:

Homicide is not an adaptation but a by-product of evolved mechanisms for non-lethal aggression, such as violence.
Homicide results from mechanisms that evolved for other purposes, such as controlling sexual behaviour through violence.
This perspective does not account for premeditated homicides.

Buss and Duntley (2002) - Homicide as an Evolved Response:

Homicide itself is an evolved adaptation designed to solve specific adaptive problems.
Homicide mechanisms are triggered under particular circumstances where killing may offer reproductive or survival benefits.
Generally, the costs of killing outweigh the benefits, but in certain contexts, killing can be advantageous.
Adaptive circumstances involve gaining reproductive advantage by eliminating competitors, accessing resources and mates, protecting oneself and others, enhancing social status, defending territory, allocating resources wisely, and avoiding investment in non-reproductive or genetically unfit individuals.

General Criminal Behaviour

r/K Theory:

r/K selection theory describes reproductive strategies on a continuum from r-strategists (high reproductive rates, low parental investment) to K-strategists (low reproductive rates, high parental investment).
r-strategists produce many offspring with minimal resources for each; suited to environments with abundant resources and low competition.
K-strategists invest significant resources in fewer offspring; suited to competitive environments with scarce resources.
Humans generally follow a K-strategy, though males are more r-selected due to higher reproductive capacity.
Individuals may shift from r-strategy in youth to K-strategy in later life.
R-strategists may exhibit behaviours associated with criminal activities, such as having many siblings, single-parent homes, and lower parental investment.

Cheater Theory:

Criminal behaviour as an evolved male strategy to maximise reproductive success.
Males pursue multiple partners (“cads”) for reproductive success; often use deception or coercion.
“Cads” are characterised by antisocial traits, while “dads” provide substantial parental investment.
Females are more selective due to biological constraints like pregnancy and lactation and a preference for partners providing resources.
Cads and antisocial traits overlap, with cads engaging in criminal behaviours like deception and coercion.

Conditional Adaptation Theory:

Reproductive strategies adapt based on environmental factors and early-life experiences.
Absence of a father or unstable environments may lead females to adopt promiscuous strategies, while stable environments encourage selective mating.
Individuals in unstable conditions are more likely to engage in risky lifestyles and criminal behaviour.

Alternative Adaptation Theory:

Genetic differences influence where individuals fall on the continuum of mating effort vs parenting effort.
Traits like risk-taking and deception are linked to higher criminal behaviour.
Traits like compassion and selflessness are linked to prosocial behaviour.
Higher intelligence is associated with better parenting effort and prosocial behaviour, while lower intelligence correlates with higher mating effort and criminal behaviour.

Staying Alive Theory:

Women’s criminal behaviour is less frequent due to evolutionary pressures to avoid risky activities and ensure survival for offspring.
Fear helps women avoid dangerous situations, focusing on securing resources through partner selection rather than competing directly.
Women’s lower criminal involvement is attributed to higher fear thresholds and evolutionary pressure to avoid risky behaviours to protect offspring.

Evolutionary Neuroandrogenic Theory (ENA):

Higher male criminal behaviour is explained by evolutionary and hormonal factors.
Competitive traits in males are favoured due to female preferences for resource-providing partners.
Testosterone influences aggressive and victimising behaviours through suboptimal arousal, leading to aggression, susceptibility to seizures causing impulsive rage, and a rightward shift enhancing spatial reasoning but reducing language skills.
Higher intelligence and better planning reduce likelihood of criminal behaviour; low IQ and poor learning contribute to criminal tendencies.

Offender-Focused Evolutionary Approaches

Individual Differences in Offending:

Variation in offending explained by demographic and environmental factors - same underlying psychological mechanisms.
Treat criminal behaviour as an alternative strategy (i.e., variation in response to adaptive problem with genetic bases) - genetic variation between criminals and non-criminals.

Hiding Criminality as an Adaptive Strategy

Blatant cheating is easy to detect.
Criminals therefore mimic law-abiding people to hide their criminality.
Psychopaths exhibit a superficial charm, learning to mimic emotions like empathy despite not feeling them, as they understand that their callousness can alienate others.

Demographic Variations

Sex:

Biological factor (not gender).
Males commit ~80% of crimes.
Males and females evolve different adaptive solutions due to different adaptive problems.

Age:

The age-crime curve shows that offending typically starts after puberty and reaches its peak in the late teens.
Males tend to become more present-focused and risk-accepting when competing for a mate, engaging in behaviours like fighting rivals, killing, and stealing to gather resources.
Fall in crime with age due to marriage and/or birth of a child.