Evolution, natural selection and aggression Flashcards
What is evolution?
The changes in inherited characteristics in a biological population over successive generations
What is natural selection?
The major process that explains evolution whereby inherited traits that enhance an animal’s reproductive success are passed on to the next generation and thus “selected” whereas animals without such traits are less successful at reproduction and their traits are not selected.
What is sexual selection?
An evolutionary explanation of partner preference. Attributes or behaviours that increase reproductive success are passed on and may become exaggerated over succeeding generations of offspring.
Why does evolution happen?
It happens because genetic differences between organisms create variation.
How are genetic differences created?
Such variation arises because genes from parents are combined and also due to spontaneous mutations in genes.
What is natural selection most commonly referred to?
Survival of the fittest
When does natural selection happen?
When there is competition for scarce resources (including reproductive males)
Why do males “guard their partners”?
Mate retention strategies are often aggressive behaviours men use to retain their partners and prevent them from “straying”.
What does guarding your offspring mean? And why do we do it?
Human parents will direct aggressive acts against other people (or animals) that threaten their children. This Aggression is adaptive because each child is a valuable genetic commodity. Aggression is a way for parents to protect their “investment” increasing the offspring reproductive chances later in life.
How does the evolutionary theory explain gender differences?
Females who are cooperative are likely to be naturally selected because cooperation helps them protect themselves and their offspring as a group. Therefore, reduced aggression is selected in females. In contrast males who are aggressive are more likely to be naturally selected because they make better hunters.
Evidence from studies of chimpanzees supports this pattern in gender differenct
What example shows that the evolutionary theory not show cultural differences?
Amongst the !Kung San people of the Kalahari aggression is discouraged from childhood and is therfore rare. In contrast the Yanomamu or Venezuela and Brazil have been describes as “the fierce people”- aggression appears to be an accepted behaviour to gain status in their structured society
What is Anisogamy?
Males produce many sperm at low physiological cost whereas females produce few eggs at high physiological cost.
What is a genotype?
An individual’s unique genetic makeup, or the speicfic combination of genes they inherit, which are coded in their chromosomes and fixed at conception.
What is phenotype?
The observable characteristics or traits of an individual, including physical traits, behaviours, and even health conditions, which are the result of the interaction between their genes and their environment.
What is Fisher’s hypothesis?
Females are attracted to males that have survival value. E.g. in birds, males with long tailes are better at flying and finding food so a female will prefer her offspring to inherit this trait. With each generation, this chaeracterisitc becomes more exaggerated.
What is the “old brain”?
- Sometimes psychologists split the brain into parts, one being the ‘old brain’ which is said to be the privative part of the brain, driven by instincts we have developed over our evolutionary history.
- The old brain is mostly the limbic system and prefrontal cortex.
- This ability to ignore our instincts and choose whether or not to act aggressively is what enables humans to live together in complex groupings- another survival trait.
What is an evolutionary theory to explain social aggression?
One explanation for social aggression is that the brain evolved in response to our complex social organisation. Individuals who were better at manipulating others to meet their own needs were more likely to survive. The process of manipulation involves forming alliances, devising strategies, carrying out plans and keeping track of all people and their relationships in the social group. The bigger the brain, the better-equipped you are to cope with the social mechanisms involved with the survival of species
Why may males express aggression?
- Need to compete with other males for access to choosy females.
- Lower status men are willing to take greater risks by using aggression or face genetic extinction.
- If the female is unfaithful the man faces paternity uncertainly.
Females have parental certainty – they know the child is theirs biologically. - Human males cannot risk wasting investment on offspring who are not their own so they should show more jealous violent aggression relating to female fidelity- both towards the male competitors and their long-term female mates if infidelity is suspected especially if the female is young and reproductively valuable
Why may females show aggression?
- If a male is unfaithful the female partner risks losing his time, resources, energy, protection and commitment to her children.
- Human females can always guarantee that their offspring are their own and compete with other females for the quality of men rather than for the availability.
- Women take fewer risk with violence and use more indirect form of aggression.
- Females become jealous if the man is with another woman. This suggests he has been sexually unfaithful and her survival and her child’s survival are at risk. She will be jealous if she suspects he is behaving in this way, which leads to aggression.
How does Brendgen critcise and support the evolutionary explanation?
- Found social aggression had an environmental link, with a higher concordance amongst non-shared environmental factors for both Mz and Dz twins
+ Found a higher concordance between Mz twins for physical aggression = genetic link to the behaviour which will have been inherited from parents gene pool
How does David Buss support the theory of aggression in evolution?
He identified 2 mate retnetion strategies used by males to control their partners: direct guarding of the female restricts her movements; negative inducesments to prevent her straying include things like financial control or the threat of violents. This could be done as there is paternity uncertainty and they dont want to wast resources
How does the theroy of evolution have scientific credibility?
The scientific method is used in research to support the theory. Darwin took careful observations and observed visible behaviour, which could be confirmed by others. There is scientific credibility in the idea of evolution and Darwin spent years making his theory clear and listing the evidence in its support.
