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Biopsych - Evolution - Y2 - Coggle Diagram
Biopsych - Evolution - Y2
Evolutionary explanations of animal behaviour
Pre-Darwinian ideas about evolution
Many pre-existing theories of evolution: pre-1859 -
Chambers (1802-1871) - theory of evolution - 'Vestiges of natural history of creation but inadequate account, as it assumed monstrous births and did not explain adaptation processes
Erasmus Darwin - all warm-blooded organisms come from the same single living filament
Lamarck (1744-1829) - his theory of evolution or transformation involved inheritance of acquired characteristics
-> An organism can pass on characteristics to its offspring that it acquired during its lifetime
-> Change through disuse of an organ - e.g. a giraffe stretched its neck, causing a nervous fluid to flow into the neck and elongate it, and thus the offspring would inherit longer necks, with further stretching elongating it over generations
-> Organs also shrink if not used
-> Use it or lose it principle of evolution
-> Organisms become more complex over time
Charles Darwin - 1809-1882
One of the most influential theories in all science - On the Origin of Species - 1859
Darwin was the first to collect evidence and propose sound theory for how animals evolve
Darwin's theory of natural selection
The struggle for existence:
Assumes that the potential population vastly outstrips the environment's means for support
Struggle occurs between -
-> Individuals within species
-> Between species
-> With the environment
As many more individuals of a species are born than can survive, there is a struggle for existence - any being, under the complex and varying conditions of life, will have a better chance of surviving with benefitting traits, and thus be naturally selected
From the strong principle of inheritance, selected variety will propagate its new and modified form - Darwin
Preservation of favourable variations and the rejection of injurious variations, is called natural selection
3 essential conditions
-> Variation
-> Selection
-> Inheritance
Evolution of primate species - Lewin (1993)
-> Humans are in the family tree of great apes
-> Humans and chimps are closer genetically than chimps are with gorillas
Migration of Homo sapiens -
-> Moved from central Africa to outer regions of Africa, India and Australia
-> Central Europe to the rest of Europe
-> Central Asia to the Americans
-> Removed competition within ecosystems, creates better niches
Evidence for the mutability of species, supporting Darwin's theory:
Fossil records
Common features of embryological development across species
Physiological and cognitive similarities between animals - tools, communication, protection, social relationship - formation of groups
Changes possible through selective breeding
Dating fossils - three approaches
Relative dating (Alemseged et al, 2006) -> putting geological events in order without knowing the exact date
Lucy - 3 million year old girl, aged 3 - discovery of hominin skeleton, oldest biped found and her skeleton is best evidence for what we looked like
Numerical ageing -> use estimated date of geological event to find precise date when fossil lived
Isotope - atoms of the same element with different numbers of neurons
Radioactive decay of elements, e.g. potassium and carbon, occurs at a constant rate - used to date rocks and fossils
Radioactive decay is the change in number of protons, neutrons or both in the nucleus
The atomic nucleus that decays is called the parent isotope - the product of the decay is called the daughter isotope
The ratio of parent and daughter isotopes in a rock sample is used to determine its exact age
Magnetism - using knowledge about changes in Earth's magnetic field over time to date a fossil
Earth's magnetic field has reversed many times in history
Small magnetic minerals in rocks point to the magnetic north
Compare magnetism of fossil against the Geomagnetic Polarity Time Scale
Common features in embryonic development
The process of populating the cortex with neurons is common to most mammals, from rodents to primates (Cahalane et al, 2014)
Changes in brain structure show stable pattern across veterbrates -> the same brain parts become enlarged when overall brain size increases (Yopak et al, 2010) ]
Some animals do not have an intermediate phase in adolescent years, and so they have more rapid brain development
Layers 5 and 6 take longer to develop (102 days in humans, 21 days in rodents)
Bones of the forelimbs
Bones adapt to different functions in the same area for different animals - a dog paw and human arm have similar functions, but different structures (homologus evolution)
Evidence of behaviour changes through selective breeding - Defries et al, 1978
Adaptations - characteristics of living organisms, including their colour, shape, physiology and behaviour
These enable them to survive and reproduce successfully in the environments in which they live
Evidence ->
Making use of existing genetic variation - light and dark forms of the peppered moth (Kettlewell, 1955) - adaptations need to relate to gene survival, unlike the black headed gull colonies and nesting locations
Black head gull colonies and nesting location - nesting centrally more advantageous than on edge because eggs are less likely to get attacked
But is nesting location an adaptation - difficulty to conclude whether it is an adaptation because we do not know if it is genetic
-> Guppies in Trinidad (Endler, 1980) - making use of existing genetic variation - female guppies like bright coloured mates, but this is not advantageous in terms of predators - debated which behaviour is a priority
Using artificially produced variation - black headed gulls remove shells from their nests (Tinbergen et al, 1967)
Hypotheses - eggshells harm young chicks, get in the way of bonding with unhatched eggs, shells harbour disease, attract attention from predators
Comparative method - comparing nests of Kittiwakes and Gulls (Cullen, 1957)
Kittiwakes nest high up in cliffs, to avoid predators
However, gulls position themselves right next to water
Adaptation through design features -
Design the ultimate sonar system for identifying small moving objects v insectivorous bats' echo location systems
Bats use of echo location
Lactose tolerance in humans - Tishkoff et al, 2007 -
Lactose is a protein found in milk
Lactose intolerance begins after weaning due to decreasing levels of the enzyme lactase-phlorizin hydrolase (LPH)
Lactose tolerance emerged as adaptation in individuals in 'pastoralist populations' e.g. northern Europe and parts of Africa
He argued that evolution occurs through natural selection, in which members of each species vary greatly in their structure, physiology and behaviour and that the heritable traits associated with high rates of survival and reproduction are those most likely to be passed onto future generations
Generation after generation, natural selection results in evolution of a species that are better adapted to surviving and reproducing in their particular environmental niche
Natural selection gets its name to emphasise its similarity to the artificial selective breeding practices employed by breeders of domestic animals
Fitness, in the Darwin theory, is the ability of an organism to survive and contribute its genes to the next generation
Some resistance to the theory, but those that understand it do not resist it
Species evolve, or systematically change to produce new ones
Three kinds of evidence -
Documented the evolution of fossil records through progressively more recent geological layers
He described striking structural similarities among living species which suggested common ancestors
Major changes that had occurred in domestic plants and animals by programs of selective breeding
Direct observations of rapid evolution in progress (Barrick and Lenski, 2013) and Grant (1991) who observed changes in finches in the Galapagos Islands after one season of drought
The Selfish Gene Theory - Dawkins (1976)
A 'genes-eyes view' of evolution -
Our bodies (robotic replication machines) are slaves to successful DNA
Here 'selfish' does not necessarily mean selfish behaviour in the normal sense - selfish genes can promote altruism or cooperation if these strategies serve their aim of replication
-> Genes build bodies not for our purpose but for their own purely selfish aim of replication
He suggests genes build bodies not for our purpose but for their own purely selfish aim of replication - to help others and help themselves survive, and own genes survive in others e.g. protecting young offspring at sake of older individuals in the species
Selfish genes in conflict with host organism -
The genes influencing some insect's mating behaviour
Surplus, untranslated DNA
Genes that influence death in ageing - makes room for offspring, benefitting its genes at the cost of the organism
Examples of selfish behaviour -
-> Female preying mantis - eats males, only need offspring and males willingly allows this, as it means passing on of genes
-> Emperor penguins push their friends into the water to see if there are predators
Examples of altruistic behaviour -
-> Worker bees
-> Parental care
-> Small birds give a special alarm call when predators are nearby, warns the other birds
Selfish genes that help organisms survive and reproduce -
Genes that protect organism against disease
Genes that encourage organisms to mate
Criticism of the gene-centric view of evolution -
Gene differences do not cause evolutionary changes in populations, they register those changes
No matter how much power Dawkins wishes to assign to genes, there is one thing he cannot give them - direct visibility to natural selection (Gould, 1990)
The unit of selection is the phenotype because it is phenotypes which interact with the environment at the natural selection interface
Kin recognition
Altruism
Between unrelated individuals -
Explanation - reciprocity of reciprocal altruism (Trivers, 1971)
Between kin - kin selection -
Explanation - increases inclusive fitness (Hamilton, 1964)
Altruism to kin - kin recognition -
3 components -
Establishing identity by a signature or recognition cue
Decoding the signature
Using the information
Possible mechanisms -
-> Phenotype matching
-> Individual allelic recognition model (green beard effect)
-> Purely spatial distribution
Examples from nature -
Brood parasites - birds that lay their eggs in other birds nests - exploit rule-based kin recognition
Gulls do not recognise their own eggs, probably because in nature their eggs cannot go very far, and thus they will happily sit on other bird's eggs or wooden dummies
Guillemots do recognise their eggs (based on speckling pattern)
Important factors -
Degree of relatedness
Certainty about relatedness (to prevent cheats and parasites)
-> Parent-offspring care more common that sibling-sibling care because offspring recognition more certain than sibling
-> Relationship most certain is with the self
Life expectancy of kin
Functions of kin selection -
Altruism towards siblings
Parent-offspring relations
Optimal breeding
Formation of aggregations
Grooming
Alarm signals
Avoidance of cannibalism
Habitat selection
Avoiding inbreeding to encourage genetic diversity
Inclusive fitness - Hamilton, 1964 -
Gene -> help other relatives with same gene + reproduce itself
Relative-helping genes - the effect is to help copies of these genes, and other genes, inside other bodies
Inclusive fitness covers these - own body (direct) and other body (indirect) effects
Hamilton's rule - the conditions under which a gene with social consequences will spread are: rb-c > 0
-> R = relatedness coefficient
-> B = benefit to the relative (in terms of their chances of surviving and reproducing) as a result of help being given
-> C = cost to self as result of doing the helping
Inclusive fitness - highly social insects - bees, wasps, termites and white ants:
Hymenoptera group of ants, wasps and bees - Haplo-diploid inheritance system
-> Queen creates females from egg and sperm copies and creates males from unfertilised eggs
-> Sisters shared 3/4 of their genes
-> All sperm is identical
Relatedness in haplo-diploid inheritance system
-> Daughter - female (0.5), male (1)
-> Son - female (0.5), male (0)
-> Mother - female (0.5), male (1)
-> Father - female (0.5), male (0)
-> Sister - female (0.75), male (0.5)
-> Brother - female (0.25), male (0.5)
Epigenetic mechanisms
Changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the underlying DNA sequence, hence the name epi (over or above) genetics
The heritable, but reversible, regulation of gene expression mediated principally through changes in DNA methylation and chromatin structure (Henikoff and Matzke, 1997)
Neo-Lamarkian - epigenetic changes to DNA
-> Two main components of the epigenetic code -
DNA methylation - methyl marks added to certain DNA bases repress gene activity
Histone modification - a combination of different molecules can attach to the tails of proteins called histones, and these alter the activity of the DNA wrapped around them
Studying the evolution of human cognition - Holloway et al, 2009:
Endocast = internal cast of a hollow object -
The cranium grows in response to brain tissue growth rather than in response to genetic guidance (which is the case for bones supporting movement)
-> Fossil skulls therefore reveal information about the brain
-> Brain volume, asymmetries, gyri and sulci (folds of the brain) and measurements of major lobes / areas
Cranial vault is the space in the skull within the neurocranium occupied by the brain
Paleoneurology is the study of brain evolution through studying the endocasts of the inside of fossilised skulls
Remains of man's earliest mammal ancestors discovered in Dorset, reported on 7th Nov, 2017
Bengston et al, 2017 - World's oldest plant fossil discovered by student pushes evolution of complex life back 400 million years
Evolution of the human brain:
Comparison of the evolution of different brain regions - for example, brain stem comparison and cerebrum are separated - brain stem regulates reflex activities critical for survival, whereas the cerebrum is involved in more adaptive processes such as learning, perception and motivation
Brain has increased in size
Most of the size increase is in the cerebrum
Increase in the number of convolutions has increased the surface of the cerebral cortex, the outermost layer of cortical tissue
However, all brains are constructed of neurons, and these can be usually found in the same locations in the brains of related species, and similar structures perform similar functions - human brain appears to have evolved from the brains of our closest primates
Miller, Scott and Okamoto, 2006 - Public Acceptance of Evolution:
There is reduced public acceptance in the US and Turkey in comparison to Scandinavian countries and the UK along with Japan
Human beings, as we know them, developed from earlier species of animals
Evolution and behaviour
Some behaviours, such as the ability to find food, avoid predation, or defend offspring increases passing on of genes - others play a subtle role
Social dominance -
Males of many species establish a stable hierarchy of social dominance through combative encounters with other males - in some species, these encounters involve physical damage, and in others it involves threat and posturing until one combatant backs down
The dominant male usually wins encounters with all other males, and the hierarchy is decided as such - once a hierarchy is established, hostilities diminish because low ranking males quickly submit, and low levels of hierarchy become vague and non-combatant, as most fighting occurs for top spots
Importance -
-> In many species, dominant males copulate more, and so pass on genes better
-> Dominant females are more likely to produce more and healthier offspring - more access to foraging etc
Courtship display -
Males approach females and signal their interest; can be visual, olfactory, auditory or tactual to elicit a signal in the female, which elicits another male response, and so on until copulation ensues
Thought to promote evolution of new species -
-> Species occur when organisms are reproductively isolated from other organisms of the same original group, causing them to evolve differently
-> When barriers discourage a group from reproducing, either side of the barrier produces different variation until cross-fertilisation does not produce fertile offspring, meaning a new species has been established
-> Barriers can be geographic, or particularly behavioural - different courtship displays can drive a reproductive barrier between themselves and the rest of their conspecifics (member of the same species) - only the suitable exchange of displays between a courting couple will lead to reproduction
Analysing evolution
Evolution is not linear - it is more like a dense bush than a ladder
Humans have no reason to claim evolutionary supremacy - last surviving species of a group that has existed for only a blip of evolutionary time
Evolution does not always proceed slowly and gradually - rapid evolutionary changes can be triggered by sudden changes in the environment or by adaptive genetic mutations - whether it occurred gradually or suddenly is still a matter of debate
Few products of evolution have survived to the present day - fewer than 1% of all known species still exist
Evolution does not progress to preordained perfection - it is a tinkerer; increases in adaptation occur through changes to existing programs of development - results are improvements, not perfections
Not all existing behaviours or structures are adaptive - evolution often occurs through changes in developmental programs that lead to related characteristics, only one of which may be adaptive - nonadaptive evolutions are known as spandrels e.g. bellybutton
Not all existing adaptive characteristics evolved to perform their current function = exaptations, evolved to serve one function, later evolve to serve another
Similarities in species do not mean common origin - structures that are similar because of common origin are homologous; similar structure from function are analogous
-> Convergent evolution causes analogous evolution, as it is similar solutions to the same environmental demands
Homosapiens mated with other Homo species they encountered - the discovery of this pattern of mating changes the way we should view our origins, as we are the product of many homo populations, not just one