Human science

Evolution is caused by natural selection - 

Limited resources in the environment + 'good tricks' for survival will result in an adaptation and more effieicent design.

• There will always be a trade off when adapting
• Evolution occurs via cummalitive change over long periods of time
• patterns of inheritance combined with the strength of selection = an evolutionary change

The human skeleton is not yet fully evolved - this is why we see so many flaws in the performance leading to health issues

Famous naturalist studying different behaviours across species.

Stated that behaviour is the measurable response of an organism to stimuli from its environment

• Behaviour links physiology and morphology to the animals environment
• Behaviour is a strong factor for natural selection as it heavily influences reproduction 
• Understanding behaviour is key for the following things: Conservation and capture of species, producing domestic animals and training companion animals, insight into human health and behaviour.

What is Adaption - A trait that increases the fitness of the animal compared to its alternatives

Proximate

1. Development ONTOGENY (how was the behaviour adapted)

2. Mehanism CAUSATION (How does this behaviour work)

Ultimate

3. Evolution PHYLOGENY (How did this behaviour come about/history)

4. Function ADAPTATION (How does this behaviour aid adaption)

• Grasping hands and feet 
• Nails instead of claws 
• Hind limb driven locomotion
• Reduced olfaction but enhanced vision
• Forward facing eyes encased in bone
• Relativley large brain
• Long gestation
• Small litters
• Long juvenile period
• Long lifespan
• Increased dependance on learning and behavioural flexibility

~ 300 SPECIES IN THE WORLD WITH 2 SUBORDERS

The strepsirrihini (Strepsirhines and the Haplorhini (Haplorhines)

Biogeography

• Tropical and arboreal
• modern range in Americas, Africa and Asia
• Ancient range in North America and Europe

Homology (sharing common ancestors)

• Morphology
• Behaviour
• Fossils
• DNA

Specific shared characteristics

• Grasping hands
• Developed vision
• Long juvenile periods
• Relativley large brain
• Physiologial and cognitive structures

4 factors determine their food requirements:

• Basal metabolic rate
• Active metabolism
• Growth rate
• Reproductive effort

common feed

Protein - insects and leaves

carbs - fruit and gum

fats and oils - insects, animla prey, and seeds

Also needs... vitamins, minerals, water

Food availability

Home range can influence what food is accessible for primates. Seeds and leaves are abundant in most areas, whereas the seasonality of fruit may leave sources sparse at some points 

- this can force groups to alter their home range which may cause rivalry between other groups. Territories will be defended aggressivley if they overlap. (A few excpetions such as capuchins)

Insectivores

• small body size, sharp cusps and crests on teeth, simple digestive system

Folivores

• Leaf eaters
• Large body, small incisors, sharp shearing crests on molars, well developed large digestive systems

Frugivores

• fruit eaters
• Medium body size
• Large broad incisors
• Low cusped fat incisors
• Large digestive system but not specialised

Gumnivores

• Small body size
• Long robust incosors
• Claws in some species

The Angiosperm hypothesis

developed visual predation and started leaping across terminal branches of trees using grasping hands - these allowed the primates to forage for flowering plants and leaves.

The earliest primates - Pleisiadapiforms 

• Insectivorous and lived for around 10 million years

After warm, wet tropical forests developed i in North america and europe (Eocene) - primates developed full suit of characteristics...2 sets:

ADAPIDS - larger, diurnal, and quadrupedal

OMOMYIDS - Smaller, nocturnal, some leapers

A feeding adaptation?

• made it easier to catch reach fruit from the ground
• ground feeding became more efficient

Energetics?

• It simply saves energy compared to using 4 limbs

Thermoregulation

• Less solar radiation is picked up when walking on 2 legs compared to 4 (an unlikely reason)

There are numerous Hominins that have been discovred across the globe that could be the ancestor that led to the development of Humans. Most are located in Africa.

Unique human traits

• Walking on 2 legs
• small canines and large molars with thick enamel
• Large brains
• Very slow life histories and long juvenile period
• talking/symbolic culture

our evolutionary path shares a common ancestor with apes when they branched off into paths evolving humans and chimpanzees...

The earliest Apes

• no evidence of an ape from less than 10 million years ago :( BUT a Skeleton was found in Uganda (The Morptopithecus)
• 20 million years old - oldest ape?
• femur indicates it climbed, had a stif flower back, face and teeth correltate to apes structure, mobility at the shoulder

Early Homo - developed from Africa ~2.3 mya

• larger brains, smaller teeth, rapid development, Au. limb proportions

The earliest ancestors of hominins - Homo Habilis (1.4 - 2.4 mya in East and South africa) and Homo Ergaster (0.6 - 1.8 mya)

DID THIS OCCUR IN THE PLEISTOCENE CLIMATE??

The morphology of the early ancestors

They had primitve qualities - postorbital: constriction, no chin, receeding forehead

Also derived qualities - less prognathic, larger brain, smaller jaws and teeth

And unique qualities - Brow ridge and occipital torus

Dispersal from Africa

• Africa was the origin site for the evolution of the early homo, they dispersed from here 1.8mya
• In Dmanisi, Georgia a skeleton was found with postcrania homo-like structure, there was also evidnce of the use of Oldowan stone tools.

Postcrania

• long legs
• narrow hips
• Barrel chest
• Modern human body proportions
• Reduced sexual dimorphism
• Limited language
• Terrestrial Biped??? (Runner maybe)

The Homo erectus 

Was discovered by Eugene Dubois - first fossil evidence for an ape - human transitional species!!!  However is does fae cranial differences with H.ergaster.....

• Thicker skull
• larger face
• more pronounced occipital torus and brow ridge
• sagittal keel

Neanderthals lived in a fluctuating environment (mostly a cooling trend)

Eurasia contained many large mammals and frigid grasslands at this point in time.

Features:

Antomy

• large brain (more than homosapiens)
• Oblong skulls (occipital bun and thin walled)
• Unique teeth

Postcranial

• short and stocky
• More robust limbs w/ better developed muscle attachments
• Wide torso
• Short arms and legs

features

• large round head with high forehead
• small face and teeth
• protruding chin
• less robust postcranial skeleton
• long limbs

Genetics

genomes of humans and chimps sequenced - theres only a 1.06% differences

However 71% of genes have a difference

Homo sapiens evolved in Africa ~200,000 years ago

a small population left africa ~60,000 years ago and interbred with neanderthals (possed a Y chromosome and mtDNA)

• They had a low genetic diversity as they decended from a small population (shows recent evolution)
• A nonrecombining Y chromosome (NRY)

mitochondrial eve - a woman in ancient history who passed down her mitochondiral DNA in an unbroken chain through her abundance of daughters (males cannot pass on mitochondrial DNA) as homosapiens spread across africa and eventually left the continent. This lead to this particular set of mitochondrial DNA becoming a common ancestor for all livinign humans today

• (does not mean she was the first woman to ever live - others before and of her time were not successful in passing on their chain of DNA)

The homo Habilis shows the earliest evidence of tool use

• they used flakes, hammer stones and cores
• Right hand use

Domestic lives - 

• They built home bases
• Used mode 1 Stone tool technology for food gathering and foraging (butchering carcasses and digging)
• Swarkrans in south Africa used bone tools (termite extraction)

Food resources aided evolution

- Collecting, hunting, and extracting food promoted tool use and design.

- Foraging caused difficult skill development casuing long juvenile periods

- intelligence and learnign caused: large brain, increased lifespan, paternal investment, reduced dimorphism, long juvenile stage.

Tools - The archeulean industry

• Mode 2 tools
• Biface (hand axes) for carcass processing , this was unchanged for ~1 million years

Meat eaters

• Evident due to tooth anatomy  and cut marks on animal bones
• hand axes were very common
• Vit A posioning was a common cause of death (shown from taphonomy) due to consuming too much high content meat - e.g. Carnivore liver

Erectus

• Used stone tools
• mode 1 in most localities - mode 2 sometimes seen in rare cases
• Possible evidence of using bamboo for tools

Heidelbergensis

• Hunted large game, using mode 3 tool technology
• Used spears - shown via butchered animal bones
• They had a diversity of food sources

Mode 3 tool use (known as mousterian)

hunted large game - bison, red deer, aurochs

Used large caves

general lifestyle

• Showed most high intelligence so far
• Burial of their dead
• Wearing personal ornaments (necklaces and body pigments)
• Although lifespan was short and they had many health issues.

What ways do we vary - 

• Physical appearance, skills, preferences, disease and illness
• This can accur wthin groups or individually 
• Effects are from genetic and environmental factors

Genetics -

Traits are influenced by single genes - selection in the genome is caused by selective sweeps. This is when large sections of DNA are carried together with selected allele that 'hitchhike' over to the offspring.This causes the advantageous mutation to eliminate or reduce variation as it increases in frequency in the population

e.g Humans In Northen europe and Northern Africa are able to tolerate milk as lactase persistence developed over time from the selection an dmutation of a single dominant gene.

Race - The race concept

Race is a bad biological term as it's based on three misconceptions

1. Humans can be easily divided in a number of distinct races
2. Races show enough genetic difference, that knowing someone's race can give information about intelligence, personality etc.
3. The difference between races is due to biological heritage.

Nature vs Nurture - 'a false dichotomy'

This is a misrepresnted contrast between 2 things whih are deemed to be entirley different, when reslly they can crossover.

• they can work simlutaneously
• behaviours have the ability to evolve

The brain is crucial in understanding this - the brain impacts behaviour, as natural selection can shape its size and abilities.

= Natural selection can shape behaviour via brain size and capabilites

Human universals

language- A human universal ruled by phonemes (sounds), humans are born with fundamental rules regarding language - babies are born with the ability to distiguish all phonemes

Inbreeding avoidance - Each human has 5 fatal allels, relatives are more likely to share them. Inbreeding occurs when mating with someone that shares them - reducing fitness and quality of life.

- primates avoid this by leaving the natal group when reaching sexual maturity so they cannot breed with relatives.

Possible phychological mechanism of avoidance in humans? Westermarck effect - adults show no sexual attraction to those that they developed in a close proximity to.

Hunter gatherers' - The first small societys

• were not domesticated, lived in small groups
• had little/no division of labour amongst there groups
• nomadic, moved freely about the land.
• Relied on readily available plants and game to sustain themselves.

The domestication revolution

Plant and animal food consumption developed in the way it was provided.

Pastoral societys - stayed in a single place in order to raise livestock for meat.

Horticultural societys - grew their own vegetables and fruit at a home base (year round) instead of foraging the wild habitat.

Social organisation

• domestication allowed humans to gain greater control over their food production
• Overall improved well being and lifestyle

(actor/recipient)

Mutualism +/+ Benefits the actor and recipient

Selfish +/- benefits only the actor

Altruism -/+ Impacts the actor but provides benefits for the recipient

Spiteful -/- negativley impacts both parties

issues with group level explanations of altruim

• It must favour the individual in order to evolve.
• group explanations just dont fit the understsanding of evolutionary theory for altruistic behaviour

Differential reproduction (individuals production of more offspring than others) is influenced by natural seelction.

• Therefore can selection ever favour altruism if ithe behaviour will ultimatley always help others at a cost to the individual?
• How does altruism evolve if its a negative outcome for the individual - natural selection should not be favouring the gene that gravitates us to help others

Indiscrimate altruists

• They do not care who receieves their help - anyone will do
• They do not care if the favour is ever returned, regardless of the cost from the help they gave.

Kin selection

• Altruism can evolve through kin selection, related individuals often cluster in groups. These groups will interact more so altruism is higher among them.
• However helping random individuals will not change the frequency of the allele for inheritance of altruism.

Fitness

A heritable design feature reproducing itself by promoting the survival and reproduction of its bearer. - The gene for altruism will encourage the bearer to mate with those who also carry the same gene, increasing the gene pool for altruists

Degree of relatedness

• 'r' is the probability that an allele present in one individual is present in another individual. (usually higher 'r' if they are related)
• alleles sampled from 2 individuals could be be idnentical by descent. This means the events of mating will organise the relatedness of individuals.
• Indivuduals with a higher 'r' value can afford more costly acts of altruism due to being related
• Hamiltons rule - rb>c (degree of relation x the total benefit to recipient = fitness cost to the provider)

Evidence of kin selection existing in humans

• Fieldman et al. - experiment showed that more pain was sustained (painful position held for long time) in order to gain a benefit (more money) for their closest relative 
• Compared to less pain being sustained for more distant relatives

Adoption of children is often cited as evidence against kin selection - rearing unrelated has no genetic benefit to the giver as their altruistic geens will not be passed on.

Silk (1990) polynesian culturesoften only adopt cousins or closer in relation. Only the agricltural families needing help for work adopt non-related children.

Stack (1993) most foster children are adopted by kin

Alcock (1993) adopting is a western phenomenon. The urge to produce and raise children is so engraved, adoption made the role of the 'giver' possible for couples that can do this naturally.

other against - giving blood, donating to charity, rescuing unrelated individuals, sacrificing your life for moral/ethical principles

Where individuals balance out their acts, shown through many different currencies e.g. food sharing, grooming.

It requires certain criteria to be labelled as such -

• Must be frequent interactions between individuals in order to develop this type of relationship
• Have to keep track of what has been given and recieved, the roles of giver and receiver should be reversed fairly.
• Always support those who support you, the likelihood of a social exchange is always based of previous interactions.
• Short term benefits of the recipient are always greater than the cost of the giver.

(Cheaters should always be recognised and expelled in order to sustain this system)

indirect reciprocation - an altruistic act cna be returned by any individual, not specifically the reciever. When you advertise yourself as an altruist, individuals will be more inclined to deal with you in the future. Et al Trivers (1971)

3 types of exchange between social equals

Generalised - Someone gives with no expectation for a like favour/gift. Common in food sharing, meat was given out but the hunter only expected to be repaid sometime in the future. (this could just be seen as a natural human instinct to share food in order to survive in a safer collective group) - This could be the reason it is the dominant distributive mode .

Balanced - Giving and expecting something in return

Negative -  Giving with the expectation of immediate return

There is non random variance in sexual success

Intrasexual - direct competition for mates between members of the same sex (usually male to male competition)

Intersexual - Differences in attractiveness to the opposite sex, usually a non-random mate choice by a female.

• "female choice" has benefits: increased nutrition , provisioning, and parental care that will ultimatley increase reproductive output or quality of offspring.
• This links to the 'good genes' hypothesis - genetically superior mates will produce fitter offspring.
• And the '**** son' hypothesis - mating with preffered fathers produces sons that have a higher mating success.

Females will produce a few, well provisioned gametes 

males will produce a large amount of cheap gametes so there is a higher probability of the females high quality eggs being fertalised.

batemans principle

• Greater variance in reproductive success increases linearly with increasing number of mates 

**** son hypothesis

Assortative mating (preference based) in a popualtion where males have the most exaggerated traits and females have the strongest preference, will cause a genetic correlation between trait genes and preference genes

• (female preference genes will hitchhike onto the successfull mate genes)
• The process of assortative mating will become self-reinforcing
• -> This can be damaging to male fitness as the trait can evolve ro the point where the only benefit to female choice is that her sons will inherit the most attractive form of the trait.

Sensory Bias (Ryan)

• Preexisitng preferences for certain traits may be hardwired in females and lead to the development of exaggerated traits in males.

The fight between males for a female mate

• can cause female ornamentation which reduces fitness at the expense of their offsrping 
• sexual selection can oppose natural selection - leading to exaggerated and maladaptive development of male traits. e.g. hecules beetles use jousting horns aginst other males, but leads to an exaggeration of body size.

Sexual dimorphism - differences between individuals of different sex from the same species

evolution predicts preferences ->

• Females limitng factor - resources (males who can supply are favoured)
• Male limiting factor - healthy fertile females

psychology of prefernces

• Number of sexual partners - men not as bothered, woman are costed by pregnancy so are more selctive and have fewer partners.
• Cultural influences  - chasitity varies across cultures, good financial prospects show uniformity across all cultures.

Males psychology

• prefer young woman with sexual fecundity (around 26yrs old) 
• Focus on the body - waist to hip ratio as a marker of fertility, narrow waist and large breasts, the smell of ovulating woman. (apparently we prefer men at this time and want to rip our clothes off for them!)
• Generally men will have more partners and engage in sex sooner within a relationship.

Females psychology

• men with resources, good job and money etc
• Higher status, generally comes with age (older man are good)
• Athleticism and high testosterone (leads to more masculine faces and features)

Shared prefernces between males and females

• kind and considerate 
• good humour
• face and body symmetry (shows good development homeostasis)

age differences

expressed preferences seem to reflect upon reproductive age differences. Woman loose fertility sooner in life while men can keep producing. therefore fathers are often older than mothers

**** - Is it a mating strategy or a control method? -> 

• females more likely to become pregenant via **** than via consensual sex - therefore if its an evolutionary adaption then the most fertile females should be getting ****d most often.
• Whereas the control/intimidation hypothesis would suggest that woman in powerful position should be ****d the most.
• It could be a maladaptive side effect - the motivation for quick sexual arousal and many partners leads to an over expression of sexual behaviour (******).

raising children - variation across culture and world, overall seen as extremley difficult job role

trade off between parenting and mating

• man most likely to provide more support for his own child than any other
• however he will care more for his stepchild than his child from a previous partner.

-> This shows that the certainty of parenthood to an offspring will affect the amount of parental (or grandparent) investment for them

• A mothers - mother is most likely to invest
• A fathers - father is least likley to invest
• fathers - mother and mothers - Father are seen as in the intermeddiate zone.

Biological vs non-biological children

• Step children are usually not given as much parental investment as a biological child 
• Step children face a higher risk of child abuse (msotly in younger children) , and are 100X more likely to be killed than biological children. 

Discriminative parental solicitude - There is a quality quantity trade off when having children

Pregnancies are often terminated if a mother is in poor health and cannot invest her energy, if the foetus has a genetic defect, or if there is a missacriage (78% of preganacies end in one)

Infanticide

Often commited if the child is ill/deforemd, not sired by the females husband, or if they parents cannot raise the child.

parental resource allocation - Males must often compete for a limited number of females

Finacial means are used in common practice to obtain a partner ->

• Bride wealth: male giving resources to females family in order to wed her
• Dowry: Females wealth and resoures that are given to the males family in order to marry. Generally paid by the brides father.

Life history - The stages of growth, reproduction, and dispersal that an individual goes through during its life from birth to death.

Stages (subject to trade-offs)

• Gestation/childhood - undergo GROWTH and maintenance
• Reproductive period - REPRODUCING and maintenance
• Post-reproductive period - MAINTENANCE

fundamental trade-offs

• The amount of energy available to life processes is finite, when energy is devoted to one function it cannot be devoted to other things. Body must prioritse specific processes.
• Biologicla processes take time, individual growing to a larger size before sexual maturation is at risk of dying before producing offspring.
• Fundamental trade-offs involving energy and time = every organisms life history is an evolutionary compromise.

Senenscense - the deteriation of cells over time, gernally with old age e.g. wrinkles, bad eyesight.

• Caused by the energy allocation to growth and fertility at the expense of maintenance and longevity.

Life history - the way and rate that an organism develops

• Fast life history: Reproduce early - die early , small body and brain, short gestation w/ large litter, high mortality
• Slow Life history: Reproduce late - live longer, large body and brain, long gesttaion with a small litter, low mortality

Natural history shapes the timing of life histories, and patterns of allocation to growth, maintenance, and reproduction throughout lifespan.

r-selected breeding - breed early and produce many small offspring (generally in unsatble environments due to higher risk of mortality)

K-selected breeding - Invest in provisioning for high quality offsping, to trade off in producing fewer overall.

1. Female reproductive success is limited to direct metabolic investments and investments from mate and kin (supplying their body needs and recieiving aid)

- In pre-modern societies reproductive sucess was determined by infant survival and interbirth interval (time between preganancies)

2. Trade-offs in pregnancy are primarily between maternal maintenance and foetal growth (maternal conflicts)

3. Trade-offs after parturition involve investment in current vs future offspring.

mediated by:

• Nursing and the mothers condition during lactational amenorrhae (temporary infertility during breastfeeding)
• Timing of introduction of supplemenatations
• Fecundity during waiting time to next conception - reduced ovulation frequency can cause poor energetic conditions and low ovarian steriod levels. (can explain conflict with offspring and father during thsi time)

1. Androgens responsible for growth and reproduction - guide prenatal development via effects in brain and body

2. Hormone quiescence in childhood

3. Adolescence - primary and secondary sexual traits develop, theres an increase in risky behaviour and male mortality spikes (possible related to sexual selection as males make more risky decisions to attract a female)

Benefits: support of spermatogenesis (sperm production), secondary sexual traits, augmentation of body weight muscle and muscle, cognitive benefits

Costs: Higher metabolic rate , reduced immune function under stress, reduction in fat (possible reduced survivorship) , may be linked to cancer development, may involve shorter lifespan.

females success of fertility over her life -

1. Rise over the first decade after menarche (slow climb to full fertility) - maybe due to selection against high potential survivorship costs of child bearing for younger females .

2. Fairly stable from mid -20's until mid-30's

3. Decline to menopause at about 50 : depletion of follicles and a higher risk of child bearing as age raises, as well as higher risk of death from other reasons.

- there are benefits from enhancing the reproduction of ones grandchildren.

• huge trade-off between existing and future children
• Further trade-off between further reproduction and survivial

(The medical affects of the bodys chocie between growth, reproduction and maintance)

• Declines in testosterone with aging leads to increased risk of obesity, insulin resistance, and  cardiovascular disease
• Exposure to reproductive hormones and older age at first birth in woman , can inrease risk of some reproductive cancers
• Hormone physiology and trade-offs may differ between human populations historically exposed to different selective pressures affecting life history.
• Body size and life history are seldom taken into account when developing and using animla models of diseases related to physiolgy.

Essentially impossible to maximise health with regard to competing fucntions that trade-off e.g. maintenance vs reproduction.