Life Sci 15-UCLA Phelan final

Describe the interplay between culture and biology.

Genes do not fully dictate our behavior, but neither does culture. We carry alleles that nudge us toward certain behaviors (bearing children at 12/13). However, culture also relays information that helps us resist genetic urges that are no longer useful in the current environment (use birth control or abstain from sex).

What is the fundamental reproductive equation and what does it reveal about the interplay between culture and biology?

sex=pregnancy=babies=maternal child care=loss of female economic opportunity=loss of female political power. However, cultural innovations have allowed the breakdown of the FRE--> culture can interfere with biology and remove initial biological constraints.

What is constrained learning?

Due to biological constraints, there are limits on species' ability to learn certain tasks. We inherit the ability to learn some things (prepared learning) when environmental cues are present. This shows how biological constraints can sometimes not be overcome by culture.

"Sauce Bearnaise phenomenon"

Humans quickly associate nausea to the food we consumed (so do rats).

example of constrained learning: rats

Rats were easily able to learn that weird tasting water led to nausea and they stopped drinking water. They could also learn that noise and lights when they drank water led to electric shock. This is due to a genetically-coded hypothesis: If I feel sick, it must be something I ate. However, they could not learn the association between noise and lights and nausea, as well as weird taste and electric shock.

example of constrained learning: languages

Humans have a narrow window of "prepared learning" time in which it is easy to learn languages (when we're young), but it is significantly more difficult to learn languages when we're older.

EEA and why is it important to be aware of it

environment of evolutionary adaptedness

explains behaviors that are mismatched to our current environment (food preference for fatty food even though it decreases our fitness due to obesity)

Why is the EEA sometimes different from the current environment?

The environment can change quickly, but evolution is slow.

3 examples of species having mismatch between EEA and current environment

1. Humans: hunter-gatherer society vs. industrial society

2. Polar bears: icy, cold climate vs. global warming and melting ice caps

3. Dogs: environment where food is scarce vs. domestication with ample food supply

mismatch and its implications

EEA does not match the current environment

Implications: instincts cannot be trusted (signal isn't reliable, leads to self-control issues)

Why is it hard to be a teenager?

Body and biology is telling us to make babies, while culture tells us that we should wait until about 28 years old. We're constantly getting nudges from our brain from genes present in our evolutionary history that are no longer useful in the current environment, and we have to constantly fight those urges.

3 examples of conflict humans experience due to the alien nature of our world

1. Obesity

2. Monogamy

3. Jealousy

Central Nervous System

Brain and spinal cord

Peripheral Nervous System

sensory and motor nerves that project to and from the central nervous system

compare and contrast hormones and nervous system

both are ways to respond to stimuli and coordinate info within the body. hormones are slow, nervous system is fast.

What do all our senses have in common?

They are all a variation on a modified dendrite of a sensory receptor embedded in a membrane that interacts with the outside world and sends info to our brains, stimulating or blocking an action potential.

action potential

self-propagating, all-or-nothing change in the membrane potential that travels down an axon

How does an action potential occur?

potassium and sodium flow in and out of the neuron through channels that open and close

Why does an action potential occur?

Neurons have semi-permeable membranes that allow ions to flow in and out and change the electrical charge of the membrane

when does an action potential occur?

when neurons fire/don't fire, in response to external stimuli, when the dendrite receives a signal from somewhere in the body and sodium channels start to open

myelin sheath

layer of fat that insulates an axon and speeds up signal propagation

learning to walk

babies aren't born with their axons fully myelinated, so the signal to walk gets lost on the way from the brain to the feet

multiple sclerosis

immune cells attack the myelin sheath and cause scarring--> signal gets lost on the way to the target cell

caffeine

caffeine mimics adenosine and binds to the adenosine receptors in the brain, inhibiting adenosine's ability to bind and build up in the synapse--> inhibits adenosine release

ecstasy

blocks serotonin re-uptake, stimulates serotonin release

cocaine

binds to dopamine reuptake receptors so that dopamine remains in the synapse and continues binding and firing at different receptors

Botox

gets into terminal button at neuron/muscle synapse and degrades several proteins that are required for fusion of vesicles to terminal button membrane--> prevents the release of acetylcholine and paralyzes muscle

LSD

mimics the effects of serotonin, causes hallucinations when it gets into the optic nerves

Meth

stimulates serotonin and dopamine release

Prozac

selective serotonin reuptake inhibitor: blocks the re-uptake of serotonin in the brain

What are ways that the process can be tinkered with?

1. using drugs to block or stimulate the release of neurotransmitters

2. increase or decrease rates of neurotransmitter breakdown in the synaptic cleft

3. block or increase affinity to receptors

How can the genotype for a single gene influence novelty-seeking behavior?

The gene codes for a protein embedded in the membrane of a post-synaptic neuron in the do-it-again centers in the brain. People w/ 2 copies of the short gene aren't as sensitive to the dopamine released during risk-taking behavior, so they don't find as much pleasure in it. People w/ 2 copies of the long gene are more sensitive and get lots of pleasure from the dopamine released during risk-taking behavior.

hormones

chemical messengers secreted from a gland that enter the circulatory system and can reach many cells, but only the target cells with hormone receptors respond, influencing their gene activity

estrogen sex differences

1. women consistently outperform men in object memory, verbal fluency, math calculations

2. women perform best and highly outperform men in tests of articulation, manual dexterity, and perceptual speed right before ovulation, when estrogen levels are the highest

3. female hormones in utero and during puberty may suppress spatial ability and lateralize their brains less

testosterone sex differences

1. mental reasoning and motor skills seem to increase with increased testosterone levels

2. taking testosterone (steroids) leads to heightened aggression, mood disturbances, paranoid jealousy

3. rat maze learning: male rats only outperformed female rats during the high-testosterone season

cortisol

released in times of stress and perceived threat, causes gluconeogenesis, breakdown of skeletal muscle and protein, and suppressed immune system

oxytocin

released with skin-to-skin contact and social bonding, causes increased trust in others, encourages social attachments, directs uterine contractions and milk production

sexual dimorphism

the more radical the sexual dimorphism, the greater the asymmetry in investment--> directional sexual selection, male-male competition, high female investment, high male variance in RS, polygyny

the more the sexes look alike, the more equal the investment--> monogamy, no significant sexual selection

female vulnerability

happens at the point of mating decision (risking 144,000 calories of gestation)

male vulnerability

happens at the point of deciding to care for the offspring (paternal uncertainty)

polygyny

one male, many females. high variance in male RS, low variance in female RS.

polyandry

one female, many males. high variance in female RS, low variance in male RS.

monogamy

one female, one male. low variance in RS for both sexes.

Why do we expect humans to be symmetrical?

There aren't separate genes that code for the left and right side of our bodies. We expect that the same instructions should produce the same physical trait.

Why aren't we symmetrical?

tumultuous environment--> it's hard to get the same result both times. However, we find symmetry to be a sign of genetic quality--> higher fitness.

lipids

9 calories per gram, not water-soluble, good insulators. saturated fat: single bonds in hydrocarbon tail, solid at room temp, easily stored. unsaturated fat: at least one double bond, liquid at room temp, reactive and easily used.

proteins

4 calories per gram. chains of amino acids. used for building cells and tissues, transport, movement, pH balance, etc.

carbohydrates

4 calories per gram. simple sugars: monosaccharides for fast, readily available energy. complex carbohydrates: chains of monosaccharides for long, slow release of energy. starch is digestible chain of glucose. fiber is indigestible chain of glucose. it all depends on the bond.

taste preferences

cross-culturally and across different species, there is a preference for fatty foods. this is because they are energetically rich, at 9 calories per gram, which was essential to survival in the EEA.

dietary fiber

complex carbohydrate that humans cannot digest that is valuable because it absorbs cholesterol and excretes it, lowering risk of cardiovascular disease

vitamins and minerals

organic and nonorganic necessary elements in our diet. the only people who should take supplements are pregnant/breastfeeding women, people on extreme caloric restriction, people who don't drink milk and have very low sun exposure, and women with a heavy flow.

revealed preference

surveys are measurements of stated preference, which can have response bias and differ from people's real preference. therefore, look at behavior-->revealed preference

alcohol

mimics GABA to reduce anxiety, increases dopamine levels, stimulates endorphin release to block pain, increases serotonin receptor activity to decrease depression, and blocks glutamate receptor to slow you down