Part 1: Why does advanced social life exist?

Chapter 1: The human condition

• The creation myth is a Darwinian device for survival. Tribal conflict was a principal driving force that shaped biological human nature. By itself, mythmaking could never discover the origin and meaning of humanity (as it attempts to do); however, the discovery of the origin and meaning of humanity may explain the origin and meaning of myths, the core of organized religion

  Part 2: Where do we come from?

  Chapter 2: The two paths to conquest

• Human groups are formed of highly flexible alliance, in which strategies for navigating these groups were written as a complicated mix of altruism, cooperation, competition, domination, reciprocity, defection, and deceit
• This array of strategies required higher degrees of intelligence and intense socialization. The brain had to measure emotions of friend and enemy, plan strategies for social interaction, build mental scenarios of short and long-term relationships, and retrieve memories far into the past and long into the future to imagine the consequences of every relationship

  Chapter 3: The approach

  Chapter 4: The arrival

• One critical point in our evolutionary past was when our ancestors developed an omnivore diet. Hunting game requires a high amount of teamwork and cohesion, and it’s worth it: meat is pound for pound more energetically efficient than vegetable food
• Another critical point was the ability to control fire, which then led to camps (i.e., nests) which served as the nucleus for social groups. Now in close proximity to one another on a regular basis, intellectual development that enhanced one’s cohesion with the group (e.g., social intelligence, empathy, deceitfulness, etc.) was selected for, propelling our intellectual development further
  • I also remember reading that cooked food also requires less energy to consume (chewing), which may have allowed resources to be directed away from the jaw to the brain region. It seems like these factors (this one and the previous point) arose in tandem, with cooked food enabling more brain capacity and social complexities driving the cerebral growth

    Chapter 5: Threading the evolutionary maze

• The following preadaptations enabled human eusociality:
• Living on land: without land dwelling there exists no possibility for the use of fire—a critical prerequisite to social flourishing in mammals * Being large: to house a brain with enough processing power to compute the complexities of social organization requires a large enough animal to house that brain. While ants are hypersocial and design intricate architecture with custom air conditioning, they are purely instinctual. And again, insects are too small to control fire * Grasping hands tipped with spatulate finger tips * Having those grasping hands free from walking, i.e., being bipedal * A shift from vegetarianism to an omnivore diet. Meat yields more energy per gram than vegetation. The social cooperation required to hunt meat also led to select for groups who could cooperate effectively * The controlled use of fire followed, facilitating the consumption of meats; mastication and digestion of cooked meats requires less energy * Persistent fire provided a refuge for early Homo species. As such, nests were formed—a precursor to the attainment of eusociality of all other known animals * With fireside campsites came division of labor, where subgroups formed and bands organized into dominance hierarchies

  Chapter 6: Creative forces

• The outcome of between-group competition for humans was determined largely by the size and tightness of the group, and the quality of their communication and division of labor
• The genetic fitness of a human being is the consequence of both individual and group selection. These two forces tend to pull in opposite directions—I could deceive and cheat in pursuit of self-interest at the expense of the group, or I could be heroic and altruistic for the benefit of the group, but at the expense of my resources
  • If the benefit from group membership falls below that which would be had from a solitary life, evolution would favour cheating or departure from the group. If personal benefit from group membership rises high enough, the members will be prone to altruism and conformity
• Group composition is unstable because of advantageous group size increases from immigration, ideological proselytization, and conquest, pitted against the advantages by usurpation within the group and fission to create new groups
• Much of culture (i.e., the content of the creative arts) has risen from the inevitable clash between individual and group selection

  Chapter 7: Tribalism is a fundamental human trait

• People must have a tribe. It gives them their own and social meaning in a chaotic world, making the environment seem less disorienting and dangerous. Each human has a system of interlocking tribes, savouring the company of like-minded friends, and yearning to be in one of the best tribes
• Groups, regardless of how they are formed, have always been observed to rank out-group below in-group—even in experiments when they were told the in-groups and out-groups were chosen arbitrarily
• The tendency to form groups and favour the in-group members has the earmarks of instinct. Children can have an inborn propensity to learn some things swiftly and decisively, known as prepared learning. Evidence suggests that in-group preference is prepared early in development, with infants being most sensitive to the sounds of their native language, regardless of whether the meaning of the speech is fully comprehended. Later, these infants look preferentially at person who spoke their native language within their hearing
• The elementary drive to form and take deep pleasure from in-group membership translates at a higher level into tribalism. We are prone to ethnocentrism, preferring the company of others of the same race, nation, clan, and religion (or anything that can be symbolically represented—as long as I can tell who belongs to my group and who doesn’t)
• Different parts of the brain have evolved by group selection to create groupishness. Studies have observed that the amygdala (fear & anger) fires when subjects are presented an image of someone of a different race

  Chapter 8: War as humanity’s hereditary curse

• Once a group has been split off and sufficiently dehumanized, justifications can be made for horrible acts towards that group, no matter how gruesome
• As a biological reproducing species, our population approaches limits set by available food and water. We are still fundamentally the same as our hunter-gatherer ancestors, just with more food and larger territories. Yet, we blindly obey the instincts that we’ve inherited from our Palaeolithic predecessors, which in our case lead to an overindulgence of energy and material resources

  Chapter 9: Breakout

• A loose rule of island biogeography is that animals smaller than 20kg tend to evolve into relative giants (e.g., the immense tortoises of the Galapagos), and animals larger than 20kg tend to evolve towards dwarfism (e.g., the dwarf deer of the Florida Keys)
  • A cousin of Homo Sapiens, branching from Homo Erectus, are the Homo floresiensis of the island Flores, who were less than 1 meter tall and with brains of comparable size to australopithecines. This evolutionary product supports the above stated loose rules
• “We should learn to promote human biological diversity for its own sake instead of using it to justify prejudice and conflict.”

  Chapter 10: The creative explosion

• Bands and communities of bands with better combinations of cultural innovations became more productive and better equipped for competition and war. Rivals either copied them or else were conquered. Thus, group selection drove the evolution of culture

  Chapter 11: The sprint to civilization

• The chiefs of chiefdoms typically micromanaged the affairs of their domain, delegating as little authority as possible to reduce the chance of insurrection. Common tactics include the suppression of underlings and fermenting a fear of rival chiefdoms

  Part 3: How social insects conquered the invertebrate world

  Chapter 12: The invention of eusociality

  Chapter 13: Inventions that advanced the social insects

• A significant change that allowed for the flourishing of ants, and other social insects in general, was the shift in arboreal flora from mostly conifers to leafy and flowered trees. Flowered trees are more diverse and thus leave a more diverse landscape in the soil below (as the portions of the trees eventually fall to the forest floor). They also coevolved with insects, encouraging pollination, and rewarding with sugar
• This change in the tree landscape also led to a symbiosis between ants and sap sucking insects (i.e., aphids). These aphids would suck sap from trees and excrete their waste below. Ants eventually learned to consume this sugary waste, and in return the aphids wouldn’t get stuck in a pile of their sticky waste
• Now, some species of ants have intricate nests with pastures laid out for their fleet of sapsuckers, much like how humans do for domesticated animals such as cows, sheep, and so on.
• Some species of ants in more earthen regions (i.e., not so foresty) have granaries to store seeds of nearby plants
• Social complexity seems to involve at some point a species developing an ability to sustain larger energy reserves. Ants develop intricate, complex nests with a caste of workers with specialized skills, as do humans in the forms of civilizations with farmers, engineers, and medics
• “The more elaborate and expensive a nest is in energy and time, the greater the fierceness of the ants that protect it.”

  Part 4: The forces of social evolution

  Chapter 14: The scientific dilemma of rarity

  Chapter 15: Insect altruism and eusociality explained

  Chapter 16: Insects take the giant leap

• One explanation as to the rarity of eusociality is that it requires specific pre-adaptations, notably the construction of a nest in which offspring are reared. Then, there comes a point where cooperation with another member of the species, e.g., one bee produces larvae while the other defends the nest. This would require an allele change (based on external environmental cues) in the bees that suppress certain behaviours, i.e., foraging for food or producing offspring
• An allele flip of this sort happened with ants as the working caste lost their wings. The idea is that this gene switch would cause offspring that would otherwise disperse to instead stay and contribute to the nest. This would occur when cooperation of the group favours survival more than if the insect lived a solitary life
• Eusociality seems to become irreversible once an anatomically distinct worker caste is developed
• In a eusocial insect group, there must be a balance in cooperation. If too many queens, there are not enough workers to maintain the colony; if too many workers, food around the nest will fall short; if not enough soldiers, predators will overwhelm the nest; and if not enough foragers, the colony will starve

  Chapter 17: How natural selection creates social instincts

• Overarching principles crucial for understanding the genetic basis of instinct and social behaviour:
  • The distinction between the unit of heredity and the target of selection. The unit is a gene/arrangement of genes that form part of the hereditary code. The target of selection is the trait/combination of traits encoded by the units of heredity and favoured/disfavoured by the environment
  • Natural selection is usually multilevel: it acts on genes that prescribe targets at multiple levels of biological organization, such as cell and organism, or organism and colony. Selection occurring at one level (e.g., the cell) can work in the opposite direction from that of the adjacent level (e.g., the organism). A runaway cancer cell causes the organism of which it is a member to sicken and die. Conversely, the community of cells stays healthy when the growth of cancer cells is controlled
  • In colonies composed of authentically cooperating individuals (i.e., humans), selection among genetically diverse individual members promotes selfish behaviour; while selection between groups of humans typically promotes altruism among members of the colony. Colonies of cheaters lose to colonies of cooperators. The degree of cohesiveness of a colony depends on the number of cooperators and cheaters, which depends on the relative intensities of individual selection versus group selection
  • Traits (targets) that group selection acts upon emerge from interactions among members of the group (e.g., communication, division of labor, cooperation, etc.). If these interactions favour the colony over another colony who uses lesser interactions, the genes prescribing the improved group performance spreads through the population of colonies
  • Individual vs. Group selection results in a mix of altruism and selfishness (virtue and sin) among society members. If a colony member devoted their life to service over marriage, the individual is of benefit to the society, even though they do not have personal offspring. If a colony member is a layabout our coward who saves their energy passes the resulting social cost onto others
• Phenotypic plasticity describes how traits prescribed by genes (phenotypes) may sometimes be rigid (in the case of the number of fingers on the hand or colour of eyes) but may also be flexible based on environmental cues. There is a species of plant, the water crowfoot, who’s leaves will adopt a different style depending on the surrounding, brushed below water and broad above
• Proximate cause: how a process or structure works
• Ultimate cause: why the process or structure occurs in the first place

  Chapter 18: The forces of social evolution

• In this chapter E.O Wilson attempts to challenge the dogma of inclusive fitness theory, i.e., the notion that degrees of altruism are proportional to the degree of genetic relatedness when trying to explain the emergence of eusociality
• While there are a few examples in which kin selection holds to explain social phenomena, group selection also offers convincing arguments as well
• One example is that of an ant colony which invests more energy into virgin females than males. This was initially though to be because this particular ant species was diploidhaploid, i.e., sisters share 3/4 of their genes with one another compared to 1/2 with their mother. Female workers investing more in the virgin females compared to males seemingly confirmed inclusive fitness theory; they invested more in the females since they’re more related. However, an alternative explanation is that males are proportionally smaller and less energy intensive to produce than females, who have fatty deposits to support reproduction. If offspring were invested in based on energy equivalency, many more males would be supported than females, which would result in wasted resources (as many males would be left without a partner). As such, more investment in females is optimal for the colony in terms of resource allocation, making it a more efficient relative to colonies that do not follow this strategy (i.e., selection at the group level)

  Chapter 19: The emergence of a new theory of eusociality

  Part 5: What are we?

  Chapter 20: What is human nature?

• Human nature is the inherited regularities of mental development common to our species
• Examples of this include:
  • Incest avoidance: most social species are exogamous, i.e., their young go off to another tribe, humans are no different. Likewise, humans follow a simple rule of thumb known as the Westermarck effect: Have no sexual interest in those whom you knew intimately during the earliest years of your life. Note, this effect occurs regardless of the degree of relatedness between two individuals
  • Colour perception: when modulating the intensity of light, we can correctly perceive the continuous nature of the intensity change. However, if we do the same with wavelength, i.e., changing colours, we bin the changes into their major colour groups (red, to orange, to yellow, to green and so on). We discretize colours, even though the wavelength spectrum is continuous, likely because it was evolutionary advantageous to do so
    • Cross culturally, the language used to describe colour follows a hierarchy (known as the Berlin-Kay progression): black and white -> red -> green/yellow -> blue -> brown -> the rest. This sequence is not random, indicating some human predisposition in describing more/less important colours

      Chapter 21: How culture evolved

• Culture is the combination of traits that distinguishes one group from another
• A cultural trait is a behaviour either first invented in a group or learned from another group, and then transmitted among group members
• The driving force leading to the threshold of complex cultures appears to be group section. A group whose members could read intentions and cooperate among one another, and predict the actions of competing groups, had an enormous advantage over competing groups. Individual selection surely still played a role in intra-group competition, yet group selection acted on inter-group competition
• Morality, conformity, religious fervour, and fighting ability were keystone to generating a united, cooperative, and effective group

  Chapter 22: The origins of language

• Three particular attributes enabled our species to approach the highest level of social intelligence: shared attention; high level of awareness required to act together in achieving a common goal; and the “theory of mind”, i.e., the recognition that their mental states are shared by others
• Language is a set of coordination devices that serve to direct the attention of others
• When the conversational gaps (the pauses between one person’s speaking and the other’s answering) of ten languages were measured, all were shown to avoid overlap, and the length of turnover gaps were found to be almost the same
• In warmer climates, languages around the world have evolved to use more vowels and fewer consonants, creating more sonorous combinations of sounds; sonorous sounds carry further, in accord with the tendency of people in warm climates to spend more time outdoors and keep greater distances apart
• The genetic basis of human language acquisition did not coevolve with language but predates the emergence of language. Language has evolved to fit the human brain, rather than the reverse

  Chapter 23: The evolution of cultural variation

• In the castes of any colonies, there exist major workers (giant soldiers that perform tasks outside of the nest) and minor workers (timid workers that perform tasks in the best such as nursing majors). Majors have a higher death rate, and are thus produced at a higher per capital rate than minors, maintaining an optimum balance in numbers between the two castes
• Cultural variation is determined mostly by two properties of social behaviour: the degree of bias in the epigenetic rule (e.g., low in dress fashion or high in incest avoidance) and the sensitivity to the usage pattern (i.e., the likelihood that group members with imitate others who’ve adapted a particular trait)

  Chapter 24: The origins of morality and honour

• The conflict between the poorer and better angels of our nature stem from the conflicts arising between individual and group selection
• Individual selection is responsible for much of what we call sin; group selection is responsible for much of what we call virtue
• Group selection shapes instincts that tend to make individuals altruistic toward one another (but now towards members of other groups); individual selection shapes instincts in each member that are fundamentally selfish with reference to other members
• Iron rule of genetic social evolution: selfish individuals best altruistic individuals, and groups of altruists beat groups of selfish individuals
• The countries with highest quality of life (in terms of education, health, crime, collective self-interests) also have the smallest divide in wealth between the wealthiest and poorest citizens
• A naturalistic understanding of morality doesn’t lead to absolute precepts and sure judgement but warns against basing them blindly on religious and ideological dogmas. When such precepts are misguided (as they often are), it usually stems from ignorance—i.e., important factors are unintentionally omitted during formulation
• Examples of these ideological dogmas include:
  • Opposition to artificial conception (sex without the intention of conception) with the (well-intended) reasoning being that sex is made to make babies. While this is true in most species, primates included, humans are slightly different in that women have concealed genitalia as to mask their fertility. This is to encourage sexual intercourse as a bonding mechanism without the intent to necessarily conceive a child. This strengthens the partners’ bonds, which is important since raising a human child requires long term support (due their relative helpless in early years) and thus additional investment from the father
  • Homophobia: under the same guise, condemning homosexuality since sex doesn’t produce offspring is misguided. Homosexuality is heritable and occurs too frequently to be the result of mutations alone. Thus, natural selection must be acting to select for homosexuality in populations. Homosexuals occupy niches and roles that support groups more than had they been absent—hence homosexuality is natural and healthy within societies

    Chapter 25: The origins of religion

• The illogic of religions is not a weakness, but their essential strength. Acceptance of their bizarre creation myths is what binds followers together
• The core of traditional organized religions are their creation myths. Creation myths come about in part from folk memories of momentous events, like mass emigration, wars, and natural disasters; stories of devils and angels likely spawn from hallucinations invoked by sleep paralysis, mental illnesses (schizophrenia), or hallucinogenic drugs (mushrooms, fungi, hemp, etc., which were commonly consumed in the Middle East when Abrahamic religions were being crafted)
• Around the late palaeolithic era humans started to reflect on their mortality, as suggested by ritual burial sites aged around ~95000 years ago
• Thus humans would have asked where dead people go, and having still seen the dead in their dreams or hallucinations, they concluded the dead must be in some spirit realm, the same inhabited by dreams or hallucinations
• Religious faith offers the psychological security that uniquely comes from belonging to a group

  Chapter 26: The origins of the creative arts

• “Art is the lie that helps us to see the truth” - Picasso

  Part 6: Where are we going?

  Chapter 28: A new enlightenment

• On free will: we are free as independent beings, but our decisions are not free of all the organic processes that created our personal brains and minds
• The opposition of the two levels of natural selection, individual and group level, has resulted in a chimeric genotype in each person, rendering each of us part saint and part sinner
• Every person feels the pull of conscience, of heroism against cowardice, altruism against greed, truth against deception, and commitment against withdrawal. These dilemmas stem from the conflicting objectives of multilevel selection
• To question the sacred myths of a religion is to question the identity and worth of its followers, which is why skeptics (including those from other tribes with equally absurd myths) are so righteously disliked

  *Why We Get Sick, The new science of Darwinian medicine, Nesse & Williams

  Chapter 1: The mystery of disease

• Proximate explanations answer “what?” and “how?” questions about structure and mechanism; evolutionary explanations answer “why?” questions about origins and functions
• Most medical research seeks the proximate explanations about how a body part works or how a disease disrupts function. The other half of biology, that tries to explain what things are for and how they got there, has been neglected in medicine
• One may worry that evolutionary explanations are mere speculation, however studies are showing that evolutionary hypotheses can predict what to expect in proximate mechanisms (e.g., morning sickness evolved to protect the developing fetus from toxins during its most vulnerable state)
• 6 categories of evolutionary explanations of disease:
  1. Defenses: while not actually an explanation of disease, this is listed because it is so often confused with other manifestations of disease. An example provided is that of a pneumonia patient who has blue-ish skin and a cough. The blue skin comes from a lack of oxygen in the hemoglobin which leads to darker blood. This is a problem that should be addressed, lack of oxygen is no bueno. The cough, however, is a defense, evolved to expel foreign material from the respiratory tract. Coughing is not a problem, and suppressing this defense puts the body at more risk
  2. Infection: we evolved defenses to counter viral and bacterial threats, viruses and bacteria have evolve ways to overcome our defenses and even use them to their own benefit. This evolutionary arms race explains why eradication of all infections is futile
  3. Novel environments (i.e., evolutionary mismatch)
  4. Genes: some of our genes are perpetuated even though they cause disease, as some of their effects were “quirks” that were harmless in our evolutionary environment
  5. Design compromises: walking upright gives us the ability to carry food, tools, and babies while walking, but predisposes us to back problems. To better understand diseases, we need to understand the hidden benefits of apparent mistakes in design
  6. Evolutionary legacies: evolution is an incremental process and cannot make huge jumps. As such, some designs at this point can be sub-optimal, e.g., our food passes over our windpipe. Once a system is in place, it is costly to re-engineer the evolutionary history

Chapter 2: Evolution by natural selection

• If tendencies towards anxiety, heart failure, nearsightedness, and cancer are somehow associated with reproductive success, they will be selected for and we will suffer even as we “succeed” in the purely evolutionary sense
• When Henry Ford asked, while in a junkyard of Model T’s, what particular systems never fail on those cars, he was answered with “the steering column never fails”. He instructed his chief engineer to redesign it, as if it never breaks, they must be spending too much on it
  • In a similar way, natural selection avoids overdesign
• Some genes that cause aging are not necessarily maladaptive. They may confer benefits during the early years of life, when reproduction (and thus selection) is at its highest potential. These benefits are more important to fitness than the later costs of aging and inevitable death
• When we ask these “why” questions about adaptive reasoning, we must guard against too readily believing fanciful stories. A bogus hypothesis to why our noses protrude would be that they evolved that way to hold up glasses. May seem plausible at first, but upon critical review it doesn’t hold up
• Hypotheses about evolutionary origins require testing, and due to the impossibility of rewinding time and re-running evolution, testing of evolutionary hypotheses are especially challenging. This is no reason not to pursue them, the work just becomes more challenging and interesting

  Chapter 3: Signs and symptoms of infectious disease

• Numerous studies have found that animals consistently seek to warm their body temperature to combat disease, and when this is suppressed, by a fever-lowering drug for example, they are more likely to die
• Studies have found that children with chicken pox take an average of 1 day longer to recover when fever was suppressed, similarly results were observed with colds
• Fever has its costs; it depletes energy reserves 20 percent faster and causes temporary male sterility. High fevers can cause delirium and seizures
• Iron deficiencies were found to be associated with infection, so physicians have in the past attempted to supplement iron. However, the body is actually trying to rid itself of iron such that it can’t be used by pathogens - supplementing iron enhances the pathogens and results in worsened infection. Care should be taken to respect the evolved wisdom of the body.
• The female reproductive system normally finds fluids flowing outwards, hence protecting the system from infection. The only exception to this is during sex, when sperm flow inwards, and have the potential to carry bacteria along with them
• This is a reason why mammals are thought to have menstrual cycles, and why humans have particularly profuse menstruation. Since human sexual activity is more constant, i.e., not constrained to a brief fertile window, females are presented with more opportunity of infection. Hence, the menstrual flush can help remove unwanted bacteria from the system
• A functional classification of the signs and symptoms of disease is important and useful. To choose an appropriate treatment, we need to know if the symptom benefits the host or the pathogen. We need to analyze the strategies taken by the pathogen and attempt to oppose each of them, rather than just relieving symptoms and trying ineffectively to kill the pathogen

  Chapter 4: An arms race without end

• Bacteria have two substantial advantages over humans:
  • High reproductive frequency: bacteria can evolve as much in a day as we can in a thousand years. Thus, we cannot evolve fast enough to escape from microorganisms
  • High numbers: due to their small size, bacteria’s enormous numbers in our body means that improbable mutations occur more frequently
• Some of the most effective antibiotics come from molds. Antibiotics are chemical warfare agents that evolved in fungi and bacteria to protect them from pathogens and other biological competitors
• Early in their discovery, antibiotics were extremely effective. However, over time the bacteria that antibiotics fended off evolved to evade their defence, and since the antibiotics are removed from their natural environment and thus less capable of adapting, they saw they their effectiveness dwindle.
• New antibiotics are churned out, and bacteria evolve resistance to those antibiotics, and the cycle continues
• Long term exposure to antibiotics, and increasing the dosage of antibiotics when they aren’t sufficiently effective, puts a selective pressure on bacteria to develop resistance to the antibiotics, enhancing them and decreasing the effectiveness of the antibiotics
• The use of antibiotics in farm animals can also end up harming the animals and the humans that eat them, this problem needs to be carefully measured against the economic gains that may be claimed from their use
• It is critical that the pharmaceutical not promote inappropriate use of antibiotics for animals and humans, as the selective pressure that ensues enhances the bacteria that they fight. It is unlikely this advice be heeded, as moral exhortations for the good of the group are often welcomed but rarely acted upon. This would require costly government intervention and a sacrifice in profits
• Within-host selection favours increased virulence (i.e., increases the diverting of resources from the host to the pathogen), while between-host selection acts to decrease it
  • Pathogens compete with one another for resources within the host, but will not be able to proliferate if their host dies before transmitting them to another host
• Diseases from vector borne pathogens (e.g., insects) tend to be more severe than those spread by personal contact. This is likely because between-host selection of person to person transmission would favour a less virulent pathogen that allows its host to go infect others; whereas, if for example a mosquito is the vector of transmission, the hosts health is of little interest to the pathogen as it will be transmitted by the insect anyways—the more vulnerable it makes the human, the easier it is for more mosquitos to suck their blood. In this case, it is in the viruses’ interest to have a mild effect on the mosquito, whilst feasting on the subsequently infected humans
• Increased transmission can lead to increased virulence, if the pathogen doesn’t have to worry much about between-host transmission, it can afford to be greedy as it is likely to be transmitted in a shorter amount of time. AIDS was thought to be particularly virulent because of high sexual activity frequency and frequent use of drug users’ unsanitized needles. Safe sex and the use of clean needles can thus cause the evolution of lowered virulence

  Chapter 5: Injury

• Risk of melanoma is related more closely to number of sunburns than to total amount of time spent in the sun. People who are outdoors often adapt to their amount of usual exposure and are unlikely to get sunburnt; people who go out infrequently do not adapt and are at increased risk of sunburn
• Sunglasses without UV protection reduce the total amount of visible light, leading pupils to dilate and admit more UV light that then damages the eye more than had the user not worn the glasses
• Why don’t our fingers regenerate when cut off? The repair machinery would have to conform to an optimal trade-off between the advantages of rapid and reliable repair, the costs of the needed machinery, and the dangers of cancer (associated with mechanisms of cell replication)

  Chapter 6: Toxins: New, old, and everywhere

• Tall fescue grass is popular because it grows fast and resists pests. A symbiosis between a fungus and the grass exists, where the fungus creates toxins that are transported to the tips of the blades of grass to discourage hungry herbivores
• If a fruit is eaten before the seeds are ready for dispersal, the whole investment of the plant is wasted. Ripeness of a fruit corresponds to the peak fertility of the seeds within
• A diverse diet helps to minimize the damage caused by dietary toxins (the evolved defenses of plants), whereas a non diverse diet may lead to a toxin overload
• Concerns over pesticides have led to attempts to breed plants that are naturally resistant to insects. This involves increasing the level of natural toxins, which tend to make humans sick as well. We are re-introducing the same natural toxins that farmers first bred out of plants generations ago. Natural toxins and artificial pesticides need be treated with the same amount of caution
• In the context of alleviating morning sickness during pregnancy: “Unfortunately, making people feel better does not always improve their health or secure other long-term interests.”
• Children avoidance of vegetables could also be adaptive. Strong-tasting vegetables contain more toxins, and during their development they would best stick to low-toxin vegetables. As such, certain vegetables repulse children, and this repulsion tends to fade as they age

  Chapter 7: Genes and disease: defects, quirks, and compromises

• Many genetic conditions that ail us now may have caused no trouble in our ancestral environment (and may have conferred some benefits), and only become a problem due to an evolutionary mismatch. For example, a craving and motivation for fatty foods might have been adaptive when foods were scarce
• “We should rebel against the tyranny of the selfish replicators.” - Dawkins

  Chapter 8: Aging as the fountain of youth

• Over the past few hundred years, the average length of life in modern societies has steadily increased, the maximum duration of life has not.
• Senescence: the process of bodily deterioration that occurs at older ages. Increased susceptibility to disease and decreased ability to repair damage
• Those with a genetic predisposition to get peptic ulcers, and die from these ulcers at old age, may benefit the individual by providing more protection throughout life from gastrointestinal infection via higher levels of stomach acid
• The whole immune system is age biased, releasing damaging chemicals that protect from infection, but also lead to accumulated tissue damage
• Genes with benefits in early age tend to contribute to senescence (trade off between effectiveness during fertile years at the expense of deteriorated function in infertile years)
• Studies showed that beetles better able to reproduce early in life reproduced more and generate more offspring, but age and die earlier. Genes will generally select for whatever maximizes reproduction.
• Any genes whose deleterious effects occur earlier than that of other genes will be selected against most strongly, thus selection acts on genes to delay deleterious effects until they are all in synchrony - hence the effect of the body’s functions decaying in seeming unison
• Postulates of impotence - pessimistic assessments of what science can accomplish can have utility (investigate this further)
• The preoccupation of living forever is likely to be supplanted by a desire to live as fully as possible, while it’s possible

  Chapter 9: Legacies of evolutionary history

• We have inherited systems that were not optimized for our bodies, they are historical legacies from our ancestors
• Examples include:
  • our air and food passages intersecting (making us vulnerable to choking),
  • a retina in front of the interior of the eyeball instead of behind (causing optic nerves and vessels to obstruct the view),
  • the appendix (used to help process low nutritional value food, rabbits still use it for example)
  • Our spine was originally designed to withstand loads from back to belly, not head to bum. Same with the joints in our leg

    Chapter 10: Diseases of civilization

• “What are the long-term consequences of such meager challenge to our body’s built-in temperature controls?”
  • In reference to our environments being constantly temperature controlled for maximum comfort (A/C, heating)
• Diseases brought about by civilization include obesity (energy excess, sedentariness), cavities (sugar excess), crooked teeth (lack of jaw development due to soft foods in diet), substance abuse/addiction (concentrations/availability of alcohol, opium, etc. would have been lower pre-agriculture, specialization led to increased potency of substances)
• Rickets was a frequent malady due to vitamin D deficiencies. When humans started occupying regions with more cloud cover, forest cover, and cold areas requiring cave dwelling and clothing, they received less sun exposure. Heavily pigmented skins admit less light for vitamin D synthesis and yield more malady in sun-starved skin, thus less pigmented skins were gradually selected for
• When faced with a problem of medical importance ask: What is its evolutionary significance?
  • If it’s an adaptive mechanism, it generally means it was adaptive in the Stone Age. Some aren’t adaptive, but represent costs to other adaptations (e.g., senescence)

    Chapter 11: Allergy

    Chapter 12: Cancer

• A common man marvels at uncommon things; a wise man marvels at the commonplace
• Multicellular organisms arose from some group of protozoa, in which each cell was a functionally independent individual. Most reproduction was asexual, with one cell dividing into two new ones.
• In some modern protozoan species, the two new individuals do not break completely apart but stick together in pairs, or the offspring of pairs stick together in filaments or sheets called colonies.
• In some colonies, cells may have differentiated into germ cells and somatic cells, meaning that some previously independent cells gave up reproduction to become genealogical dead ends. They would supply nutrients and protection to the few germ cells that sexually reproduce
• All cells within these colonies had the same genes, so if sacrificing reproduction improved the genetic progress of the colony the cells would do so
• For large colonies of cells, we may expect a mutant cell to appear that behaves in ways other than what maximally benefits the colony. Such large colonies thus need adaptations for maintaining discipline among the many component cells
• In the human body, among our ten trillion cells there exists a small chance (say, 0.01%) that a cell reproduces when it shouldn’t. This leaves a billion of such faulty cells. Given the amount of defence mechanisms to detect these cells, however, they rarely get to proliferate. There exists a web of defences, though eventually a cancerous cell can fall through the cracks—especially as we age, and senescence causes cell regulatory capability deterioration
• A cancer’s success can never be more than short term, because it has no way to disperse to other hosts, and its host’s death means its death too
• The more menstrual cycles a woman has, the more likely she is to develop reproductive-system cancer. This could be because historically women would have a later menarche (harsher living conditions), then would be pregnant or lactating, which both inhibit menstruation. Perhaps the reduced frequency of these processes lead to reduced cellular processes in the mammary glands and gonads that protect against cancers
• Oral contraceptives may reduce ovarian and uterine cancer risk, though they have their own side effects

  Chapter 13: Sex and reproduction

• The reason sexes exist at all, and that asexual reproduction isn’t as prevalent, is that:
  • It introduces more genetic variation;
  • It can prevent the accumulation of deleterious mutations; and
  • It decreases vulnerability to pathogens. If a pathogen finds the key to exploiting a genetically identical colony it will be able to wipe out all of them. If they are more genetically diverse, this is more difficult to accomplish. This idea is support by the fact that asexual reproduction occurs in areas with fewer parasites
• Large gametes have abundant energy stores, but are expensive to make; small gametes are inexpensive and can be produced in enormous numbers, but can’t survive for long
• Trees are hermaphrodites, carrying both eggs and sperm(?) cells, can do so because reproduction can be done by vector transport by air currents or insects. This is not possible with mammals, thus there are no mammal hermaphrodites
• Extra nutrients in sperm are more likely to retard its swimming, so low nutrient, fast sperm have been selected for
• There exists a battle between fetus and mother, as both share only 50% of genes with each other. As such, fetuses have strategies to increase nutritional consumption from the mother, and the mother’s system has methods to counter act these exploitative tactics
  • Fetuses secrete a hormone that increases and retrieves glucose from the blood, which increases the mother’s insulin production. This can produce pregnancy onset diabetes
  • Fetuses also secrete substances that increase blood flow to the placenta by constricting blood vessels throughout the body and increase blood pressure. Moderate increases in maternal blood pressure are associated with lower infant mortality
• Fetuses produce human chorionic gonadotropin (hCG), which blocks menstruation so that the fetus stays implanted. The mother’s body likely measures levels of hCG as means of detecting whether a fetus is viable or not. High hCG levels are the fetuses way of screaming “wait, don’t abort me!”

  Chapter 14: Are mental disorders diseases?

• Definitions of mental disorders were formed so research findings across different studies could be compared, however this emphasized sharp boundaries around symptoms instead of a continuous emotional process influenced by psychological factors, past events, and life situations
• Sleep tends to be dominated by visual sense. We’re hard pressed to reimagine sounds, smells, taste, and touch from our dreams. This could be because sight is rather useless as night, so dreams can fully employ sight, whereas sound, smell, and touch may have been necessary to stay online in the background to detect threats during sleep

  Chapter 15: The evolution of medicine

• Genetic instructions are assembled in preparation for the future, but are caused by the past