Anthropology 160.001 The Human Life Course
Week 5 Readings: No readings(Tuesday, Thursday September 20, 22): Life History Theory and the Evolution of the Human Life Course – Hominid CharacteristicsEXAM 1 online, due 9/24 midnight
Continuation of Lecture 4…
Individual level: precisely looking at effects of natural selection through environmental and cultural factors. Natural selection favors both anatomical and behavioral traits.
Group selection: certain traits operate for the good of others (altruism) at the group level, even if disfavored for the individual.
Group Selection: mathematically improbable
∙ 1965: John Maynard Smith showed that in order for group selection to work, groups must go extinct at a faster rate than migration outward
o But in the real world migration and dispersal are extremely common
o When food runs out, the species migrates
Rejection of Group Selection:
1. There are no natural phenomena that require a group selection explanation
a. More parsimony at individual level We also discuss several other topics like What is the scientific study of interactions between organics and their environment?
2. There is a natural regulation of animal numbers that operates to prevent the kind of massive extinctions Wynne-Edwards imagined
3. Actual data on breeding success suggest that animals are reproducing as rapidly as circumstances permit and without concern over the possibility the species will survive some future resource limitation
a. Those with access to more resources tend to reproduce more
4. Group selection is a weak force and depends on very low migration rates
a. No large scale genetic differences between populations The problem of altruism: If you want to learn more check out What is strategic business manager?
Appears that individuals are making great sacrifices for the benefit of others
(See some examples from last week)
-How can these concepts be seen as altruistic? How can they be seen as individually beneficial?
Four types of social acts: selfish, altruistic, cooperative, and spiteful. On the horizontal axis: implications of a behavior to the donor (the one acting out the behavior)
On the vertical axis: impact that behavior has on the recipient Examples in nature:
-Soldier aphids protect their sisters, but never reproduce -Soldiers have evolved independently at least three times QUESTION: How could the genes for soldiers have increased in frequency if they do not reproduce?
ANSWER: soldiers are produced during an asexual stage genetically identical to their mothers. If, by protecting the gall, they increase their We also discuss several other topics like What is meant by reaction formation?
mother’s reproduction more than by reproducing themselves, their fitness is actually higher.
-Lay eggs in the nests of other species
QUESTION: why do the receiving species allow it?
-Yearlings and older remain with parents for long periods of time and help raise their siblings
QUESTION: Why do they not leave and reproduce on their own? ANSWER: there is high competition for nesting areas; therefore most tend to remain longer in order to avoid competition.
-One of the most basic forms of social exchange
-Among the Ache, all food is shared completely, yet some hunters produce more than 5 times as much as others -Ache children are taught to share from very young age
QUESTION: why is food sharing so important in human societies? ANSWER: food sharing is most common among kin or between those who posses a benefit for the sharer.
Adoption and Alloparental Care
-Adoption is also frequently practiced in humans
-Among the Efe, babies are passed from person to person and cared for by many If you want to learn more check out Deuterostomes exhibit what characteristics?
QUESTION: why is adoption/caring for the kin of others commonly accepted and practiced?
ANSWER: more often than not there is a .25 level of relatedness among human societal adoption.
Cooperative childcare in Efe occur at .125 relatedness
-Individual calling draws attention to the individual
-Predator hard-wired specific alarm calls in vervet monkeys QUESTION: is this true altruism?
ANSWER: ground squirrels call in proportion to the amount of kin present
ANSWERING THE QUESTIONS:
Inclusive Fitness and Kin Selection
Indirect fitness: the proportion of your genetic material shared in other individuals from common ancestor (aunt, sister, cousin, etc.)
*Fitness of a gene depends not only on its effect on the reproduction of the organism in which it is housed but also on its effects on the reproduction of other organisms in which the gene is housed. Inclusive fitness: the combination of direct and indirect fitness
Hamilton’s Rule: Benefits to the recipient (B) devalued by the coefficient of relatedness (r) must be greater than the costs to the donor (C) for altruism to be favored
Br > C
*Answers in green written after this segment
Importance of Kin
∙ Social life in pre-state societies are governed by kinship rules, and even much of social life in state societies is dictated by kinship
∙ Many anthropologists think this has nothing to do with kin selected altruism; kinship is defined differently in different societies and the concept of fictive kin is universal
∙ Humans preferentially associate with kin for the same reasons that other organisms do, but the importance of reciprocity in human societies often leads to the extension of social kinship to individuals with whom we share reciprocal aid
Study Guide for Exam 1
*This guide was given as a conceptual map for what to look for on the test and know how to answer in short answer questions. *The exam is online and will be open from today (9/20) until next week (9/27)
1. What is the Naturalistic Fallacy? Why must science avoid it? The confusion of what is with what ought to be. Humans are invested in the answers because we are studying ourselves.
2. Name some interesting adaptations of the Herring Gull. Uniquely adapted to it’s environment –trying to prevent chick lose through cannibalism, predation, inadequate growth rates. Nests are evenly spread apart, 3 eggs hatch synchronously to avoid competitive differences; eggs blend with the nest. Both parents brood them *highly vascularized patch on belly for heat transfer. Male feeds female while she lays eggs. Chicks are recognizable for feeding. Red spot on parents’ beak, when poked by children food is regurgitated. POINT OF THIS EXAMPLE: adaptation via environmental forces and selection pressures. Consistent selection pressures breed organisms well suited to their environments.
How do human universals mirror this?
3. Name three scientific methods, explain each.
Comparative –across species, cultures, individuals, etc. -Good for generalizability, bad for determining causal relationships
-Good control for consistency and causality.
-Ethic standards huge here!! This method can lead to immoral, impractical, or artificial data
-Undirected change is observed and measured by scientists Example: the ache started gardening/ enacted agricultural lifestyle after contact with outside culture
4. What are the advantages/disadvantages of each method when studying humans?
The comparative method holds generalizability however causation cannot be inferred.
The experimental method allows for control of variables however when using humans, many ethical concerns arise.
Natural observation is biased in the way that studying our own selves leads to preferred/intuitive conclusions that may not be correct.
5. What does effective science require? What are hypotheses, variables (dependent and independent), theory, etc.? What is the scientific method?
Clearly framed research question:
Descriptive: describes natural observations / the way things are Explanatory: says why something happens
Null hypotheses (no change) versus alternative hypotheses (change)
Assign definitions to predictor and controlled variables Measurement method:
3 as stated above
Decide how data will be collected
Identify sample population:
Representative of the greater population
Statistical evidence as scientific research
Use theory to interpret data and come to conclusions
THEORY: a set of principles regarding causal connections between variables that unites previously unconnected observations in a common framework and makes new predictions about previously unstudied relationships in a fashion that can withstand the scrutiny of empirical
6. What is a species?
-A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.
7. Name three fundamental components of Darwin’s Theory of Evolution by Natural Selection. How do those three components fit together to frame his theory?
1. There must be variation in a trait
2. That trait must be heritable
3. Beneficial to survival and reproduction
8. What kinds of traits can natural selection act upon? -Natural selection favors a suit of traits; environmental context helps determine which of those are expressed in the phenotype.
9. Explain Thomas Malthus' idea about population growth. What impact did it have on Darwin's theory of evolution by natural selection?
-Finite resources but infinite population growth. Malthus saw population growth as inevitable, which is contradictory to Darwin’s idea of selection.
10. What evidence did Darwin use to support his theory? How do things like anatomy, embryology and vestigial organs support the theory of evolution by natural selection?
- Artificial selection, geographical distribution, fossil record, comparative anatomy, comparative embryology, vestigial organs - Idea that certain things become less critical in the surrounding environment and eventually adapt out of the species like vestigial organs.
11. What are the two types of evolution? hint: one essentially improves on existing species and the other results in "new" species. Give an example of each.
1. Phyletic Phenotype changes
a. Dog breeds. Would someone who has never seen a dog think a Great Dane and Chihuahua belong to the same species?
2. Speciation divergence of a species
a. The Galapagos finches as seen in previous lecture
12. Explain "fitness" in the evolutionary context. Take a hard look in the mirror, really, how fit ARE you? How does this relate to “survival of the fittest?”
-How many offspring continue to reproduce generation after generation
13. How is evolution a creative process? Especially considering the random nature of genetic mutations?
-Does not generally innovate new traits. Evolution alters existing traits to come up with new expressions of them.
14. What is a phenotype?
-Expression of genes
-The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
*Natural selection acts on these
15. What is a genotype?
-Genetic make up of individuals
-Actual genetic code
*Used to measure the progress of evolution
16. How does natural selection act on each? (Partially answered above)
-Natural selection is physically observable through phenotype; the genotype helps track the progress of evolution and which traits are more likely to be selected.
17. Stabilizing, directional, and disruptive selection –define each and give an example.
Stabilizing: selection that favors the mean traits stay the same Disfavors the outliers spread of deviation decreases
Directional: favors one of the extremes, disfavors the other. The mean is altered.
Example in humans: brain size in Homo sapiens
Disruptive: favors both extremes, disfavors the mean
Example: males versus females
18. What are reaction norms/phenotypic plasticity? Why do we expect them to be adaptive? What are some examples? -Reaction norms: range of phenotypes that can be expressed from one particular genotype
Examples: puberty, cultural expression/identity
∙ Based on central nervous system
∙ Faster alteration of phenotypic expression than evolution -Phenotype plasticity: the ability to change reaction pattern to the environment that has evolved rather than a single invariant phenotype
Example: red blood cell density based on oxygen concentration of environment
19. Dung flies, crickets, sunfish – how do these examples show us that behavior can evolve?
Dung flies: use physical positioning to better their chances of mating Crickets: inhibited natural tendency to make noise in order to survive and reproduce
Sunfish: utilize physical make up to avoid predation and have higher chance of mating
20. Culture and learning – how do these relate to reaction norms? Do other species show learning biases? Humans? Culture shapes our reaction norms through formal and informal control. Cultural context and reaction norms are learned as well as widely variant in the world.
21. Levels of causation – proximate versus ultimate Proximate –what makes this behavior happen at any given moment? Hormonal cascade? Mechanism, physiological, neurotransmitters, male
Example: smoking has proximate causation by opening dopamine pathways, triggering immediate reward sensors Ultimate –in what ways does this behavior influence the survival and success of the organism? WHY? Fitness outcomes. Function or adaptive value, male rage
Example: tobacco lowers parasite load. Social smoking may lead to reproductive benefits due to social “attractiveness” of smoking
22. “Group” versus “Individual” selection is a REALLY important concept for this part of the class. Explain the implications of each in detail. Why was group selection originally proposed? **SHORT ANSWER QUESTION
Group: made to explain altruism
*Group selection relies on high extinction rates, low migration rates these prove to be mathematically impossible in the real world. No phenomena require group level explanation. Inclusive fitness and kin selection disprove group selection as well.
Group –helps the group to keep the population from overexploiting the resources
Individual -having babies too close together, some deformity of child
23. What is altruism? Pure altruism? How does it relate to group selection?
Definition: performing a behavior at the cost to oneself in order to refer a benefit to someone else
24. When Darwin said: “if a species was ever found to do something entirely for the good of another individual, his whole theory would fail” what did he mean? Why such drastic words?
He claimed his whole theory would fail if altruism were true because of the fact that natural selection favors certain traits that are beneficial to individual survival and reproduction. Altruism would ignore both aspects.
25. There are certain phenomena in the natural world that have been used to argue for group selection. Among them alarm calls, and food sharing. Use detailed descriptions of each of these phenomena to reject group selection theory.
Alarm calls: protect kin in the near by homes
Food sharing: strengthens kin
26. Explain kin selection, Hamilton’s rule, and how it is related to theories of group selection, individual selection and altruism. Examples in nature of kin selection? Examples in humans?
Hamilton’s Rule: Benefits to the recipient (B) devalued by the coefficient of relatedness (r) must be greater than the costs to the donor (C) for altruism to be favored. Br > C
27. Human universals – what are some of them and what do they show us about human evolution/ humanity?
-We expect to see human universals because we have common ancestors and they reflect solutions to shared adaptive problems / consistent adaptive pressures.
Example: mother ease as a language / mental maps
-We see such differences in actual behaviors because of reaction norms in different cultures
28. What do children with William’s syndrome show us? -Some areas/functions of the brain, such as language, can be left perfectly in tact while other areas are underdeveloped or damaged.
29. What do children with autism show us?
-Some areas of the brain can be maladapted without necessarily being damaged
30. What do populations like the Hutterites show us? -We have a brain that without law will keep track of group sizes about 150-200 individuals. After that number is exceeded, they break apart.