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Lift up your middle finger (not towards anyone!) and compare its length with your thumb. How does that ratio compare to other primates?
Gorilla and chimps between 35-40% and humans 55%.
What derived traits do humans share with apes?
Standing posture, absence of tail, large brain, flexible wrist and thumbs, flexible hips and ankles
Who are the extant representatives of the African great apes? What derived traits do humans share with African great apes?
Bonobo, chimps, gorillas Share elongated skulls, enlarged brows, fusion of wrist bones, enlarged ovaries, short canine teeth, changes in muscular anatomy, reduced hairiness
What data was used to produce the phylogeny shown in Fig. 20.2?
Strength of immune reaction between rabbit antihuman ABs and primate albumins measuring similarity. The similarity between albumin proteins reflects the species’ evolutionary kinship.
Which of the phylogenies shown in Fig. 20.3 has the most scientific support currently?
The relationship between African great apes and humans is characterized the best by the tree. Humans and chimps are more closely related than gorillas are to both of them.
Based on Fig. 20.7, when did the lineages of chimps and humans diverge?
Split 5.4+/- 1.1 mya
How do humans and African great ape karyotypes differ? What is thought to be responsible for that difference?
Gorillas and chimps have 24 pairs of chromosomes, humans have 23 pairs. In the ancestors of humans, two chromosomes fused to become chromosome 2.
How genetically similar are chimps and humans? How does this compare to the genetic difference between mice and rats?
4% of our genome differs from chimps, and 29% identical proteins. Humans are more similar to chimps than rats are to mice.
How do chimp, bonobo and human behavior compare?
Chimps are dominated by males, heterosexual. Bonobos are dominated by females and aggressive towards males. Humans are flexible culturally and evolutionarily.
What does the term ‘hominin’ refer to?
A species more closely related to humans than chimps
What was stunning about the Sahelanthropus cranium found in 2001? What was the scientific controversy concerning that fossil?
6-7 mil years old and shares traits with chimps and human-related species. Its age is close to when humans and chimps diverged. Looks like a chimp from behind, a human in front. The fossil represents the human side of the family tree because it resembles hominins more.
What is a genus of an undisputed (scientifically) early hominin? What were the physical features of this group?
Australopithecus and Kenyanthropus. Skulls with small braincases, and large faces. Males 1.4-1.5 m tall. Walk on two legs
How long was Australopithecus thought to be on the planet?
3.5 mya to less than 2 mya
How did Paranthropus compare to Australopithecus?
Small braincases, large faces. Paranthropus had robust jaws and large jaw muscles, and enormous cheek teeth
Were Homo habilis and Homo rudolfensis human?
Transitional hominins, among the first humans
Who is the undisputed (scientifically) earliest human, and what is their phenotype?
Homo ergaster. Smaller, flatter face, smaller teeth and jaws, longer legs, greater height, reduced sexual size dimorphism
How was Homo sapien Cro-Magnon I buried?
In a prepared grave with two adult men, an adult woman, and an infant. Buried with animal bones, jewelry, and stone tools. Sign of culture
What is interesting about Fig. 20.22? Why is the data not arranged in an evolutionary tree?
The horizontal axis gives approximate time ranges for species The phylogenetic relationships among the species of fossil hominins have not been definitively established.
What hypotheses about the evolution of hominins are well supported?
Record is detailed to conclude H. sapiens is the sole survivor
What is controversial about the Homo genus designation?
Know that humans are descendants, but don’t know how or where transition occurred from H. ergaster/erectus to H. sapiens.
Where were humans before Homo ergaster/erectus evolved? Where were the oldest Homo ergaster/erectus fossils found?
Africa Oldest fossil at Koobi For a in Africa, Dmanisi E Europe, Longgupo Cave in China, and Sangria and Mojokerto in Java (1.6-1.9 mya)
How did humans get from Africa to other parts of the world? (discuss Fig. 20.26)
African replacement Racial variation is the result of recent geographic differentiation that occurred the last 100-200k years Hybridization and assimilation/multicultural evolution
What can be determined from a comparison of human mitochondrial genomes shown in Fig. 20.29?
Phylogeny shows all non-African sequences branching from within the African sequences. Common ancestor of humans mitochondrial DNA lived in Africa.
Overall, what does the genetic and morphological data suggest about how modern humans descended from African ancestors?
Evolved in Africa, then replaced archaic humans elsewhere
What evidence prompted the ‘leaky replacement’ model for human origin?
2.5% of the genome of non-African modern humans derived from Neanddertal. 4.8% of the genome of Melanesians comes from Denisovans. Refutes African replacement model, consistent with replacement, hybridization and assimilation.
How does genetic diversity of humans differ from that of African great apes?
Human diversity occurs within individuals rather than in populations and much of the variation takes the form of rare alleles.
What traits distinguish humans from other primates?
Humans walk upright, large brains, reduced body hair, use tools, language
How do chimps use tools? How does human tool use differ from that of chimps?
Strip stems and twigs of leaves, use rods to fish termites out. Leaf umbrellas, napkins, and sponges. Rocks to open nuts Sophistication of manufacturing
What may be the first uniquely human tools? How old are the tools? Who made them?
Sharp edged stone flakes, handheld chopping tools 2.6 mil years old No evidence to indicate who made them.
How do human thumbs and chimp thumbs differ? Who cares?
Humans have more elaborate musculature Paleoanthropologists use thumb metacarpals to diagnose whether extinct hominins made and used stone tools.
“How far back in our evolutionary lineage can we trace the existence of language, and on what evidence?”
32,000 years, but do not know for sure. Cave paintings in Germany and France. Need language to build boats and cross the ocean.
How does the hyoid bone and the presence/absence of air sacs from the vocal tract affect language?
Increase low-frequency resonance, makes sound bigger, louder
Just a few decades ago, almost none of the fossils described in this chapter had been found. At that time, it was expected that when early hominin fossils were finally found, the first distinctly human feature—that is, the first derived trait of hominins that would distinguish them morphologically from the chimpanzee lineage—would prove to be an enlarged brain. It was thought that a large, human-sized brain must have evolved either before or simutaneously with bipedality. Now that we have the fossils to test this question, what do the fossils show? Which came first, large brains or bipedality?
Bipedality came first
How were Sarich and Wilson able to test the genetic relationships of humans to great apes when at the time (1967) it was not possible to sequence DNA?
Made antibodies for human albumin and looked at the strength of the reaction of the antibodies on primates and put them in phylogenies
The data in this chapter show that humans and the chimpanzees are each other’s closest relatives. Is it accurate to say that humans evolved from chimpanzees? How about that chimpanzees evolved from humans? Is it accurate to say that humans evolved from apes?
No, sister species because they have common ancestors. No, have been evolving separately for 3.5 mil yrs Yes, the immediate ancestor is African Great Ape
Look again at Figure 20.4, and this time focus on the diversity of sequences within each species. The length of the colored lines indicates the degree of genetic diversity within each species. a. Do humans have a large or small amount of genetic diversity, compared to the other primates studied? Which other species show similar patterns to humans? Why do you think some species have greater diversity than others? b. One of the human sequences is distinct from the other five. Can you guess the geographic location of this person?
A. Small based on the length of the horizontal lines compared to other species. Gibbons and bonobos similar because of their small geographic range, less gene flow b. Africa, traditional hunter gatherer
14 We reviewed genetic studies showing that non-African human populations are descended from African populations. Some people might conclude from these data that modern African people are in some sense “primitive.” What are the logical flaws in this thinking?
Not primitive because their culture advances with the rest of time.
15 Different ethnic groups within Africa are more diverse than the ethnic groups on all other continents put together. What does this imply about the common U.S. practice of categorizing people into groups of so-called Africans, Caucasians, Asians, Hispanics, and Native Americans?
Doesn’t make sense since they are homologous. Better to split each category into smaller categories.
20 The ancestors of horses are each known from dozens, hundreds, or in some cases even thousands, of virtually complete specimens. Yet hominin species of the same age are often known only from one or a very few partial specimens, such as the crushed partial skull of Sahelanthropus. As a result, we understand equine evolution much better than we do hominid evolution. Speculate as to why this is so: Why are hominin fossils rare? Does the scarcity of hominin fossils invalidate the conclusions of paleontologists? Put another way, is it really possible to learn anything useful from a single bone fragment?
Humans were restricted geographically and lived in forests while horses occurred worldwide.
Can you breed mice to be aggressive pup defenders?
Yes, inherited behavior
What are the four kinds of social interactions?
Mutual, selfish, altruistic, spiteful
Why do greater ani pairs nest with other pairs? How is this a mutual benefit?
The females lay eggs and work together to incubate them, feed chicks, interact, and defend the nest. Each pair has higher reproductive success
How do you clear a pond of cane toads? Why does this technique work? What is the advantage of cannibalism to cane toad tadpoles? Why is this selfishness?
By baiting funnel traps with bufagenins (tadpoles attracted to) Nutrition and the reduction of future competition, attracts other members The tadpoles benefit at the expense of the ones being eaten
Why is a Belding ground squirrel whistle selfish, but a trill is altruistic?
Gives a loud trill when danger is present, raises alarm to itself having a higher chance of being eaten.
How is bacteriocin production spite?
A bacterial cell that constructs and deploys them reduces the direct fitness of susceptible recipient cells
What is Hamilton’s rule?
Genetic model showing how an allele causing altruistic behavior can spread. Altruism is more likely to spread when the benefits to recipient are great, cost to actor is low, and participants closely related. Br-C>0 Br = benefit to recipient, C = cost to actor (units of surviving offspring)
What is the difference between direct and indirect fitness? What is kin selection?
Direct fitness- Reproduction an individual achieves on its own Indirect fitness- Additional reproduction by relatives that is made possible by the individuals actions Kin selection- Natural selection by indirect fitness gains
In what ways do black-tailed prairie dogs show kin selection?
Both males and females were more likely to give an alarm call if genetic kin, self-sacrifice directed at close relatives and results in indirect fitness.
How does relatedness influence the chance for adoption by red squirrels? What is cuter than Fig. 12.13a?
Only adopted kittens when they were relatives. Adopt kittens when the result is a net gain in the mother’s inclusive fitness.
What do human wills have to do with kin selection? Do Canadian wills follow Hamilton’s rule?
We have wills to provide resources for our kin when we die. Wealth is given to children, if none, then to relatives.
Do college students trust their kin? Do college students act selfish towards their kin? Is Western college student behavior typical of all humans?
Trusted fake relative over stranger, but no difference in selfishness Yes, optimistic
Explain cooperative breeding in birds. How does the extent of promiscuity influence the potential for cooperative breeding in birds?
Young that can breed will still help their parents with their siblings. Decreases promiscuity when cooperative occurs
In engineered E. coli, why did the frequency of cooperators increase over time if selection favors selfish freeloaders?
Cooperators increased because they provided common good to groups.
Why is there no ‘I’ in ‘team’ for plants?
Individual selection did not achieve maximum leaf area, only group max
How were honey sticks used to assess cooperativity with the Hadza? Does the extent of cooperativity affect how Hadza bands form?
More cooperative if donated stick. Grouped together if cooperative
Explain why weaning conflict occurs based on Fig. 12.29.
The offspring will be weaned when the cost is low and benefit is high
How is female promiscuity and chick begging related in barn swallows?
Higher female promiscuity, lower relatedness, chicks beg louder. Greater promiscuity is less cost
Why do white-fronted bee-eater fathers harass their sons into helping the father’s young-raising? What evidence supports this? How can this behavior be selected for?
Trying to break up nesting attempts of kin and do this to recruit helpers. 16/47 of harassment cases, behavior resulted in recruitment. Harassing a son may increase the cost of rearing young, helping is more favorable for the son
How does siblicide differ between the masked booby and the blue-footed booby? How are masked bobby parents involved? Why?
Masked booby- Bigger sibling pushes younger out. Parents tolerate siblicide, only one usually survives
Blue footed- Don’t push younger out right away, but will when famine occurs. Parents try to prevent death of offspring
Which baboons are most likely to respond to a threat grunt?
Listeners that had been groomed by the caller will move closer than those that were threatened.
How common is reciprocity in animals?
Rare, but common in intelligent and social species. Humans
Do people cooperate when there is no punishment for cheaters?
Punishment enhances cooperation. Humans can detect cheaters in social exchanges
What is a eusocial animal?
Animals with overlapping adult generations. Nonreproductives cooperatively care for young, extreme altruism
Compare the haplodiploidy hypothesis, with the monogamy hypothesis, with the ecology and life-history hypothesis for explaining the evolution of eusocial behavior.
Haplodiploidy- Males haploid, females diploid. Females more closely related to sisters than their offspring. Females are workers that care for non-offspring Monogamy- Facilitates eusociality. Full siblings increases individual’s inclusive fitness the same as offspring does Ecology and life history- Eusociality evolved by nest building and caring for larvae. Evolved multiple times, independently in insects that had primary factors favoring reproductive altruism involving details from ecology and life history
Suppose adult bee-eaters could raise only 0.3 more offspring with a helper than without a helper. Would you still expect male bee-eaters to give in to the harassment of their fathers, or would male bee-eaters tend to fight off their fathers? Explain your reasoning.
They should resist harassment and raise their own broods because they will raise .51 nestlings of their own, but by helping, they only add .3 more siblings. Equally related to their offspring and siblings
The cubs of spotted hyenas often begin fighting within moments of birth, and often one hyena cub dies. The mother hyena does not interfere. How could such a behavior have evolved? For instance: a. From the winning sibling’s point of view, what must B (benefit of siblicide) be, relative to C (cost of siblicide), to favor the evolution of siblicide? b. From the parent’s point of view, what must B be, relative to C, for the parent to watch calmly rather than interfere? c. In general, when would you expect parents to evolve “tolerance of siblicide” (watching calmly while siblings kill each other without interfering)
A. Siblicide should evolve only when benefit to the winning cub is half of the cost of siblicide. The winning cub is related to its sibling by .5. Winning cub increases survival and reproduction chance, making up for their sibling’s loss. B. Mother equally related to both cubs. This is an adaptive behavior, death must be balanced by survival of one cub. Implies that one or both of the cubs would have died anyway. C. Parents are expected to tolerate when reduction of offspring number improves chance of survival for surviving offspring. Most common reason is for limited food.
Blue jays (Cyanocitta cristata) seem better than American robins (Turdus migratorius) at recognizing individuals. In one study (Schimmel and Wasserman 1994), blue jays raised with robins could distinguish strange from familiar robins better than the robins themselves. Do you think these species differ in occurrence of kin selection or reciprocity (or both)? Why
Blue jays have kin selected altruistic behaviors and may exhibit reciprocal altruism. Blue jays need to recognize and identify individuals. Robins leave their families after leaving the nest and do not have altruistic behaviors. They do not recognize and remember individuals well.
The text claims that eusociality has evolved several times independently within the hymenoptera. What is the evidence for this statement? If it is true, in what sense is eusociality in ants, bees, and wasps an example of convergent evolution? (See Chapter 4)
Evolved in two lineages that are distantly related. Sphecid wasp/honeybee and paper wasp/ant lineage. Evolution of similar traits in distantly related lineages from similar ecological pressures is convergent evolution
Human siblings often show intense sibling rivalry that typically declines during the teenage years. Suggest an evolutionary explanation for this pattern
Rivalry lessens with age, young siblings are in conflict for parental resources (care). Later in life, children become less dependent on parents and are more likely to cooperate with siblings
What two innovations led to a dramatic decline in tuberculosis (and other infectious disease) in the early to mid-1900’s?
Antibiotics and sanitation, germ theory
What two populations are evolving in relation to health?
Evolution of pathogen population and host cell populations within patients
Why are pathogens very effective at evolving?
Large population sizes, short generation times, high mutation rates
What is hemagglutinin? Why were researchers interested in influenza A antigenic sites?
Coat protein in Influenza A, initiates infection by binding to sialic acid on surface of host cell. Main protein recognized by immune system Specific parts of foreign protein that immune system recognizes and remembers, hypothesized that flu strains of these sites would have a selective advantage. They looked at mutations that altered these sites.
What is interesting about the evolution of the influenza A hemagglutinin gene? Where were most of the amino acid substitutions in hemagglutinin in surviving virus?
Immune system does have strong selection on flu virus hemagglutinin genes and virus populations evolve in response. Evolve linearly. Most amino acid subs were in the antigenic sites.
Where does the flu name “H1N1” come from? How is it possible that two flu strains can have some genes that are closely related and others that are distantly related?
Refer to groups of hemagglutinin or neuraminidase, viral subtype (hemagglutinin-1, neuraminidase-1) Flu strains can trade genes
Why is it thought that the 1968 flu pandemic was so virulent? How do human flu stains acquire genes from bird strains?
Acquisition of H3 from nonhuman strain Bird strains can infect pigs, infecting humans
How do antibiotics undermine their own effectiveness?
Selection pressure on a specific pathogen instead of everything
Do bacteria within humans evolve resistance to antibiotics?
Yes, can become TB resistant
Is there a short-term cost of antibiotic resistance for bacteria? Is there a long-term cost?
Yes, viruses can increase in frequency in some cultures Yes, more evolution over time but a lower frequency of sensitive bacteria
What is the best way to maintain antibiotic effectiveness? Should doctors wash their hands between patients?
Don’t prescribe antibiotics for viral infections, if so, finish the prescription fully. Yes
What is virulence? How can increased virulence be an advantage to the pathogen?
The harm that is done by the pathogen to host Can increase the chance of being transmitted
Why is there a difference in the virulence of vector-born vs. directly transmitted diseases?
Disease transmitted by direct contact cannot be virulent, but vector born can travel on its own (insect, mammal)
Why might virulence vary with the degree a bacteria is transmitted by water?
Water can be a vector, so it can travel to others in an incapacitated host.
To what environment are humans adapted?
Used to occupy desert to arctic tundra.
How does a typical hunter-gatherer diet differ from yours? How about their daily exercise?
Energy from lean meat, fruits and veggies, few grains and milk products, varied diet Walked 5-6 miles a day. Modern people walk 1.5 miles a day.
Why might the lifespan for carriers of a cystatin C mutation have changed over the last 100 years?
Individuals with L68Q die in 30s now but used to live longer. Thought to be from lifestyle change of increased carbs and salt.
Is myopia heritable? Why wouldn’t myopia be selected against in human evolution?
Nearsightedness. Predisposition partially heritable. Probably was selected against but in modern society, may have adapted. Partially heritable because alleles that predispose some humans to myopia do not cause in hunter-gather environment.
Why is the rate of breast cancer so high in humans?
May be caused by pathogen
May be caused by interaction between genes and new environments.
Why might breast cancer be related to the prevalence of certain mice in the environment?
Mice carry mammary tumor virus causing mouse breast cancer. Could potentially cause breast cancer in humans. Mice more likely to carry MMTV in specific countries have higher rates of breast cancer.
What is the relationship between breast cancer and menstrual cycling? How do researchers know when Dogon women are menstruating?
Menstrual cycling elevates risk of breast cancer because of combination of estrogen and progesterone. Sleep in special menstruating huts. Pregnant more, nurse children longer, suppressing menstruation, 1/12 breast cancer rates than in North America.
How has human body mass changed in the U.S. over 150 years? How might our gut flora be related to changes in obesity rates?
Steadily increased over time Some antibiotics change gut microbiota, can contribute to obesity.
What evidence indicates that fever is an adaptation for iguana? Should an iguana take an aspirin when it has a fever?
Those that mimicked the behavioral fever temp survived while those at a lower temp died. No, iguanas develop behavioral fevers, but the meds prevented fevers, killing them.
Do anti-fever medicines have any effect on the course of the common cold in humans?
Interfere with immune response, fever is adaptive defense
Why not allow fever to take its course?
Fevers are an adaptive response to only some pathogens. Some can grow faster at fever temps. High temps can also cause tissue damage.
Why would we expect humans to be better parents to their own genetic offspring?
Care is expensive, reserving efforts for genetic offspring provides higher reproductive success.
How does parental effort vary in male reed buntings?
Chicks sired by males other than mother’s social mate in many nests and males adjusted parental effort accordingly
Do fathers in Trinidad spend more time with their biological children or stepchildren?
Biological children
How does cortisol levels vary in children of Dominica? Why?
Stepchildren had higher cortisol levels. More stress
a. As a review, summarize the evidence discussed in this chapter that antibiotic resistance is due to evolution (i.e., due to new mutations that increase in frequency due to antibiotic exposure). b. What would health-care workers, patients, and healthy people do if they wanted antibiotic resistance to evolve as quickly as possible? Do you know of any cases where humans are (unintentionally) doing this?
A. Can evolve resistance when exposed to antibiotics for many generations. Traced to particular mutation, KatG gene of tuberculosis bacteria. Population wide surveys show correlations of antibiotic use with rising antibiotic resistance. B. Exert strong selection by using antibiotics whenever possible. Common practice in human and vet med. Ex. Routine dosing of food animals with antibiotics, regular washing of surgery rooms with the same antibiotics, unnecessary prescriptions, and widespread otc use of antibiotic soaps.
a. In the study of streptomycin resistance, why did Shrag and colleagues use genetically manipulated bacteria, instead of the original wild-type bacteria, to compare sensitive versus resistant strains? b. Summarize the key finding of Shrag et al.’s study. Why are these results worrying to the medical and veterinary professions?
A. He wanted to test is back-mutation sensitivity would be favored after multiple generations of evolution with antibiotic use. Spliced back mutation gene into resistant strain B. After antibiotic is withdrawn, bacterial populations still resistant. Back mutations to sensitivity will not be favored. Bad news for efforts to reduce resistance by reducing antibiotic use.
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