Evolution Exam 4

Lift up your middle finger (not towards anyone!) and compare its length with your thumb. How does that ratio compare to other primates?
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Terms in this set (104)
-the last common ancestor of these three probably passed on behavioral traits such as culture and hunting and preparing food.
-Chimp societies are dominated by males, typically heterosexual
-Bonobo societies are dominated by females and are aggressive towards males, have sex in all combinations
-Humans belong to a lineage in which behavior is flexible culturally and evolutionarily
What was stunning about the Sahelanthropus cranium found in 2001? What was the scientific controversy concerning that fossil?-the nearly complete cranium stunned paleoanthropologists, it was 6-7 million years old, and it shares traits of a chimp and other species that are more closely related to humans -some think it's the oldest known hominin but there is another fossil that is arguably the oldest hominin -For one thing, it was 6 to 7 million years old. This places it toward the older end of the window during which molecular biologists estimate that humans diverged from chimps. For another, it shows a curious mixture of traits. Its small braincase makes it look like a chimp from the back, but from the front it looks like a closer relative of humans because of its relatively flat face. -The reconstructed Sahelanthropus resembles known hominins more strongly than it does chimpanzees or gorillas, bolstering Brunet's view that his fossil represents the human side of the family tree. The issue is likely to be resolved only by the discovery of additional fossils, including postcranial remains.What is a genus of an undisputed (scientifically) early hominin? What were the physical features of this group?-Australopithecus and Kenyanthropus -Have skulls with small braincases, and relatively large, projecting faces. Females grew to heights of about 1.1 meters, whereas the males were some 1.4 to 1.5 meters tall. Both species walked on two legs.How long was Australopithecus thought to be on the planet?-Lived 3.5 million years ago. Archaic hominina assigned to the genus Australopithecus persisted until less than 2 million years ago. 2-4 myaHow did Paranthropus compare to Australopithecus?-Like Australopithecus, they had relatively small braincases and very large faces. Unlike Australopithecus, they had enormous cheek teeth, robust jaws, and massive jaw muscles, sometimes anchored to a bony crest running along the centerline on the top of the skull.Were Homo habilis and Homo rudolfensis human?-They are transitional hominins that many researchers consider to be among the first humans.Who is the undisputed (scientifically) earliest human, and what is their phenotype?-Homo ergaster -A relatively smaller, flatter face; smaller teeth and jaws; greater height; longer legs; and reduced sexual size dimorphismHow was Homo sapien Cro-Magnon I buried?-His skeleton was found in a prepared grave along with those of two other adult men, an adult woman, and an infant. The group had been buried with an assortment of animal bones, jewelry, and stone tools. First sign of cultureWhat is interesting about Fig. 20.22? Why is the data not arranged in an evolutionary tree?-The horizontal axis gives approximate time ranges for the species we have mentioned. Colors indicate rough groupings based on morphological and (inferred) behavioral and ecological similarity. -The phylogenetic relationships among the species of fossil hominins have not been definitely established.What hypotheses about the evolution of hominins are well supported?-The hominin fossil record is sufficiently detailed to allow us to conclude that Homo sapiens is the sole survivor among a diversity of species.What is controversial about the Homo genus designation?-Paleoanthropologists generally agree that modern humans are the descendants of some or all of the populations in the H. ergaster/erectus group. However, how and where the transition from H. ergaster/erectus to H. sapiens took place is a matter of debate.Where were humans before Homo ergaster/erectus evolved? Where were the oldest Homo ergaster/erectus fossils found?-Africa -The oldest examples of H. ergaster/erectus, however, appear in the fossil record nearly simultaneously at Koobi Fora in Africa, at Dmanisi in the Caucasus region of eastern Europe, at Longgupo Cave in China, and ar Sangria and Mojokerto in Java - all 1.6 to 1.9 million years ago.How did humans get from Africa to other parts of the world? (discuss Fig. 20.26)-African replacement - present-day racial variation is the result of recent geographic differentiation that occurred within the last 100,000 to 200,000 years, after anatomically modern H. sapiens emerged from Africa. -Hybridization and assimilation/multicultural evolution - present-day racial variation represents a mixture of recent and ancient geographic differentiation. At least some of the differences among modern humans from different regions may derive from geographic differentiation among H. ergaster/erectus populations and could thus be as much as 1.5 to 2 million years old.What can be determined from a comparison of human mitochondrial genomes shown in Fig. 20.29?-Their phylogeny has strong statistical support and shows all non-African sequences branching from within the Africian sequences. It appears that the common ancestor of all present-day human mtDNAs lived in Africa.Overall, what does the genetic and morphological data suggest about how modern humans descended from African ancestors?-Analyses of modern human DNA suggest that modern humans evolved in Africa, then replaced archaic humans elsewhere.What evidence prompted the 'leaky replacement' model for human origin?-Reich and colleagues estimate that 2.5% of the genome of non-African modern humans is derived from Neandertals, and that an additional 4.8% of the genome of Melanesians comes from Denisovans. This result refutes the African replacement model and is consistent with a scenario between replacement and hybridization and assimilation. It is described as the "leaky replacement"How does genetic diversity of humans differ from that of African great apes?-Most of the genetic diversity among living humans occurs as differences among individuals within populations, rather than as differences between populations. If there are genetic differences that distinguish human populations, then individuals from the same geographic region should have similar group-membership profiles and they do. -The lesson is that genetic differences among modern human populations do exist, but they are subtle enough that it takes extraordinarily large data sets and considerable computational effort to find them. -Much human variation takes the form of rare alleles.What traits distinguish humans from other primates?-Humans walk upright, have large brains, use fire, have reduced body hair, use tools and communicate with languageHow do chimps use tools? How does human tool use differ from that of chimps?-They strip stems and twigs of leaves and use the resulting rods to fish termites out of termite mounds. They use leaf umbrellas, napkins and sponges. They use rocks as anvils and hammers to open nuts. Some of the individuals in the population reliably throw missiles, while other individuals do not. -What separates human tools from those of chimps is the sophistication of their manufacture and use.What may be the first uniquely human tools? How old are the tools? Who made them?-The earliest tools to appear in the archaeological record that are beyond the capacities of chimps are sharp-edged stone flakes and handheld chopping tools. (Oldowan-style stone tools) -2.6 million years old -While there is no good circumstantial evidence to indicate that Paranthropus may have been responsible for Oldowan tools, some indirect evidence of their tool-using capabilities comes from their anatomy.How do human thumbs and chimp thumbs differ? Who cares?-Humans have more elaborate musculature. They even have muscles, such as the flexor pollicis longus, that chimps lack. Associated with their more elaborate musculature, humans have thicker metacarpal bones with broader heads. These differences in anatomy make the human hand more adept at precision grasping than the chimp hand. Susman argues that the modified anatomy of the human thumb evolved in response to selection pressures associated with the manufacture and use of complex tools. -Paleoanthropologists because we can 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?"-Expert opinion is diverse. Noble and Davidson assert that the only reliable evidence is located in the archaeological record. The first unequivocally arbitrary symbols occur in cave paintings, found in Germany and France, that are about 32,000 years old. Even Noble and Davidson cannot quite accept that language is as recent an innovation as that. They note that Homo sapiens had colonized Australia by 40,000 years ago - possibly as early as 60,000 years ago - and confess that they cannot imagine how people could build boats and cross the open ocean without language to facilitate planning and coordination. However, Noble and Davidson hold the line at about 40,000 years. This date would imply that H. sapiens is the only species ever to use language. -In contrast, after examining casts of the insides of the brain cases of specimens of Homo habilis, Phillip Tobias suggested that language may be as much as 2 million years old. In addition to their sheer size, the endocasts revealed what appear to be derived structural traits characteristic of our genus. Among them were enlargements of Broca's and Wernicke's areas. By his own account, this discovery converted Tobias from a skeptic to an advocate of the hypothesis that language first emerged, at least in rudimentary form, in the earliest Homo sapiens.How does the hyoid bone and the presence/absence of air sacs from the vocal tract affect language?-Among their effects is to increase the low-frequency resonances of vocalizations, which makes the vocalizer sound bigger.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 si-multaneously with bipedality. Now that we have the fos-sils to test this question, what do the fossils show? Which came first, large brains or bipedality?Bipedality came first. This was a surprise to most paleontologists. The breakthrough discovery was the famous australopithecine fossil "Lucy," which contained the necessary parts to test this question. Subsequent discoveries have confirmed that bipedality is the trademark of the hominine lineage; it was apparently a breakthrough adaptation that evolved immediately after, or during, the split from the chimpanzee lineage. But only a few hominins went on to evolve enlarged brains—and only quite recently.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?Sarich and Wilson took advantage of a natural tool provided by mammalian evolution: the immune system's antibodies. Infection with any foreign protein (antigen) causes the immune system to produce antibodies that will bind to just that one antigen. Antibodies are so precise in their binding affinities that they can distinguish between very closely related proteins—and for this reason have become a major tool of molecular biologists. Sarich and Wilson simply injected purified human serum albumin into rabbits, and then tested the rabbit's antibodies for their strength of binding to serum albumin from other primates.The data in this chapter show that humans and the chim-panzees 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?Saying that one of a pair of sister species "evolved from" the other is never correct (any more than would be saying that one sibling descended from another). We can say that humans and chimps shared a common ancestor, and it's possible that that ancestor resembled chimps more than it did humans. But chimpanzees have been evolving separately from humans for 3.5 million years or so, and are themselves derived, relative to that ancestor. It is, however, accurate to say that humans evolved from apes. The immediate ancestor of humans and chimpanzees was certainly an African great ape, whatever its mixture of human—like or chimpanzee—like traits.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) Humans have very little genetic diversity compared to common chimpanzees, gorillas, and orangutans, especially considering the relatively large number of individuals tested. Gibbons and bonobos appear to also have rather low genetic diversity (though fewer individuals were tested in their cases.) This is probably related to small geographic range (in the case of bonobos or gibbons) and/or recent genetic bottlenecks (in the case of humans). B) Since the most diverse human sequences occur in Africa, it is a safe guess that this sequence is from Africa. In fact, the sequence in question is from a !Kung tribesperson of South Africa. The other five humans included three other Africans of different tribes, an Asian, and a "presumably, Northern European."Jared Diamond finds ethical dilemmas in the close kinship between humans and chimpanzees: "It's considered acceptable to exhibit caged apes in zoos, but it's not ac-ceptable to do the same with humans. I wonder how the public will feel when the identifying label on the chimp cage in the zoo reads Homo troglodytes" (Diamond 1992, p. 29). Diamond finds the use of chimpanzees in medical research even more problematic. The scientific jus-tification for the use of chimpanzees is that chimpanzee physiology is extremely similar to human physiology, so chimpanzees are the best substitute for human subjects. Diamond notes that jails are a very rough analogue to zoos, in the sense that they represent conditions under which we do consider it acceptable to keep people in cages without their consent (if not to display them). But there is no human analogue to research on chimpanzees: Under no conditions do we consider it acceptable to do medical experiments on humans without their consent. Is it ethically justified to keep animals in zoos? To use animals in medical research? Does the phylogenetic relationship between ourselves and the animals in question matter? If so, how and why?These questions are largely matters of personal morals and ethics. The phylogenetic relationship between our species and the other species in question does matter to the extent that it informs both the potential usefulness of those animals (e.g., for biomedical research) and the potential harm we do by exploiting them (the response of chimps to being caged in artificial settings may be more similar to humans being kept under similar circumstances than the response would be regarding fish or small mammals)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?Although non—African human populations are descended from African populations, so are modern African human populations. That is, both modern African and non—African human populations are "equally evolved" from their most recent common ancestor; modern African human populations cannot, therefore, be considered "primitive."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?Assuming that naming a group implies that members of that group are more similar to each other than they are to members of other groups, the "African," "Caucasian," "Asian," "Hispanic," and "Native American" categories badly misrepresent human genetic diversity because there is more variation within the group "African" than there is among the other groups. To be accurate, we should "split" the African group into several different ones and "lump" many of the non—African groups together.The ancestors of horses are each known from doz-ens, 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?The primary reasons appear to be that the ancestors of the hominin species were geographically very restricted, occurring only in relatively small locations on a single continent, whereas equines occurred worldwide. Second, the great apes were probably never very abundant in population, and certainly never approached the high population densities of plains grazing animals. Third, it appears that the human/chimpanzee ancestors may have lived in forest environments, which is a very poor location for fossilization. It is a testament to the persistence of field paleontologists in the last 50 years that we now have as many hominin fossils as we do. Fragmentary fossils certainly demand expert anatomical skill on the part of the paleontologists. Rarely is any scrap of bone so thoroughly scrutinized as when it is from a potential human ancestor. Luckily, it is indeed possible to learn something from a single bone fragment, if it is the right fragment—for example, a knee joint, a tooth, or a part of the braincase. The best course of action is undoubtedly to look for more fossils; and paleontologists continue to do exactly that.Can you breed mice to be aggressive pup defenders?-yes, after about 8 generations of breeding, the females were defending their pups more and more vigorously than the control groupWhat are the four kinds of social interactions?-mutual benefit interaction (actor and recipient), selfish interaction (actor benefits), altruistic interaction (actor sacrifices for benefit of other), and spiteful interaction (both actor and recipient are negatively impacted)Why do greater ani pairs nest with other pairs? How is this a mutual benefit?-all the females lay eggs and all the adults work together to incubate the eggs, feed the chicks, social interaction, and defend the nest -each pair reaches higher reproductive success by working together than any of the pairs could aloneHow 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 - cane tadpoles find bufagenins irresistible. -nutrition and the reduction of future competition, also attracts other members of the species -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 off a loud trill in response to danger approaching to let know know to flee, but the squirrel raising the alarm reduces its own chances of dying by informing the hawk that the caller has seen itHow is bacteriocin production spite?-by making and releasing bacteriocins, a bacterial cell that constructs and deploys them reduces the direct fitness of susceptible recipient cellsWhat is Hamilton's rule?-genetic model showing how an allele causing altruistic behavior can spread - Br - C > 0 , where B is the benefit to the recipient and C is the cost to the actor. Both variables are measured in units of surviving offspring -shows that altruism is more likely to spread when the benefits to the recipient are great, the cost to the actor is low, and the participants are closely relatedWhat is the difference between direct and indirect fitness? What is kin selection?- Direct fitness: results from reproduction an individual achieves on its own - Indirect Fitness: results from additional reproduction by relatives that is made possible by the individuals actions - Kin Selection: natural selection leading to the spread of alleles that increase the indirect component of fitnessIn what ways do black-tailed prairie dogs show kin selection?-in an experiment, it was found that both males and females were more than likely to give an alarm call if the coterie includes genetic kin, self sacrifice is directed at close relatives and thus should result in indirect fitness gainsHow does relatedness influence the chance for adoption by red squirrels? What is cuter than Fig. 12.13a?-the mother squirrel adopted kittens only when they were a relative, the association between kinship and adoption is consistent with Hamilton's rule. They adopt the kittens when the result is a net gain in the mother's inclusive fitnessWhat do human wills have to do with kin selection? Do Canadian wills follow Hamilton's rule?-humans care what happens to our wealth when we die because we want the resources we have accumulated to keep working on our genes behalf, if this is true Hamilton's rule should predict who people bequeath money to. Most wealth will be given to direct offspring, if they don't have it, then whatever relatives they have, so it is always given to kin - in Vancouver, 38.6% of wealth went to offspring, 7.9% went to siblingsDo college students trust their kin? Do college students act selfish towards their kin? Is western college student behavior typical of all humans?-Yes -Took the person's own avatar and ½ blended it with a random person and created a fake relative, they were more willing to trust this fake relative than random strangers -They do act selfish towards their kin -Yes-ish, college students are optimistic so must look at these studies with caution (page 477)Explain cooperative breeding in birds. How does the extent of promiscuity influence the potential for cooperative breeding in birds?-In species from a wide variety of bird families, young that are old enough to breed on their own instead remain and help their parents rear their brothers, sisters, or half-siblings. Helpers assist with nest building, nest defense, and/or food delivery to incubating parents and chicks. -Decreases, "how do they know that, I don't know" - Mark HammerIn engineered E. coli, why did the frequency of cooperators increase over time if selection favors selfish freeloaders?-The cooperators increased over time because they provided a common good to their social groupsWhy is there no 'I' in 'team' for plants?-when individuals that interfere with their neighbors that are present in a group, the entire group may suffer. They bred different populations that had high to low leaf areas, or selected the groups that had the maximum leaf areas. Individual maximum leaf area did not give benefit to the entire group, wanted to select for the group maximum leaf areaHow were honey sticks used to assess cooperativity with the Hadza? Does the extent of cooperativity affect how Hadza bands form?-each individual got honey sticks to give or donate, the ones that were donated were put into a pot, then the researchers added more sticks to the pot and they were given back to those that donated -when the scores were compared they found more variation, more cooperative ones seemed to group together, seemed to be an affinity for those who worked togetherExplain why weaning conflict occurs based on Fig. 12.29.-Until the offspring is reaching the maximum benefit, they are going to carry you until you are able to go out on your own, the time to wean is when the cost is low and the benefit is high.How is female promiscuity and chick begging related in barn swallows?-in an experiment with barn swallows they found that chicks attempt to influence the way the parent distributes food by begging. When a bird species evolves a higher level of female promiscuity and thus a lower average relatedness among chicks in the nest, the chicks beg louder. Greater promiscuity means less costWhy 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?-they interpret this behavior by proposing that instigator are actively trying to break up the nesting attempts of close kin and they suggested that instigators do this to recruit the targeted individuals as helpers at their own nest - in 16 of the 47 observed cases of harassment, the behavior actually resulted in recruitment, the harassed individuals abandoned their own nesting attempts and helped the instigator, 62% of those success cases were father-son - they payoff from having helpers vs not having helpers is close enough to suggest that parents can change the cotton line of the fitness accounting, harassing a son may tip the balance by increasing his cost of rearing young, and then helping becomes a more favorable strategy for the sonHow does siblicide differ between the masked booby and the blue-footed booby? How are masked bobby parents involved? Why?- masked boobies usually lay only two eggs and one is born before the other and after a couple days after the second one hatches, the bigger one pushes the younger one out, the blue footed boobies don't always push the younger ones out right away, and they even let them eat more when food is scarce, but if the famine continues for a long time, the older one will attack the younger one which reduces competition and increases its own survival - masked booby parents tolerate siblicidal chicks while blue footed patents try to prevent the death of other offspring - why masked booby parents tolerate siblicide is unclear. Only one offspring typically survives so it doesn't matter if one dies and only one survivesWhich baboons are most likely to respond to a threat grunt?-listeners that had been groomed by the caller were more likely to move closer than were listeners who had been threatened by the callerHow common is reciprocity in animals?-thought to be fairly rare, but common in intelligent and social species like humansDo people cooperate when there is no punishment for cheaters?-punishment enhances cooperation, but it's important to recognize the tendency to punish insufficient cooperation varies across cultures -humans are good at detecting cheaters in social exchanges and punishment is a strategy used to limit itWhat is a eusocial animal?-animals that have overlapping adult generations in which nonreproductive individuals participate in the cooperative care of young, extreme form of altruismCompare the haplodiploidy hypothesis, with the monogamy hypothesis, with the ecology and life-history hypothesis for explaining the evolution of eusocial behavior.- haplodiploidy: males are haploid and the females are diploid. Males develop from unfertilized eggs, females from fertilized so females are more closely related to their sisters than their own offspring. It was argued that females can maximize their inclusive fitness by acting as workers and investing in the production of sisters, rather than by acting as reproductives - monogamy: lifelong monogamy facilities the evolution of eusociality. When an individual can be certain that future siblings are full siblings, a new brother or sister increases indifical's inclusive fitness as much as an offspring does - ecology and life-history: the evolution of eusociality hinges on ecological and life-history factors such as nest building and caring for larvae. Through an evolutionary tree it was determined that eusociality evolved multiple times, independently, in groups of insects that had primary factors favoring reproductive altruism involving details from ecology and life-historySuppose adult bee-eaters could raise only 0.3 more off-spring 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.Male bee-eaters should evolve to resist parental harassment and should tend to raise their own broods instead of helping at their parents' nest. If they try to raise their own broods, they will, on average, raise 0.51 nestlings (average nest success with no helpers), but if they help at their parents' nest, the helping will add only 0.3 more siblings, on average. Since 0.51 is substantially higher than 0.3, and since males are equally related to their own offspring and to their siblings (r = 1/2), males should try to raise their own offspring.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 sib-lings kill each other without interfering).A) Siblicide should evolve only when the benefit to the winning cub, B, is at least half of the cost of siblicide, C. This is because the winning cub is related to itself by r = 1.0 and is related to its sibling by r = 0.5. The winning cub must be increasing its chance of survival and reproduction markedly, enough to produce an entire additional offspring, in order to make up for the loss of the sibling. B) The mother is related equally to both cubs (r = 1/2). By tolerating siblicide, she loses an entire offspring. If this is an adaptive behavior, the death of the losing cub must be balanced by the survival of the winning cub. (It is also possible that the mother hyena may be able to produce a few additional future offspring herself, by not having to care for as many cubs in the present.) This implies that one or both of the cubs would have died anyway even if no siblicide had taken place. C) Generally, parents are expected to tolerate siblicide whenever reduction in the number of offspring greatly improves chances of survival for the surviving offspring. The most common reason for this is limited foodBlue 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 reci-procity (or both)? Why?Blue jays have a complex social system and remain in small family groups for several months after leaving the nest. They are suspected to have kin-selected altruistic behaviors and may also exhibit reciprocal altruism. Both of these behaviors (after leaving the nest) require the ability to recognize and identify individuals. American robins, in contrast, leave their families when they leave the nest, and are not known for any altruistic behaviors. In consequence, their ability to recognize and remember individual birds is not as highly developed as in blue jays.The text claims that eusociality has evolved several times independently within the hymenoptera. What is the evi-dence for this statement? If it is true, in what sense is eusociality in ants, bees, and wasps an example of con-vergent evolution? (See Chapter 4.)The evidence for independent evolution of eusociality in the hymenoptera is summarized in the phylogeny in Figure 12.37 on page 485. Eusociality evolved in two lineages that are quite distantly related to each other-the sphecid wasp / honeybee lineage, and the paper wasp / ant lineage. Evolution of similar traits in unrelated or distantly related lineages, due to 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.-The evolutionary explanation for sibling rivalry that lessens with age is that human siblings are (subconsciously) in conflict for parental resources during a time of life when parental care is especially important. Since a child is related to itself by r = 1 but is related to siblings by r = 1/2, evolutionary theory predicts that each sibling should try to get more than its share of parental resources (food, protection, living space, information, etc.). This puts siblings in direct conflict with each other. However, siblings should not try to completely monopolize parental resources-they should aim for siblings to have one-half the parental resources that they themselves get. -Later in life, as children become less dependent on their parents, the benefits of monopolizing parental resources become less and less significant. Humans are then more likely to cooperate with or even assist their 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 (housing and nutrition), germ theory of disease - things we can't see are causing diseases and sicknessWhat two populations are evolving in relation to health?-evolution of pathogen population and host cell populations within individual patientsWhy are pathogens very effective at evolving?-they have large population sizes, short generation times, and high mutation ratesWhat is hemagglutinin? Why were researchers interested in influenza A antigenic sites?-the predominant coat protein in influenza A which initiates an infection by binding to sialic acid on the surface of a host cell. It is also the main protein recognized, attacked, and remembered by the immune system -these sites are specific parts of a foregin protein that the immune system recognizes and remembers, it was hypothesized that flu strains with these sites would enjoy a selective advantage. For the protein to stay alive, it needs hosts that have never been exposed or it must alter the protein, so they looked into the mutations that alter those sitesWhat is interesting about the evolution of the influenza A hemagglutinin gene? Where were most of the amino acid substitutions in hemagglutinin in surviving virus?-It appears that the human immune system does, indeed, exert strong selection on flu virus hemagglutinin genes and that virus populations evolve in response. They evolve in a very linear rate -the most amino acid substitutions were in the antigenic sitesWhere 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?-the labels give the year of isolation and the viral subtype (hemagglutinin-1, neuraminidase-1) -flu strains can trade genesWhy is it thought that the 1968 flu pandemic was so virulent? How do human flu stains acquire genes from bird strains?-the acquisition of H3 from a nonhuman strain -bird strains sometimes infect pigs. Humans become infected from pigsHow do antibiotics undermine their own effectiveness?-selection pressure to a specific pathogen instead of putting it in everythingDo 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, in different cultures a virus increased in frequency in 14.14 -Yes, more evolution over time but a lower frequency of the sensitive bacteriaWhat is the best way to maintain antibiotic effectiveness? Should doctors wash their hands between patients?-Usually don't prescribe antibiotics for viral infections, but if you do, finish your prescription fully instead of stopping when you feel better -YesWhat is virulence? How can increased virulence be an advantage to the pathogen?-the harm done by a pathogen to its host -Can increase its chances of being transmittedWhy is there a difference in the virulence of vector-born vs. directly transmitted diseases?-diseases that are transmitted by direct contact cannot afford to be virulent but vector born can travel on its ownWhy might virulence vary with the degree a bacteria is transmitted by water?-Water is a community place and can act as a vector, so even in an incompacitated host it can still travel and infect othersTo what environment are humans adapted? (Humans have spent 5% of our time as agriculturalists, Agriculture 10,000 ya, Homosapiens 200,000 ya)-all humans used to live as hunter-gathers, who occupied anything from desert to arctic tundra but that is nothing like the modern urbaniteHow does a typical hunter-gatherer diet differ from yours? How about their daily exercise?-get energy from eating leaner meat, more fruits and vegetables, fewer cereal grains, and fewer milk products, theirs was more varied -they walked about 5 to 6 miles a day and a modern american office worker is usually around 1.5miles per dayWhy might the lifespan for carriers of a cystatin C mutation have changed over the last 100 years?-individuals with L68Q usually die in their 30s nowadays when they used to live longer and its thought to be because of a lifestyle change, the increased consumption of carbs and saltIs myopia heritable? Why wouldn't myopia be selected against in human evolution?-nearsightedness is partially heritable, predisposition not the condition -it probably was but we live in a modern visual society where the eyes probably adapt and change, it can be partially heritable because the alleles that predispose some modern humans to myopia do not cause myopia in a hunter-gather environmentWhy is the rate of breast cancer so high in humans?-2 reasons: 1. breast cancer may be caused by a pathogen such as a virus or bacterium 2. Breast cancer may be a disease of civilization - it may be caused by the interaction between genes and novel environments our ancestors weren't exposed toWhy might breast cancer be related to the prevalence of certain mice in the environment?-mice carry a virus called mammary tumor virus that causes the mouse equivalent of breast cancer and its thought that it potentially could cause breast cancer in humans, some mice are more likely to carry MMTV and those countries with those mice are seen to have a higher rate of breast cancerWhat is the relationship between breast cancer and menstrual cycling? How do researchers know when Dogon women are menstruating?-menstrual cycling appears to elevate the risk of breast cancer because the combination of estrogen and progesterone present during the postovulatory phase stimulates cell division in the linings of the milk ducts -these women sleep in special menstruating huts. They are pregnant more than in developed countries and they nurse their children longer which both suppress menstruation so they have 1/12 the breast cancer rates than in North AmericaHow has human body mass changed in the U.S. over 150 years? How might our gut flora be related to changes in obesity rates?-has steadily increased overtime -some antibiotics may play a role in changing our gut microbiota, disruption of the gut microbiota can contribute to obesityWhat evidence indicates that fever is an adaptation for iguana? Should an iguana take an aspirin when it has a fever?-they infected iguanas with bacteria then prevented them from thermoregulating, most that mimicked the behavioral fever temperature survived when the ones kept at a lower temperature died -no, the iguanas still developed behavioral fevers despite the medication and then they died since the drugs prevented the need for a feverDo anti-fever medicines have any effect on the course of the common cold in humans?-antifever medications interfere with the immune response to the common cold and therefore that fever is an adaptive defense against the diseaseWhy not allow fever to take its course?-fever may be an adaptive response to some pathogens but not others, some bacteria or viruses grow and reproduce faster at fever temps, and even when a fever is beneficial it carries other costs such as tissue damageWhy would we expect humans to be better parents to their own genetic offspring?-care is expensive for the caregiver, and caregivers who reserve their efforts for their own genetic young should have higher reproductive successHow does parental effort vary in male reed buntings?-chicks were sired by males other than their mother's social mate in many nests and the males adjusted their parental effort accordinglyDo fathers in Trinidad spend more time with their biological children or stepchildren?-Biological childrenHow does cortisol levels vary in children of Dominica? Why?-Stepchildren had the highest levels of cortisol, more stressa. 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. Schrag et al.'s study showed that a population of bacteria can evolve antibiotic resistance when exposed to an antibiotic for many generations. Many similar studies have traced the origin of resistance to a particular mutation, such as mutations in the KatG gene of tuberculosis bacteria. Doing such studies in humans is obviously impossible, but Bishai et al. were able to study the origin of a rifampin-resistant strain of tuberculosis (TB) from a single patient. They demonstrated that the resistant TB strain was genetically identical to the patient's earlier sensitive strain, except for a single point mutation conferring resistance, and that it was different from all rifampin-resistant strains examined. This is evidence that that patient's resistant TB strain arose from a new mutation, probably in that one patient. Bloch et al.'s survey of isoniazid resistance in tuberculosis patients showed that occurrence of resistant strains in particular patients is correlated with whether that patient has previously been treated with antibiotics. Finally, population-wide surveys frequently show close correlations of antibiotic use with rising antibiotic resistance, as in Austin et al.'s population-wide study of penicillin resistance in Pneumococcus of Icelandic children. b. The surest way to accelerate evolution is to exert strong selection. In this case, that means using antibiotics routinely wherever possible. Unfortunately, this has been common practice in human and veterinary medicine. Some examples are the routine dosing of food animals with antibiotics, regular washing of surgery rooms with the same antibiotics after every surgery, unnecessary prescriptions of antibiotics for human patients, and widespread over-the-counter 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. Shrag et al. wanted to test whether a back-mutation to sensitivity would be favored after many generations of evolution in the presence of antibiotics. Comparing the resistant strain to a wild-type strain would not be a fair test of this question because the wild-type strain would lack whatever other genetic differences might have accumulated during the generations of evolving in the new environment. Their solution was to splice just the sensitive gene-the desired back-mutation-into the resistant strain. b. The key finding is that even after an antibiotic is withdrawn from use, bacterial populations may continue to be resistant. Back-mutations to sensitivity will not necessarily be favored. This is bad news for efforts to reduce antibiotic resistance by reducing use of antibiotics.The male reed buntings in Dixon et al.'s study (Figure 14.31) seem to be consciously aware of genetic relationships and "trying" to increase their reproductive success. Can evolution cause reed buntings (and other animals) to behave as if they are aware of the evolutionary consequences of their actions, without actually being aware of them? Does your answer also apply to humans?Evolution is expected to result in behaviors that have certain precise consequences for reproductive success, but without the animal having any awareness of those consequences. The internal motivation is not important to natural selection. Any internal motivation will do, as long as the behavior occurs, and as long as it is heritable. To put it in intuitive (and anthropomorphic) terms, the reed buntings might be feeling an internal motivation along the lines of "I just feel like feeding these babies. . . . I don't know why, but I just do." Or perhaps "I feel like feeding these babies because I spent a lot of time with this female, and I like hanging out at her nest." Or the birds might not be thinking anything at all. They are certainly not thinking "I need to enhance my reproductive success, and probability of paternity is higher in this nest."The same may very well be true of humans. In fact, the human behaviors thought to be most strongly influenced by evolution tend to be governed by "hot-blooded" emotions that are not very susceptible to reason. A person who discovers his or her mate has been unfaithful does not sit down and calculate r values of relatedness and probability of paternity; he or she is more likely simply to fly into a jealous rage.In 1999, a mysterious outbreak of human encephalitis occurred in the northeastern United States. The cause was tentatively identified as St. Louis encephalitis virus. At the same time, an unusual number of dead birds were noticed along the northeastern Atlantic coast. Figure 14.36 shows genetic relationships of three known encephalitis viruses (St. Louis, Japanese, and West Nile) and several viruses isolated from the birds, from two human patients that died, from one dead horse, and from mosquitoes. (Data compiled from Anderson et al. 1999 and Lanciotti et al. 1999.)The birds, horse, and humans were all suffering from West Nile virus, which is now well known to be spread by mosquitoes.An avian influenza virus of type H5N1 has recently evolved a "high pathogenicity" (hp) strain that causes severe illness in most wild birds (except ducks) as well as in domestic poultry. A few humans have been infected. The World Health Organization (WHO) currently inspects every human case with particular attention to how the patients contracted the virus. Why is this virus a cause for concern, and why are WHO officials so interested in each patient's source of infection?The worst human flu epidemics have been due to influenza A viruses that have moved to humans from another species (usually pig or bird). The worst epidemic of the last century was due to an avian influenza that may have moved directly into humans. Since H5N1 has recently developed the ability to move from birds directly to humans, and because it is a "high pathogenicity" strain, WHO officials are concerned that it could cause another epidemic. They are particularly interested in whether each human patient contracted the disease from a bird or from another human. If H5N1 evolves the ability to move from human to human, it will be much more likely to cause an epidemic.