Antho Notes Overall
Chapter 2: Genetics
Variant
The particular form of a trait. For example, blue eyes, brown eyes, and gray eyes are variants of the trait eye color.
Cross:
In genetics, a mating between chosen parents.
Gene
A segment of the chromosome that produces a recognizable effect on phenotype and segregates as a unit during gamete formation.
Independent Assortment
The principle, discovered by Mendel, that each of the genes at a single locus on a pair of homologous chromosomes is equally likely to be transmitted when gametes (eggs and sperm) are formed. This happens because, during meiosis, the probability that a particular chromosome will enter a gamete is 0.5 and is independent of whether other nonhomologous chromosomes enter the same gamete. Thus, knowing that an individual received a particular chromosome from its mother (and thus a particular allele) tells nothing about the probability that it received other, nonhomologous chromosomes from its mother.
Chromosome
A linear body in the cell nucleus that carries genes and appears during cell division. Staining cells with dyes reveals that different chromosomes are marked by different banding patterns.
Nucleus
The distinct part of the cell that contains the chromosomes. Eukaryotes (fungi, protozoans, plants, and animals) all have nucleated cells; prokaryotes (bacteria) do not.
Mitosis
The process of division of somatic cells (normal body cells) through which new diploid cells are created.
Diploid
Of a cell: containing pairs of homologous chromosomes, in which one chromosome of each pair is inherited from each parent. Also refers to organisms whose somatic (body) cells are diploid; all primates are diploid.
Meiosis
The process of cell division in which haploid gametes (eggs and sperm) are created.
Homologous Chromosomes
Sets of chromosomes have the same genetic loci, but often these loci contain different alleles. Human cells contain 23 pairs of homologous chromosomes. One member of each pair comes from the mother and the other from the father.
Haploid
Of a cell: containing only one copy of each chromosome. Gametes are haploid, as are the cells of some asexual organisms.
Allele:
One of two or more alternative forms of a gene. For example, the A and S alleles are two forms of the gene controlling the amino acid sequence of one of the subunits of hemoglobin.
Homozygous
Of a diploid organism: having chromosomes that carry two copies of the same allele at a single genetic locus. Organisms that are homozygous are called homozygotes.
Heterozygous
Of a diploid organism: having cells that carry copies of two different alleles for a particular genetic locus. Organisms that are heterozygous are called heterozygotes
Genotype
The combination of alleles that characterizes an individual at some set of genetic loci. For example, in populations with only the A and S alleles at the hemoglobin locus, that locus has only three possible genotypes: AA, AS, and SS. (SA is the same as AS.)
Phenotype
The observable characteristics of organisms. Individuals with the same phenotype may have different genotypes.
Recombination
The creation of new genotypes as a result of the random segregation of chromosomes and of crossing-over.
Locus
The position that a particular gene occupies on a chromosome.
Genome
All the genetic information carried by an organism.
Linked
Of genes: being located on the same chromosome. The closer together two loci are, the more likely they are to be linked.
Unlinked
Of genes: located on different chromosomes
Crossing Over
The exchange of genetic material between homologous chromosomes during meiosis. Crossing-over causes recombination of genes carried on the same chromosome.
Deoxyribonucleic acid (DNA)
Deoxyribonucleic acid, the molecule that carries hereditary information in almost all living organisms. DNA consists of two very long sugar–phosphate backbones (called "strands") to which the bases adenine, cytosine, guanine, and thymine are bound. Hydrogen bonds between the bases bind the two strands.
Base
One of four molecules—adenine, guanine, cytosine, and thymine—that are bound to the DNA backbone. Different sequences of bases encode the information necessary for protein synthesis.
Protein-coding gene
A gene that encodes instructions for making proteins.
Enzyme
A protein that serves as a catalyst, increasing the rate at which particular chemical reactions occur at a given temperature. Enzymes can control the chemical composition of cells by causing some chemical reactions to occur much faster than others.
Regulatory gene
A DNA sequence that regulates the expression of a structural gene, often by binding to an activator or repressor.
Protein
A large molecule consisting of a long chain of amino acids. Many proteins are enzyme catalysts; others perform structural functions.
Amino Acid
A molecule that is linked in a chain to form a protein. There are 20 amino acids, all of which share the same molecular backbone but have a different side chain.
Primary Structure
The sequence of amino acids that make up a protein
Chapter 3:
Population Genetics: The branch of biology dealing with the processes that change the genetic composition of populations through time.
Genotypic Frequency: The fraction of individuals in a population that have a particular genotype.
Gene Frequency: The fraction of the genes at a genetic locus that are a particular allele (also called allele frequency). For example, a population that contains 250 AA individuals, 200 AS individuals, and 50 SS individuals has 700 copies of the A allele and 300 copies of the S allele; therefore, the frequency of the S allele is 0.3.
Modern Synthesis: An explanation for the evolution of continuously varying traits that combines the theory and empirical evidence of both Mendelian genetics and Darwinism.
Environmental Variation: Phenotypic differences between individuals that exist because those individuals developed in different environments.
Mutation: A spontaneous change in the chemical structure of DNA.
Mate Guarding: A behavior in which the male defends his mate after copulation to prevent other males from mating with her.
Sex Ratio: The number of individuals of one sex in relation to the number of individuals of the opposite sex. By convention, sex ratios are generally expressed as the number of males to the number of females.
Canalized: Of traits: the quality of being very insensitive to environmental conditions during development, resulting in similar phenotypes in a variety of environments
Plastic: Of traits: the quality of being very sensitive to environmental conditions during development, resulting in different phenotypes in different environments
Positively correlated: Of two variables: having a statistical relationship such that larger values of one variable tend to co-occur with larger values of the other variable. For example, in human populations, the height and weight of individuals are positively correlated.
Negatively Correlated: Of two variables: having a statistical relationship such that the larger values of one variable tend to co-occur with smaller values of the other variable. For example, the size and number of seeds produced by an individual plant are negatively correlated in some plant populations.
Pleiotropic effect: A phenotypic effect created by a gene that influences multiple characters.
Correlated response: An evolutionary change in one character caused by selection on a second, correlated character. For example, selection favoring only long legs will also increase arm length if arm length and leg length are positively correlated.
Maladaptive: Detrimental to fitness.
Sampling Variation: The variation in the composition of small samples drawn from a large population.
Genetic Drift: Random change in gene frequencies due to sampling variation that occurs in any finite population. Genetic drift is more rapid in small populations than in large populations.
Fixation: Of a population: a state in which all the individuals in the population are homozygous for the same allele at a particular locus.
Cameratype eye: An eye in which light passes through a transparent opening and is then focused by a lens on photosensitive tissue. Camera-type eyes are found in vertebrates, mollusks, and some arthropods.
Compound Eye: An eye in which the image is formed by many discrete photoreceptors. Compound eyes are found in insects and other arthropods.
Development: All the processes by which the single-celled zygote is transformed into a multicellular adult.
Chapter 4:
Microevolution: Evolution of populations within a species.
Macroevolution: Evolution of new species, families, and higher taxa.
Biological Species Concept: The concept of species as a group of organisms that have the potential to reproduce with one another and produce fertile offspring, and that are reproductively isolated from other such groups. Adherents of the biological species concept believe that gene flow tends to maintain similarities among members of the same species and that lack of gene flow is necessary to maintain differences between closely related species.
Gene FLow: The introduction of genetic material from one population or species to another through the successful reproduction of migrating individuals. Gene flow makes the genetic composition of the populations or species more similar to one another.
Anagensis: A form of speciation where a single lineage evolves, with a daughter species replacing its parent species without branching.
Cladogensis: A form of speciation where a single ancestral lineage branches into two or more descendant lineages.
Allopatric speciation: Speciation that occurs when two or more populations of a single species are geographically isolated from each other and then diverge to form two or more new species.
Prezygotic isolation: A mechanism of reproductive isolation that occurs before the zygote has formed via the fusion of sperm and egg.
Reproductive Isolation: A relationship in which no gene flow occurs between two populations.
Character displacement: The result of competition between two species that causes the members of different species to become morphologically or behaviorally more different from each other.
Reinforcement: The process in which selection acts against the likelihood of hybrids occurring between members of two phenotypically distinctive populations, leading to the evolution of mechanisms that prevent interbreeding.
Parapatric speciation: A two-step process of speciation in which (1) selection causes the differentiation of geographically separate, partially isolated populations of a species and (2) later the populations become reproductively isolated as a result of reinforcement.
Sympatric speciation: The hypothesis that speciation can result from selective pressures favoring different phenotypes within a population without positing geographic isolation as a factor.
Niche: The way of life, or "trade," of a particular species—what foods it eats and how the food is acquired.
Adaptive radiation: The process in which a single lineage diversifies into several species, each characterized by distinctive adaptations. The diversification of the mammals at the beginning of the Cenozoic era is an example of an adaptive radiation.
Phylogeny: The evolutionary relationships among a group of species, usually diagrammed as a "family tree."
Hominoid: Any member of the superfamily Hominoidea, which includes humans, all the living apes, and many extinct apelike and humanlike species from the Miocene, Pliocene, and Pleistocene epochs.
Taxonomy: A branch of biology that is concerned with the use of phylogenies for naming and classifying organisms.
Locomotion: The way animals move through their environment.
Quadrupedal: Of locomotion: moving on all four limbs.
Knuckle Walking: A form of quadrupedal locomotion in which, in the forelimbs, weight is supported by the knuckles rather than by the palm or outstretched fingers. Chimpanzees and gorillas are knuckle walkers.
Comparative method: A method for establishing the function of a phenotypic trait by comparing species.
Systematics: A branch of biology that is concerned with the procedures for constructing phylogenies.
Analogy: A similarity between traits that is due to convergent evolution, not common descent. For example, the fact that humans and kangaroos are both bipedal is an analogy.
Homology: Similarity between traits that is due to common ancestry, not convergence. For example, the reason that gorillas and baboons are both quadrupedal is that they are both descended from a quadrupedal ancestor.
Ancestral trait: A trait that appears earlier in the evolution of a lineage or clade. Ancestral traits are contrasted with derived traits, which appear later in the evolution of a lineage or clade. For example, the presence of a tail is ancestral in the primate lineage, and the absence of a tail is derived. Systematists must avoid using ancestral similarities when constructing phylogenies.
Derived trait: A trait that appears later in the evolution of a lineage or clade. Derived traits are contrasted with ancestral traits, which appear earlier in the evolution of a lineage or clade. For example, the absence of a tail is derived in the hominin lineage, and the presence of a tail is ancestral. Systematists seek to use derived similarities when constructing phylogenies.
Outgroup: A taxonomic group that is related to a group of interest and can be used to determine which traits are ancestral and which are derived.
Genetic distance: A measure of the overall genetic similarity of individuals or species. The best estimates of genetic distance use many genes.
Molecular clock: The hypothesis that genetic change occurs at a constant rate and thus can be used to measure the time that has elapsed since two species shared a common ancestor. The molecular clock is based on observed regularities in the rate of genetic change along different phylogenetic lines.
Fossil Calibration: A method of calculating the divergence time between species, which is based on estimates of 1) the amount of genetic dissimilarity between the species, and 2) the yearly mutation rate, as determined by the amount of genetic dissimilarity between the species and an outgroup species whose divergence time from the two species is known from the fossil record.
Pedigree: A family tree showing the kinship relationships among individuals in a population.
Genus: A taxonomic category below family and above species. There may be several species in a genus and several genera in a family.
Family: A taxonomic level above genus but below order. A family may contain several genera, and an order may contain several families. Humans belong to the family Hominidae, and the other great apes belong to the family Pongidae.
Superfamily: The taxonomic level that lies between infraorder and family. An infraorder may contain several superfamilies, and a superfamily may contain several families. For example, humans are a member of the superfamily Hominoidea, which contains the families Hominidae and Pongidae.
Cladistic taxonomy: A system for classifying organisms in which patterns of descent are the only criteria used. Also called cladistics
Evolutionary taxonomy: A system for classifying organisms that uses both patterns of descent and patterns of overall similarity.
Chapter 5:
Viviparity: The trait of giving birth to live young.
Conspecific: A member of the same species.
Sexual Dimorphism: Differences in body size or morphology between sexually mature males and females.
Opposable thumbs: Of a thumb or big toe: capable of touching one or more of the remaining digits of the same hand or foot. Most primates, including humans, have an opposable thumb, whereas most primates, but not humans, also have an opposable big toe and can bend their big toe to touch the other toes on the same foot.
Hind limb dominated: A form of locomotion that depends mainly on the hind legs for power and propulsion.
Molar: A broad, square back tooth that is generally adapted for crushing and grinding in primates. Anthropoid primates have three molars on each side of the upper and lower jaws.
Incisor: A front tooth in mammals. In anthropoid primates, incisors are used for cutting, and there are two incisors on each side of the upper and lower jaws.
Canine: A sharp, pointed tooth that lies between the incisors and the premolars in primates.
Premolar: A tooth that lies between the canines and molars.
Brachiation: A form of arboreal locomotion in which animals suspend themselves from their hands and move by swinging from one hold to another.
Binocular vision: Vision in which both eyes can focus together on a distant object to produce three-dimensional images.
Stereoscopic vision: Vision in which three-dimensional images are produced because each eye sends a signal of the visual image to both hemispheres in the brain. Stereoscopic vision requires binocular vision.
Strepsirrhine: Any member of the group containing lemurs and lorises. The system classifying primates into haplorrhines and strepsirrhines is a cladistic alternative to the evolutionary systematic taxonomy, in which primates are divided into prosimians and anthropoids, and tarsiers are grouped with prosimians.
Haplorrhine: Any member of the group containing tarsiers and anthropoid primates. The system that classifies primates into haplorrhines and strepsirrhines is a cladistic alternative to the evolutionary systematic taxonomy, in which primates are divided into prosimians and anthropoids, and tarsiers are grouped with prosimians
Dental Formula: The number of incisors, canines, premolars, and molars on one side of the upper and lower jaws.
Maxilla: The upper jaw.
Mandible: The lower jaw.
Bilaterally symmetrical: In animals, the quality of having the morphology on one side of the body's midline be a mirror image of the morphology on the other side.
Prehensile: Of hands, feet, or tails: capable of grasping objects, such as food items or branches.
Cooperative breeding: A mating system in which there is one breeding female and all group members help care for the offspring.
Basal metabolic rate: The rate of energy use required to maintain life when an animal is at rest.
Secondary compound: A toxic (poisonous) chemical compound produced by a plant and concentrated in the plant's tissues to prevent animals from eating the plant.
Alkaloid: A type of secondary compound produced and kept in a plant's tissues that makes the plant distasteful or even poisonous to herbivores.
Gum: A sticky carbohydrate that some trees produce in response to physical damage. Gum is an important food for many primates.
Frugivore: An animal whose diet consists mostly of fruit.
Folivore: An animal whose diet consists mostly of leaves.
Gummivore: An animal whose diet consists mostly of gum.
Dominance matrix: A square table constructed to keep track of dominance interactions among a group of individuals. Usually, winners are listed down the left side and losers are listed across the top, and the number of times each individual defeats another is entered in the cells of the matrix. Individuals are ordered in the matrix so as to minimize the number of entries below the diagonal. This ordering is then used to construct the dominance hierarchy.
Transitive: A quality of triadic (three-way) relationships such that the relationships between the first and second elements and the second and third elements automatically determine the relationship between the first and third elements. For example, if A is greater than B and B is greater than C, then A is greater than C. In many primate species, dominance relationships are transitive.
Social Organization: The size, age–sex composition, and degree of cohesiveness of primate social groups.
Polygyny: A mating system in which a single male mates with many females. Polygyny is the most common mating system among primate species.
Mating system: The form of courtship, mating, and parenting behavior that characterizes a particular species or population. An example is polygyny.
Polygynandry: A mating system in which both males and females mate with more than one partner of the opposite sex
Chapter 6:
Mating Effort: All of the activities related to conception, including the effort required to find mates and gain access to them. This may involve courtship displays, competition with rivals, or establishing a territory.
Parenting effort: All of the activities related to the care of offspring after conception occurs, such as sitting on the nest after eggs are laid or nursing infants after birth.
Interbirth interval: The period of time between the birth of one infant and the birth of the next infant.
Sexual selection: A form of natural selection that results from differential mating success in one sex. In mammals, sexual selection usually occurs in males and may be due to male–male competition.
Intrasexual selection: A form of sexual selection in which males compete with other males for access to females. As a result, traits that make males more successful in such competition, such as large body size or large canines, are selected for.
Intersexual Selection: A form of sexual selection in which females choose with whom they mate. As a result, traits that make males more attractive to females are selected for.
Estrus: A period during the reproductive cycle of most mammals (and most primates) when the female is receptive to mating and can conceive.
Sexual selection infanticide hypothesis: A hypothesis postulating that infanticide has been favored by sexual selection because males who kill unweaned infants can enhance their own reproductive prospects if they (1) kill infants whose deaths hasten their mothers' resumption of cycling, (2) do not kill their own infants, and (3) can mate with the mothers of the infants that they kill.
Chapter 7:
Altruism: Behavior that reduces the fitness of the individual performing the behavior (the actor) but increases the fitness of the individual affected by the behavior (the recipient).
Mutualism: Interactions that are beneficial to the actor and the recipient.
Kin Selection: The theory that altruistic acts will be favored by selection if the product of the benefit to the recipient (b) and the degree of relatedness (r) between the actor and recipient exceeds the cost to the actor (c); in other words, if rb > c
Group living can lower mortality rates (a key determinant of the adaptive pace of life history strategies) because living in groups reduces the risk of predation. Animals with a slower life history can afford lengthy juvenile periods to acquire the knowledge and skills to better exploit their ecological and social worlds. Big brains are metabolically expensive, and group living offers the opportunity to learn from other knowledgeable individuals the difficult food extraction techniques that yield higher quality nutrition.
Hamilton’s Rule: A rule predicting that altruistic behavior among relatives will be favored by natural selection if rb > c, where r is the coefficient of relatedness between actor and recipient, b is the sum of the benefits of performing the behavior on the fitness of the recipient(s), and c is the cost, in decreased fitness of the donor, of performing the behavior.
Coefficient of relatedness r: An index measuring the degree of genetic closeness between two individuals. The index ranges from 0 (for no relation) to 1 (which occurs only between an individual and itself or between identical twins). For example, the coefficient of relatedness between an individual and its parents or its full siblings is 0.5.
Phenotypic matching: A mechanism for kin recognition in which animals assess similarities between themselves and others.
Grooming: The process of picking through hair to remove dirt, dead skin, ectoparasites, and other material. Grooming is a common form of affiliative behavior among primates.
Affiliative: Friendly.
Coalition: An interaction in which two or more animals jointly initiate aggression against, or respond to aggression from, one or more other animals.
Matrilineage: Individuals related through the maternal line; a maternal kin group.
Parent-offspring conflict: Conflict that arises between parents and their offspring over how much the parents will invest in the offspring. These conflicts stem from the opposing genetic interests of parents and offspring.
Reciprocal altruism: A theory that altruism can evolve if pairs of individuals take turns giving and receiving altruism during many encounters.
Chapter 9:
Third-party relationship: A relationship among individuals other than oneself. For example, individual monkeys and apes are believed to understand something about the nature of kinship relationships among other members of their groups.
Redirected aggression: A behavior in which the recipient of aggression threatens or attacks a previously uninvolved party. For instance, if A attacks B and B then attacks C, B's attacks are an example of redirected aggression.
Theory of mind: The capacity to be aware of the thoughts, knowledge, or perceptions of other individuals. A theory of mind may be a prerequisite for deception, imitation, teaching, and empathy. Researchers generally think that humans, and possibly chimpanzees, are the only primates to possess a theory of mind.
Behaviours that suggest primates possess theory of mind
Concealing or faking emotions
Subordinate pursuing a food item a dominant cant see
Deceiving other group members about where food is hidden
Teaching complex tasks
Lecture 1 Slide Material
Darwin
Species not independently created
Species change
No special creation for humans
Malthusian Catastrophe: predicted crisis where rapid, exponential population growth outpaces the linear growth of food production and resources, resulting in widespread famine, disease, war, and a drastic population reduction
Darwin’s Postulates:
There is a struggle for existence (more organisms that can survive + limited resources)
There is variation in features related to survival and reproduction
This variation is assessed from generation to generation
These three postulates make evolution by natural selection inevitable
Fitness - potential for an individual to survive and reproduce
Reproductive success - number of reproducing offspring an individual produces
Natural selection - differential survival and reproduction due to differences in phenotype
Lecture 2:
Why did natural selection act on the medium ground finch on Daphne Major?
A drought changed the environment where the finches lived
Selection acts on individuals
Selection is cumulative and can give rise to complex structures via small changes
Intermediate forms can be adaptive. For example its better to have 5% of an eye than no eye at all
Living mollusks show the steps of eye evolution
Evolution is a tinker not an engineer
How might an anthropologist explain the evolution of an
organ as complex as the human eye?
The human eye is the result of many small incremental adaptations that were
each beneficial on their own.
Microevolution: Genetic changes in a population or species over a few, several, or many generations, but without speciation.
Macroevolution: Larger-scale or more significant genetic changes in a population or species, usually over a longer time period, which result in speciation.
Gene = basic unit of heredity passed from parent to child
Allele = variant of a gene
Lecture 3
Chapter 3: The Modern Synthesis
Mendel believed variation to be discontinuous (yellow vs green, wrinkled vs round)
Darwin believed evolution worked through gradual accumulation of small changes in continuously variable traits
How variation is maintained
Mutation in gametes
Variation hidden in polygenic traits
Heterozygote individuals
Correlated Characters:
Example people with albinism also have vision problems
Pleiotropy: when one gene influences several traits
Example: mutation in the gene coding for melanin results in white hair, skin, and light eyes. Alongside changing how the eye develops causing shaky eyes, light sensitivity
Ghosts of evolution
Example: avocado have massive seeds because they used to be consumed by giant sloths
Evolutionary Mismatch:
Example: humans crave salty sweet fatty foods as those used to be rare however they are no abundant and cheap yet we still crave them
Humans have a nearly insatiable appetite for sugar, fat, and salt because:
such appetites were an adaptive response to pre-modern environments.
Path Dependence and Fitness Landscapes:
The relationship between trait values and fitness is not linear – it is curvy like a mountain profile.
Selection causes populations to “go uphill” and increase fitness from their current position to a local optimum (A, B, C).
To travel from A or C to B, a population would need to cross a valley of lower fitness, but selection opposes traits in those zones
Constraints of physics and chemistry:
Animals are limited in how large in size they can become as mass increases as a function of body length and strength of bones and muscles has an upper limit
Chapter 4: Speciation and Phylogeny
What is macro evolution?
The formation of new species
Biological Species Concept:
Species are a group of interbreeding organisms that are reproductively isolated from other organisms.
A species is a group of organisms that can reproduce with one another to produce fertile offspring and is reproductively isolated from other organisms.
Problems with Biological Species Concept:
Different “species” can often interpret
How could species be identified using ancient fossils or where there is no measure of reproductive isolation
Ecological Species Concept:
Reproductive isolation not necessary
Natural selection keeps species distinct from each other
Example: observed medium and large ground finches can interbreed yet remain distinct
Offspring have lower survival
Some species have little or no gene flow
Stay the same due to natural selection
Models of Speciation
Anagenesis
A single population evolving through time
The descendant population with evolve to significantly diverge from parent population
Cladogensis
One population evolves into two populations
The descendant populations live at the same time and are different enough and reproductively isolated enough for taxonomists to classify them as different species
Reproductive Isolation:
Reduces or eliminates successful interbreeding between populations
Contributes to genetic divergence
Two types:
Prezygotic - before formation of zygote
Species do not encounter each other
Species have different courtship behaviours or preferences
Bodies or genitalia differ too much
Incompatible sperm and egg
Postzygotic - soon after formation of zygote
Hybrid inviability
Hybrid sterility
Mechanisms for speciation:
Allopatric
Different habitats, totally isolated
A new species evolves in geographic isolation from its ancestor
Physical barrier
Selection may favor different phenotypes in the different environments
A combination of reproductive isolation, natural selection, and drift is involved.
Parapatric
Occupy neighboring habitats
Partial genetic isolation + natural selection
Sympatric
Shared habitat
No physical barrier
Character displacement: The result of competition between two species that causes the members of different species to become more different from each other
Ecological niche
The way an organism “makes a living”
More niches leads to more species.
Adaptive radiation
Rapid diversification fills niches.
Lecture 4:
The molecular clock:
Mutations add up at constant rate in related species
More time passes = more mutations
Cant use coding DNA cause of selection
3 mutations per cell division
Looks at noncoding regions of DNA
Nuclear DNA:
Good for comparing distantly related species
Slow rate of mutation accumulation
Mitochondrial DNA:
Maternally inherited
High mutation rate (20x faster than nuclear DNA)
Easier to reconstruct family tree
Good for migration studies or very recent evolutionary splits
Maximum Parsimony:
Assumption: The phylogeny requiring the fewest evolutionary changes is the best estimate of the true phylogeny.
A reasonable assumption because evolutionary change is rare, and more changes are less likely than fewer changes.
Ancestral Traits:
Traits that appear early in individual development (ontogeny) are ancestral.
Traits that appear earlier in the fossil record are ancestral.
Traits that appear in outgroups are ancestral
Chapter 5:
Why we study primates:
Reasoning by homology
We share inherited similarities in anatomy and behavior
Reasoning by analogy
How does evolution shape bodies and behaviors?
Interpret human fossils
adaptations in environments occupied by ancestors
What is a primate?
Physical
Grasping hands and feet (opposable thumb)
Nails instead of claws
Enhanced vision, reduced olfaction
Forward facing eyes encased in bone
Movement
Hind limb driven locomotion
Life-history
Long gestation
Small liters (one or two)
Long juvenile period
Long lifespan
Teeth
All primates have
Incisors, canines, premolar, molars
Formula is I-C-P-M
Humans and Catarrhines are 2:1:2:3
Unspecialized molar teeth
Location
Tropical animals, mostly forest dwelling
Modern range: central and south america, africa, asia
Fossil range: included north america and europe
Strepsirrhines:
Features
Mostly nocturnal
Mostly solitary
Tooth comb
Claws
Acute sense of smell
Wet noses (rhinarium)
Slightly smaller brain
Tapetum (reflective layer in back of eye)
Scent glands
Two Infraorders
Lemuriformes (lemurs)
Lorisiformes (lorisi, galagos, pottos)
Haplorrhines
Tarsiformes (tarsiers), platyrrhini (New world monkeys), and Catarrhini (Old world monkeys)
Platyrrhines (New World Monkeys)
Live in mexico, south and central america
Mainly diurnal
Tropical forests
Arboreal - many have prehensile aka grasping tails
Quadrupedal through some suspensory climbers
2-1-3-3 dental formula
Suspensory locomotion traits
Longer arms than legs
Long fingers
Shortened lumbar region of the spine
Catarrhines (Old World Monkeys and Apes)
Live in africa and asia
All diurnal
Some arboreal some terrestrial
Broad habitat range
Larger body size
Large groups
Male dispersal; female bonds
Dental formula 2-1-2-3
Old World Monkeys have tails and parallel ridges on molar teeth
Apes have no tail and no ridges
Hominoids (Apes)
Lesser apes (Hylobatidae)
Asian apes
Gibbons and siamangs
Arboreal, brachiators
Very long arms, swing across gaps in forest canopy
Pair bonding; male parental care
Males and females sing coordinated territorial duets to establish and maintain territory
Great Apes (Hominidae)
Orangutans (Pongo)
Found only in tropical rainforests of Borneo and Sumatra
Largest arboreal animal in the world
Arboreal means long arms and long curved fingers and toes
Eats fruits, leaves, and bark
Most solitary anthropoid
Intense male/male competition for mates
Males defend home ranges of adult females and attack other male trespassers
Gorillas (Gorilla)
Three subspecies
Exhibit marked sexual dimorphism
Spend little time in the trees
Spend most of the day feeding on ground plants, leaves, bark, fruits, and other vegetation
Live in troops of males and females with offspring
Chimpanzees (Pan)
Light faced infants
live in large groups, males and females together
“Fission-fusion”
Often split into smaller parties, which are not always composed of the same members
These smaller, temporary groups change depending on the activity
Well studied
Live in equatorial africa
Knuckle walk and tree climb
Female dispersal
Diverse diet: fruit, vegetation, insects, meat
Sophisticated tool use
Termite fishing poles
Using leaves as sponges
Rocks to crack open nuts
Highly intelligent
Bonobos (Pan)
Dark faced infants
Pink lips
live in large groups, males and females together
“Fission-fusion”
Often split into smaller parties, which are not always composed of the same members
These smaller, temporary groups change depending on the activity
Hippies very much peaceful
Live in small area in democratic republic of congo
Not well studied
Female dispersal
Eat fruit, vegetation, some meat
Humans (Homo)
Global species
Diversity in social and mating organization with tendency to pair bond
Diversity in diet, primarily omnivores
Complex verbal language
Bonobo Socio - sexuality
Sexual activity separate from reproduction
Diverse sexual behaviors
Face-to-face sexual interactions with genital contact between females (unique among primates)
Reducing tension, promoting bonding
Occurs after aggressive conflicts (repair social relationships) or when groups come together (build new relationships)
Why the difference in behavior between chimps and bonobos?
Richer food patches and less periods of food scarcity in forests inhabited by bonobos = relaxed competition
Female bonobo sexuality, more female centric society, lower aggression
Apes
Larger body and brain size
Longer life span
Longer intervals between births
Tendency toward upright posture
Shorter and lesser projecting face and muzzle
No tail
Locomotion:
Suspensory and vertical climbers
Gorillas, chimps, and orangutans spend considerable time on the ground.
Primate Ecology
Primate Diets
Protein
Insects
Animal prey
Young leaves
Carbohydrates
Fruit
Gum
Fats and Oils
Insects and animal prey
seeds
Diet Specialization
Insectivores
Small body size
Sharp cusps on teeth
High, sharp crests of molar teeth
Simple digestive system
Folivores
Large body size
Small, sharp incisors
Sharp shearing crest on molars
Enlarged, well developed digestive system
Frugivores
Medium body size
Large broad incisors to puncture rind of fruit
Low cusped relatively flat molars (crush)
Relatively large digestive system, but not as large and complex as folivores
Gummivores
Small body size
Claws in some
Long robust incisors
Some have projecting incisors and canines to scrape bark from tree
Unspecialized digestive system
Among primates, folivores tend to have
Small sharp incisors
Home Range Versus Territory
Home range: the entire area occupied by a primate group
Within the home range is a core area where the group is more frequently
This core area (“Territory”) is defended against intruders
Other parts of the home range might overlap with other groups, but not the core area
Gorillas:
Leaves and other vegetation
Small home range b/c
Vegetation = Hyper-abundant
Chimpanzees:
Fruit, some leaves, some red colobus monkeys
Large home range b/c
Travel far to find ripe fruit
Different fruit ripen at different times
How does the diet of a primate affect its home range?
Availability of food
Leaves and seeds are often more plentiful than fruit.
Seasonality of food
Ripe fruit and leaves are not always present.
Primate Territoriality
Varies by species
Costs:
must defend the area
Dangerous aggressive interactions
Benefits:
Can protect limited resources such as mates and food
If benefits outweigh cost then territoriality is favored however is resources not limited the cost is likely larger than the benefit
Dominance
Many primates organized in dominance hierarchies
They reduce violence as dominant individuals can threaten without attack
Males and Females
Separate hierarchies
Males dominant over females besides lemurs and bonobos
Monogamous pairs are codominant
Female Hierarchies:
Mother rank
Can change during life depending on age, aggression, time in the group, intelligence
Dominance learned as infants
Infant observes how mother responds to others and how she treats others
Gestures, fascial expressions behavior
As they get other they play wrestle with peers
Communication
Many intentional forms such as gestures, facial expressions, vocalizations
Displays (complex combinations of behaviors example: tortillas chest slapping
Threatening communications
Intense stare
Branch breaking
Yawn to show canine teeth
Crouch bobbing back and forth
Mounting
Submission
Crouched position
Presented hindquarters
Reassurance
Touching, patting
Grooming
Hugging, holding hands
Grooming:
Using fingers to pick through fur of another individual
Hygiene: removes dirt and insects
Pleasurable, comforting
Mothers groom infants
Males groom sexually receptive females
Subordinates groom dominants
Restores peaceful relationships after conflict
Defense against Predators:
Fleeing or taking cover
Vocalizations
Interspecific associations
Increased group size
Detection: more eyes to see predator
Deterrence: mobbing behavior
Dilution: lowers individual risk of death
Why are Primates Social?
Benefits
Avoidance of predators
Feeding competition (defense of food patch)
Costs
More competition for food and mates
Increased disease transmission
Primate Social Systems
Polygynandry
Multiple males, multiple females
Both males and females mate with more than one partner
One of the two most common forms of social organization in primates
Polygyny
One male, multiple females
Male mates with multiple females, but females mate with the resident dominant male only
Intense male - male competition
One of the two most common forms of social organization in primates
Bachelor Groups
Travel together
Hierarchical
Waiting for future opportunities (most=none)
One may challenge the resident male (not coalition)
Monogamy
Pairs
Some extra-pair copulation
Solitary
Associated with polygyny
Adult female home range is alone or with dependent offspring
1 males territory overlaps with several adult females
Lecture 6: Chapter 6
Sexual Selection
Spread of traits owing to positive effects on mating competition
Explains armaments like large canines on male gorillas
Increases opportunities to mate with females
Intersexual Selection
Selectivity mating with individuals of the opposite sex with attractive traits
Can reduce survivorship but increase reproductive success so still passed on
Intrasexual Selection
Usually male-male
Results in differential reproductive success which provides the force of natural selections
Often occurs when males monopolize resources in some manner
Sexual Dimorphism:
Be greatest in species that can monopolize the most mates
Harem breeders = most dimorphism
Monogamous = the least
Sexual Dimorphism Example: Canines, body size, sagittal crest
When intrasexual competition is strong especially in polygynous
Gorillas are most sexually dimorphic primate
One male, multi female
Polygyny
Body size (2x)
Canines
Sagittal crest
Upper body musculature
Orangutans are the second most dimorphic primate
Solitary
Polygynous
Body size (nearly 2x)
Canines
Facial flanges
Throat sacs
Pair bonds have little male–male competition and little dimorphism.
One-male multi-female systems have huge body and canine dimorphism.
Multimale multifemale systems have large dimorphism
Sex difference in mating strategies:
A male can mate with as many females possible, suffer little reductions in fitness if he mates with a poor quality female
A female suffers great costs of time and energy by mating with a poor quality male
Reproduction is slower and more costly for females than males
Female Strategies
Invest heavily in offspring
Long pregnancies, brain growth, energetically expensive offspring
Lactation
Very long infant period
Very few offspring
Resources critical for female reproduction success
More food = more offspring
Sexual selection: Sperm competition
Successful conception, not just mating
In some species, fertile females mate with multiple males
Competition continues after mating: sperm competition
Sexual Selection and Testis Size
Males with larger sperm volume have greater chances of fathering offspring.
Primate males that pair-bond or live in one-male multifemale groups have relatively small testes.
Evolution: males who pair-bond or monopolize a group of females are nearly guaranteed paternity
Males in multimale multifemale groups have larger testes
More male-male competition
Sexual selection: Cryptic female choice
Relevant for species in which females mate with multiple males in one repro cycle (multi-male/multi-female groups)
female’s reproductive tract is the arena for sperm competition
female’s anatomy and physiology might influence the fate of gametes from rival males
Females engage in Cryptic Female Choice: paternity biases resulting from female morphology, physiology, and behavior after coupling
Benefits of high-quality male mating
Protection of alpha male, social benefits
Survivorship and health of offspring
Female Ovulation advertising
Female mandrills have brighter colors on face during follicular phase of menstrual cycle, to advertise fecundity and sexual receptivity
Female strategy to attract highest quality mates
Sexually-selected ornaments for females
All species with female sexual swellings are multimale, multi-female groups
Only evolved in old world monkeys and Pan (apes)
Polygynadrous
Adaptive functions
Attracts males
Male-male competition (favoring high-quality or high-status males)
Females control who mates with them
Promote paternity confusion!
Swellings often longer than actual fertile window
Reducing infanticide risk
Influences of Female reproductive success
Nutrition
Longevity: 50–70% of variance
Group size (small group=more offspring)
Rank
Social connectivity
Female Reproductive trade Offs:
Quality over quantity
Example: Lactation
Much energy needed to produce milk
Not enough energy for another pregnancy
Mother does not ovulate to avoid unsustainable pregnancy
Male Reproductive Trade-Offs:
Mating effort versus parenting effort
Finding new mates is prioritized if offspring can be raised by one parent
Helping offspring survive is prioritized if offspring need help of more than one parent
Male Reproductive Tactics: Monogamy
Pair boning
Paternal care
Mate guarding
Male Reproductive Tactics: Polygyny and Polygyanyandry
Males compete for females
Dominance hierarchy established
Higher rank = more mating opportunities
No paternal care
Female Counter strategies to Infanticide
Aborted pregnancies
Closely timed puberty and ovulation
Paternity confusion
Hide timing of ovulation
Manatee promiscuously
Males compete mainly over access to mates
Females strategize mainly over offspring survival
Male reproductive strategies:
Mate monopolization (one-male groups, mate guarding)
Dominance competition (fighting, rank hierarchies, canines, body size)
Sperm competition (large testes, frequent mating in multi-male groups)
Infanticide (eliminating unrelated infants to accelerate female return to fertility)
Paternal care (pair bonding)
Males compete mainly over access to mates
Females strategize mainly over offspring survival
Female reproductive strategies:
Mate choice and mating bias (preferring high-quality or protective males)
Ovulation signaling (sexual swellings)
Paternity confusion (mating with multiple males to reduce infanticide risk)
Cryptic female choice (post-copulatory biasing of fertilization)
Reproductive timing strategies (lactational amenorrhea, conceiving quickly after takeovers, pregnancy termination)
Lecture 7: Life Histories
Primate Mothers
A lot of time and energy invested in each offspring
Long gestation, +25% extra calories
Long phase of lactation, 50% extra calories
Close bond with infant
Small number of babies in a female’s lifetime
Brains are expensive organs, so maintaining a large brain is very costly. Even though human brains only make up about 2% of our body weight, our brains use up what percentage of our metabolic energy?
20%
Life History Theory:
Different way to describe species
Types of traits: physical, behavioral, etc
Traits that describe the shape of the life cycle
LH traits are interconnected
LH traits balance trade offs
Extrinsic mortality risk calibrates LH strategies
Die younger, reproduce younger
LH strategies on fast-slow continuum
Live fast die younge
Live slow die old
Across the life course, different domains are prioritized by LH strategy
Example: childhood focuses on growth while young adulthood focuses on reproduction while those with an illness focus on maintenance
Examples:
When to be born
How many offspring per liter
How fast to grow
When to wean/reach maturity
When to die
Offspring investment strategy:
Quantity and quality of offspring
Current and future reproduction
life history trade-offs in the chronological order that a primate, over its lifetime, would encounter each trade-off conflict and make the energy allocations. Place the trade-offs encountered closer to birth first.
Somatic effort (growth) vs. reproductive effort (offspring production)
Quality vs quantity of offspring
Current vs future reproduction
Primates have larger brains than expected for their body size, so their life history allocations must support the growth and maintenance of large brains they do so by…
More somatic effort, less reproductive effort
Higher quality of offspring, lower quantity of offspring
Lower investment in current reproduction, higher investment in future reproduction
Trade Offs:
A trade-off means that when investment in one trait increases, investment in some other trait must decrease. Since resources are limited, costly traits are only affordable if reductions in spending are made in other areas of an organism’s budget. Therefore, selection cannot maximize all traits; it must optimize across traits instead.
Size vs quantity of offspring
Energy usage
Energy is limited
Energy allocation: growth, maintenance, reproduction
A calorie spent on process 1 can’t be spent doing process 2
There must be trade-offs between calories spent on different life processes in the body, examples…
Ovulating versus digesting food
Building brain versus building muscle
Selection favors adaptive strategies that maximize reproductive success
Time
A minute spent doing Activity 1 can’t be spent doing Activity 2
There must be trade-offs between time spent on different life tasks, e.g.
Mate seeking versus food acquisition
Being pregnant versus lactating
Selection favors adaptive strategies that maximize reproductive success
Some mammals give birth to one offspring at a time, and others to larger litters. Since more offspring per birth could mean higher reproductive success, why doesn’t natural selection favor large litters in all mammals?
Reproducing involves a number of trade-offs, including quantity (number) versus quality of offspring. Larger litters mean lower-quality individual offspring.
Fast Life History
High Mortality (lots of predators)
Grow up fast
Small brain
Small body
Reproduce often – many, small offspring
Die “young”
Shorter gestation length
Slow Life History
Low Mortality (few predators)
Grow up slow
Large brain
Reproduce slowly – few, large offspring
Die “old”
Large body
Long gestation periods
Primate Life History:
Have slow life histories
Slow maturation, large brains, long gestation, small litter, long life span
There is variation within primates.
Monkeys have slower life histories than strepsirrhines.
Apes have slower life histories than monkeys
Low mortality rates allow for delayed reproduction which permits time for brains to grow large and big brains facilitate extraction of higher quality foods, better problem solving skills, and sophisticated sociality, which in turn promotes low mortality rates.
Senescence:
Why grow old and die? Our bodies heal, why not continue maintenance forever?
A gene that acts on the young affects most members of the species
A gene that acts on the old affects relatively few
Selection Shadow:
Declining force of selection
Allele with negative effect restricted to late life will likely already have been passed on to offspring
Selection inefficient at eliminating the apple from the population
Senescence should be more rapid in species with high extrinsic mortality
investing heavily in maintenance is unlikely to pay off with reproductive success
If extrinsic mortality is low
Prolong other life phases
Invest in larger body size, more time learning, and more years to reproduce
It’s worth it to invest in maintenance because low risk of random death from external source
Animals with long life histories, like primates, grow for a long time at the expense of their:
Early fertility
Primate longevity:
Protection from predators and high-quality food:
Arboreal
Intelligence
Sociality and cooperation
Antagonistic Pleiotropy
Image a gene that will:
Increase your fertility while you are young
E.g. increase your reproductive success by 1 during your 20s.
Cause you to senesce and die sooner
E.g. decrease your reproductive success by 1 during your 40s.
This gene will spread because its effect on 20 year olds is more likely to be observed than its effect on 40 year olds.
If individuals have a short predicted lifespan due to high predation pressure, we can expect that natural selection favors animals with ____ life histories.
Fast
Evolution of the Large Primate Brain
Social Brain Hypothesis (aka social intelligence hypothesis)
Primates have complex social relationships
The larger the group, the harder to keep track of relationships
Sociality is a survival strategy
Predicts a positive correlation between brain size and social group size.
Proportionately larger brains in species with larger groups, more social complexity
Ecological Brain hypothesis
Need large brains to cope with the challenges of finding, catching, processing, or sharing food in complex and seasonal environments.
Finding fruit in forests
spatial knowledge
memory
complex processing techniques
Predicts a positive correlation between brain size, especially the hippocampus, and foraging complexity
Proportionately larger brains in species with more extractive foraging or more ecological challenges
In apes the social brain hypothesis is not supported
Smaller group sizes than most monkeys yet they have sophisticated extractive foraging techniques
Evidence better support ecological brain hypothesis due to bigger brains in a species with more food processing steps and more complicated foraging niches
Lecture 8 Evolution of Cooperation
Altruism: Altruism refers to helping another in a way that benefits them, but at a personal cost to yourself.
Group Selection:
To avoid overexploitation of resources (followed by population crashes) individual animals restrain their reproduction for the good of the group.
Is group selection an important source of adaptation?
For group selection to be a powerful force, there must be stable variation between groups.
Groups containing many altruists (e.g. restrained reproducers) may do better over the long term than groups with few altruists.
However, these group differences are not likely to persist through time, owing to:
Selection within the group
Migration between groups
Problems with Group Level Explanations
Natural selection typically operates on the level of the individual not the group
Group level explanations don't fit out understanding of evolutionary theory
How can we explain altruism?
Mutualism
Reciprocal altruism (reciprocity)
Kin selection
Mutualism:
Mustelism benefits both participants
Vulnerable to cheaters
If individuals can reap rewards without the cost, then mutualistic behaviours do not persist
Reciprocal Altruism:
Individuals balance reciprocal acts
There are many currencies including
Grooming
Food sharing
Coalitionary support
Criteria
Frequent interactions
Ability to keep track of actions given and received
Supporting those who support you
Kin Selection:
W.D. Hamilton
Not all members of a group are equally related
Related individuals often cluster
Altruism can evolve through kin selection
Direct Fitness: derived from individuals own offspring
Indirect Fitness: derived from helping relatives to produce more offspring than they would on their own
Combination of Direct and Indirect Fitness is called inclusive fitness
Hamilton's Rule:
r is the coefficient of relatedness: probability of shared genes by descent from a recent common ancestor.
Fitness cost to actor: C.
Fitness benefit to recipient: B.
Inclusive fitness benefit: rB.
The net effect on inclusive fitness is positive when: rB > C.
Such traits spread by "kin selection"
Altruism expected when rB > C
Costlier acts of altruism (higher c) are expected to be directed to closer kin (higher r).
When altruism is directed to more distant kin, it is expected that it will have a high benefit:cost ratio
r is the probability that two individuals will share an allele inherited from a recent common ancestor
Kin Recognition
Contextual clues
Infants in contact with mother
Siblings connected through mother
Phenotypic matching
Recognize kin through smell or likeness to themselves
Kin Biases in Behavior: Grooming (Costs vs Benefits)
Most instances between mother and infant
Occurs more often between kin than distant kin or nonkin
Grooming benefits
Hygiene
Reinforce social relationships
Conflict resolution
Grooming costs
Time and energy
Kin Biases in Behavior: Coalitions
coalitions/alliances
Form during disputes
Qualify as altruism
Benefit: may result in victory in dominance contest
Cost: risk of injury
Maternal support
Maternal rank transferred to offspring in many primates
Matrilineage hierarchies
Stability in female hierarchies
Kin Biases in Behavior: Cooperative Breeding
Altruistic behavior of helping other raise their babies
“Helpers at the nest”
Takes time/energy away from individuals reproductive effort
Investing in indirect fitness with a direct fitness cost
Parent-Offspring Conflict
Within families, conflict can still arise, even between parents and offspring.
Parents are often more closely related to offspring than offspring are to each other.
The fitness of future offspring comes at the expense of current offspring.
Benefits mother
Does not benefit current offspring
Lecture 9: Chapter 9
Paleozoic (540-250 mya)
Bugs
Fish
Amphibians
Reptiles
Triassic (250 - 200 mya)
Cynodonts turn into mammals
Dinosaurs emerge and spread
Small population of cynodonts become first mammals in dinosaurs shadow
By end of triassic non mammal version disappears
Late triassic (200 mya)
Dinosaurs still around
First true mammals
Small (mouse sized)
Warm blooded, covered in hair
Ate insects and seeds
Internal fertilization but then laid eggs
Brief history of mammals
Late Permian and Triassic periods
Cynodonts, a diverse group of animals with mammal-like traits
Warm blooded and covered in fur
Triassic period
First true mammals evolve from one cynodont
Small, nocturnal, egg-laying, seedand insect-eating animals
End of Mesozoic era
Mass extinction of large dinosaurs
Cenozoic era
Rapid diversification of mammals, including primates
All cenozoic epochs end in “...cene” and is more recent than dinosaurs
What are fossils?
Preserved remains of dead organisms
Insects and plants preserved in amber
Remains of plant parts
Preserved feces
Molecules such as DNA and proteins
Where to die to become a fossil:
By a shallow lake
In a cave
Downslope of sediment
Down a sinkhole
Want to die in environment conductive to mineralization
“Low energy environment" = not too much destructive processes (erosion, trampling, crushing)
Buried quickly to avoid being scavenged by animals
Fossilization Process:
Bones are made of a combo of living and nonliving materials
Bacteria decay the living part
Groundwater seeps into bone and fills the spaces
Minerals from the water form a copy of the original bone
exposed/uncovered, lucky!
Biases of the fossil record:
Favored certain habitats like lakeshores and caves over tropical rainforests
Favored species that lived in lakeshores and caves instead of those living in tropical forests
Favored teeth and dense bones of less dense bones like vertebrae
Scarcity of fossils
Only small percentage actually fossilize while even smaller percentage are found
Always underestimates how much time a species was present on earth
Fossil Dating Types:
“Absoulte” Methods: directly sample something and measure its age
“Relative” methods: dating the stuff around, dating by comparison
Fossil Dating:
Radiometric techniques = methods based on isotopes
Eventually isotopes “run out” because all unstable isotopes decay
Slow clock for older stuff
More, larger errors
Decays slowly
Example: potassium-argon dating (sampled from volcanic rock)
Only used if fossil at least 500,000 years old
Faster clocks for more recent stuff
More specific
Decays fast
Example: carbon 14 dating (sampled directly from the fossil)
Only used if fossil less than 40,000 years old
Uranium–lead dating
Also radioactive decay, in cave rocks
Thermoluminescence
Measures time since object exposed to heat or light
Paleomagnetic dating (relative dating)
Earth’s magnetic poles sometimes switch (like compass pointing N/S), can see this in rocks
Biostratigraphy - “Faunal dating” (relative dating)
Uses the combination of other animal fossils that have already been dated precisely (e.g. pigs, giraffes, rodents, elephants)
Which of the following fossil dating techniques CANNOT be used on a sample roughly a million years old?
Radiocarbon dating
Oxygen Isotopes and Paleoclimate:
Oxygen occurs in two forms
18O (heavy)
16O (light)
Foraminifera fossils are found in ocean cores.
Tiny single-celled organisms that live in ocean water
They contain calcite (CaCO3), a mineral
Tiny single-celled organisms that live in ocean water
They contain calcite (CaCO3), a mineral
Ratios of 18O/16O in calcite fluctuate across core depths (time)
Reconstructing Global Temperature
When it’s cold, the ocean becomes more concentrated with 18O
so, higher 18O/16O ratio
The higher 18O levels in ocean water are incorporated into Foraminifera, which die and become fossils
Researchers take deep-sea cores and check 18O/16O ratio
See how global temps change over time
Evolution of Early Primates:
Mesozoic era: domination by gymnosperms (seed producing plants)
Cretaceous period: angiosperms (flowering and fruit bearing plants) evolved and diversified
New ecological niches for animals
Primates evolved to exploit these niches
Grasping hands/feet; forward facing eyes
Timeline of primates:
Paleocene
Early cenozoic period; lasted from 65-54 mya
Climate very warm and wet
First Primate like species
Eocene
Very warm global temperatures
First haplorrhines and strepsirrhines
54-34 mya
Oligocene
34-23 mya
Colder
First anthropoids (catarrhines and platyrrhines)
Miocene
23 - 5 mya
Warming period
First apes appear
Pliocene
5 - 1.8 mya
Planet cooling and temperature fluctuate rapidly through plio and pleistocene (1.8 - 12 kya)
First hominins appear (bipedal apes)
Holocene (12kya - now)
Current climate crisis caused by humans
Accelerated, unprecedented rate
Climate has always changed (just less rapidly)
Changing environments and climates track the evolutionary history of primates
Scientists do NOT have a very good idea of which Miocene apes are the direct ancestors of humans, as well as of all the other modern apes.
Climatic changes in the late middle Miocene reduced hominoid diversity in Asia and Europe.
Paleocene “Pre” or “Early” Primates: Plesiadapiforms
Paleocene
Found in north america (was attached to Europe)
Wyoming and surrounding states
Lush forests at the time
fossil animals that scientists think most closely resembles the common ancestor of all primates
Fossil evidence from plesiadapiform fossils suggests that grasping hands and feet evolved before forward-facing eyes
Different from modern strepsirrhines
Smaller brains
Eyes on side of eye (no stereoscopic vision)
No post orbital bar
long narrow snouts
Similar to modern strepsirrhines:
Grasping hands and feet
Nail on its big toe but claws on other digits
Probably used hands + feet to grasp small branches as they climbed in the terminal branches of fruiting trees eating fruit
Eocene Primates: Adapids and Oomyids
Full suite of primate characters
Forwards facing eyes with postorbital bar
Short snout
Larger brains
Nails no claws
Hindlimb dominated locomotion
Grasping hands and feet
Adapids:
Larger than omomyids
Diurnal (size of orbits)
Fruit or leaves (shape of teeth)
Quadrupedal, arboreal (shape of limbs)
Similar to lemurs
But no toothcomb
Strepsirrhine ancestors?
Famous adapid: Ida
47 mya
Exceptionally well preserved Eocen adapid
Fur on its body
Leaves and fruit in its stomach
Based on their teeth, paleoanthropologists expect adapids primarily fed on
Fruit or leaves
Omomyids:
Smaller than adapids
Nocturnal (big eye sockets)
Fed mainly on insects, fruit, or gum (teeth)
Quadrupedal, arboreal (shape of limbs)
Some leapers
Similar to tarsiers
Tarsier ancestors?
Fayum Depression, Egypt
5 groups of strepsirrhines
2 group of omomyids
3 groups of haplorrhines: first anthropoids (monkeys + apes)
Eocene/oligocene boundary
Now a desert but in the Oligocene, Swampy lush forest
Anthropoids in the Fayum Depression, Egypt
3 kinds:
Parapithecids
Very diverse group
This is a relatively diverse group of fossil primates, the largest of which were the size of a guenon, and the smallest were the size of a marmoset. They had a 2.1.3.3/2.1.3.3 dental formula and unspecialized, primitive teeth.
Teeth and postcranial anatomy primitive
2-1-3-3 (like strepsirrhines and platyrrhines)
Common ancestor of Anthropoids (platyrrhines and catarrhines)?
Oligopithecids
Mix of Anthropoid and primitive features
fully encased eye orbit bone
2-1-2-3, like Catarrhines (OWM and Apes)
These primates share many primitive features with the Fayum haplorrhines, but have the same dental formula as propliopithecids. Members of this group may have ranged beyond the Fayum into North Africa and the Arabian Peninsula.
Propliopithecids
2-1-2-3, like Catarrhines (OWM and Apes)
This is a somewhat diverse group of fossil primates. Although they were larger in body size, they still showed signs of arboreal quadrupedalism. They had a 2.1.2.3/2.1.2.3 dental formula and ate mainly fruit.
Most famous genus: Aegyptopithecus
Last common ancestor of the Catarrhines (OWM and Apes)
2-1-2-3
Fruit + leaf eater (ape-like teeth)
Sexually dimorphic • Arboreal quadruped
Diurnal
Relatively small brain (strepsirrhine-like)
Large body (13 lbs)
South America Primates:
also during the Eocene/ Oligocene boundary
36 mya: primate-y teeth in Peru
32-26 mya: platyrrhine-like monkeys in Bolivia
Later Miocene (12-10 mya) many primates in Argentina, Chile, Colombia
How did primates get to south america?
During Eocene
Monkeys living along the Atlantic coast of Africa were swept up in intense storms.
Clung to storm debris that formed natural rafts.
Currents carried these platforms of vegetation across the ocean.
Large islands along the way
Recap:
These were all in North America, Eurasia, and Africa, which were connected!
Paleocene (65-54 mya) Plesiadapiforms (ancestor of all primates)
Eocene (54-34 mya) Adapids (ancestor of strepsirrhines) and Omomyids (ancestor of tarsiers)
Eocene/Oligocene boundary (36–33 mya) Parapithecids, Oligopithecids, Propliopithecids (ancestors of Anthropoids — all monkeys and apes)
Evolution of Platyrrhines
New world monkey ancestors in south america
36-10 mya
Fewer fossils because of ecology
Shared by contemporary monkeys and early fossil primates
They have long tails
They have arms and shoulders fit for quadrupedal locomotion
They have fleshy sitting pads
Shared by apes and apelike primates
They do not have tails
They have arms and shoulders fit for suspensory locomotion
They do not have fleshy sitting pads