Anthr 201, Winter 2005

Important Terms and Concepts

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The terms, concepts, definitions, and links on this page are not an alternative to attending lecture, but an addendum to it. You will need to complete the readings and take notes on lecture, and especially attend and complete the labs in order to do well in this class. You may find that these terms and concepts will assist you in organizing your studying and preparation for the midterm and final exam, and that they help to clarify issues related to lectures. Each term will include an opportunity for you to comment, as questions, or start or participate in discussions with your classmates on the topic. Please keep comments topical.

Linear Concept of Time

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Our notion that time passes in a single, non-repeating flow is actually relatively recent. Notions of time and the way it passes vary from culture to culture, and within a given culture through time.

Many of the Classical philosophers believed that time was linear, but that it necessarily resulted in decay. They felt that the world began in a "Golden Age" when the gods roamed the earth. Later came a "Silver Age," which was the time of the heroes of legend and their epic adventures. Finally, the "Age of Bronze" or "Age of Iron" was a time when the gods had retired to Olympus and there were no more great heroes. In the later ages, people had to toil and perform unpleasant, difficult, but not very meaningful labor, just to survive, politicians were distructed, businessmen, religious leaders and socially influential were considered largely corrupt, and everything seemed to be generally pretty lousy. (Remember, this is Ancient Greece and Classical Rome we're talking about.)

By the Dark Ages, after the fall of Rome, Europeans generally adopted a "cyclic" view of time. Time followed the seasons, in Spring, people planted crops, in Summer they watered crops, in Autumn, it was harvest time, and in Winter, it was time to repair tools and get ready to start the whole process over again. Each new king was more or less indistinguishable from the previous one, and nothing ever really seemed to change. So the notion that time was a cycle that just kept going around and around seemed to make sense to a lot of people.

By the Rennaisance and particularly in the Baroque era of Newton, Leibniz, Descartes John Wilkins and John Ray, the linear concept of time began to be considered likely again, only now it seemed that as time changed, things improved. The notion of "progress" inspired many Enlightenment-Era thinkers, and progress is necessarily an idea about the passage of time. Industrial-Age Europeans were quite fond of the notion of progress, and it inspired many of their philosophies, including the notion of progressive evolution proposed by Lamarck (see below).

Stratigraphic Relative Dating

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In the 1660s, Bishop Nicolas Steno studied the Stratigraphy, or sequence of layers of rock in the cliffs near his home. He realised that each stratum, or rock layer, must have been deposited at a different time. In particular, his Principle of Superposition provided an explicit statement that in any undisturbed stack of strata, the stratum on the bottom must already have been present in that location before more superficial strata were deposited. Thus each successively higher stratum in a sequence was successively younger than the ones below it. Therefore, the sequence of strata in any given stack was an indirect measure of the passage of time.

William "strata" Smith extrapolated from Steno's findings to develop the Principle of Strata Identified by Fossils. Index fossils were fossils that occurred in in two distinct locations. Given Cuvier's discovery of the reality of extinction (see below), Smith realized that species, and therefore their fossils, should have a limited distribution in time. Thus we could correlate stacks of strata across space, even when we could not trace them through continuous distribution across space. A stratum in England that contained a specific type of fossil must be the same age as a stratum with the same type of fossil in France, the United States, or anywhere else.

Together, the principle of superposition that demonstrated that depth is a measure of time and the recognition that the fossils in any given layer differed from the fossils in strata above and below it demonstrated that evolution must have happened. But it would take several decades before Darwin was able to explain how it happened.

Extinction

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In the early 18th century, Georges Cuvier demonstrated that species could become extinct. He promoted this discovery in an attempt to discredit the notion of evolution proposed by Jean Lamarck (see below). Lamarck's ideas seemed to suggest that extinction was not possible, since any species would simply evolve to adapt to any change in environmental conditions. Religious thinkers who believed that the world had been created by a benevolent God appreciated Lamarck's ideas, since they accorded well with the notion that a loving God would not allow his creations to become extinct.

In light of the anti-clerical sentiments of many of the French Revolutionaries, Cuvier challenged Lamarck's ideas in part because they seemed to be religiously, rather than scientifically inspired. Cuvier believed that the reality of extinction disproved the possibility of evolution. It certainly presented a powerful, even fatal counter-argument to Lamarck's ideas of how evolution worked, although about 60 years later, Darwin found that extinction and evolution both contributed to forming the diversity of life on earth.

Dating Techniques

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Numerous materials change at regular, predictable rates, and measurements of the amount of change, divided by the rate of change, can give us very precise estimates of the age of the materials.

In the 1950s, A. E. Douglass (an astrophysicist) developed a technique known as Dendrochrnology. Douglass was interested in sunspots and suspected that they also occurred with regular, predictable frequency. (He was right; the sun goes through periods of heightened activity every 11.5 years.) He measured the widths of annual growth rings in long-lived trees. He found that the rings in trees of the same species living in the same area could be correlated, so that the sequence of rings in a living tree could be partially overlapped with the sequences of rings in older, fallen trees and even in wood that had been used in construction in archaeological sites. Dendrochronology is not generally used in paleoanthropology because its maximum range of accuracy is only about 6000 years, at most, but Douglass' success inspired others to find other "natural clocks."

Radioactivity refers to the tendency of some heavy elements to release electrons and other sub-atomic particles into their surroundings. The regularity of release of these particles, and the resulting change in the atomic structure of the element allow us to use some radioactive materials to determine the ages of events that happened long before recorded history.

Radiocarbon dating is also not often used in paleoanthropological analyses, as its effective range is only about 60,000 years, which covers part of the span of existence of humans, neandertals, and the recently discovered Homo floresiensis. Radiocarbon decays back into nitrogen at a steady rate, so we can determine the age of the remains of the organism that contains the carbon by comparing the difference between the ratio of radio- to normal carbon today with the ratio of the two forms of carbon that was present when the organism was alive.

The Carbon Cycle refers to the movement of carbon throughout the biosphere. Radiocarbon is created in the upper atmosphere by the impact of cosmic ray particles on stable atoms of nitrogen-14, which transform the nitrogen into carbon-14. C-14 then bonds with oxygen to form radioactive CO2, which is inspirated by plants in the same ratio as it exists in the atmosphere. The plants are consumed by animals, so the ratio of radioactive carbon to regular carbon in the atmosphere and in the plants is also included in the animals. Once the plant or anmal dies, it stops consuming new carbon, so the ratio of normal carbon (which is stable) to radiocarbon (which is not) begins to change as the radiocarbon decays and the stable, normal carbon stays where it is. The half-life of radiocarbon is about 5730 years.

Half-Life: The amount of time it takes for 50% of a radioactive element to decay into its stable daughter product. After one half-life, half of the original amount of the radioactive element has changed to its non-radioactive decay product. After two half-lives, half of that half remains (or 25% of what was originally there). After three half-lives, one half of one half of one half, or 12.5% of the original radioactive material remains, and so on. In general, after about 10 or 12 half-lives, there is too little remaining radioactive material to be measured, so radiometric dating techniques do have an upper limit. For radiocarbon, that limit is about 60,000 years, but for some other materials, such as Strontium/Rubidium dating, only a few half-lives have passed since the beginning of the universe.

Potassium/Argon: Radioactive potassium 40 decays into
Uranium, with a half-life of around 1.25 Billion Years.

Potassium 40 decays into Argon 40 half-life= 1.25 Billion Years

Rubidium 87 decays into Strontium 87 half-life= 48.8 Billion Years

Thorium 232 decays into Lead 208 half-life= 14 Billion Years

Uranium 235 decays into Lead 207 half-life= 704 Million Years

Uranium 238 decays into Lead 206 half-life= 4.47 Billion Years

Carbon14 decays into Nitrogen14 half-life= 5730 years

Jean Lamarck

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Jean Lamarck, a French nobleman, served as a tutor to the children of the Compte de Buffon, and in the process, learned of Buffon's ideas about evolution, which Lamarck later went on to explicate and popularize. Lamarck proposed that two major mechanisms were involved in causing evolution; the Principle of Use and Disuse, and the Inheritance of Acquired Characteristics.

Use and Disuse refers to the tendency for an organ or tissue mass to grow or be exaggerated when it is used, and to atrophy or whither when it is not employed. For example, muscles are increased in mass through exercise. Lamarck argued that this tendency created specific variations in response to the needs of the organisms.

Inheritance of Acquired Characteristics was Lamarck's notion that a character that was exaggerated by an organism over the course of its lifetime could be passed on, in that exaggerated form, to the organism's offspring. Lamarck noted that the eldest sons of blacksmiths generally had muscular arms, and he believed that this muscularity had been inherited from their muscular fathers.

We now know that proteins and enzymes are formed on the basis of genetic instructions but the inscription of instructions only goes one way. Genes can direct which tissues to manufacture so changes in the genes can create differences in the tissues, but the reverse is not true. Changing the tissues of the body can not re-write the sequence of the genes.

Charles Robert Darwin

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Charles Robert Darwin was the first person to recognize that natural selection was a major cause of biological evolution. In the 1830s, he joined Capttain Robert FitzRoy abord the H.M.S. Beagle for a voyage around the world. While in South America, Darwin noted that geographical distance is correlated with anatomical differences, and that chronological distance is also correlated with anatomical differences. Space and time were both related to anatomical difference in some way. Darwin realized, after a colleague explained to him the relationships between the finces of the Galapagos Islands, that physical form is an adaptation to environmental context. The phenotypic characteristics that help an organism survive and reproduce will become increasingly common in each successive generation, as those organisms that bear them have more offspring than those that do not. As long as environment is stable, the same characteristics will be favored, but when environments change, different characteristics will be favored. This form of environment unconsciously "selecting" which characteristics will be copied and which will not was the reason that geography and time were both correlated with physical variation. Darwin first spelled out his ideas in his Notebooks on Transformationism, and finally published them in abstracted form in his On The Origin of Species by Means of Natural Selection (1859).

Forces of Evolution

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Natural Selection: The differential survival and reproduction of individuals, due to their differential adaptation to their specific environments.

Gene Flow: The transmission of genes from one gene pool of a species to another gene pool of the same species.

Drift: The random, non-selective removal or retention of genes. Often, neutral traits change frequency as a result of drift, but some adaptive characters can change that way as well.

Mutation: refers to errors in copying of DNA. Most mutations will have little or no effect on the phenotype. Those few that do have an impact on the phenotype can either be bad for the survival or reproduction of the organism or can improve the organism's ability to survive and/or reproduce. The disadvantageous changes will be removed from the gene pool as organisms who bear them will fail to attract mates. The "beneficial" mutations will accumulate in the population's gene pool, as those organisms which bear them will have greater than the average number of offspring.

Particulate Inheritance

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Prior to the work of Gregor Mendel, most people thought that inheritance was a blend of parental traits, and that children would be "half-way" between each of their parents. Mendel's experiments demonstrated that inheritance was "particulate." Genes are discrete particles, and individuals inherit one particle (gene) from each parent.

Details of Inheritance

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Genes: The "particles" of inheritance, which can be metaphorically thought of as the "instructions" for building a body.

Dominant: refers to the version of a gene that will preferentially be expressed by a cell if possible.

Recessive: refers to the version of a gene that will not be expressed if an alternative, dominant allele is available.

Alleles: the variant versions of a gene.

Homozygous dominant: refers to individuals who inherited the dominant allele for a given gene from both parents. Because of independent assortment (see below) being homozygous dominant for one gene does not alter the probability of inheriting the dominant allele for any other genes.

Homozygous recessive: refers to individuals who received the recessive allele of a gene from both parents. It is only homozygous recessive individuals who will express the recessive trait in their phenotype.

Heterozygous: refers to individuals who received the dominant allele from one parent and the recessive allele from the other parent. Individuals who have the heterozygous genotype will express the dominant phenotype.

Genotype: The collection of genes an individual has inherited from its parents.

Phenotype: The "body" that is built on the basis of genotypic instructions.

Punnet square: A graphical way of expressing the probability of the genotypes of offspring when the genotypes of the parents are known.

Gregor Mendel

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Gregor Mendel, an Austrian monk, discovered the basis of genetic inheritance through his experiments in cross-breeding garden peas. Mendel noted two major principles controlled inheritance.

Principle of segregation: for any particular gene, the pair of alleles of each parent separate and only one allele passes from each parent on to an offspring.

Principle of independent assortment: different pairs of alleles are passed to offspring independently of each other.
(Definitions taken from O'Neil 2003)

Parts of the Cell

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Cell Membrane: the flexible, semi-permeable boundary of the cell.

Cytoplasm: the interior fluid of the cell, in which the nucleus and organelles are suspended.

Nucleus: The "command center" of the cell, where genetic instructions are stored. The yolk of an egg is the nucleus of that cell.

Rhibosomes: The "factories" of the cell that carry out genetic instructions for making proteins and enzymes.

Mitochondria: The "energy plants" of the cells that convert sugars and other nutrients to Adenosine Triphosphate (ATP), which is the chemical form of energy that the cells can use.

DNA

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DNA, or deoxyribonucleic acid, is the chemical basis of inheritance, as well as the chemical "instructions" for building cells. It is composed of a "backbone" of sugars and phosphates in a long chain, and these backbones are connected to a series of bases, adenine, thymine, cytosine, and guanine, the sequence of which acts as a base four digital "code" that specifies the productive activity of ribosomes in the cell through the intermediary of RNA.

RNA

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RNA, or Ribonucleic Acid, is one of the two major proteins involved in cell functioning and replication. It makes use of four bases, like DNA, but uses Uracil in place of Thimine.
Messenger RNA makes copies of cequences in the bases of DNA and transports them out of the nucleus and into the cytoplasm. Then transfer RNA copies the mirror image of the string of messanger RNA (which is the original sequence of the segment of DNA that was copied, with the substitution of U for T) and transports itself to the ribosomes, where the sequence of bases acts as instructions for the construction of amino acids that form proteins and enzymes.

Reproductive Isolation

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Reproductive isolation refers to barriers between populations that prevent the genes in one population from being transmitted to the gene pool of the other population. These barriers can take multiple forms.
Pre-zygotic isolating mechanisms are barriers to gene flow that prevent fertilization from ever taking place. Geographic distance is an obvious example. Differences in the season of fertility is another pre-zygotic isolating mechanism. Organisms that are only fertile in the Spring can not transmit genes directly to organisms that only mate in the Autumn. Mechanical differences, such as size, can also preent gene flow. In most animal species, fertilization of one species by a member of another is impossible. Even when it is attempted, no zygote will form from the mating at all.

Post-zygotic isolating mechanisms are barriers to gene flow that occur after fertilization has taken place. In many cases of mating between two species, a zygote forms but is not viable and miscarriage results. In other cases, the zygote forms and even grows to adulthood, but is sterile (mules, for example). Hybrids are easier between plants, but viable, fertile hybrids among animals are almost unknown.

Speciation

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Speciation refers to the splitting of a single lineage into two (or more) descendant species that are reproductively isolated from each other. It is also known as "macroevolution," which despite its name, has no implications about the amount of phenotypic difference that is visible. Two populations that have speciated (i.e. undergone macroevolutionary change) may appear almost indistinguishable to us. On the other hand, a single species may contain a vast array of variation.

Several factors are involved in speciation/macroevolution.

"Sympatry" refers to populations living in the same environment. It is contrasted with "Allopatry," which refers to organisms living in geographically (or otherwise, e.g. temporally) seperated environments, and "Peripatry," which refers to populations in abutting, or perhaps slightly overlapping environments.

Most researchers now think that allopatric populations are the most likely to speciate, since distance inhibits gene flow.

There are two forms of speciation as well. Anagenesis refers to accumulative change within a single lineage, while cladogenesis refers to a splitting of a single population into two (or more) descendant populations between which gene flow is limited. Most biologists, paleontologists, and anthropologists believe that cladogenesis ("splitting") is the more common form of macroevolution, although anagenesis certainly happens.

Punctuated Equilibrium

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Punctuated Equilibrium is the hypothesis, devised in the early 1970s by S. J. Gould and N. Eldredge, that evolutionary changes to the phenotype of organisms will occur quite rapidly (in geological time, which may be thousands of years), and will most often occur in small, geographically isolated populations. Rapid phenotypic change (punctuation) will be followed by long periods of stability (stasis) of form. Gould and Eldredge estimate that the rapid change in phenotype should take only about 1% of the entire duration of a species' existence, and the remaining 99% of the life of that species will be typified by relatively minor fluctuations around a population average.

Punctuated Equilibrium, if correct (which most agree it is), helps explain why forms of fossils are recognizable as the same species throughout many geological strata, but then disappear and are replaced relatively suddenly.

Cladistic Taxonomy

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Devised by Willi Hennig, cladistic, or "numerical" taxonomy is the attempt to classify organisms in terms of their relatedness, and nothing else. Similarities of appearance are used as indicators of similarity of ancestry. It is much more rigorous than other forms of classification, but is also much more precise and reliable.

Types of Similarities

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Homologies: Similarities between taxa that are due to common inheritance of those characters from an ancestor shared by both taxa.

Homoplasies: Similarities between taxa that are due to a common adaptation to similar environments. These similarities (e.g. wings in birds, bats, and butterflies) do not indicate common derivation from a shared ancestor that had the character, but to convergent evolution.

Hardy-Weinberg Equilibrium

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Hardy-Weinberg equilibrium is a mathematical test to determine which, if any, forces of evolution are operating on a given population at a given time. The model assumes a bi-allelic Mendelian trait. We can distinguish individuals with the homozygous recessive genotype, because they will express the recessive phenotype. We can not distinguish the heterozygotes from the homozygous dominant individuals by looking, but we can determine their frequency mathematically. Label the frequency of the dominant allele P, and the frequency of the recessive allele Q. Then P+Q=100% of the alleles for that gene, which we label P+Q=1, for mathematical convenience.

Squaring the equation (p+q)^2 = 1^2, and factoring that, p^2+2(pq)+q^2=1

Q^2 is the frequency of the recessive allele multiplied by itself, so it corresponds to the odds of an individual inheriting the recessive allele from mother, times the odds of inheriting the recessive allele from father. P^2 refers to homozygous dominants, and 2(pq) refers to the two ways an individual can be heterozygous.

We can identify homozygous recessive individuals by phenotype, so we know what q is just by looking; it is the square root of the number of individuals (out of every 100) who have the recessive phenotype. Subtract that number from 100%, and we know P, the frequency of the dominant phenotype, so we can simply plug in those numbers and solve the equation.

Types of Characters and Attribute States

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Plesiomorphies : The ancestral forms of heritable traits.

Apomorphies : The derived form of heritable traits.

Symplesomorphy : A shared retention of the ancestral form between two or more taxa. For example, frogs and humans both have five fingers on each hand, because we have retained the ancestral (plesiomorphic) state of "pentadactyly." Horses have lost fingers, so they are "Unidactyl" animals. Symplesiomorphies are not useful for determining closeness of relationship between taxa.

Synapomorphies : Shared derived versions of a character. These similarities are useful for determining the degree of relatedness between taxa.

Autapomorphies : Unique, unshared, derived versions of a character. These characters are useful in distinguishing between closely related taxa.

Cladogram

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A visual representation of the nested sets of similarities between taxa.

Classification

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Classification is the art and science of sorting the infinite variety of phenomena of the universe into smaller, more managable, meaningful collections of things that are similar to each other in some way. There are an infinite number of possible ways to classify organisms, but the most familiar is the system devised by Carolus Linnaeus. Linnaeus decided to group all organisms into ever more inclusive categories. A collection of individuals comprised a species, several species could be combined into a genus. Multiple genera could be grouped together into a family, and so on.

Taxonomists are the professionals of classification. Their job is to arrange named units (taxa) into some system of organization. Linnaeus was the first of the modern taxonomists, but others had attempted similar systems of classification long before.

Most early forms of classification were "phenetic," that is, based on the phenotype of the organism. Phenetic taxonomists generally choose a few visible traits from each species that they consider particularly informative or important. Cladistic taxonomy is a more recent approach (see below) that sorts organisms in terms of their "clades," rather than their physical appearances, per se.

Outgroup

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In a cladistic analysis, an "outgroup" is chosen as the basis of comparisson of the taxa one wishes to sort. The outgroup should be a taxon of Linnaean scale equal to the members of the ingroup (i.e. if the ingroup members are genera, the outgroup should be a genus, if the ingroup are species, the outgroup should be a species too), and the outgroup is chosen because it is assumed to be no more closely related to any member of the ingroup than to any of the others. When classifying species all of the same genus, the outgroup should be chosen from a different genus. When all members of the ingroup are of the same family, the outgroup should be a different family, and so on.

Similarities of attribute states between the outgroup and any member of the ingroup are assumed to be plesiomorphic, since they must have been present in the shared ancestor of the outgroup and that member of the ingroup. Differences are therefore assumed to be apomorphic. (There is more to it than that, of course, but that's teh basic idea.)

Biological Species Concept

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In the 1940s, Ernst Mayr proposed the Biological Species Concept (BSC), which states that two organisms can be recognized as members of the same species if, and only if, they can and will reproduce in the wild and their offspring is both viable and itself reproductively fertile.

Characters and Attribute States

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In a cladistic analysis, characters are the categories or variables (usually phenotypic or genetic) of the taxa being sorted, and attribute states are the values of each of those variables for each of the taxa. Usually, the characters have two attribute states. Cladistic analyses of multi-modal and continuous characters
have been constructed, but those attempts are much more complicated and many cladists are skeptical of the results.

Nodes and Internodes

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The "branches" and connections between branches in a cladogram. The internodes represent the acquisition of a derived (apomorphic) character state in one set of descendants of an ancestor that is not shared with the other descendants of the same ancestor. (Note that the nodes represent observable differences and the order of branching; they do NOT represent ancestors.)

Terminal Taxa

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The taxa (usually species, but they can be at any Linnaean scale) that are used as the end-points in a cladogram. These are the units the cladogram is attempting to sort in order of their similarities.

Unresolved Nodes

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In a cladogram, unresolved nodes indicate divergence of two or more taxa that can not be placed in their correct order, due to lack of defining characteristics.

Encephalization Quotient

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The ratio of brain size to body size. The size of the brain is partly determined by the size of the body; larger animals have larger brains and smaller animals have smaller brains. Graphic representations of the size of the brain plotted against the natural log of the size of the body display a linear trend (brain size is bigger as body size is bigger in a roughly straight line). The primates in general have larger brains than one would expect for mammals of their size, so they plot above the line of other mammals.

Primates

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Primates are one of the families of mammals. Although there is a considerable amount of variation within the primates, all share one distinctive feature.
In the primates, the External Auditory Meatus (ear hole in the temporal bone) leads to the Auditory Bulla, and the Petrus portion of the Mastoid Process of the Temporal bone forms the posterio-inferior wall of this bulla. In the primates, the petrus portion fuses to the mastoid in infancy, or often in pre-natal development. In other mammals, it generally does not fuse at all, or it fuses only in adulthood.

Mammals

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Mammals are defined by their warm blood, body hair, and differentiated teeth. Most of the living mammals are also placentals, in that they have "live" births, but a few are marsupials, and three species are "Monotremes" (egg-laying mammals). The monotremes retain the plesiomorphic trait of laying eggs. It is most likely, given their concentration in the continents that were once parts of Gondowana, that the marsupials derived from the monotremes first, and the placental mammals either evolved seperately from monotremes or branched from the marsupials.
Mammals are most likely the descendants of the Therapsid reptiles, which lived at the same time as the dinosaurs but were not dinosaurs themselves. The Therapsids, like the mammals, have differentiated teeth. The teeth of all other reptiles are undifferentiated (each species of reptile has only one type of teeth, mammals have several different kinds of teeth).

Purgatorius ceratops

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P. ceratops is the oldest primate that has yet been discovered. It lived about 60 million years ago in North America. There is some evidence both from genetic analysis and from statistical estimates of the number and stratigraphic dispersal of the known primate fossils, that the primate clade split from the other mammals as much as 80 million years ago, but to date, no earlier fossils that are recognized as primates have been found.

P. ceratops had a body structure that was similar to modern tree shrews. On the grounds that form is related to function, we suspect it had a lifestyle similar to shrews as well. It was small, probably nocturnal, and probably an insectivore.

Laurasia and Gondowana

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Laurasia and Gondowana are the two "supercontinents" that existed at the time of the earliest known primates. Gondowana was the southern supercontinent, composed of the landmasses that are now Africa, Australia, Antarctica, South America, and India. Gondowana had no primates. The primates evolved in Laurasia, which included the modern landmasses of North America, Greenland, and EurAsia.

The mid-Atlantic ridge, a rift in the sea floor, split both of the supercontinents in half, and later tectonic movements brought them to their current locations. Tectonic activity continues to move the continents. The Atlantic is gradually expanding and the Pacific is getting smaller (which is why volcanic and seismic activity is so much more active along the Pacific rim than it is on the east coast of North and South America.

Dryopithecus

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Dryopithecus occupied south and west Europe during the Miocene. There was originally some debate about its taxonomic affinity but studies of its facial anatomy show that it is most closely related to the south Asian apes and not to the African clade.

Sivapithecus

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Sivapithecus occupied south and southeast Asia during the Miocene, lived in the trees, and subsisted mainly on fruit (evidenced by dental wear). It had a facial structure similar to an Orangutan, but a body about the size of a chimpanzee.
Ramapithecus and Gigantopithecus were originally considered to be different genera from Sivapithecus, but most paleontologists who study them believe that Sivapithecus was simply a very diverse genus and Ramapithecus and Gigantopithecus are considered junior synonyms.

Y-5 Molars

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The cusps on the occlusal surface of the molars of the African apes all form a "Y-5" pattern, which is distinct from the X-4 pattern of the non-Hominoid members of the Infraorder Catarrhini.

Micropithecus

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Micropithecus evolved in the early Miocene, and all species of this genus have the same dental pattern as the later African apes. Micropithecus clarki bears some phenotypic resemblance to living species of the genus Hylobates, particularly in the face, and those features suggest that it may be ancestral to that genus.

Dendropithecus

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Several species of Dendropithecus, including Dendropithecus macinnesi occupied Africa during the early Miocene. Their dental pattern (2:1:2:3) is shared with all of the Old World apes, and many suspect that it was an early Miocene ancestor of at least some of the later apes.

Miocene Gap

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The Miocene Epoch, 23.8 to 5.3 mya, was warmer than either the preceding Oligocene or the following Pliocene and Pleistocene. The breakup of Gondowana changed global ocean circulation patterns and cold Antarctic water did not mix with warm water in tropical latitudes. The global climate change caused an apparent increase in rainfall in the tropics and a decrease in rainfall in temperate latitudes. As Antarctica reached its current position later in the Miocene, glaciation of that continent began, and global sea levels decreased, while Africa and India both connected with Eurasia, leaving the Mediterranean as the last small remnant of the Tethys sea. Grasslands expanded in the continental cores, reducing primate habitat, and most African primates lived in the few remaining tropical rainforests, which generally have very acidic soil that does not favor preservation.

One important side-effect of this global climate change is that few fossil primates have been recovered from this epoch until quite recently. (Today, the Miocene gap is gradually being filled in.)
Proconsul, Limnopithecus, Dryopithecus, Sivapithecus (including the junior synonyms "Gigantopithecus" and "Ramapithecus"), and Kenyapithecus are known from the early and mid-Miocene. In particular,
Proconsul africanus is likely to be an ancestor of all of the African apes, as was one of its descendants, one of the various species of Kenyanthropus. More research is needed from this period, because it was during the Miocene that the Gorillas, Chimps and hominids diverged into their seperate clades.

Ecological Effects on Fossilization

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The majority of fossils form in sedementary deposits. There are a few notable exceptions, such as Washington State's Blue Lake rhino an the fossil hominid tracks at Laetoli that are found in igneous rocks, but in general, sedimentary rock is where we are most likely to find fossils. Unfortunately, not all sediments are equal in their probability of containing fossils. In particular (for our purposes), sediments that originate in tropical forests are generally more acidic than sediments that derive from montaine or grassland environments. As a result, species that live (and die) in rainforest habitats usualy deposit their bones in acidic soils, where they are rapidly decomposed and do not have a chance to mineralize. In addition, tropical environments tend to be biotically very rich, and the biological diversity of tropical environments includes scavenging animals, acidic plant roots, and of course insects, all of which rapidly decompose "soft" tissues. The "practical effect" is that tropical species, including many of the primates, are not well-represented in the fossil record, and grassland species (including both herbivores and their predators) are over-represented.

Geological eras

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For this course, we will mainly be focusing on the Cenozoic Era, which began about 65 Million Years ago, with the extinction of the non-avian dinosaurs (although the earliest primates are probably late Cenozoic in age, perhaps as much as 80 MYA).
The Cenozoic (= "recent life") is divided into two Periods, the Tertiary (65-3 million years ago) and the Quaternary (3 MYA-Present).

The Quaternary is divided into two Epochs:
The Holocene 10,000 years ago-present, the era of modern climate, and
the Pleistocene, 3 Million to 10 Thousand years ago, the epoch of the most recent great Ice Ages.

The Tertiary is divided into 5 Epochs
Pliocene 5-3 MYA
Miocene 25-5 MYA
Oligocene 38-25 MYA
Eocene 55-38 MYA
Paleocene 65-55 MYA

Hominids

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Hominids is the informal name for all of the members of the (Linnaean) Family Hominidae, in the superfamily Hominoidea, in the Order Primates (Class Mammalia, Phylum Cordata, subphylum Vertebrates). The hominids are identified among the primates by their habitual bipedal locomotion. The hominids are divided into several genera.

Australopithecus is a genus that includes several distinct species in two recognized clades; the "gracile" or small-bodied species, and the "robust" or larger-bodied clade (also known as Paranthropus and sometimes as Zinjanthropus, although both are considered junior synonyms by most anthropologists). They typically have large teeth with thick enamel, although smaller canines than any of the living apes, and the teeth are often arranged in a V-shaped dental arcade, which appears to be transitional between the U-shaped mouths of the living non-human primates and the parabolic dental arcade of humans.

The genus Homo is the other variant of the hominids. Members of the genus Homo all made some form of stone tools, which are unknown in all but one of the species of Australopithecus, and all but one have cranial capacities above 550 cubic cenimeters.

A few other genera have been named, including Sahelanthropus, Orrorin, and Ardipithecus. These less well known, and only recently discovered genera may end up being incorporated into Australopithecus, and some paleoanthropologists would like to see all of these genera recognized as junior synonyms of Homo. (Some even wish to include the genera "Pan" (chimps and bonobos) and "Gorilla" in our own genus and restrict the family Pongidae to Orangutans.)

Leakey family

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Dr. Louis Leakey and his wife Dr. Mary Leakey are two of the most famous physical anthropologists. Their son, Richard and his wife Maeve carried on the family business, which has now been joined by a third generation, Louis and Mary's granddaughter, Dr. Louise Leakey.

Anatomical Position

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The body in anatomical position is viewed from the front, arms to the sides, palms forward. All anatomical directions are described with respect to anatomical position. When positioned in this way, all bones are visible (if the hands are placed with the back of the hand forward, the radius partially obscures the ulna).

Anatomical Planes and Directions

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Midline (body) or Midsagittal Plane(head): separates body or head into Right and Left parts.
Medial : Toward the midline.
Lateral: Away from the midline.

Coronal Plane: separates the body into Anterior (ventral) and Posterior (dorsal) parts.
Anterior: Toward the ventral (stomach) side.
Posterior: Toward the dorsal (back) side.

Transverse (or Horizontal) Plane: separates the body into Superior and Inferior parts.
Superior: Towards the head.
Inferior: Away from the head.

The ends of the Limbs are not labeled "superior" or "inferior" because they can change position. Instead, they are labeled:
Proximal: Toward the trunk.
Distal: Toward the fingers/toes.

Anatomical Directions of the Teeth

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Buchal: Toward the cheeks.
Labial: Toward the lips.
Lingual: Toward the tongue.
Occlusive: The upper surface of the lower teeth or lower surface of the upper teeth; the biting surface.
Interstitial: Between the teeth. (The flossing zone.)

Frontal

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The bone of the forehead. It articulates posterio-superiorly with the parietals at the Coronal Suture.

Parietals

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The paied bones of the sides of the head that meet at the top of the head and fuse along the Sagittal suture.

Occipital

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The bone at the back and base of the skull. It includes the:
Lambdoidal suture: the superior surface, where the occipital articulates with the parietals.
Occypital Condyles: on the inferior surface, the articulation of the skull with the upper vertebrae.
Foramen Magnum: the large foramen (hole) through which the spinal cord passes, connecting the brain to the rest of the body.

Temporals

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The paired bones of the side of the head that include:
Styloid Process: The anterio-inferior spur of bone, immediately adjacent to the ear.
Mastoid Process: the bulge inferior and posterior to the external auditory meatus.
External Auditory Meatus: the "ear hole" that funnels sound into the bones and tissues of the inner ear.
Zygomatic process of the Temporal: the posterior portion of the zygomatic arch or "cheekbones."

Zygomatic Bone

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The paired bones of the central part of the "cheekbone" or Zygomatic Arch that serves as a channel for some of the chewing muscles. The Zygomatics articulate anteriorly with the maxilla, posteriorly with the Temporals, superiorly with the Frontal, and inferio-posteriorly with the Sphenoid.

Maxillary

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The paired bones of the middle of the face, including:
Zygomatic process of the Maxillary: the lateral projections that articulate with the Zygomatics, forming the anterior end of the "cheekbones" or Zygomatic arch.
Palatine Process of the Maxillary: the posterio-inferior projection of the face that forms the anterior 2/3 of the roof of the mouth.
Alveolar process of the Maxillary: the tooth sockets of the "upper jaw."

Palatine Bones

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The palatines are the paired left and right bones of the posterior of the hard palate. They articulate with the maxillae, vomer, and sphenoid.

Mandible

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The mandible (also known as the "jaw bone") is composed of several parts.
Mandibular ramus: The vertical projection of the mandible
Coronoid Process: The attachment of the temporalis muscle used in chewing.
Mandibular Notch: The space between the coronoid process and the mandibular condyle
Condyloid Process: The rounded protrusion of the ascending ramus that articulates with the Temporal bone.

Alveolar process: the superior surface of the Mandible that is the location of the dental alveoli ("tooth sockets").

Orbits

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The "eye sockets" formed at the articulation of the frontal (superior), Lacrimal(medial), Zygomatic (lateral), Maxilla (inferior), Sphenoid (anterior) and Ethmoid (medio-inferior).

Supraorbital ridge

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The protrusion of the anterio-inferior surface of the Frontal, immediately superior of the orbits. (Lower left side of this image.)

Nasals

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The paired bones of the anterio-superior portion of the nose.
http://medstat.med.utah.edu/kw/osteo/osteology/bonenasal.html

Post-Cranial Skeleton

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The skeleton, not including the bones of the cranium and mandible. Details are available at http://medstat.med.utah.edu/kw/osteo/osteology/post.html

Holotype

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The first formally named and described member of a species. The "Taung Baby" skull was the holotype of Australopithecus africanus, for example. The holotype is used as the "standard" against which other proposed members of the species are compared.

Junior synonym

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A name of a species or higher level taxon proposed after the species has already been formally named.

Paratype

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A biological specimen other than the holotype that is used for the development of the original description of a taxonomic group.

Allotype

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A biological specimen that is the opposite sex of a holotype.

International Commission on Zoological Nomenclature

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The International Commission on Zoological Nomenclature (ICZN) is the official body of taxonomists whose responsibility it is to ensure that every animal has a unique and universally accepted scientific name. They publish the International Code of Zoological Nomenclature that lists the rules for naming species, in order to minimize confusion that would ensue if two or more distinct species were assigned the same name, if a single species was assigned multiple names by multiple researchers, or if adults and subadults and/or males and females of a single species were assigned different names. In general, the first name proposed is the one that is used, even when it later turns out that the name is inappropriate or inaccurate. (For example, "Australopithecus" literally means "southern ape," and the name is retained even though it is known that the several species in that genus were not restricted to the southern hemisphere, nor were they "apes" in the colloquial sense.)

Lumpers and Splitters

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The "lumpers and splitters" distinction refers to modern paleoanthropologists' preferences for naming fossils as newly discovered species or as members of already described species. "Lumpers" tend to combine individuals into as few categories (named taxa) as possible, while "splitters" prefer to subdivide categories on the basis of very subtle (some would say "trivial") differences between individual fossil specimens. Both approaches have value. Splitters call attention to important variations between individuals, while lumpers point out similarities, and therefore continuity, between named groups. Keep in mind that the named groups of fossils are constructed for our convenience, and do not necessariy represent biological species. (See Paleospecies Concepts, below.) The dividing line between species in a single evolving lineage is necessarily arbitrary, since the individuals were connected by an unbroken chain of ancestor/descendant relationships.

Paleospecies Concepts

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The Biological Species Concept (BSC) proposed by Ernst Mayr (1940) states that "(s)pecies are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups." Such a concept is inapplicable to extinct organisms, so a variety of other concepts have been suggested to determine the boundaries of extinct species. Many of these alternative species concepts rely on morphology (see "Phenetic species concept," "Typological species concept," and "Morphospecies" at http://science.kennesaw.edu/~rmatson/Biol%203380/3380species.html).
A common "rule of thumb" for determining the range of variation that is acceptable in a single extinct species is to estimate the range of anatomical variation that exists in the closest living related species. Obviously, this practice is less precise than the BSC, but the alternative, avoiding classifying individual fossils into more inclusive groups like species and genera, also presents problems, particularly for organization.
When considering paleospecies, keep in mind that the named group is simply an abstraction, and does not necessarily indicate that all members of one group were reproductively compatable, nor that they were necessarily reproductively isolated from all other contemporaneous groups. It is
hoped that such is the case (i.e. that paleospecies were valid biological species), but it is not possible to demonstrate that belief using available technology.

Sahelanthropus tchadensis

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Sahelanthropus tchadensis dates to between 6 and 7 MYA, which places it right at the point where the human and chimpanzee lineages diverged. It is not clear whether this species belongs on our side or the chimps' side of that cladogenic event. It has some features that are similar to the later Australopithecus species, (such as brow ridges and small canine teeth) but other characters that are very "ape-like" (for example, a very small brain). More information is available at:
http://www.talkorigins.org/faqs/homs/species.html#tchadensis
http://www.sahelanthropus.com/
http://www.fossilmuseum.net/UD%20desktop/UD_destop_postings/Paleobiology/Sahelanthropus_tchadensis.htm
and
http://wiki.cotch.net/index.php/Sahelanthropus_tchadensis

Orrorin tugenensis

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Orrorin tugenensis was found by B. Senut and colleagues in Miocene strata in Kenya in early 2001, and was nicknamed "Millenium Man." The strata are between 6.2-5.65 million years old, making O. tugenensis not only one of the oldest known, but one of the oldest possible hominids (recall our split from the chimps occurred between 5-7 mya).

Further information can be found at:
http://www.modernhumanorigins.com/tugenensis.html
http://www.pbs.org/wgbh/evolution/humans/humankind/a.html
http://cogweb.ucla.edu/ep/Orrorin.html
http://www.talkorigins.org/faqs/homs/species.html#tugenensis
http://bric.postech.ac.kr/science/97now/01_2now/010222c.html
and
http://www.d.umn.edu/cla/faculty/troufs/anth1602/pcorrorin.html

Ardipithecus ramidus

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Ardipithecus ramidus was described by Tim White in 1994, and dates to between 4.389 and 4.388 million years ago. The dentition is very ape-like, although the canines resemble Australopihecus morphology more than any living or extinct non-hominid primate. Pieces of the occipital and temporal bones indicate an anterior position of the foramen magnum, which in turn suggests bipedality. Few individuals have been recovered and described so far. Another individual was found after the initial publication, but has not yet been fully described. Further information can be found at:

http://www.archaeologyinfo.com/ardipithecusramidus.htm
http://www.modernhumanorigins.com/ramidus.html
http://www.geocities.com/palaeoanthropology/Aramidus.html
http://www.talkorigins.org/faqs/homs/species.html#ramidus
and
http://news.nationalgeographic.com/news/2001/07/0712_ethiopianbones.html

Ardipithecus kadabba

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Ardipithecus kadabba was discovered by Yohannes Haille-Selassie in the 1990s. First thought to be a subspecies of Ardipithecus ramidus, many now believe it is a distinct species. Further information can be found at:
http://www.priweb.org/ed/ICTHOL/ICTHOL04papers/42.htm
http://www.rednova.com/news/display/?id=48591 (Beware, non-malicious, but annoying pop-up ads)
http://www.cmnh.org/kadabba/temporarybackgrounder.htm
http://www.berkeley.edu/news/media/releases/2004/03/04_Akadab.shtml
and
http://www.iol.co.za/index.php?set_id=1&click_id=31&art_id=iol1078472150849R362

Australopithecus anamensis

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First discovered in the mid 1960s, but not formally recognized or named until about 30 years later, this species has a mixture of "primitive" and "advanced" characters. Its dental anatomy is very ape-like, but the post-cranial anatomy has clear indications of bipedality. In particular, the inferior Tibia is thick in areas that are exposed to stress during bipedal walking, and the tibial articulation with the Talus is oriented inferiorly, as in a biped, rather than antero-inferiorly, as in quadrupeds. The relative lengths of the Tibia and Humerus displays a very "human-like" ratio, more so than many of the later members of the genus Australopithecus, despite its great age (4.17-3.5 MYA) and some have suggested that this "advanced" feature may indicate that A. afarensis was a side branch, rather than a lineal ancestor of humans.

Additional information can be found at: http://www.modernhumanorigins.com/anamensis.html
http://www.archaeologyinfo.com/australopithecusanamensis.htm
http://www.jqjacobs.net/anthro/paleo/anamensis.html
http://www.msu.edu/~heslipst/contents/ANP440/anamensis.htm
http://www.pbs.org/wgbh/evolution/humans/humankind/c.html
http://africanhistory.about.com/library/glossary/bldef-australopithecus_anamensis.htm
and
http://www.talkorigins.org/faqs/homs/species.html#anamensis

Chronometric dating

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Chronometric dating is the attempt to determine the sequence of a series of events. Several distinct dating techniques exist. Palomar College Department of Anthropology has a list of several techniques. Many dating methods provide "relative dates" in which events are sorted in their chronological order (first, second, third, etc.) but not assigned callendar ages. Others provide absolute dates, in which the ages of events are expressed in years or other standard units of time.