Studied by 3 people
Subfields (American Anthropology)
Biological: the study of the evolution of humans and related species as biological organisms; including the study of the relationships between biology and culture
Archaeology: the study of past cultures through examination of their material remains (artifacts); significantly concerned with the nature and reasons for cultural evolution — overlaps with bio anth and geology but is predominantly a social science
Linguistic: the study of language in a social context; evolution of language and contemporary usage
Cultural: the study of current/recent cultural phenomena; studies the evolution of culture
Biology & Culture: Definitions
Biology: refers to the chemical and mechanical processes associated with life.
Subfields include anatomy & physiology, genetics, ecology, paleontology, etc. — many of which are directly associated with anthropology
Culture: refers to learned, socially acquired traditions and behavior; symbolic behaviors,
Anthropologists see culture as being extra-somatic and a choice
Scientific Studies
Attributes:
Openly defined
Transparent
Repeatable
Based on concrete units of measure
Elements:
Theory — The broad principles by which an explanation is achieved
Hypothesis — A proposed explanation for the existence of a specific set of things and/or events
Method — The way in which a hypothesis/theory is tested
Conclusions — An interpretation as to whether the data support the hypothesis/theory
Philosophy & The Scientific Method
Philosophy: Science is a way of viewing existence where conclusions must follow logically from relevant and appropriately obtained data
Method: A logical system of results in the intellectual ordering of phenomena
Karl Popper
Pointed out that science cannot prove anything — it can only disprove
ALL scientific knowledge is provisional
New data always has the potential to alter a conclusion
A Priori Conclusions
Conceived before a study is conducted
Science is data driven and therefore rejects a priori conclusions
Most (and arguably all) previous/other comprehensive explanatory systems have been/are based on a priori conclusions
Science is therefore unique in human history
Aristotle
Was among the first t posit serious explanations regarding the relationships between living creatures
Proposed the Great Chain of Being: a ranking of organisms according to their supposed complexity, intelligence, and importance
Influenced future biological thought whether directly or indirectly
Other Influential Thinkers
Linnaeus: Developed the hierarchal classification system known as taxonomy which classified species based on their physical characteristics — influenced by the "Great Chain" and Christian thought and viewed species as being immutable
Comte de Buffon: Enlightenment thinker that was one of the first serious researchers to propose that species evolved but offered no workable theory as to how this might occur. Also believed that there was a dynamic relationship between organisms and their environments. As well as that Biblical creation was the start of life but that forms evolved after this time — did not believe that species could change into another but that forms degrade. Seemingly non-functional aspects for evolutionary change. Earth was older than Biblical estimates (160k years)
Erasmus Darwin: Grandfather of Charles Darwin. Proposed one of the first structured theories of biological evolution in Zoonomia. Believed that all life had arisen from an original filament and in evolution but offered no specific mechanisms explaining how evolution change comes about.
Georges Cuvier: Opposed the idea of evolutionary change. Proposed the theory of Catastrophism which viewed earlier animal species as being wiped out by a series of natural disasters — these animals were then replaced by stronger, more intelligent, invading species
Jamed Hutton: Geologist that proposed that the "operations of nature are equitable and steady" in Theory of Earth. Refuted catastrophism.
Jean-Baptiste Lamarck: Proposed the Theory of Inheritence of Acquired Characteristics/Lamarckianism. Stated that evolution occurs during the lifetime of a natural organism and did not believe that species went extinct. Was ultimately wrong but arguably the first biologist to understand the profound role of environments in evolutionary processes. Also arguably developed the first coherent theory of biological evolution. Coined the term "biology"
Charles Lyell: Geologist that developed and promoted the principle of uniformitarianism in Principles of Geology. Stated that the same geological processes have occurred throughout all time. Proposed the earth to be much older than dates obtained form Biblical sources (hundreds of million year at least). His ideas set the stage for the emergence of modern evolutionary thought in that the provide an enormously long, time frame in which evolution can occur
Charles Darwin: Sailed the Galapagos Islands on the Beagle. This voyage provided the raw material for Darwin's evolutionary ideas. Developed the concept of Adaptive Radiation which refers to how all Galapagos finch and tortoise species (among others) descended form one single mainland species. They diverged into multiple lineages to meet new local environments. In essence, Darwin believed that species evolved and that given enough time, they could change radically. Natural conditions could produce all the world's organisms. All organisms can trace their ancestry to a single ancestor. Understood that organisms within a species were all slightly different.
Thomas Malthus: Economist that pointed out that organisms can reproduce exponentially, in numbers that are ecologically unsustainable — therefore, not all organisms born can live to reproduce
Alfred Russell Wallace: Independently developed the idea of natural selection.
Binomial Nomenclature
When organisms are referred to simply by their genus and species name (such as Homo sapiens)
Essentialist Thoughs & Populational Thinking
Essentialist Thought: A concept proposed by Plato. Essentialists believe that each organism has a fundamental, unchanging "essence" at its core. Variation within a population is seen as deviations from the perfect essence
Populational Thinking: Rejects essentialist thought. There is no unchanging essence among species. Species are defined primarily by reproductive isolation
Genotype & Phenotype
Genotype: The genetic make-up of an individual organism
Phenotype: An observable or measurable feature of an organism — often used to describe an organism in its entirety, beyond its DNA
Darwin's Dilemmas
Understood the importance of variation between individuals but did not know how this variation was created. Also did not understand the mechanics as to how traits passed from one generation to the next. However, did know that offspring CANNOT simply be a blending of all their parent's traits.
During his lifetime, some of these issues were resolved by Gregor Mendel, a researcher whose work Darwin was apparently not familiar with
Gregor Mendel
Worked out the basic laws of heredity by observing the passing on of traits across generations of plants and animals
Obtained his most useful data through experiments with pea plants
"Mendels Postulates:"
Hereditary characteristics (traits) are controlled by particulate unit factors that exist in pairs in universal organisms — offspring get one of these factors from each parent
When an individual has two different unit factors only one is expressed and is said to be dominant
During the formation of gametes (sex cells), the paired unit factors segregate randomly meaning that each sex cells receives one or the other with equal likelihood
During gamete formation, segregating pairs of units assort independently of each other. This is now known as Mendel's Law of Segregation
Worked the basics of what is known today as genetics solely through observation of phenotypes through generations
Punnett Squares: Demonstrate recessive and dominant genes a.k.a. Incomplete and Co-Dominance — Bb bb Bb bb / PP Pp Pp pp
Mendel's Limitations:
With pea plants, Mendel chose plants where the traits he was following were controlled by only one gene a.k.a. simple inheritance
Most traits in complex organisms re controlled by multiple genes making the study of genotype-to-phenotype expression much more complicated than he envisioned -Genes do not always segregate independently
In some cases, both traits (alleles) can be expressed — Co-Dominances
Incomplete Dominance is also possible — the dominant gene does not fully mask the recessive gene's traits, creating an intermediate trait
Mendel's work does not explain how new genetic variation is created
Polygenic Traits & Pleiotropy
Polygenic Traits — Phenotypic traits that are governed by more than one gene
Pleiotropy — One gene effecting multiple phenotypic traits
Mutations & Events
Mutation is an "error" (a chemical substitution) that occurs in the replication of Genetic material (DNA)
Typically neutral to an organism, either because they are not expressed in the phenotype or because the expressed trait neither helps nor hinders the organism's survival though some are detrimental.
Create new genetic variation
Events: Random Mutations — Occur through chemical substitution as DNA recreates itself. These have no patterns to them and seem to be a bi-product of the DNA replication process and do not seem to be influenced by outside factors
Induced Mutations — Occur due to the influence of toxins, other chemicals, and radiation. These can cause developmental issues in the phenotype (can occur in gametes and can cause diseases such as cancer when occurring in somatic cells)
Evolutionary Synthesis
Mendel's research was published in an obscure journal and had little impact in his lifetime but was later rediscovered and has been combined with the ideas of Charles Darwin.
This evolutionary synthesis forms the baseline of modern biology
Watson & Crick
Genetics stalled for decades after Mendel's era but major breakthroughs came from geneticist James Watson and biophysicist Francis Crick whom discovered the basic structure of DNA. This worked is viewed as the beginning of modern genetics
Cells & Complex Organisms
Definition: A microscopic entity in which genetic material and other structures are separated from the environment by a semi-permeable membrane.
Can exist as a single organism or with other cells as part of a complex organism
Types of Cells:
Prokaryotes — Single-celled organisms without a nucleus (bacteria) — first appeared on earth roughly about 3.5 billion yrs. ago
Eukaryotes — Cells where genetic material is separated from the rest of the cell by a structure known as a nucleus — First appeared on earth roughly 1.2 billion yrs. ago
All multi-cell life forms are eukaryote based.
Complex organisms are multicellular and sexually reproducing and feature two basic types of cells:
Gametes — Cells that are directly involved in reproduction
Somatic Cells — Cells that are not Gametes (all other cells that make up an organism) — Derived from soma which si Greek for body
Mitochondria
Capsule-shaped organelles where metabolic reactions take place resulting in the production of energy-rich molecule (ATP — adenosine triphosphate) that fuels the cell
Have their own DNA that is not contained in the nucleus and its different from the DNA found in the cell's nucleus
Were potentially separate prokaryotic cells at some time in their evolutionary history
Human mitochondria each feature 37 genes
Hundreds to thousands can be found in a cells (depending on the type of cell)
Endoplasmic Reticulum (ER) & Ribosomes
A complex organelle in the cytoplasm that has a "folded sheet" appearance
Provides increased surface area for various metabolic reactions to take place
Rough Endoplasmic Reticulum — An area of the Er with "knobs" called ribosomes
Ribosomes:
RNA forms a large percentage of the ribosomes
They serve as sites where protein synthesis takes place
The information to create proteins (ribosomes) exist in a cell's nuclear DNA
The synthesis begins in the nucleus but must be completed in the cytoplasm
Completed ribosomes cannot pass thru the nuclear membrane
DNA — Deoxyribonucleic Acid
A complex protein that codes for the development of the phenotype — aspects of an organism beyond its DNA
Contains the information in your body needs to create amino acids (which are combined to make proteins — does this in conjunction with RNA)
Can replicate itself
DNA Structure:
The DNA molecule is a double helix
Three major units of DNA (and RNA) are:
(Nitrogenous) Nucleotide bases (made up of carbon and nitrogen atoms)
Sugars (deoxyribose in DNA and ribose in RNA
Phosphates
Nucleotide Units and Bases:
The DNA molecule has four different nucleotide units featuring different bases — humans have around 3 billion nucleotides
There are two classes of bases:
Purines: Adenine (A) and Guanine (G)
Pyrimidines: Cytosine (C) and Thymine (T)
A purine always bonds with pyrimidine and vice-versa
Adenine always bonds with Thymine (AT)
Cytosine always bonds with Guanine (CG)
They are held together by weak hydrogen bonds which can be easily broken
DNA is unusual in that it is stable in all potential forms which is not the case with many other molecules
NO possible base sequence is unstable
This also makes it an excellent vehicle for transferring genetic information between generations
DNA Replication:
Mitosis — Somatic cell division in which a single cell divides to produce two daughter cells
Meiosis — Cell division that only occurs in the testes and ovaries that leads to the formation fo sperm and ova, which combine to create gametes
DNA replication can only affect heredity if it occurs in the gametes
Genetic Code
The information to make proteins (amino acids) is contained in the sequence bases of the DNA molecules
The part of DNA molecule that contains for one polypeptide chain (a protein) is called a gene
One gene can feature hundreds of thousands of bases and humans have between 20,000-25,000 genes (there can be more in some cases)
Codons
Nucleotide bases code for proteins in groups of three. These three-base sequences form a single amino acid.
There are 64 possible codons and only 20 amino acids
Most amino acids are represented by more than one codon
Termination codons do not code for an amino acid but instead signal that a protein chain has come to an end where as Initiation codons signal the beginning of a polypeptide chain (also represents the amino acid methionine)
Transcription & Translation
The information is "transcribed" from the DNA to the RNA
The mRNA then separates (upon which the DNA molecule closes) and carries the information from the nucleus to the cytoplasm, where protein synthesis (translation) eventually occurs.
Protein synthesis occurs at the ribosomes (on the Rough ER, in the cytoplasm)
Note: A single mRNA molecule can be read by several ribosomes at the same time which means several copies of a protein can be made from one transcription/translation
Exons & Introns
When the mRNA returns to the cytoplasm it is subject to Post-Transcriptional Processing through bonding with transfer RNA (tRNA)
Sequences of the mRNA are spliced out and the molecule is reassembled
Introns are NOT expressed in a protein whereas Exons are
Coding and Non-Coding DNA
In humans, only 3% is coded for protein synthesis
Most human DNA is non-coding DNA
Roughly 80% of non-coding DNA serves in gene regulation
Gene Types
Structural Genes — Determine physical characteristics (of the phenotype)
Regulatory Genes — Regulate the effects of other genes
Chromosomes
Most of the time, DNA exists in uncoiled strands, a state called chromatins
During mitosis or meiosis, the DNA tightly coils itself into structures called chromosomes.
(Each somatic cell in a person's body has the same number of chromosomes)
Most organisms have two copies of each chromosomes in each cells (one from each parent)
The total number of chromosomes in a cell is called the diploid number
Gametes have only half the number of chromosomes, which is known as the haploid number
In a diploid cell, the members of each pair of chromosomes are known as homologous chromosomes
Genes are distributed across the chromosomes — A gene is also known as locus (plural loci)
Somatic cells also have two copies of each gene which are called alleles.
When a person has the same allele (trait) at each locus on each chromosomes they are called homozygous for that gene
If there are different alleles at each locus of each chromosomes a person is called heterozygous for that gene
Humans have 23 chromosomes (haploid — 45 diploid)
In mammals, sex chromosomes are labeled as X (female) and Y (male)
Females = XX
Males = YX
Mitosis & Meiosis
Mitosis is the basis of cell creation
it occurs during the growth of an organism, during healing, or other times when cells need to be creates
Meiosis occurs in the tests and ovaries
leads to the formation of gametes, which have a haploid number of chromosomes
When sperm and egg unite to create a zygote (fertilized egg), the diploid number of chromosomes is established
Crossing Over:
double-stranded homologous chromosomes team up, forming units made up of four chromatids (threadlike strands)
The strands then send genetic material across to the other strand, creating new DNA combinations
(does NOT create new genetic material — any mutation would have had to occur prior to this point)
Epigenetics
Refers to the environmental factors creating an inheritable trait with no change in DNA structure
Occurs through methylation — the attachment of a methyl group to an area of the DNA molecule
(Methyl is a simple chemical that had many functions in the human body, including the regulation of gene expression)
This can cause changes in the way genes are expressed or cease their expression in the phenotype
Factors causing these processes are chemical exposure, radiation, nutrition, and even stress
This field of study is in its infancy and many of the specific cues and outcomes of methylation are not yet well understood
Race & Subspecies
Race: Refers to the division of humans into groups based on biological characteristics; the human equivalent of the subspecies concept developed by biologists mainly to classify non-human life
Subspecies: Refers to local populations that share part of the geographic range of a species and can be differentiated from other subspecies by one or more phenotypic traits
The "Naked Ape"
Humans have become largely hairless (compared to other primates) in part response to heat dissipation needs — shoutout to sweat lol (it's efficient)
Melanin
The relative lightness or darkness of the skin is largely determined by the amount of melanin, (polymer pigments derived from amino acids)
Melanin protects the skin from the sun in proportion to its abundance so the more melanin one's skin contains, the darker one's skin
However, melanin also reduces the photochemical reactions that lead to the creation of vitamin D
Environments & Skin Color
The more humans are exposed to the sun the greater the opportunity their bodies have to synthesize vitamin D
Humans with higher degrees of sun exposure can afford to have relatively dark skin because there is so much potential for vitamin D synthesis
They also need dark skin to be protected from the sun's damaging effects
Selective advantages in these environments would go to those with relatively dark skin
In colder, darker environments, there is less potential for vitamin D synthesis because there is less sunlight. Therefore the skin needs to do more work and melanin hinders this process. This environment also created a lesser need for melanin because the skin is less subject to damage because of the relative weakness of the sun.
Selective advantage in these environments would go to individuals with relatively fair skin
Diet also plays a part in skin color.
Human groups with regular access to vitamin D-rich food sources often have dark skin than would be predicted by their latitude
Coastal people often fall into this category because of seafood resources are generally rich in vitamin D
Sun Exposure
Lack of body hair exposes skin to damage by the sun, through ultraviolet radiation (folate breakdown)
The loss of vitamin B folates can create problems in humans in many areas, such as reproduction
Genetic Drift — Continued
Early in human history, populations in many parts of the globe were very small in numbers and for long periods of time (relatively) isolated from other human groups. This means that genetic drift has likely played a significant role in the way humans appear today
Founder(s) Affect:
Founder populations would not have carried the full genetic compliment of the groups off of which they had split and because of this, certain traits would have been over or under-represented
Traits with (little or) no selective value would have proliferated, creating relatively minor differences in appearance between the descendants of the founder population and their descendants of the original population
Cultural Attributes
Can affect biological evolutions
For example, the wearing of clothes (and spending a lot of time indoors) means less skin is exposed to the sun
In cold climates, humans tend to wear more clothing and spend more time indoors, leaving less of their skin exposed to the sun
This means exposed skin must be able to take in even more vitamin D, prompting the selection for even fairer skin (e.g. Fennoscandia)
Bergmann's Rule
Large (more stout and round) body sizes should evolve in colder climates to conserve body heat
Limbs will be shorter
Relatively short bodies are favored
Bodies also evolve to store more subcutaneous fat in these climates
Allen's Rule
In warmer climates the limbs are longer relative to body size (this helps dissipate heat)
Peoples in these climates are often very tall and thin with very long arms and legs
Feature relatively little subcutaneous fat
Ethnicity
This term has been developed in recent decades and is largely replacing "race" (at least in the sciences and humanities)
Refers mostly to culture, while acknowledging biological differences between groups
Hypoxia
Hypoxia: Oxygen content in the atmosphere lessoning with altitude
Populations living for long periods in high altitudes have evolved in ways in which their body can circulate blood and oxygen through their systems more efficiently than other humans
People from the Himalayas and to a lesser extent, those from the high Andes have evolved such traits
Those without such traits living in such environments for sustained periods can develop hypoxia, a condition where the body cannot take in enough oxygen to function properly.
Short term symptoms include: headaches, dizziness, and nausea.
Long-term hypoxia can lead to severe damage to the heart, lungs, and brain
Sickle-Cell
A trait that occurs through the expression of a recessive gene, leading to sickle-cell anemia
Changes the shape of red blood cells in a manner that makes it difficult to impossible for them to circulate through the body
It can lead to severe health problems and even daht
It is very common in Africa (where at least the modern strains of malaria seem to have developed) and much less so in parts of Asia
Sickle-Cell Traits & Malaria The recessive gene that leads to sickle-cell anemia is maintained in human populations because it is favored as a (balanced) polymorphism
Individuals who inherit this trait from only one parent are resistant to malaria and these individuals have slightly smaller red blood cells, which are less optimal hosts for the mosquito-spread parasite that causes the diseases
Today, malaria is most common in tropical and subtropical zones however, the sickle-cell trait is generally common in sub-Saharan Africa and in populations who trace their (relatively recent) ancestry to this part of the world
African-American communities have a higher percentage of sickle cell anemia than most sub-Saharan African groups. This is because of their smaller populations, which means this recessive trait is more likely to be expressed.
Has been greatly amplified due to racism and white ethnocentrism
Has kept their gene pools from blending these continent's populations to the same degree as other groups
Lactose Intolerance
Milk products contain a sugar called lactose and in order to digest this, mammals need a protein called lactase. Most mammal's bodies produce this protein when they are young so they can digest their mother's milk and as they are weaned, their bodies cease production to lactase.
Humans follow this pattern, generally. However, groups that evolved in pastoralist or sedentary agricultural societies that emphasized milk-producing animals have evolved to produce lactase into adulthood.
Most adult humans today are lactose intolerant to some degree
TEXTBOOK — Terms
Heteroplasmic — Refers to a mixture of more than one type of organellar DNA, such as mitochondrial DNA, within a cell or a single organism’s body, usually due to the mutation of the DNA in some organelles but not in others.
Karyotype — The characteristics of the chromosomes for an individual organism or a species, such as a number, size, and type. The karyotype is typically presented as a photograph of a person’s chromosomes that have been arranged in homologous pairs and put in numerical order by size.
Patriline — DNA whose inheritance can be traced from father to son via the Y chromosome
Matriline — DNA, such as mitochondrial DNA, whose inheritance can be traced from mother to daughter or to son
Haplotypes — A group of alleles that tend to be inherited as a unit due to their closely spaced loci on a single chromosome
Haplogroups — A large set of haplotypes, such as the Y chromosome or mitochondrial DNA. that may be used to define a population
Translocation — Rearrangements of chromosomes due to the insertion of genetic material from one chromosome to another
Nondisjunctions — Refers to the failure of the chromosomes to properly segregate during meiosis, creating some gametes with abnormal numbers of chromosomes
Monosomy — Refers to the condition in which only one of a specific pair of chromosomes is present in a cell's nucleus
Trisomy — Refers to the condition in which an additional chromosome exists within the homologous pair
Microevolution — Small-scale evolution, such as changes in allele frequency, that occurs from one generation to the next
Macroevolution — Large-scale evolution, such as a speciation event, that occurs after hundreds or thousands of generations
Spontaneous Mutations — Random changes in DNA that occur during cell division
Induced Mutations — Refers to those mutations in the DNA resulting from exposure to toxic chemicals or to radiation
Mutagens — Substances, such as toxins, chemicals, or radiation, that may induce genetic mutations
Antigens — Specific proteins, on the surface of cells, that stimulate the immune system's antibody production
Antibodies — Molecules that form as part of the primary immune response to the presence of foreign substances, they attach to the foreign antigens
Cline — A gradual change in some phenotypic characteristic from one population to the next
Balanced Polymorphism — A situation in which selection maintains two or more phenotypes for a specific gene in a population
Functional Adaptions — Biological changes that occur during an individual's lifetime, increasing the individual's fitness in the given environment
TEXTBOOK — People
Robert Hooke — Scientist that studied the microscopic structure of fossil wood. After observing that the tissue structure of the fossil wood was identical to the same tissue structure of living trees, Hooke concluded that the fossil wood derived from once-living trees; pioneered microscopy.
Proved that fossils are organisms' remains and revealed that fossils would provide the history of past life
Thomas Henry Huxley — A biologist that was known as "Darwin's Bulldog" for forcefully promoting Darwin's theory of evolution by natural selection. Among Huxley's contributions was the concept that humans evolved from apelike animals.
Hardy—Weinberg — Godfrey Hardy, a mathemetician, and Wilhelm Weinberg, an obstetrician independently recognized that some alleles are in a state of equilibrium. Simply, a single locus has A (dominant) and a (recessive) alleles, with respective frequencies of p and q. In assessing the population as a whole, it is assumed that males and females have both alleles.
The Hardy-Weinburg law predicts the genotype of frequencies for the next generation after one mating where p2 is the genotype frequency for the AA homozygous alleles, 2pq is the genotype frequency for the Aa (heterozygous) alleles, and q2 is the genotype frequency for the aa homozygous alleles.
(The total population (100%) should be the sum of the frequencies of three genotypes expressed by the simple mathematical equations p2 + 1pq + q2 = 1. If a hypothetical population where 60% A (p = .6) and 40% a (q =A), then the genotype frequencies in the next generation would work out to AA = .36, Aa = .48, and aa = .16.
In essence, the Hardy-Weinberg equilibrium hypothesizes that gene frequencies remain the same because no evolutionary change takes place. The Hardy–Weinberg equation establishes expectations as to whether evolution is operating on a particular gene. If the genotype frequencies change from one generation to the next, the population is not in equilibrium—it is evolving. If frequencies remain the same, the population is in equilibrium and is not evolving, at least with respect to the locus being studied.
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