Human Var Exam 1 Flashcards
Approaches to studying Human Variation
Two persistent themes are classification vs adaptation and types vs variation
Classification
Naming and description of discrete groups, types of questions that are asked is the relationship between groups (evolutionary/biological, historical, geographical)
Carleton Coon defined 18 races of humans, sometimes with and sometimes without justification
Adaptation
Looks at correlations between human variation and the environment, types of questions asked are do physical variations correlate with the environment and can adaptive traits be separated from neutral ones. Also looks at patterns of variation and dynamics that are responsible for it (could be evolutionary or from population)
It can sometimes reject classification but it also commonly accepts rigid classifications and uses them as markers for groups/human populations
Types
Connected to the Platonic ideal of essentialism where the world is viewed as a series of types that have a universal validity. Types can be seen as real or ideal and some anthropologists posit that ideal ‘types’ can be created through a process of weeding out variation. Variations can be seen as imperfect degenerations of a given type
Variation
All entities exist within ranges of variation that can be continuous (within a normal or Gaussian curve) or discrete (a binomial or polynomial distribution)
Groups are sometimes categorized and evaluated differently before it is established that separating two groups is valid or justified
Perspectives on race studies
Primarily European, scales of division are continental, national, and ethnic groups within a nation
From the late middle ages to renaissance, there was a monogenesis camp where there was one human creation and subsequent variation due to differentiation. Connected to the essentialist idea of “types” where those who don’t fit that type (indigenous groups, Africans, etc) are “lost tribes” or “lesser”
There was also a polygenesis camp where each “race” was a separate creation. Since the Bible only mentioned one “divine race” this led to hierarchical rankings of races. Polygenesis was later reinterpreted as different races being descended from different past human species or apes
In both of these viewpoints there was a recognition that all humans come from a European ideal and bred racist thinking
Carolus Linnaeus
Included 4 subspecies of Homo sapiens based on skin color, hair color, hair texture, and eye color. Linnaeus was concerned with classification which was determined by a combination of geography, physical appearance, culture economics, psychology (often inferred), reflects prejudice of his time
Georges Louis Leclerc
Attempted to describe and explain the diversity of living humanity by attempting to historically relate people based on resemblances and differences and also relate differences to general environmental characteristics
Johann Freidrich Blumenbach
First large scale attempt to categorize people, emphasized observable physical characteristics but there was still racial prejudice in characterizing personalities
Anthropometry
Study of measurements and proportions of the human body. This attempted to quantify differences between human groups and allow for the identification of “deviant” forms of humans
Led to phrenology which was the study of the shape and size of cranium as an indication of character and mental abilities, criminology, and psychology
Samuel Morton
Amassed a large collection of skulls mostly around the US and focused on how race correlates with cranial capacity and how that correlates with other traits, produced a rank order of brain size and race
There were problems with the rank order, some accused him of faking the data, used small sample sizes, did not account for body size which scales with brain size
Anders Retzius
came up with cephalic index (length/width ratio) and tied it into the racial history of European ethnic groups
Paul Broca
Identified Broca’s area of the brain and used a microscope for pathology. Also made attempts to describe human physical differences systematically and concluded that males have larger brains than females which led to a delay in female education, founder of physical anthropology
19th Century Evolutionary Anthropology
Associated with Lewis Henry Morgan, represented a commonly held view that all societies progress through a series of stages (savagery, barbarism, civilization), some societies make faster progress and others make less progress, existing social variation can be used to document the past, and societies at “higher” levels have a responsibility to help the others “catch up”
Commonly held view that differences between people is the result of different abilities and that the human population can be improved through directed or controlled breeding
Eventually there was a desire to document every aspect of variation (anatomy, blood groups), but little was known as to how to analyze variation so many statistics were rejected/ignored and a typological framework was used
Francis Galton
Developed eugenicist thinking and founded a laboratory to document the heredity of behavioral traits and physiques
Cesare Lombroso
Criminologist who posited criminality was associated with “primitive” groups of people with “ape-like” features
Alphonse Bertillon
Police officer who used anthropometrics for personal identification and rejected the idea that certain populations have a predisposition to crime
Franz Boas
Developed the distinction between Race-Language-Culture where a clear separation between biology and culture was identified. Emphasized the plasticity of the human biological form (due to factors such as health and nutrition) and rejected the idea of progress. Instead posited that “progress” is accompanied by trade-offs or regressions in other areas
Dr. William Montague Cobb
First Black American to earn a Ph.D. in physical and biological anthropology. Used skull craniometry to demonstrate that there were no anatomical differences between Black and Caucasian athletes, common belief that Black people were physically superior
What were some of the effects of racial eugenics?
It was universal in Western Europe and North America and it directly affected immigration laws, marriage laws, segregation, forced sterilizations, etc. Nazi’s actively referred to American laws/writings to justify actions
What were some differences between how race was studied before and after WWII?
DNA was identified to be genetic material so genetics was merged with Darwin’s theory of natural selection/evolution. Race and geographical classification was therefore no longer deemed as an appropriate subject of study
Carleton Coon
proposed human races reach a Homo sapiens stage at different times which explains differences
Richard Lewontin
founded population genetics and posited ~85% of total human genetic variation is found within any given population and only 15% reflects allele frequency differences between populations
Nuclear vs Mitochondrial genome
Mitochondrial genome has 37 genes that encode 13 proteins and 24 that encode RNA’s, made up of 0.0005% of the nuclear genome
One mitochondrion contains multiple copies of mitochondrial genome and numerous mitochondria, so cells can contain several thousand copies of a mitochondrial genome but only 1 copy of a nuclear genome
Nuclear DNA is inherited such that each parents provides 1 chromosome, mitochondrial DNA inherited from egg donor
Organizational features and functions of DNA
Proteins encoded by genes may be structural, enzymatic, regulatory, or contain several of these functions. These products from multiple genes can combine to form a protein molecule
Genes contain an exon/intron structure along with intergenic regions
Haplotype
everything inherited together on the same chromosome (either the entire chromosome or a portion of the chromosome)
Aneuploidy
Abnormal number of chromosomes, almost always occurs in egg rather than sperm, commonly due to nondisjunction
Balanced translocation
even exchange of material between two chromosomes with no genetic information extra or missing, this generally means full functionality occurs but sometimes the coding sequence is disrupted, regulatory regions are separated from the transcription unit, or genes are fused together. This involves different chromosomes meaning no recombination between homologous chromosomes occurs
Unbalanced translocation
occurs when the exchange of chromosomal material is unequal which results in extra or missing genes, this often results in a miscarriage but can be variable
What are some functions of intergenic regions and introns (“junk” DNA)?
“Junk” DNA can allow new variability to emerge. VNTR (Variable number tandem repeats) which are highly variable and classified based on size and number of repeats or level of variability (Microsatellites are short tandem repeats 1-6, minisatellites are 8-100 nucleotides, satellites are 1000-10,000 nucleotides)
Also may contain transposable element insertions such as SINE (short interspersed nuclear elements) and LINE
May contain promoter or enhancer regions
These regions may also encode for non-coding RNA molecules which can affect the gene regulatory process
~10-15% of the noncoding human genome can be regulatory elements such as promoters or enhancers
Promoter
usually 100-1,000 bp upstream from transcription start site and other proteins bind to turn transcription “on” or “off”
Enhancer
can be further away and can upregulate or downregulate transcription, sometimes proteins that bind to an enhancer region can bind to proteins that bind to the promoter region since DNA wraps and has tertiary structure. Tertiary structure means distant elements can come into closer proximity with the gene that is being regulated
How are non-coding RNA molecules significant to gene regulation?
microRNAs or siRNAs can block mRNA translation and bind closer to the start of mRNA in order to respond to environmental cues more readily, small RNAs can modify target RNAs and allow for the synthesis of telomeric DNA, alter chromosome structure medium and large RNAs can cause X chromosome inactivation, promote gene transcription, promote synthesis of microRNAs or small RNAs
What kinds of mutations can cause a significant alteration of phenotype?
Frameshift mutations and mutations on exon regions tend to have a larger phenotypic effect. Mutations earlier in the gene sequence also tend to have a larger phenotypic effect especially with frameshift mutations, so location matters
Where a mutation occurs on a protein also matters, whether it occurs in a critical region such as the active/functional site of an enzyme or a less critical region
What kind of amino acid change that occurs is also significant. A non-conservative change where the property/charge of the amino acid changes also tends to cause more phenotypic effects
Mutations in promoter or enhancer regions that regulate gene activity can cause an upregulation or downregulation of gene expression
Mutations can affect gene copy number where duplication leads to too much of a protein and deletion leads to too little of a protein, leads to potentially adaptive variation. Gene copy number can be linked to diet/environmental factors (higher starch diet associated with higher amylase production)
Ankylosing spondylitis
chronic inflammatory arthritis that affects the spine, differs by a single amino acid change in a critical region of the molecule. Amino acid change is also non-conservative where there is a mutation from aspartic acid (- charge) to histidine (+ charge), so binding profile of molecule changes
Lactase persistence
Lactase allows for digestion of lactose, lactase is highly expressed during lactating phase of development but generally drop after weaning, but some humans retain high levels of lactase expression into adulthood
Promoter variant can be “turned off” due to a mutation
Alternative splicing
a process of rearranging exons to alter proteins and create splice variants, occurs under “normal” conditions. Mutations nearby the splice site can affect the binding of splicing factors along with proper splicing
Alternative splicing of sp140 associated with arthritis since mutation prevents one exon from being part of protein