Lecture 2: Heredity, Evolution and Human Diversity

Myths of Origin

  • All human cultures seem to have a theory of belief surrounding the origins of humans
  • Holism and culture as the foundation and paradigm of all the sub-fields of anthropology
  • Idea of the origin myth – “Where do we come from? How did we originate?”
  • Universally addressed through the origin myth
  • Almost all of them have the idea that humans are the ultimate product of human creation

Fixity of Species

Species, once created can never change

  • Darwin stepped out of the boundaries of science to come up with his species
  • Reflected powerful religious system in Europe
  • We are in the same state today as we were on the day of our creation
  • Fixity – no change
  • Conflict by religion and science
  • All the scientists in the 1800's believed in the fixity of species, but Darwin did not

Great Chain of Being

Aristotle – Came up with the idea of the great chain of being

  • First philosopher to put humans on the same platform as all others
  • Important because he put us on a continuum with the animals
  • Humans at the top of the hierarchy

Genus and Species

John Ray – Responsible for coining the term “species”

  • Determined that there were difference and similarities of organisms
  • Certain organisms had successful reproduction – species
  • First one to categorize organisms thru characteristics
  • Similar species – Genus
  • Cannot reproduce within themselves

Systema Natura

Linneaus – Binomial nomenclature

  • Classified living and non living org into a hierarchy of taxonomic categories
  • Important because taxonomy categories are still used today
  • Differ from Darwin’s idea because they still believe in fixity
  • Added class and order to Ray’s species and genus (Kingdom, Phylum, Class, Family, Order, Genus, Species)


Charles Lyell – 1833

  • Processes shaping the earth are the same today as they always were – uniform and continuous in nature
  • Set the time scale of the earth back millions of years ago
  • Creationist
  • Geological processes that happen on the earth are the same since the earth was created
  • Important because it suggested the processes that shape the earth are the same since the earth was created and because he set the age of the earth back by millions of years
  • Age of the earth thought to be thousands of years old before Lyell
  • Still believed in the fixity of species

Survival of the Fittest

Thomas Malthus – 1798

  • Essay on the principles of population
  • Speculated that -
  • Human populations multiply geometrically
  • Food resources grow arithmetically
  • Therefore -
  • Human populations will outgrow resources unless there is a constant check to maintain a certain population size
  • Not everyone born can possible survive
  • If a population is left unchecked, it will outgrow its food resources which will lead to its demise
  • Suggested that there must be something that maintains the population size according to its resources because not a lot of evidence of population loss
  • Idea heavily borrowed by Darwin
  • Important because he came up with the idea of differential survival
  • Reproduction of organisms will rise at a greater rate than food if left unchecked


Lamarck - 1809 - Biologist during Darwin’s time

  • Similarities and differences between Darwin and Lamarck
  • The first to move away from the idea of the fixity of species
  • Most influential pre-Darwin evolutionist

Non-Darwinian features - Difference from Darwin

  1. Inheritance of acquired characteristics – Any characteristics that you acquire may be passed on to your kids (Example - Of jacked kids and melanin production)
  2. Orthogenesis – Humans are the ultimate product of complexity
  3. Vitalism – Inheritance is self – motivated
  • Darwin believes that evolution is random.
  • Believed that organisms can change from one generation to the next – similar to Darwin
  • Difference from others – Didn’t adhere to the fixity of species

The Giraffe Example – Got their long necks thru self motivation; stretched their necks to reach better leaves and the offspring inherited that which led to long necks

Charles Darwin

  • 1809 – 1882
  • Alfred Wallace 1823 – 1913
  • Selection is key to evolution
  • Struggle for existence means that those individuals with favorable variations survive and reproduce more successfully

HMS Beagle as their naturalist – with malthus.

Three Observations

  1. Finches beaks
  2. Biological variation within all species - All species capable of reproducing at a faster rate than food supply – role of the environment
  3. Competition for limited resources

Five Deductions

  1. Individuals with favorable traits have an advantage – White moths were more successful than the black on birch trees so the white ones out-reproduced the white ones but then the birch trees turned black due to pollution during the Industrial Revolution, so the population started becoming more black because the white ones were being eaten by birds
  2. Traits are inherited and passed on to the next generation
  3. Environment determines which traits are favorable
  4. Over geological time, successful variations accumulate so that later generations may be distinct from their ancestors
  5. Geographical isolation may lead to a new species

Important Notes

  • Traits are found in humans, but it is the population that evolves
  • Macro – How we form new species or how they disappear
  • Micro – Looking at natural selection

Andrew Wallace

Came up with almost identical ideas of natural selection independently

  • Darwin and Wallace presented a paper together
  • All their ideas came out of observation
  • Did not have concrete evidence as to how traits passed on from parent to child

Gregor Mendel

  • 1822 – 1884
  • Produced evidence for natural selection
  • Father modern genetics
  • Provided mechanisms of natural selection through breeding experiments with peas
  • Determined how one trait passed from one generation to the next
  • Experiments were discovered after his death
  • Coming together of Mendel and Darwin’s works
  • Mendel provided evidence of theories suggested by Darwin

Mendel’s principles

Principle of Segregation

  • Each unit pair separates in gamete production, so that each gamete contains 1 member of each pair. During fertilization individual units come together.
  • Traits were inherited independently

Principle of Independent Assortment

  • Units (Genes) that code for different traits assort independently of each other during gamete formation and recombine in offspring.
  • Traits must be randomly assorted
  • Produced tall and short plants – not medium ones

Mendelian inheritance

Homozygous - Same variants of a trait (alleles) come together

Heterozygous - Different variants of a trait come together

Recessive - Trait not expressed in heterozygous state

Dominant - Trait expressed in the heterozygous state

Genotype - Genetic makeup of an individual – What you cannot see

Phenotype - Observable physical characteristics of an organism

  • Trait is the gene, the expression is allele
  • Gene – Height
  • Allele – You're tall

Mendelian vs Polygenic Inheritance

Mendelian examined traits that are only controlled by a single gene


  • Discrete or discontinuous
  • Discrete categories
  • Influenced by 1 gene
  • Distinct phenotype

Example - ABO blood type


  • Continuous
  • No discrete categories
  • Influences by 2 or more genes

Example - Skin colour

  • Account for most readily observable human traits

Modern Synthetic Theory

Population genetics

Diversity seen as the result of microevolutionary forces – Small changes in allele frequencies acting on the human gene pool

Vs Macroevolution

Looks at the way species can be changed

  • Appearance of new species due to many generational changes in allele frequencies

Micro-Evolutionary Forces acting on a Population


Copying mistakes during cell division leading to new alleles through gene alteration

  • Chance event

Genetic Drift

Chance fluctuations of the allele frequency in the gene pool of a population

  • Significant in small populations

Example - Earthquake

  • In a small population
  • Gene Pool – All available traits in a population

Gene Flow

Introduction of new genes from another population

  • Immigration and emigration


Process by which organisms achieve a beneficial adjustment to an available environment

  • Natural selection makes evolutionary change adaptive

Directional - Natural selection promotes change

Stabilizing - Natural selection promotes stability



A single ancestral species gives rise to 2 or more descendant species

  • Physical & social barriers
  • When you create new species
  • One ancestral species creates 2 descendants so differing that they cannot successfully reproduce together


Two phylogenetically unrelated organisms develop greater similarities

  • Similar environments

Basic Environmental Variables

Thermal environment

  • Sweating
  • Vasodilation vs Vasoconstriction
  • Body proportions
  • Larger surface area dissipates the most heat
  • Larger body mass retains heat

Bergmann’s Rule – Individual who live closer to the arctic

Population living in cold environment has a lesser surface area to conserve heat.

Allen’s Rule – Deals with individuals who live in high thermal environment (Close to the equator).

Population living in hot environment have larger surface area to dissipate the heat.


  • High altitude - Reduced barometric pressure because concentration of oxygen has dropped.
  • Hypoxia
  • Transport & utilize oxygen more efficiently
  • Increased RBC production (In moderate altitude)

Ultraviolet Light

  • Increased melanin production with greater sunlight exposure
  • Rickets – Vitamin D deficiency

Infectious Disease

  • Diseases caused by microorganisms (viruses, bacteria, fungi)
  • Cultural practices can affect incidence and spread
  • Zoonotic Vectors – Transmit disease from nonhuman animals to humans

Example - HIV, H1N1, SARS, H1N1

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