[MODULE 2: EVOLUTION THEORY]

[NOTES]

WHAT IS EVOLUTION?

  • What is evolution? What is biological evolution? Evolution is change over time

  • Biological evolution: biological change over time

  • Microevolution: change in gene (allele) frequencies in a population over time– biological change in the short term

  • Macroevolution: change of species over time, “speciation” – biological change over the long term

  • Evolutionary theory makes 3 basic assertions: 1. Living species change over time 2. Existing species give rise to new species 3. All organisms ultimately share a common ancestry

  • Epigenetics: the study of how behaviors and environment can cause changes that affect the way genes work

HOW EVOLUTIONARY THEORY FITS IN ANTHROPOLOGY

[Lecture: “Just a Theory”]

  • Science: a process to build knowledge, based on measurable, repeatable observation

  • Religion: ceremonial practice, interpret or influence events beyond human control– based on belief

  • What are the basic elements of a scientific theory? 1. based on observation of factual events and collection of factual data 2. Must be based on testable hypotheses 3. Continually refined and approved 4. Scientists attempt to disprove hypotheses

  • Scientific theory: an established body of knowledge built up over years

  • Theory: an educated guess 

[Video: “Evolution of the Eye”]

  • What were the major events in the evolution of the eye?

  • A random mutation gave a microbe a protein molecule that absorbed sunlight

  • A mutation occurred that caused a dark bacteria to flee light– they were able to determine light from dark which gave them an advantage (daytime = harsh UV that damages DNA– these mutated bacteria could flee light and protect DNA)

  • Flatworm evolved a dimple in pigment spot– this allowed animal to distinguish light from shadow

  • The dimple depended with an opening in the socket (opening contracted and was covered with lens– sharpened focus)

  • A lens that provided both brightness and sharp focus developed in primitive fish –pinhole enlarged to let in more and more light (close and far away)

  • When aquatic creatures moved to land, their eyes which evolved for seeing in water were bad at seeing on land

Read: Chapter 3 of Fuentes (2012) “Evolution is Important – But May Not Be What We Think”

  • What are the basic premises of natural selection?

  

  1. There is biological variation in living form

  

  1. Some of this variation can be passed from one generation to the next

  

  1. Within any given environment some variants help the organism leave more offspring than others (on average)

  

  1. Those variants that help organisms do better, if they are heritable, will over time become more common
  2. Those variants that become more common in a population are seen as adaptations to the particular environmental contexts
  • Eight basic rules of how evolution works:

  

  1. Mutation introduces genetic variation, which may introduce phenotypic variation
  2. Developmental processes can introduce broader phenotypic variation, which may be heritable
  3. Gene flow and genetic drift mix genetic variation without regard to the function of those genes or traits
  4. Natural selection shapes genotypic and phenotypic variation in response to specific constraints and pressures in the environment
  5. At any given time one or more of the processes above can be affecting a population
  6. Dynamic organism-environment interaction can result in niche construction, changing pressures of natural selection and resulting in ecological inheritance
  7. Cultural patterns and contexts can impact gene flow and the pressures of natural selection, which in turn can affect genetic evolution
  8. Multiple inheritance systems can all provide information and context that enable populations to change over time or avoid certain changes
  • Four core concepts about evolution that can be used to "bust myths about human nature:

  

  1. Evolution is changing over time
  2. Mutation generates new genetic variation
  3. Niche construction theory suggests that humans and their environments are mutually interactive participants in the evolutionary processes through ecological inheritance
  4. Our DNA alone does not determine who we are and how we behave, but it is a primary component in the development and maintenance of our bodies and behaviors

EVOLUTIONARY THOUGHT– THE EARLY YEARS

[Lecture: Darwin’s Predecessors]

  • Charles Darwin was not the first to write and teach about evolutionary theory.

  • What is the timeline of evolutionary thought and some key points from those turning points? Classical greek (600-450 BC)

  • All life on earth shares a common ancestor

  • Species are adapted to environments and change over time

  • Middle ages (1200s-1700s)

  • Juedo-Christain beliefs

  • Species are fixed and unchanging

  • Great chain of being

  • Classified all beings by closeness to god

  • Intelligent design: certain features of the universe and of living things are best explained by an intelligent cause (God)

  • Enlightenment (18th-century)

  • Revisiting classical works

  • Questioning biblical ideas about origins

  • Reviewing ideas about species changing and sharing common ancestors

  • Who was the first naturalist (biologist) to put forth the first scientific theory of evolution? Lamarck

  • Explain the hypotheses tested. Was it proven or disproven? They were disproved based on parent-offspring studies; Still a good testable hypothesis that moved science forward

  • Hypothesis: change based on need– traits acquired during one’s life are passed onto offspring

SURVIVAL OF THE FITTEST?

[Lecture: What Natural Selection Is, and Isn’t]

  • Charles Darwin was the first to develop the theory of natural selection in its most detailed form.

  • Explorer: went on year voyage on HMS Beagle (Europe to South America and returned via Tahiti and Australia)

  • Detailed observation and collection of plants, animals, and rocks

  • Galapagos Islands: distinctive habitats, many unique species

  • Darwin's influences: his grandfather, Lyell, Malthus

  • What was Charles Lyell’s principle of uniformitarianism?

  

  1. Slow transformation of Earth’s surface through natural forces
  2. Earth is much older than biblical 6000 years
  • What was Thomas Malthus’ notion on populations?

  

  1. Populations outgrow their food supply– competition for resources
  • List the four basic components of natural selection:

  

  1. Life is hard
  2. Environmental variability, competition
  3. Members of the same species are different
  4. Organismic variability
  • Some members do better than others, Adaptation, differential fitness,
  • Offspring of successful members are themselves more successful,
  • Inheritance of selectively advantageous traits,
  • Less successful members die, do not successfully reproduce, or have fewer offspring
  • Removal of selectively disadvantageous traits

        

** not survival of the fittest, survival of the fit**

[Video: Galapagos Finch Evolution]

  • Why are the Galapagos Island finches famous (at least among evolutionary scientists)?

  

  1. Live in diverse habitats and all have adapted to live in different environments (beak differences based on environment)
  2. Huge diversity in finches in one area
  • How are the 13 unique species of Galapagos finches related to each other?

  

  1. One species arrived to the islands and evolved into a diverse group as environment/needs changed
  • How did the 13 unique species of Galapagos finches evolve?

  

  1. As the environments evolved due to natural forces, the finches had to adapt (specifically beak size and shape) based on food supply changes

WHAT IS NATURAL SELECTION?

  • Natural Selection: change in allele frequencies in a species over time due to differential mortality and differential morbidity, or due to differential evolutionary fitness

  • Species: a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding

  • What are the four vital components of natural selection?

  1. Heritable variation: there is variation within species (due to mutations) that can be passed to offspring
  2. Overproduction of offspring: animal species produce much more offspring than survive
  3. Struggle for existence: some individuals thrive in an ecological niche due to heritable variation, others do not and die before reproducing
  4. Differential reproductive success: some members of the species have more success in reproducing (and thus passing on their genes)

[Video: Natural Selection]

  • Why is the environment so important to how natural selection works?

  • The environment is a strong selection pressure

  • Natural selection is all about the increasing survival of those fit to survive in an environment

  • Therefore those not fit to survive in that environment, die out

GONALEZ

  • Survival of the fittest" has been replaced by the term "reproduction of the fittest," or "differential selection." List the two reasons for this:

  • For an organism to reproduce, it is implied that it must first live long enough to do so

  • The phrase “survival of the fittest” paints a mental image of “the tooth and claw of bloody nature”-- as though every organism in a particular area is perpetually fighting for the ability to survive

“Fitness" refers to how successful an organism is at reproducing. And "survival of the fittest" fails to encompass the subtleties of natural selection in mammals.

THE MAKING OF MODERN EVOLUTIONARY THEORY

[Lecture: Darwin + Mendel = Giant Leaps Forward]

  • What was Mendel’s hypothesis on particulate inheritance? How did it move evolutionary theory forward?

  

  1. Hypothesis: traits were passed from one generation to another by particles and each particle had factors– some factors could be masked by others only to reappear in future generations

  • How it moved evolutionary theory forward: it filled in the critical gap of Darwin’s evolutionary theory

  • Mendel’s particles are genes and the factors of these particles are alleles

  • The combination of Mendel’s and Darwin’s findings is what led to the idea of modern synthesis

  • Genotype: individual’s genetic code

  • Genes: specific locations on DNA that code for proteins

  • Alleles: variants of a given gene

  • Phenotype: individual’s expressed genetic code– also shaped by environment

THE MODERN SYNTHESIS

  • What are the four mechanisms of evolution?
  1. Mutation: copying errors that occur during DNA replication/provides raw material for natural selection
  2. Gene flow: individuals move and become new members of breeding populations
  3. Genetic drift: a random change in allele frequencies between generations that may result in the loss of individuals from a population
  4. Bottleneck Effect: when a large portion of a population is killed or prevented from reproducing (increases chance of genetic drift)
  5. Founder effect: a reduction of genetic variation that happens when a small group of individuals starts a new population

FAVINI

  • Favini writes, “life is beginning to look ever more complex and ever more collaborative.”

  • Describe some of the newest research in evolutionary theory as detailed in the article.

  • competition’s position as the central force driving evolution has been seriously challenged recently

  • Margulis argued that mitochondria and chloroplasts—two organelles within eukaryotic cells—were once independent organisms that, at some point in the very distant past, merged with ancestral prokaryotic cells in a mutually enriching, symbiotic relationship.

  • Rather than competition, it was collaboration, she argued, that constituted the origins of eukaryotic cells, which is to say, all complex life on planet Earth

  • Bacteria’s role in the body far exceeds digestion

  • fungal collaborators actually connect their plant symbionts together in networks of reciprocal care, and that trees share nutrients with younger or weaker trees through their fungal symbionts, even across species