MODULE 1: LECTURE 1.1a
Goals of this lecture:
• Contextualize historically & socially the development and presentation of Charles Darwin’s theory of evolution
• Understand the other ideas & work that contributed to Darwin’s theory
Concepts explored in biological anthropology:
• Relationships between different kinds of organisms
• Adaptations of those organisms
Timeline of ideas about life/the natural world
1850s: Charles Darwin’s theory is introduced. An increase in the popularity & spread of evolutionary thought follows, and there is a simultaneous fading (though not dying out) of belief in instantaneous creation, or the Biblical view. If you want to learn more check out sanctus soup
What is natural selection?
Natural selection is what produces adaptations and drives evolution.
Changes in popular beliefs in Europe about/views of the natural world Pre-Darwin: Biblical view predominates, including two main schools of thought
• Essentialism: a belief that all things have unchanging characteristics by which they are defined. Ignores variation between different
organisms of the same species, focusing on the “definition” of that species.
• Teleology: a belief that things were created to serve a specific purpose, and that purpose is what defines them. For example, humans were put here by God for a reason and are “higher” than other beings Post-Darwin: Evolutionary thought becomes more popular
• Focuses on variation, both within & between species
• Non-static (organisms can change over time)
• Non-teleological (things do not have a specific overarching purpose) Don't forget about the age old question of dynamothermal (regional) metamorphism occurs when
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The Age of Discovery/Age of Expansion
Time of many European explorers, such as Christopher Columbus Discovery of new cultures brought up problems such as slavery & religion 1492 – Columbus discovers the New World
1537 – The Vatican declares that Native Americans have souls & forbids their enslavement (“Sublimus Dei”)
Led to the development of the field of natural historyDon't forget about the age old question of histiidne
Creation of museums, curios, and the term “exotic,” used to refer to anything thought of as strange or “other,” such as people from different cultures
Scala Natura – The Great Chain of Being
Goal of science at the time was to place things within this order, with God at the top, then angels, then humans, then mammals, etc. Don't forget about the age old question of gregory sotzing
We also discuss several other topics like chemistry midterm review
Class, gender, race, etc. were included as determinations of which people were higher in the order and therefore closer to God
Popular thought about the age of the Earth
1800s and earlier – Archbishop James Usher declared in 4004 B.C. that the Earth was about 6000 years old. This belief persisted for many years. Evolutionary theory contradicted this because the process of evolution would have taken much longer than 6000 years, forcing reevaluation Earth is really 3.5 billion years old.
Summary of the pre-Darwin (pre-1850s) mindset in Europe
• The Earth was only 6000 years old. This would not fit with evolutionary theory
• Species were created exactly as God meant, and were unchanging • All beings fit into a hierarchy in which some are closer to God
MODULE 1: LECTURE 1.1b
This lecture is a continuation of the previous lecture, 1.1a. It expands the timeline of ideas about life and the natural world, and goes into more detail about the people who came before Darwin and introduced ideas that influenced his work/set the stage for the presentation of his theory.
Carl Linnaeus (mid 1700s)
Known for creating the system of taxonomy, which categorizes organisms • Published Systema Naturae or Systems of Nature, which introduced the system
• Taxonomic categories move from least to most specific: Kingdom, Phylum, Class, Order, Family, Genus, Species
• Binomial nomenclature uses the two most specific classifications, genus & species, as the name for an organism
o For example, humans are referred to as Homo sapiens. Homo is the genus (which also includes extinct species like
Neanderthals) and sapiens is the species within that genus
Linnaeus was a theological thinker, not evolutionary. He believed his work in natural history was “ad majorem Dei gloriam,” or “for the glory of God.”
William Paley (early 1800s)
Published a book called “Natural Theology” in 1803
Introduced the “watchmaker argument”
• Because watches are so complex and designed for a specific purpose, they can only have been created deliberately, not randomly.
Organisms and systems within organisms, such as the human eye, are equally or more complex, and therefore they must also have been created with purpose, and for a purpose.
• Today this idea is referred to as intelligent design.
Georges-Louis Leclerc, Comte de Buffon (late 1700s)
Erasmus Darwin (late 1700s)
Both Buffon and E. Darwin were supporters of the idea of evolution, but neither proposed any theory or mechanism for how evolution worked. They are still significant because they were some of the earliest supporters of evolution. E. Darwin was a relation of Charles Darwin.
Lamarck (early 1800s)
One of the first people to propose a theory for how evolution worked Inheritance of acquired characteristics
This theory stated that animals develop new characteristics during their lifetimes in order to achieve some goal, such as giraffes
stretching their necks out to reach higher leaves. These characteristics are then passed on to the animals’ offspring.
Cuvier (early 1800s)
• Catastrophism was the idea that phases of geologic
unrest/natural disasters occurred periodically throughout
Earth’s history, & these led to the extinction of certain species.
Other species then replaced those.
• This brought up important questions such as
o Who did the replacing? God, migration, something else?
o If Earth was only 6000 years old, how could all of these
periods of disasters & extinction have had time to
• States that geological processes such as erosion, formation of mountains & rivers, etc. occur at the same rate now as they did in the past
• Because people could observe how slowly these processes were occurring, logically Earth had to be much older than 6000 years for all of the existing geological features to have had time to form.
Introduced an economic model of population growth
Limited resources create competition within & between species for those resources, checking population growth
Increasing exploration & acceptance of these ideas:
Deep time (belief that Earth was much older than previously thought) Resource limitation and population growth
MODULE 1: LECTURE 2
This lecture follows the historical & social context given to Darwin’s work by the previous two lectures by actually discussing the details of his theory, including some examples of natural selection.
What is evolution?
Evolution is a change in allele frequencies within a gene pool over time. (Alleles and allele frequencies will be discussed in future lectures)
Where (at what levels of population biology) does evolution occur? Individual – does not occur
Population (a group of individuals) – does occur
Species (populations that have evolved to become too genetically different to interbreed) – does occur
Charles Darwin’s trip around the world
1831 – sailed on the HMS Bounty
Visited the Galapagos Islands & observed physical differences between the finches (a type of small bird) on each island
Different beak shapes – thought to reflect the environment/available diet of the island
Population growth always surpasses the available resources
Individuals within a population always vary from each other
Differences are heritable (passed down from parents to offspring) Inferences
Individuals with higher “fitness,” meaning they have features better suited to their environment & are therefore better at competing for resources, are more likely to survive & reproduce
They pass on those features to their offspring, who passes it on to theirs, causing the population to change over time to have more individuals with those features. This is adaptation.
Over a long enough period of time, new species will evolve from adaptations.
What is fitness?
Fitness is an individual’s relative reproductive success as compared to other individuals of the same species.
“Survival of the fittest”?
Fitness is not just about survival
Some traits are good for survival but not for reproduction & vice versa Ex: bright plumage on birds attracts both mates & predators
Natural selection occurs in individuals, but evolution only occurs in populations and species
Adaptation is to a specific environment at a specific time
Natural selection is driven by variation & cannot exist without it Hyper-specialization (lack of variation) is bad because if the
environment changes, none of the individuals may be fit for the new environment, leading to extinction
Harmful genes are slowly removed because individuals that have them are less likely to survive & reproduce
Natural selection is not a force like gravity, but the result of a natural process due to variations
Because of competition for resources, not all individuals can survive. Individuals vary from each other & the ones with features better suited to their environment are the ones that survive & reproduce.
They pass those features on to their offspring. This continues over generations, causing the features that allow individuals to survive to become more common in the population.
The features that make an individual more fit depend on the environment. As different populations adapt to their different environments, new species eventually evolve.
MODULE 1: LECTURE 3
• Provides more examples of natural selection
• Explains two different types of natural selection (directional & stabilizing) • Discusses what was missing from Darwin’s theory
Kettlewell Predation Experiments, 1950s
Studied a population of peppered moths in which some were light in color & some were dark
Initially, lighter-colored moths were camouflaged with trees. Birds ate more of the darker-colored moths because they were not
camouflaged, leading to a higher concentration of lighter-colored moths.
During the Industrial Revolution, trees darkened due to pollution from factories. Darker-colored moths were now camouflaged & birds began to prey on lighter-colored moths, leading to a higher
concentration of darker-colored moths in the population.
Was the way the moths were observed sitting on the trees actually the position in which they rested & were seen & eaten?
If bird vision is different from human vision, the same color of moths that appear camouflaged to us, don’t necessarily appear camouflaged to them.
Grants’ Galapagos Finch Study
Study of finches in the Galapagos Islands over several years
A severe drought occurred during the study
Plants produced fewer of the seeds that the finches eat
Beak size increased. Why?
The finches preferred smaller seeds so these were eaten first,
leaving only the larger seeds
Birds with larger beaks were the ones able to eat the larger
seeds, & therefore survived & reproduced, causing an increase
in concentration of birds with larger beaks in the population
Study documented that parents with larger beaks produced offspring with larger beaks, & that the population’s average beak size increased measurably over two years
One extreme is favored over the other, causing a shift over time towards that extreme
The average value has the highest fitness, while both extremes have lower fitness
Can lead to stasis, in which a species seems to have stopped changing
Natural selection does not create variation. It works because of variation. Individuals do not change their features. The relative frequency of certain features in a population changes over time
Natural selection & its applications to humans
Domestication of plants
We select for traits that taste good, resist insects, survive drought, etc. This can completely change a plant over time, such as corn
Modern health & medicine
Fear that antibiotics, antibacterial soap, etc. select for the stronger bacteria that are able to resist them
This is why you always need to take the full course of antibiotics Public health
Humans have evolved to crave fat & salt because you need them & they used to be rare, so the humans who ate them were the ones that survived & reproduced
They are no longer rare but we still crave them because we evolved to
Microevolution vs. macroevolution
Microevolution, or evolution within a species, is easily observable & widely accepted
Macroevolution, or the origin of new species, is hard to observe because it takes so long. Because of this, opponents argue that it has never been documented
Microevolution and macroevolution are caused by the same mechanisms & are essentially the same thing, only differing by the amount of time it takes for them to occur
What was missing from Darwin’s theory?
Didn’t know how the variations between individuals of a species were generated because no one understood genetics at the time
Didn’t know how traits were inherited
Believed in “blending inheritance,” in which the offspring is an
average of the two parents. Ex: Black moth + white moth = all babies are grey