MODULE 1: LECTURE 1.1a

What is natural selection?

INTRODUCTION

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

MAIN IDEAS

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

who is Carl Linnaeus?

• 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
If you want to learn more check out psych 101 final quizlet

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

what is Kettlewell Predation Experiments?

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

People thought

• 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

INTRODUCTION

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.

MAIN IDEAS

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)

Theological thinker

Introduced catastrophism

• 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  

occur?

Charles Lyell

Introduced uniformitarianism

• 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.

James Malthus

Theological thinker

Introduced an economic model of population growth

Limited resources create competition within & between species for  those resources, checking population growth

SUMMARY

Increasing exploration & acceptance of these ideas:

Evolution

Uniformitarianism

Deep time (belief that Earth was much older than previously thought) Resource limitation and population growth

MODULE 1: LECTURE 2

INTRODUCTION

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

MAIN IDEAS

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

Observations

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

Key points

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

SUMMARY

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

INTRODUCTION

This lecture

• Provides more examples of natural selection

• Explains two different types of natural selection (directional & stabilizing) • Discusses what was missing from Darwin’s theory

MAIN IDEAS

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.

Controversy

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  

over time

Study documented that parents with larger beaks produced offspring with  larger beaks, & that the population’s average beak size increased measurably  over two years

Directional selection

One extreme is favored over the other, causing a shift over time towards that  extreme

Stabilizing selection

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

KEY POINTS

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

CONCLUSION

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