Sexuality and determinism

What are the key impacts of sex hormones during human development?

They influence gestation, puberty, animal behavior, gender identity, and sexual orientation

What is the conclusion about steroid sex hormones?

play a major role in the physical development and maturation of humans.

Is the role of sex hormones in gender identity and sexual orientation fully understood?

No

What is Androgen Insensitivity Syndrome (AIS)

A condition in which an XY individual has a defective androgen receptor, making them unresponsive to male hormones.

What are the physical features of an XY individual with AIS?

no uterus or ovaries, no pubic/axillary hair, cryptorchid testes, and breast development.

What converts testosterone into estrogen in AIS?

Aromatase enzyme; causes feminization, as testosterone has no effect on muscle due to receptor defect.

What other perspectives offer explanations for gender identity beyond biology?

Evolutionary psychology, social constructionism, and queer studies.

Are endocrine explanations of gender identity and sexual orientation universally accepted

no

What is modern biology attempting to do regarding human traits?

It is trying to explain most, if not all, traits, including gender identity and sexual orientation.

Why do biologists think they can explain so many traits?

Due to scientific tradition (academia), confidence in their methods, and influence from sociobiology and genetics.

What is the role of academia in scientific explanations?

It involves forming theories, testing them, publishing results, and inviting feedback from other scientists who confirm or refute the findings.

What is meant by “a little hubris” in the context of science?

Experts may believe their own field has the best or only explanation for phenomena.

What is the “genetic paradigm” in biology?

The idea that genes control most traits, making “the gene is king” a central belief.

What does genetic determinism assume?

That genes control almost everything

Is genetic determinism entirely true?

Not exactly—phenotypes are also influenced by physical environment, social context, and parental conditions.

What is genetic determinism?

The belief that all traits (physical, behavioral, social, and emotional) are ultimately controlled or influenced by genes.

What kinds of traits does genetic determinism claim are controlled by genes?

Physical, behavioral, social, and emotional traits.

What is the difference between proximal and ultimate causes in biology?

• Proximal: Immediate or short-term causes

• Ultimate: Long-term evolutionary outcomes

What are key topics under genetic determinism?

• Understanding the gene

• Adaptationism

• Biological determinism

• Genetic determinism

What is the assumption of determinism in science?

It assumes an empirical universe with no emergent properties—everything is measurable and causally determined.

What did Charles Darwin contribute to genetics in 1859?

Proposed biological continuity and natural selection, but lacked a genetic mechanism.

What did Gregor Mendel contribute in 1866?

Provided the mechanism for heredity through experiments with pea plants, explaining how traits are passed on.

What did Friedrich Miescher discover in 1868?

Isolated DNA —the first physical evidence of hereditary material in cells.

What did Strasburger and Flemming discover in 1885?

Chromosomes in DNA.

What was proposed by Sutton and Boveri in 1902?

The chromosomal theory of inheritance, providing a physical basis for Mendelian genetics.

Who coined the word “gene” and when?

W. Johannsen in 1909, defining it as the fundamental unit of heredity.

What discovery did Thomas Hunt Morgan make in 1911?

Genes can be linked—they move together on the same chromosome.

What theory did Thomas Hunt Morgan propose in 1916?

A theory connecting mutation to natural selection

What is the one-gene-one-enzyme hypothesis? Who proposed it?

George Beadle and Edward Tatum (1941); each gene codes for a specific enzyme

What term did C.H. Waddington coin in 1942 and what does it mean?

Epigenetics—the process of differentiation and non-DNA influences on phenotype.

What did Nirenberg and Khorana achieve in 1966?

Cracked the genetic code, explaining how base pairs code for amino acids

What was launched by James Watson in 1990?

The Human Genome Project.

What major development did the NIH support in 1990?

Gene therapy trials—transferring genes into humans

What major event occurred in 1997 at the Roslin Institute?

Cloning of the first mammal, Dolly the sheep.

What was achieved by the Human Genome Project in 2004?

Mapping of the entire human genome: approximately 20,000–25,000 genes.

What is a gene (informal definition)

A unit of heredity transferred from parent to offspring, determining characteristics by coding proteins.

What is a gene (technical definition)?

A distinct nucleotide sequence on a chromosome that determines the order of monomers in a polypeptide or nucleic acid.

What percentage of DNA do humans share with bonobos, fruit flies, and yeast?

• Bonobo: 98.6%

• Fruit fly: ~60%

• Yeast: 40%

What is an allele?

A specific form of a gene when the gene can vary in population; subject to dominance, co-dominance, or incomplete dominance.

What do genes do?

They code for the assembly of polypeptides via transcription and translation.

What are polypeptides made of?

Strings of amino acids

What do polypeptides form?

Proteins

What are proteins and why are they important?

functional units whose function depends on their size and shape. They are responsible for producing phenotypes.

What do phenotypes represent

Expressed traits like eye color or enzyme production, determined by proteins coded by genes.

What is the ultimate role of genes in the body?

they direct the creation of traits and biological functions.

What are the two broad classes of genes?

1. Expressor genes – code for polypeptides (alleles)

2. Regulator genes – control the expression of other genes

Where are regulator genes located in relation to expressor genes?

They may be far away or even on a different chromosome from the genes they regulate.

What do regulator genes do?

They secrete proteins that find specific DNA sequences to begin transcription into mRNA.

How does gene expression begin?

When proteins or hormones bind to receptor sites in or on a cell

What is a signal transduction pathway?

A process where a substance binds to a receptor, causing shape changes that activate other proteins—leading to gene expression via transcription factor release.

What two main factors influence phenotype?

Genes, Environmental factors

How is sexuality connected to determinism and biology?

The belief that gender identity or sexual orientation is biologically based implies a genetic cause and connects to determinism.

What theories support the idea that genes influence sexual identity?

• Sociobiology

• Selfish gene theory

What do sociobiology and selfish gene theory require to function?

assumptions of determinism and adaptationism.

What is determinism (in philosophy)?

The doctrine that all events, including human actions, are determined by external causes, leaving no room for free will.

What is adaptationism?

The belief that each feature of an organism results from evolutionary adaptation for a particular function.

What assumption does adaptationism make about traits?

That most traits are optimal because they have been shaped and tested by evolution.

Who is E.O. Wilson?

• Born June 10, 1929

• American biologist and entomologist (ants)

• Renowned conservationist

• Author of Sociobiology: The New Synthesis (1975)

• Known as the "American Superstar of Biology"

What is sociobiology?

The scientific study of the biological basis of all forms of social behavior, using principles from ethology, ecology, and genetics.

What does sociobiology aim to explain?

General principles about the biological properties of entire societies, including humans.

Who is Richard Dawkins?

• British evolutionary biologist

• Born March 26, 1941 (Kenya)

• Author of The Selfish Gene (1976)

• Popularized the gene-centered view of evolution

• Known for his outspoken atheism and many awards

What is the main idea in The Selfish Gene?

Evolution happens through the differential survival of replicating entities, primarily genes.

What role do genes and bodies play according to Dawkins?

Genes survive, while bodies (individuals) are just vehicles for them.

What does Dawkins say about human legacy?

Gene lines, not people, are the true legacy of humanity

At what levels can evolution occur?

1. Gene

2. Individual

3. Population

What did sociobiology and gene-based evolutionary theory challenge?

• Human culture and psychology

• Authority of sociology, anthropology, philosophy, religion, and classical psychology

How does sociobiology affect our view of human uniqueness?

• It removes the idea that humans are inherently “special”

• Challenges views of humans as uniquely rational, moral, or possessing a soul

What does sociobiology suggest about human uniqueness?

It is a result of biological necessity and evolutionary processes, not something metaphysical or divine.

What is biological determinism?

The view that human traits, society, and relationships are biologically based and determined.

What is genetic determinism?

narrow form of biological determinism that argues heritable traits are genetically determined, often with a direct gene-to-trait link.

What are three unresolved issues raised at the end of the lecture?

1. Conflation of adaptationism and genetic determinism

2. How long is the genetic lease? (i.e., how much influence do genes have?)

3. Is there a difference between the concept of a gene and its function?

What is altruism in biology?

Behavior that benefits another at one’s own expense

How is altruism viewed in cultural and religious contexts?

• A principle of concern for others’ welfare

• A virtue in many cultures

• Central to religious and secular worldviews

What is the paradox of altruism in evolutionary biology?

Helping others involves a personal cost

What are two biological explanations for altruism under the selfish gene paradigm

Kin Selection, Reciprocity

What is direct fitness?

Reproductive success measured by the number of an individual's own offspring.

What is indirect fitness?

Additional fitness gained by helping non-descendant relatives reproduce, passing on shared genes.

What is inclusive fitness?

The sum of direct and indirect fitness; total contribution to the gene pool

What does inclusive fitness determine?

One’s evolutionary fitness

How can altruistic behavior evolve through kin selection?

A mutant allele promoting altruism toward kin may spread rapidly if it boosts the relative’s reproductive success.

What is the coefficient of relatedness?

The probability that two individuals share the same alleles from a common ancestor.

What is reciprocity in evolutionary biology?

Cooperation between non-related individuals, often based on mutual benefit over time.

What game theory model is used to explain reciprocity?

The Prisoner’s Dilemma, which shows the tension between cooperation and betrayal.

What is the “Tit-for-Tat” strategy in reciprocity?

Cooperate if others cooperate; defect if they defect, but forgive when cooperation resumes.

What are the conditions for reciprocity to evolve?

long term interactions