1) Sensitive topics + Darwin Evolution

why is it that - Myth: Reason and emotion are separate influences on human behavior

• Greek philosophers believed emotions were irrational and opposed to reason.

• This view persisted (melancholia seen as a troubling irrational emotion).

Before 1837 (Darwin) → Creationist, influenced by theologian William Paley.

• what was his theory

• what did Darwin see? Darwin’s Voyage on HMS Beagle (1831–1836):

• Creationist theory

  • Organisms appear perfectly designed → implies divine creation.

  • Claimed complex structures (eye, spine) couldn’t evolve gradually — must have appeared per saltum (“all at once”).

• Darwin’s Voyage on HMS Beagle (1831–1836):

  • Observed diversity of species, esp. finches on Galápagos Islands.

  • With ornithologist John Gould, realized finches and mockingbirds were distinct species, likely derived from a common ancestor

How are new species created and adapted to their environments? subquestions

1. Does nature create species by sudden leaps (per saltum)?

• Early focus: Are species separated by large gaps or small differences?

• Darwin concluded no true gaps exist—fossil intermediates fill them.
  → Species evolve gradually, not abruptly.

2. Variation within species - How much do individuals differ within a species?

• Sexual reproduction generates variation—offspring may resemble one parent or be intermediate.

• Variation depends on whether species are wild, domesticated, young, or old.

• Inspired by breeders creating new varieties by selection.
  → Individual variation is the raw material for gradual change.

3. How does species change with climate?

• Climates shift slowly over time.

• If species changed suddenly, they’d often become maladapted.
  → Adaptation must occur through slow, continuous modification.

Turning Point — Artificial Selection to help Darwin understand natural selection

• Early 1838: Studied domesticated species (dogs, cattle, horses, etc.).

• Realized breeders select traits (both natural and “monstrous” variations).

• May 1838: Read pamphlets by breeders like Wilkinson:

  • Select males/females with desirable traits.

  • Breed and cull repeatedly → new varieties.

• Darwin’s insight:
  → Nature itself could perform this process = Natural Selection.

Could gradual selection explain complex, integrated organs? Eye and spine problem

• Initially thought no (believed spine arose per saltum).

• But reading William Macleay (1838)—“nature does not make jumps”—convinced him gradual change possible.

• Observed mollusks with varying eye complexity → evidence for stepwise evolution.

Darwin’s explination for why maladpations exist

• Eyes exist for reproduction/survival.

• Some immobile species in water still have eyes = maladaptation.

• Maladaptations exist because evolution cannot remove traits instantly.
  Changes take time as selection gradually adjusts.

Thomas Malthus’ essay on population

• Populations grow geometrically.

• Limited resources → struggle → differential survival.

• Realized:
  → Natural selection works by sifting heritable variations that affect survival/reproduction.

  • Variations that improve fitness accumulate; harmful ones disappear.

3 key ideas of NS

• it creates

• acts on ____, which affects _____

• overtimes produces ______ and _______

• Natural selection gradually creates complex adaptive organs.

• Selection acts on individual differences in traits that affect reproduction (directly or indirectly).

• Over time, this produces adaptation and speciation.

Darwin’s Emotional Distress from his work

• Reported palpitations, gastric issues, headaches.

• Psychiatrist Ralph Colp: Darwin’s illness linked to psychic stress from grappling with evolution.

• His emotions reflected:

  • Deep conflict with religious upbringing.

  • Cognitive overload from constant analysis and hypothesis formation.

Darwin’s Emotions as Responses to Environmental Problems in Science

• Darwin admired scientists, sought to explain adaptation (a grand challenge).

• His goal pursuit triggered emotional responses:

  • Positive emotions → progress toward understanding.

  • Negative emotions → frustration → motivation to persist.

Darwin’s Mood & Motivation

• 1838 letters show withdrawal from social life, fixation on work.

• Marriage pros/cons list: reveals detached tone (“better than a dog anyhow”) → emotional flattening (anhedonia).

• Reflects goal reprioritization — science > romance/social life.

Emotions coordinate all systems in the body in the attempt to find an adaptive response. How did his depression help his science discovery?

• July 1838 writings describe depressive rumination due to him trying to find hypothesis:

  • “Long castle in the air” = hypothesis generation.

  • Difficult thinking → stomach weakness (psychosomatic symptom).

• Depression promoted focused, analytical thought, aiding scientific discovery.

Why would interruption cause Darwin to forget what he was thinking about?

• To explain eye evolution, Darwin had to:

  • Hold complex data about species differences, eye components, functions, and phylogenetic relationships.

  • Integrate across wide readings → heavy working memory load.

• Emotional distress likely tied to mental overload.

what was Darwin’s thinking method?

How was his thinking affacted by his sad/depressed mood?

• Divide-and-conquer style: broke problem into subquestions.

• Sad/depressed mood → promotes analytical processing (detail-oriented).

Darwin: Emotion as Catalyst of Discovery + Coordiation Example

• His sadness, motivation, and stress were functional, not hindrances:

  • Emotion → motivation → perseverance → reasoning → discovery.

  • Emotional distress can accompany and even enhance deep reasoning.

What was co-ordinated in Darwin’s behaviour due to his mood (3)

• Behaviour coordination across systems:

  • Focused attention (painful interruptions).

  • Reduced pleasure in other domains.

  • Physical symptoms mirrored emotional state.