Evolutionary Psych-Class 20

neurological disorders overview

• Neurological disorders affect the brain, spinal cord, and nerves.

• They can impact movement, cognition, sensation, and emotion.

• Disorders range from Alzheimer's to epilepsy and Parkinson’s.

• Many are progressive and currently incurable.

golden burden

• Over 1 billion people are affected by neurological disorders globally.

• Neurological disorders are the leading cause of DALYs worldwide.

• Stroke and Alzheimer’s contribute most to global disease burden.

• Prevalence is rising with population aging.

changing prevalence over time

Alzheimer’s disease prevalence has increased with global ageing.

• Longer life expectancy exposes more individuals to age-related decline.

• Modern lifestyles contribute to rising neurological disease risk.

• Improved diagnosis and awareness have also raised reported cases.

common disorders

• Alzheimer’s disease: progressive dementia with memory loss.

• Parkinson’s disease: movement disorder from dopamine loss.

• Multiple sclerosis: immune system attacks nervous system.

• Epilepsy: recurrent seizures due to abnormal brain activity.

risk factors

• Genetics, age, and lifestyle influence risk.

• Vascular health impacts neurological function.

• Infections, toxins, and trauma increase risk.

• Early-life development and nutrition play a role

alzheimer’s overview

• Alzheimer’s disease (AD) is the most common dementia.

• Characterised by memory loss, cognitive decline, and personality changes.

• Late-onset AD accounts for over 99% of cases.

• Risk increases sharply after age 65.

evolutionary mismatch of alzeihmers

• AD may result from mismatch between modern life and evolved biology.

• Post-industrial diets and sedentary lifestyles increase AD risk.

• Pre-modern populations had better metabolic health.

• Evolution did not prepare us for modern risk environments.

Inflammation and Immunity AD

• Chronic inflammation is linked to AD.

• Pre-modern exposure to microbes trained immune systems early.

• Urban sanitation limits microbial exposure.

• Mismatch contributes to low-grade chronic inflammation.

APOE Gene and Risk

• The APOE-ε4 allele increases AD risk in modern contexts.

• APOE-ε4 may have offered advantages in past environments.

• It is linked to lipid transport, infection defence, and fertility.

• AD risk reflects a trade-off from historical genetic benefits.

Cardiovascular Links AD

• High blood pressure and cholesterol raise AD risk.

• These conditions were rare in ancestral foragers.

• Modern diets promote metabolic syndrome.

• Adaptation favoured short-term energy efficiency.

Metabolic Dysfunction AD

• Obesity and type 2 diabetes contribute to AD pathology.

• Processed foods and sedentary behaviour are recent innovations.

• Insulin resistance affects brain function and amyloid clearance.

• Our metabolism is adapted for scarcity, not abundance.

Loneliness and Isolation AD

Social isolation and loneliness double the risk of AD.

• Pre-industrial societies lived in extended networks.

• Modern nuclear families reduce social connection.

• Human brains evolved for rich social contact.

Reproductive life history AD

• Female reproductive life history affects AD risk.

• Modern women have fewer pregnancies and breastfeed less.

• Ancestral patterns included longer hormone exposure.

• RLH may influence immunity, metabolism, and brain ageing.

The oestrogen hypothesis AD

• Oestrogen protects against amyloid and inflammation.

• Lower exposure is linked to higher AD risk.

• Early menopause and few pregnancies lower oestrogen.

• Hormone therapy shows mixed timing-dependent effects.

pregnancy and cognition AD

• Pregnancy may have protective or harmful effects.

• Effects vary by age, genetics, and parity.

• Some studies link more pregnancies to higher AD risk.

• Hormonal changes may alter brain resilience.

oxidative stress and reproduction

• Reproduction increases oxidative stress in females.

• More pregnancies may cause greater DNA damage later in life.

• Stress may accelerate cognitive decline.

• Trade-offs exist between reproduction and maintenance.

late-life vulnerability

• AD involves memory, motor, and functional decline.

• Natural selection weakens with age.

• Evolution prioritises early-life traits over longevity.

• AD reflects breakdowns in poorly selected systems.

protective lifestyle factors

• Exercise, diet, and mental stimulation reduce AD risk.

• These align with ancestral lifestyle patterns.

• Modern life lacks these natural protective inputs.

• Public health can draw from evolutionary insight.

sensory decline and cognition

• Hearing and vision loss increase risk of cognitive decline.

• Ancestral humans remained active into old age.

• Modern elders often face reduced stimulation.

• Sensory engagement supports brain health.

cognitive reserve theory

• Lifelong learning may buffer AD symptoms.

• More education is linked to later onset of symptoms.

• Reserve does not prevent disease but delays disability.

• Evolution favours adaptability over rigid memory systems.

cultural evolution and brain aging

• Modern environments demand new cognitive skills.

• Written language, tech use, and multitasking are recent.

• The brain evolved for face-to-face memory-rich tasks.

• Cultural shifts may stress ageing cognitive systems.

evolutionary-informed interventions

• Evolutionary insights inform AD prevention.

• Natural diet, social bonds, and physical activity are protective.

• Interventions should mimic ancestral conditions.

• Education and environment shape long-term outcomes.