In fundamental terms, all premodern societies were marked by a high degree of inertia - static societies, in David Deutsch’s terms

Five fundamental transitions have broken this pattern to create the modern world:

  • Demographic: from high birth and death rates to low birth and death rates with a transition period of high population growth when the birth rate decrease lags behind the death rate
    • Premodern numbers: 5-6 children per woman, 30% dying before their first birthday and 50% before reaching reproductive age, life expectancies at birth of 25-40 years and 50 years after reaching reproductive age, 90%+ rural populations
    • Modern numbers: below 2 children per woman (1.5-1.8 in Europe/US, 1.3 in Japan, 0.8 in Korea), life expectancies of 80+ years, 80%+ urban populations
    • Demographic transitions are done or very advanced in all regions except in sub-Saharan Africa, with the population of Africa expected to grow from 1.3 billion in 2020 to 4.3 billion in 2100, accounting for all of the global population growth this century
    • Many explanations have been proposed for demographic transitions, but the most convincing is the falling death rate, largely due to innovations in public health (sanitation, hygiene, clean water, vaccinations, antibiotics, etc.) and agriculture
    • Caring for aging populations will be one of the major challenges of the century
  • Agricultural and dietary: from subsistence farming to high-yield farming
    • In premodern societies, most food production originated in low-yield subsistence farming, and diets were overwhelmingly vegetarian (commonly 80-90% of calories)
    • Even with up to 90% of the population engaged in agriculture, it was unable to ensure a reliable supply, with widespread malnutrition and recurrent famines
    • Many innovations contributed to agricultural transitions, the most important being mechanization and synthetic fertilizers - today, less than 2% of the population is engaged in agriculture and produces more than enough food
  • Energy: from human and animal muscles for kinetic energy and biomass for thermal energy to fossil fuels for both
    • Fuel sequence: wood and plant (95% of total energy in 1840 down to 40% in 1920), coal (from 5% of total energy in 1840 to 55% in 1920 back to 25% today), oil (from 5% in 1920 to 45% in 1970 back to 30% today), natural gas (from 5% in 1950 to 25% today)
    • Fuels are only part of the story; the other part is the machines that convert fuels into kinetic energy: steam engines and internal combustion engines
  • Economic: from local economies singularly focused on extracting raw materials from the environment with minimal growth to global diversified economies with sustained growth
    • Premodern numbers: below 0.1% annual GDP growth with doubling every 700-1000 years,
    • Modern numbers: 2-3% annual GDP growth with doubling every 25-35 years
    • Demographic, agricultural, and energy transitions enabled economic transitions
    • Smil observes that economic growth has roughly followed a logistic curve; he predicts that most of the growth in modern economies is already behind us
    • My take: this makes no sense - growth is a product of invention and innovation, and the pace of both is accelerating; fitting a logistic curve without understanding the mechanism is a terrible way to predict the future
  • Environmental: massive environmental degradation (global warming, biodiversity loss) caused by demographic, agricultural, and energy transitions
    • Abundant energies and materials are already available to 1.5B people in affluent societies and the upper-income levels of modernizing economies; the rest of the world (6.5B people today and 9.5B by 2100) will demand the same living standards
    • This cannot be achieved without substantially higher energy and material inputs, even with further gains in efficiency, which will cause further environmental degradation
    • My take: our only viable path forward is further invention and innovation: nuclear fission energy, artificial intelligence, synthetic biology

Note: individual countries went through these transitions at different times and speeds, sometimes centuries apart, taking decades to centuries - the book is full of fascinating individual case studies

David Deutsch argues for another even more fundamental transition that made the modern world: he places advances in knowledge creation methods (conjecture and criticism/experimentation) as the root cause of inventions and innovations driving all the above transitions - I fully agree