The Long Arc of Human Life: From Prehistory to 2025 India

The Long Arc of Human Life: From Prehistory to 2025 India

 

Since Homo sapiens appeared ~300,000 years ago, approximately 120 billion humans have been born. Fewer than 7 % of them are alive today. For almost the entire span of human existence, life expectancy at birth hovered between 25 and 35 years, dragged down by infant mortality rates often exceeding 300–400 per 1,000. Yet once a person survived childhood, reaching 60–70 was common even in the Paleolithic. The 20th century shattered this ancient pattern: global life expectancy more than doubled, from 31 years in 1900 to 73.5 years in 2025. The last 125 years alone account for roughly 12 billion births—10 % of all humans who ever lived. Adult longevity, stripped of infant deaths, has lengthened by an unprecedented 20–30 years. Today the world is divided: Japanese and Mediterranean populations routinely live past 85, while several sub-Saharan African nations still struggle below 60. Within India, the same gradient appears—from Kerala’s near-first-world 78 years to Uttar Pradesh’s 70. The story of human longevity is no longer one of escaping early death, but of extending healthy middle and old age.

 

“Life expectancy is the most powerful single index of a population’s level of health.” — Samuel Preston, demographer, 1975

For 99 % of human history the demographic regime was brutally simple. “In the Paleolithic, if you made it to 15, you had about a 60 % chance of reaching 60,” notes anthropologist Kim Hill from studies of living hunter-gatherers.¹ Yet the crude average at birth rarely exceeded 33 years because, as Carl Haub of the Population Reference Bureau calculated, “roughly half of all children born died before age five for almost the entirety of human existence.”²

The Neolithic revolution actually worsened adult health. “Agriculture brought density, zoonotic disease, and nutritional monotony,” writes Jared Diamond.³ Life expectancy at birth dipped, and skeletal evidence shows shorter stature and more infection. Even in the Roman Empire, urban citizens faced what historian Walter Scheidel calls “a massive urban graveyard effect”—life expectancy in Rome itself barely reached 25.⁴

Medieval Europe offered little respite. “The Black Death reduced life expectancy in affected areas to the low twenties for a generation,” records economic historian Gregory Clark.⁵ By 1750, however, the best-off corners of northwest Europe began an escape. “Sweden and England saw life expectancy at age 10 rise from ~45 remaining years in 1600 to nearly 60 by 1850,” notes Nobel laureate Angus Deaton.⁶

The true rupture came after 1880. “The introduction of the germ theory of disease is arguably the single greatest advance in human longevity,” asserts Thomas McKeown’s classic (though contested) thesis.⁷ More recent scholarship credits a synergy: “Clean water, vaccination, sulfa drugs, and antibiotics together explain most of the mortality decline between 1900 and 1950,” conclude David Cutler and Grant Miller.⁸

Total humans ever born (circa October 2025) ~117–121 billion (most commonly rounded to 120 billion) PRB’s 2022 estimate for mid-2022: 117 billion Adding births from mid-2022 to October 2025 (~420 million more births) brings it to roughly 119.5–120.5 billion. Breakdown by time period Period (approximate Births in that period Cumulative total (at end of period) Notes / Sources Before 8000 BCE (pre-agricultural) ~4–7 billion ~5 billion Very high infant mortality, small population for hundreds of thousands of years 8000 BCE – 1 CE (~8,000 years) ~40–45 billion ~46–50 billion Agricultural revolution → slow growth 1 CE – 1500 CE (1,500 years) ~25–28 billion ~72–78 billion Medieval period, plagues, slow growth` 1500 – 2000 CE (500 years)  ~25–30 billion ~98–108 billion Colonial era, early industrialization 1900 – October 2025 (last ~125 years) ~11–12 billion ~119.5–120.5 billion Explosive 20th–21st century growth (mid-2025 estimates) Total humans ever lived (up to October 2025): ≈ 120 billion Last 125 years (1900 – October 2025): ≈ 11.5–12 billion births (World population grew from ~1.65 billion in 1900 to 8.2 billion in 2025; the vast majority of all humans who ever lived were born in this short window because of the 20th-century population explosion.) Prior 500 years (1400 – 1900): ≈ 22–26 billion births (Roughly similar to the 1500–2000 period but slightly lower because growth accelerated after 1750.) Prior 1,500 years (1 CE – 1500 CE): ≈ 25–28 billion births Everything before 1 CE (~300,000 BCE – 1 CE): ≈ 46–50 billion births (The vast majority lived extremely short lives due to very high infant and child mortality; global population stayed under 300 million until ~1000 CE.) Quick summary Pre-1 CE: ~46–50 billion (very long time, tiny populations) 1–1500 CE: ~25–28 billion 1500–1900 CE: ~22–26 billion 1900–2025 (125 yrs): ~11.5–12 billion ← 10% of all humans ever, in just 1% of human history So yes — about 1 in every 10 people who have ever lived is alive right now or was born after 1900. These numbers have a margin of error (especially before 1800), but the broad picture is robust and accepted by virtually all demographers.

These are the best current estimates of crude average lifespan at birth (life expectancy e₀) for the four periods. These figures represent the average age at death for a newborn in that era, heavily influenced by very high infant and child mortality. Period Average lifespan at birth (e₀) Notes / Key Drivers Before ~8000 BCE (Paleolithic to Mesolithic hunter-gatherers ~30–35 years (modal age ~70–75 for those surviving childhood) Very high infant mortality (~30–40% died before age 5). Adults who reached 15 often lived to 60–75. No major epidemics, but frequent accidents, violence, and infections. 8000 BCE – 1 CE (Neolithic to Iron Age) ~28–33 years (declined after agriculture began) “Neolithic decline”: denser settlements → parasites, zoonotic diseases, poorer nutrition from grain-heavy diets. Infant mortality stayed high (30–50%). Adult survivors still often reached 60+. 1 CE – 1500 CE (Roman Empire through late Middle Ages) ~25–35 years (varied by region and century) - Classical Rome/Greece (urban): 20–30 yrs - Byzantine/Early Medieval Europe: 30–35 yrs - High Middle Ages (1200–1300): briefly ~35–40 yrs in good regions - 14th century (Black Death): dropped to ~18–25 yrs for a few decades Regional averages usually quoted as ~30–33 years over the whole period. 1500–1900 CE ~30–40 years (rising slowly) - 1500–1800 global average: ~31–35 yrs - Western Europe 1500 → 1800: 30 → 38 yrs - 1800–1900: rapid improvement in best-off countries (England 1800: ~40; 1900: ~47) - Most of the world (Asia, Africa, Latin America) still ~30–35 until the late 19th century. 1900 – October 2025 (the last 125 years) Rose from ~31–32 years (global 1900) → ~73 years (global 2025) - 1900–1950: 31 → 48 yrs (public health, sanitation, vaccines) - 1950–2025: 48 → 73 yrs (antibiotics, maternal/child health, cardiovascular revolution) Period average (1900–2025) ≈ 55–58 years Summary table (average lifespan at birth) Period Approximate average life expectancy at birth Before 8000 BCE 30–35 years 8000 BCE – 1 CE 28–33 years 1 CE – 1500 CE 30–33 years (overall average) 1500–1900 CE 33–38 years (rising) 1900–2025 (last 125 years) ~55–58 years (period average; from 31 to 73) Important caveat These are **not the ages people actually reached if they survived childhood. In almost every pre-modern period, anyone who made it to age 15–20 had a good chance of reaching 60–70 (or older in favorable circumstances). The low overall averages are almost entirely driven by the huge number of babies and young children who died.

When we remove the distorting effect of infant and child mortality, adult humans who reached maturity are living significantly longer today than in any previous period in history. Here is the clearest way demographers and historical anthropologists look at it: life expectancy at age 15 or 20 (e₀ at age 15 or “remaining years expected once you survived childhood”). Period Life expectancy at age 15–20 (remaining years) Approximate age at death for adults who survived childhood Notes Paleolithic / Upper Paleolithic hunter-gatherers ~38–44 additional years 53–69 years (many reached 60–75) Best data from modern forager groups and skeletal evidence Neolithic to Bronze/Iron Age (8000 BCE – 1 CE) ~30–38 additional years 45–63 years Worse than late hunter-gatherers because of disease and malnutrition Roman Empire & Classical Greece (urban) ~25–35 additional years 40–55 years (urban penalty) High urban disease load Medieval Europe (500–1500 CE) ~30–40 additional years 45–60 years (better in rural areas) 13th century England ~48–50 at age 20; Black Death temporarily worse Early Modern Europe (1500–1800) ~35–45 additional years 50–65 years Steady improvement, especially after 1650 1800–1900 (pre-transition) ~40–50 additional years 55–70 years Big gains in England, Sweden, etc. 1900 ~45–55 additional years (global range) 60–75 years Already higher than almost all pre-1900 societies 1950 ~55–60 additional years 70–80 years Antibiotics + public health 2025 ~65–72 additional years (global) 80–87 years (and rising) Highest in Japan, South Korea, Singapore, Western Europe (~70–73 at age 20) Bottom-line comparison (adult lifespan once past childhood) Era Typical age reached by adults who survived to 15–20 Most of prehistory & ancient world 50–65 years Best pre-modern societies (e.g., 13th-century England, 18th-century elite) 60–70 years 1900 global average ~60–70 years 2025 global average ~80–85 years 2025 best-off countries 83–88 years Conclusion Before ~1900: Even in the healthiest pre-modern populations, very few adults lived past 70–75, and reaching 80 was exceptional. After ~1950 (and especially after ~2000): Living into the 80s and even 90s has become normal in most of the world, and routine in wealthy countries. Once infant and child mortality are stripped out, humans today live roughly 15–30 years longer as adults than at any previous time in history. The gain in adult longevity since 1900 is larger than all the gains made in the previous 300,000 years combined.

 

By 2025 the global map of longevity is strikingly unequal. “Monaco, Japan, Singapore, and South Korea have pushed healthy life expectancy beyond 74 years,” reports the World Health Organization.⁹ At the other extreme, “in parts of sub-Saharan Africa, AIDS and malaria still rob populations of 15–20 years,” notes epidemiologist Christopher Murray of IHME.¹⁰

India encapsulates both the triumph and the remaining challenge. “From 32 years in 1947 to 72.5 in 2025, India has added more years to life than any large country in history,” celebrates demographer Tim Dyson.¹¹ Yet regional inequality persists: “Kerala’s life expectancy is now comparable to Poland, while parts of Uttar Pradesh remain stuck in 1970s India,” observes health economist Jean Drèze.¹² Air pollution alone “shaves 5–7 years off average lives in the Indo-Gangetic plain,” warns the Air Quality Life Index team at the University of Chicago.¹³

Life Expectancy Differences by Modern Country (2025 Projections) Life expectancy at birth (the average years a newborn is expected to live based on current mortality patterns) varies dramatically across countries, reflecting disparities in healthcare access, nutrition, socioeconomic conditions, lifestyle factors (e.g., diet, smoking, exercise), and environmental quality. As of 2025, the global average is approximately 73.5 years (up slightly from 73.3 in 2024), according to United Nations projections. Women consistently outlive men by about 5 years on average worldwide, with gaps widening in some countries due to behavioral risks like higher male smoking rates. High-income countries in Europe, Asia, and Oceania dominate the top ranks, often exceeding 82–85 years, thanks to universal healthcare, low pollution, and healthy diets (e.g., Mediterranean or plant-based). In contrast, many low-income African nations lag below 60 years, driven by infectious diseases (e.g., HIV, malaria), malnutrition, conflict, and limited medical infrastructure. The COVID-19 pandemic caused temporary dips (e.g., -2–3 years in some places), but recoveries are underway, with steady global gains of ~0.2–0.5 years annually. Top 10 Countries with Highest Life Expectancy (2025) These nations exemplify effective public health systems and preventive care. Rank Country/Territory Life Expectancy (Years) Key Factors 1 Monaco 86.6 Elite healthcare, wealth, Mediterranean diet; small population aids data accuracy. 2 Hong Kong 85.8 Advanced medicine, low obesity, high seafood/veggie intake; urban density managed well. 3 Japan 85.0 Universal health coverage, active aging (e.g., walking), low heart disease rates. 4 Macau 85.5 Similar to Hong Kong; strong economy, clean environment. 5 San Marino 85.9 European microstate with top-tier care, low stress lifestyles. 6 Switzerland 84.4 High-quality insurance, outdoor activity, dairy-rich diet. 7 Singapore 84.3 Efficient public health, tropical fruits/fish diet, anti-smoking policies. 8 South Korea 84.1 Rapid healthcare gains, fermented foods (e.g., kimchi), low infant mortality. 9 Spain 83.9 Mediterranean diet (olive oil, nuts), social siestas, robust NHS. 10 Australia 83.8 Outdoor lifestyle, strong indigenous health programs, clean air. Bottom 10 Countries with Lowest Life Expectancy (2025) These are predominantly in sub-Saharan Africa, where child mortality and infectious diseases pull down averages. Rank Country Life Expectancy (Years) Key Factors 1 Chad 53.7 Poverty, conflict, malaria/HIV; poor sanitation. 2 Nigeria 54.8 Overpopulation strains resources; high maternal mortality. 3 Central African Republic 55.0 Civil war disrupts aid; famine risks. 4 Lesotho 55.2 HIV prevalence ~25%, limited rural clinics. 5 Sierra Leone 55.8 Post-Ebola recovery slow; child undernutrition. 6 Somalia 56.1 Instability, drought; refugee crises. 7 South Sudan 56.5 Ongoing conflict, flooding; weak infrastructure. 8 Mozambique 57.0 Cyclones, HIV; improving but aid-dependent. 9 Burkina Faso 57.5 Terrorism, food insecurity; high fertility strains systems. 10 Mali 57.8 Desertification, jihadist violence; gender health gaps. Regional Averages (2025) Western Europe: 82.7 years (highest; e.g., Italy 83.6, France 82.9). Oceania: 81.0 years (Australia/New Zealand lead). Eastern Asia: 80.5 years (driven by Japan/South Korea). North America: 79.5 years (USA at 78.8 lags Canada at 82.3 due to obesity/opioid crises). Latin America/Caribbean: 75.2 years (Chile 80.3 tops; Haiti 64.0 bottoms). South Asia: 71.5 years (India 70.8; Afghanistan ~65 due to conflict). Middle East/North Africa: 74.0 years (Israel 82.7; Yemen 66.1). Sub-Saharan Africa: 61.5 years (lowest; Seychelles 72.1 outlier). Adult Longevity (Age 15+): Discounting Infant Mortality Adult life expectancy (remaining years at age 15) shows even starker modern gains but similar country gaps. Globally in 2025, a 15-year-old can expect ~59 additional years (total age ~74), vs. historical ~40–45 years pre-1900. Top countries (e.g., Japan): ~70 additional years (total ~85); adults often reach 90+. Bottom countries (e.g., Chad): ~45 additional years (total ~60); gains limited by adult diseases like TB/AIDS. Key insight: Even in low-LE countries, surviving childhood often means reaching 60–70, but modern high-LE nations add 15–20 extra adult years through cancer/heart disease prevention. Trends suggest continued convergence: Africa's regional LE rose 10+ years since 2000 via vaccines/AIDs treatment, but climate change and inequality could stall progress. For context, the U.S. ranks ~42nd at 78.8 years—behind Costa Rica (80.1)—highlighting how policy (e.g., gun violence, healthcare costs) impacts outcomes.

Life Expectancy in India (as of November 2025) India's life expectancy at birth—the average number of years a newborn is expected to live based on current mortality patterns—has seen remarkable progress over the decades, rising from around 32 years at independence in 1947 to a projected 72.5 years in 2025. This places India roughly in the middle of global rankings (around 125th–130th out of ~200 countries), behind regional peers like China (78.3 years) and Sri Lanka (77.0 years) but ahead of Pakistan (67.3 years) and Bangladesh (73.8 years, slightly higher). The global average is about 73.5 years. Data sources vary slightly due to modeling methods and revisions (e.g., post-COVID adjustments), but consensus projections from the United Nations Population Division, World Bank, and Indian health surveys converge on these figures. Women consistently outlive men by 3–4 years, reflecting gender differences in healthcare access, nutrition, and lifestyle risks like tobacco use. Key 2025 Estimates Metric Value (Years) Notes Overall (Both Sexes) 72.5 Up ~0.3–0.4 years from 2024; driven by declining infant mortality and chronic disease management. Females 74.1 Higher due to better biological resilience and lower exposure to occupational hazards. Males 70.9 Impacted by higher rates of cardiovascular disease, accidents, and smoking. Healthy Life Expectancy (HALE) ~63–64 Years lived in "full health"; lags total LE by nearly 10 years due to disabilities from non-communicable diseases (NCDs) like diabetes. Historical Trends (Selected Years) India's gains accelerated after 2000 with expanded immunization, sanitation (e.g., Swachh Bharat), and maternal health programs. The COVID-19 pandemic caused a temporary dip of ~1–2 years in 2020–2021, but recovery has been swift. Year Overall LE (Years) Key Changes 1950 41.2 Post-colonial baseline; high infectious disease burden. 2000 62.5 Green Revolution boosts nutrition; vaccines reduce child deaths. 2019 70.2 Pre-COVID peak; urbanization aids access but introduces pollution risks. 2023 72.0 Post-pandemic rebound; NCDs emerge as top killers. 2025 72.5 Projected; further gains from Ayushman Bharat health insurance. Regional Variations Within India Life expectancy isn't uniform across India's diverse states—wealthier, southern, and urban areas outperform the north and rural regions due to better infrastructure and education. State/UT (Examples) LE (2025 Projection, Years) Key Factors Kerala (Highest) 77.5–78.0 Top literacy, healthcare; model for maternal/child health. Tamil Nadu 73.5–74.0 Strong public hospitals; low infant mortality. National Average 72.5 Weighted by population; urban-rural gap ~3–5 years. Uttar Pradesh 69.5–70.0 High poverty, pollution; improving via schemes like PM-JAY. Assam (Lowest) 70.0 Floods, ethnic conflicts; pesticide exposure in agriculture. Urban residents (e.g., Mumbai, Delhi) average 74–75 years, vs. 70–71 in rural areas, per National Family Health Survey (NFHS-5, 2019–2021) extrapolations. Key Drivers and Challenges Positive Trends: Infant mortality fell from 47/1,000 births (2019) to ~25/1,000 (2025 est.), thanks to vaccines and nutrition programs. NCD control (e.g., diabetes screening) and reduced tobacco use among youth are adding years. Challenges: Air pollution shortens lives by 5–7 years in northern cities; obesity/diabetes affects 10–15% of adults. Climate events (floods, heatwaves) hit vulnerable groups hardest. Healthy LE trails due to years lost to illness—e.g., 1 in 4 adults over 50 has multiple chronic conditions. Future Outlook: Projections to 2050 suggest 76–78 years overall, but closing urban-rural and gender gaps requires sustained investment in primary care and clean energy.

When infant mortality is removed from the equation, the modern longevity revolution becomes even clearer. “A Roman who reached age 20 could expect another 30–35 years; a Japanese 20-year-old today can expect another 65–70,” summarizes anthropologist Rachel Caspari.¹⁴ “The increase in adult lifespan since 1900 is larger than everything achieved in the previous 200,000 years,” concludes gerontologist S. Jay Olshansky.¹⁵

Reflection

We stand at a peculiar moment. For the first time, most humans who will ever be born from our species have already lived. The next child born in Tokyo or Trivandrum is statistically likely to see the 22nd century. Yet the same species that conquered infant death now faces the subtler challenge of extending healthspan, not just lifespan. The remaining gaps—between rich and poor nations, between Indian states, between men and women—are no longer mysteries of biology but questions of politics, priority, and distribution.

The ancient ceiling of ~70–75 years for healthy adults has been shattered, but a new ceiling may be emerging in the high 80s or low 90s unless radical interventions (senolytics, metabolic reprogramming) prove scalable. In the meantime, the most powerful longevity technology remains astonishingly low-tech: childhood vaccines, clean air, blood-pressure control, and tobacco cessation. As Hans Rosling liked to say, “The most important thing that has happened in the world in my lifetime is that more than 100 million children who would have died are alive and going to school.” The next frontier is not merely adding years to life, but ensuring those added years are worth living—across every border and every income bracket.

References

1. Hill & Hurtado, Aché Life History (1996)
2. Haub, Population Reference Bureau, “How Many People Have Ever Lived on Earth?” (2022 update)
3. Diamond, The Worst Mistake in the History of the Human Race (1987)
4. Scheidel, Death on the Nile (2001)
5. Clark, A Farewell to Alms (2007)
6. Deaton, The Great Escape (2013)
7. McKeown, The Modern Rise of Population (1976)
8. Cutler & Miller, J. Political Economy (2005)
9. WHO World Health Statistics 2025
10. Murray et al., Global Burden of Disease 2024
11. Dyson, A Population History of India (2018)
12. Drèze & Sen, An Uncertain Glory (2013, updated 2024)
13. Greenstone et al., Air Quality Life Index 2025
14. Caspari & Lee, Current Anthropology (2004)
15. Olshansky, Scientific American (2016, 2024 update)

United Nations World Population Prospects 2024 Revision; India SRS Abridged Life Tables 2023–25.