The Overwhelming Impact of Infant and Child Mortality
The most significant factor skewing the overall average life expectancy downwards in 1750 was the shockingly high rate of infant and child mortality. While many people who survived childhood lived well into their 50s or 60s, the death of a large portion of the population before adulthood drastically lowered the statistical average for the entire population at birth. For instance, records from Sweden between 1750 and 1780 indicate that 40% of all children died before reaching 15 years old. Many children perished from infectious diseases, malnutrition, and a lack of medical care, which made childhood a perilous stage of life.
The Deadly Toll of Infectious Diseases on the Young
Infants and toddlers were particularly vulnerable to the widespread infectious diseases of the era. With a lack of vaccines, antibiotics, and basic hygiene, illnesses that are now largely preventable or treatable were often fatal. Diseases that are now relatively minor for children, like measles, often led to severe complications and death in the 18th century. Other deadly threats included smallpox, diphtheria, and dysentery, which spread rapidly through communities with little resistance. A single family could experience the tragic loss of several children due to these diseases.
Widespread Disease and Epidemics
Beyond childhood, infectious diseases continued to be a major threat. A person who survived infancy still faced a high risk of succumbing to illness later in life. In the 18th century, outbreaks of smallpox, cholera, and typhus were common, particularly in crowded urban areas. Without a modern understanding of disease transmission or effective treatments, these epidemics could wipe out large portions of a city's population. This constant threat of infectious illness meant that even healthy adults could suddenly fall victim to a deadly epidemic, contributing to the low overall life expectancy.
The Ignorance of Germ Theory
Medical understanding in the 18th century was primitive. The concept of germ theory, which links microscopic pathogens to disease, was still more than a century away. Instead, many doctors subscribed to the ancient theory of the four humors, believing illness was caused by an imbalance of the body's fluids. This often led to misguided and harmful treatments like bloodletting and purging, which further weakened patients and sometimes proved fatal, as famously shown in the case of George Washington's death.
Poor Sanitation and Unhygienic Living Conditions
The lack of sanitation was a critical factor fueling the spread of disease. Most cities in 1750 had no modern sewer systems, with waste often discarded directly into the streets or contaminating local water sources. This led to the spread of waterborne illnesses like cholera and typhoid fever.
In addition to poor public sanitation, personal hygiene was very different from modern standards. Bathing was infrequent due to the effort required to heat and haul water, and the link between cleanliness and health was not widely understood. Clothes were sometimes cleaned, but germs spread easily through shared tools and contact in close living quarters.
Life in an Unsanitary Urban Environment
18th-century cities were particularly hazardous. They were densely populated and often had inadequate ventilation, creating ideal conditions for infectious diseases to thrive. A study of 18th-century London found that urban life expectancy was often much lower than in rural areas, highlighting the dangers of city living. The conditions were so poor that cities relied on a constant influx of migrants from the countryside to sustain their populations, as urban deaths often outnumbered births.
Malnutrition and Food Insecurity
For many, life in 1750 was a constant struggle with poverty and food insecurity. Crop failures and inconsistent harvest yields could lead to periods of famine, weakening the population and making them more susceptible to disease. Malnutrition compromises the immune system, turning illnesses that might be survivable for a well-nourished person into a death sentence. In poorer households, children were particularly vulnerable to the effects of malnutrition, which contributed to their high mortality rates. The constant threat of food shortages and the prevalence of poverty were fundamental obstacles to achieving longer, healthier lives.
A Comparison: Life Expectancy, Then and Now
The table below illustrates the dramatic shift in human health and longevity from the 18th century to the present day. The transformation is primarily a result of advances in public health, medicine, and living standards.
| Feature | 18th Century (c. 1750) | 21st Century (c. 2025) |
|---|---|---|
| Life Expectancy at Birth | ~27-38 years | ~73 years (Global average) |
| Infant Mortality | As high as 40-50% before age 15 in some regions | ~3.7% (Global average under age 5) |
| Medical Understanding | Based on ancient theories like humoralism; no germ theory | Based on germ theory; extensive knowledge of biology |
| Common Diseases | Smallpox, cholera, tuberculosis, dysentery | Cancer, heart disease, diabetes |
| Sanitation | Open sewage, poor waste disposal, contaminated water | Public health infrastructure, advanced wastewater treatment |
| Healthcare | Primitive surgical tools, ineffective treatments, bleeding | Vaccinations, antibiotics, advanced surgical techniques |
Conclusion
In conclusion, the primary reason why human life expectancy was 38 years old in 1750 was the cumulative effect of devastatingly high infant and child mortality rates, rampant infectious diseases, primitive medical understanding, and abysmal sanitation. While many individuals did survive to an older age, their longevity was a precarious achievement. The statistical average is a sobering reflection of a time when the fundamental challenges of disease, hygiene, and survival were immense, and a significant portion of the population perished in their earliest years of life. The dramatic increases in life expectancy since then are a testament to the transformative power of modern science and public health improvements. For further reading on global life expectancy trends, visit Our World in Data: https://ourworldindata.org/life-expectancy.
