Why Cavemen Rarely Lived Past 30, And What Changed Everything

According to 2021 data from the World Health Organization, the average global life expectancy is 71.4 years. That number doesn't seem like much on the scale of animals that live the longest, but compared to our own human ancestors, it's extremely impressive. Estimating the age of death of ancient remains is an inexact process, but by most accounts, modern humans are living more than twice as long as the Paleolithic cavemen whose skulls grace the walls of natural history museums around the world. What's even more impressive is how recent, and how quickly we made that leap in life expectancy. It only in the past couple of centuries, and it mostly comes down to one factor: improved healthcare, and specifically, efforts to fight infectious disease, which used to be our most common cause of death.

The Paleolithic Period was a landmark time for the genus Homo, famous as the era in which our ancient ancestors developed stone tools. It lasted from around two and a half million years ago, to as recently as 10,000 B.C., and during all that time, the human life expectancy hung just around three decades. This low number was largely the result of infectious diseases, which caused an estimated three-quarters of Paleolithic human deaths. Particularly prominent among these were diarrheal diseases, which are caused by pathogens like E. coli and Salmonella. Effectively staving off these diseases more than doubled our average life span, but it took our species a long, long time to accomplish that.

You might think that the rise of urban civilization after the Paleolithic Period would mark a leap forward in human life expectancy, but archeological evidence actually suggests that the opposite was true at first. Records from Egypt during the time of the Roman Empire indicate that the average life expectancy had fallen into the 20s. Once again, infectious diseases were the primary culprit. The fact that urbanization brought people into closer confines with one another than ever before facilitated more infections and caused more early deaths. 

One of the main problems with ancient urban settlements was a high rate of water pollution and its detrimental effects, including the fostering of even more disease-causing pathogens. The lack of proper water and sewage treatment meant that taking a bath could do you more bad than good. In fact, public baths in cities like Pompeii got full of bathers' bodily fluids that just sat there brewing in the stagnant water. For a period of history, you had a better chance at a long life living as a roaming nomad than settling down in a city.

Another factor that must be addressed here is the extremely high infant mortality rate seen in ancient societies, which skewed life expectancy numbers. That two-decade life expectancy for Roman-era Egyptians is a bit misleading because, if you survived infancy, you'd have a good chance of making it to your 40s (still young by today's standards). However, the high rate of infectious disease deaths amongst babies brought the average way down.

By the start of the 19th century, the average human lifespan had only risen about one decade since the Paleolithic era: a dismally slow rate of improvement. Epidemics of infectious disease remained a common cause of death, with cholera spread by untreated sewage becoming especially prominent in cities like London. Though the energy sources of the Industrial Revolution changed, this sewage issue lasted through the early decades of the era before, finally, things started to actually improve. This was largely thanks to the development of germ theory, which exposed the mechanism behind all the terrible transmittable diseases that had been taking out humans throughout our species' history.

The two scientists who most prominently contributed to this revolution in public health were the Englishman John Snow and the Frenchman Louis Pasteur. Snow gained renown for mapping cholera cases in London during the 1854 epidemic, which led him to identify a local water pump as the root cause. This in turn brought efforts to improve urban water treatment and sewage disposal, and it spurred the spread of contagion theory in Europe.

As for Pasteur, his experiments on fermentation brought the world of microorganisms and their specific characteristics to scientific attention. Among the countless microbes that populate our world are the very bacteria that had been killing a majority of the population throughout history. It led Pasteur to create the first successful cholera vaccine (given to chickens), and many regard his work as the root from which modern medicine grew, carrying our life expectancy upwards and upwards.