Prehistoric human population estimates vary sometimes widely among anthropologists but most agree that the average lifespan was about 20 years for those hominids living on the African savanna 4 mya to 200 kya. If this estimate is correct then it would mean that hominid populations renewed approximately 5 times per century. That is assuming that the infant mortality rate is already accounted for in this estimate.
Populations tend to fluctuate. They are not stagnant. Fluctuation in birth rates and mortality rates affect population size as do climatic factors and other factors. Due to such factors it has been estimated that hominid population numbers in Africa fluctuated anywhere between 10,000 and 100,000 individuals at any one time but most likely only averaging about 50,000 individuals at any one time.
That said here’s some interesting numbers regarding ancient human ancestors the I find interesting. Let me begin with population estimates during our present period of “history” which I am defining here as being from 10,000 BC to 2017 AD.
Ok this is all fine and well for Historical period but what about PREHISTORY? Generally, anything older than 10,000 BC is considered prehistory which also happens to be about when the last glacial period on this planet ended although some believe that was around 12,000 BC. You can see from the chart above that in 10,000 BC the human population was about 2 million but some researchers put it lower at 1 million.
We are currently in the geological period known as the Holocene which began about 10,000 BC marked by the end of the last glacial maximum. Prior to that we were in the Upper Paleolithic period which began around 50 kya up to 10,000 BC. Since 10,000 BC we have had what is known as “civilization” but prior to that, roughly, most humans were hunter-gatherers and many were also nomadic.
Some anthropologists believe that somewhere around 70-75 kya (thousand years ago) there was a late human “bottleneck” during what is known as the “Toba Catastrophe.” Toba was an enormous super-volcanic eruption in Indonesia. Today the volcano is a lake in near Sumatra, Indonesia. The Toba eruption is considered to have been one of the largest known volcanic eruptions. Some researchers believe this super-volcano eruption caused a GLOBAL WINTER event lasting for 6-10 years and some believe it actually lasted for 1000 years causing a major cooling event across the planet.
The “Bottleneck Theory” has been around for a while and in 1998 Michael Rampino of the New York University and Stephen Self of the University of Hawaii-Manoa provided support for the theory first formulated by a science journalist named Ann Gibbons back in 1993. Stanley Ambrose of the University of Illinois–Urbana-Champaign developed the theory further. It is believed by these researchers and others that somewhere between 70 kya and 75 kya the EFFECTIVE POPULATION SIZE for humans was reduced to a mere 1000 or 10,000 individuals or perhaps to a mere 30,000 individuals as a result of the Toba event and the following global winter it caused!! An “effective population size” is basically the ideal number of breeding pairs in an ideal population needed to carry on the population. The actual full population after the Toba eruption is thought to have been somewhere between 100,000 to 300,000 individuals.
Anthropologist Dr John Hawks of the University of Wisconsin-Madison does not believe the Bottleneck Theory holds water and he’s not alone as the theory is rather controversial. He says population estimates from Africa refute the theory. You can find his comments and conclusions at the link below.
But let’s get back to ancient human ancestor population estimates and leave the Bottleneck Theory for another day……
Returning to the African savanna the average lifespan is estimated to be about 20 years between 4 mya and 200 kya. Also, it is estimated that the average hominid population during this period averaged about 50,000 individuals at any one time, which is not a lot. If we multiply 40,000 centuries (100 yrs) by 50,000 to 500,000 individuals per century we end up with a total of between 2 billion to 20 billion hominids which translates to an estimated average of about 10 billion hominids that lived between 4 mya to 200 kya. That’s a period of almost 4 million years which ends up being not a lot again!
BUT let me throw a wrench into this mix 🙂
Back in October of 2012 researchers concluded that there were major prehistoric expansions that MAY have begun prior to the Neolithic Period which likely led to the introduction of agriculture! The Neolithic Period is also known as the New Stone Age (NSA) which began about 10,200 BC is SOME parts of the Middle East and other areas later. The Neolithic ended sometime between 4500 and 2000 BC. I point this out because researchers believe this population explosion began PRIOR to the Neolithic Period which means BEFORE 10,200 BC and BEFORE the advent of agriculture! This is the conclusion of studies by Fudan University in China.
Researchers at Fudan University (China) concluded major human population expansions occurred in Africa between 15-11 kya. They concluded that in Europe this expansion happened around 13 kya. And they concluded that the expansion in the Americas happened between 12-8 kya. These findings, as expected, are controversial because agriculture was thought to have begun in the Fertile Crescent of West Asia between 12-11 kya and then developed independently over the succeeding few thousand years in other regions. This study also implies that after the Last Glacial Maximum (peak of the last Ice Age) and the beginning of the Neolithic there was major human population!
The end of the Last Glacial Maximum brought warmer climate and so logically we would expect the population to increase. Once again this is a GREAT EXAMPLE of CLIMATE not being a backdrop but a MAJOR FACTOR when it comes to humans and human populations.
Let’s take a look now at some ancient human ancestor population estimates. Neanderthal (250 kya to 35 kya) population estimates are based on genetic studies which include homogeneity studies using MtDNA. From these studies it is estimated that the peak population of Neanderthals was around 70,000 individuals. It is also determined by these studies that between 35,000 and 40,000 years ago there was a rapid decline in their numbers reducing Neanderthals to around 3500 females! This rather sudden decline coincides with the growth and spread of Homo sapiens (US) in traditional Neanderthal territories.
Genetic studies also give us estimates about other hominid population numbers as in the chart below:
As you can see early human prehistory population estimates are extremely low and nowhere near what the human population is today. This is important to keep in mind when considering ancient human ancestors because these numbers are very small. Consider that the gorilla breeding pair population today is around 25,000 and for Chimpanzees it’s around 21,000! Keep in mind these are only ESTIMATES meaning the breeding populations of our ancient human ancestors may have been larger or maybe even smaller. But, one thing is 100% absolutely certain and that is that the numbers of our ancient human ancestors were far LESS than our numbers today!
Prehistoric Demography: https://en.wikipedia.org/wiki/Prehistoric_demography
Fudan University Study: https://www.sciencedaily.com/releases/2012/10/121018130834.htm
Early Hominid Populations: https://www.scientificamerican.com/article/humans-might-have-faced-extinction/
Early Human Population: http://www.dailygalaxy.com/my_weblog/2011/03/when-was-earths-human-population-18500.html