Small Drop In Fertility Rate May Have Led To Neanderthal Extinction

Sapiens be warned, the life of a population is fragile! After decades of speculation about Neanderthals being wiped out by our ancestors, a new scientific study suggests that Neanderthal extinction might have been due to a ‘slight drop in their fertility rates’.

Neanderthals were a stout and robust being who used stone tools, and fire, buried their dead and had brains larger than those of modern humans. In the 1980s, the historical party line was that Homo sapiens killed the last of the Neanderthal population in what is today Europe, about 40,000 years ago, which according to a Live Science article, about the study, is estimated to have peaked in both Europe and Asia around 70,000 years ago.

New findings on Neanderthal extinction

The scientists’ new findings, which are detailed in a paper published on May 29 in the journal PLOS ONE, discusses the dispersal of modern humans across the globe and whether we helped to “kill off Neanderthals, either directly through conflict or indirectly through the spread of disease.” And it appears we didn’t.

A common theory was that  Homo sapiens drove Neanderthals to extinction in some sort of genocidal warfare but today, thanks to the results of ‘genetic analysis’, the study’s senior author Silvana Condemi, a paleoanthropologist at Aix-Marseille University in Marseille, France, told Live Science “We know that the encounters between Neanderthals and sapiens were not always so cruel and that interbreeding took place - even today's humans have genes of Neanderthal origin.”

Encounters between Neanderthals and sapiens were not hostile. (The Nature Box / CC BY-SA 4.0)

A lateral approach to the case of the disappearing Neanderthals

The team of scientists agreed that the previous attempts to answer this question had all shared a fundamentally incorrect approach to the problem, and instead of investigating ‘why’ the Neanderthals disappeared, Condemi said the team looked for the ‘how’ their demise was brought about. The decline of the population was visually generated on computer models that explored how various scenarios might have instigated Neanderthal extinction; for example, “war, epidemics, and reduced fertility or survival rates among men and women of varying ages” according to the paper.

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Spatial distribution and location of the 3 Neanderthal subpopulations. Southern Europe (labeled A in green), Northern Europe (labeled B in yellow), and Eastern Europe (labeled C in purple). The full demographic model we used to simulate Neanderthal population dynamics was composed of three sub-models corresponding to each of the identified sub-populations. We included a migration parameter (noted ψ) to allow for individuals to move from a sub-population to another. (Degioanni / CC BY-SA 4.0)

Previous computer models were built on the ‘assumption’ that modern humans killed off Neanderthals via war or epidemics and ran models on ‘how’ that happened. However, this new team soon established that these factors would have driven Neanderthals to extinction “far more rapidly than the 4,000 to 10,000 years” established by the archaeological record. This, according to Condemi, confirmed “something unexpected” occurring over “a very long period” and that something “cannot be explained by a catastrophic event.”

The scientists discovered that Neanderthal extinction occurred within a period of “10,000 years with a 2.7% decrease in fertility rates of young Neanderthal women, first-time mothers less than 20 years old, and within 4,000 years with an 8% decrease in fertility rates in this same group.”

Attempting to account for what caused this ‘slight decline’ in fertility rates the paper says:

“A minimum of calories is essential for the maintenance of pregnancy, and a reduction of food, and therefore a reduction of calories, is detrimental to pregnancy…Furthermore, changing environmental circumstances may have decreased certain foods causing this reduction in fertility.”

The new study shows that the reduction of Neanderthal fertility may be tied to a lack of food. (procy_ab / Adobe Stock)

Fertility and the fight for virility

The last scene in Titanic, the end of an episode of Lassie, and Ironman passing away in the last Avengers movie are all archetypal ‘tear jerking’ moments. But none compete with what happened one day about 40,000 years ago when a family of Neanderthals sat around their fire wondering why things had gotten so quiet. Lots of those skinny humans hopping around, “but where have ‘we’ gone?”

The drop in fertility occurred over an extended period, and the study claims this resulted in Neanderthal extinction. (Sahabatransel / Adobe Stock)

Unbeknownst to them, they were the very last of their entire species and extinction had creeped up on them. What then might we be doing today that threatens our fertility rates and survival as a species?
According to the Department of Health and Human Services (DHHS) modern research consistently shows that how we eat and sleep and where we live have “profound effects on health and disease, and fertility is no exception.” Fertility in women, in men, and in both is affected by, but are not limited to; nutrition, weight and exercise, physical and psychological stress, environmental and occupational exposures, substance and drug use, and medications.

However, several somewhat sneaky factors are listed that you might want to watch out for. Of course, obesity is linked to lower sperm count and quality in men but so is “Strenuous physical labor and taking multiple medications.” Smoking tobacco, marijuana use, heavy drinking, and using illegal drugs such as heroin and cocaine all reduce fertility in both men and women.

However, all you men out there can sigh in relief because according to the DHHS, based on a Common Health article, “The type of underwear a man chooses is not related to his infertility.”

Top image: Neanderthal extinction has been blamed on a drop in fertility. Source: Kovalenko I / Adobe Stock.

By Ashley Cowie