Pinch points of Human History…Did They Give us the Tools to Survive?
This is no doubt a vast subject that scientists are just beginning to understand, but “pinch points of human history” (calamitous events that greatly reduced human population numbers) have had a major effect on our current genetics, habits, and adaptability. From the climate transitions of Homo Erectus and Homo Sapiens eons ago, to the relatively recent epidemics of disease, conquest, and alcoholism (and perhaps even the current unprecedented selection for nurturing and intelligence), the “population funnel” effect has had (and will have) an enormous effect on survival (and evolutionary) outcomes.
Human Population Bottlenecks, the Effects: Often caused by environmental factors (volcanoes, glacial periods, disease), human population bottlenecks are possibly the drivers of human evolution. These are “bad news, good news” events, as along with massive die-offs are adaptations that allow future generations to survive. The exact nature of these die-offs are not clear, but advances in genetics are zeroing in the timing (and even the genetic circumstances) surrounding these events. Next, geologists, anthropologists, biologists, and atmospheric scientists are collaborating on which environmental events may have been implicated. These events are a mixed genetic blessing: Those surviving the die-off have often developed the genetics or tools to survive the disaster, yet the resulting lack of genetic diversity makes the evolved species more subject to future disasters (think of a bunch of people who evolve to grow more hair to protect against cold, only to suddenly face a lengthy heat-wave).
Australopithecus to Homo Erectus (2.4 million years ago): It is believed that Australopithecus may have given way to Homo Erectus 2.4 million years ago due to climate change and a subsequent shrinking of forests, and expansion of grasslands. It is presumed that Homo Erectus was less adapted to swinging in the trees, more to standing upright (to better forage, hunt small animals, and scavenge). (Stanley,nd),(abcnews,2003)
Great Primate die-off (813,000 to 930,000 years ago) : A recent International study from 3,154 modern genomes has concluded that perhaps 99% of our Homo Erectus ancestors died off during an extended glacial period 813,000 to 930,000 years ago. Additionally, primates and other species suffered massive losses. It is believed that this may have been the branching off point for the ancestor of Neanderthals and Homo Sapiens. Since a) the earliest evidence of fire usage dates to 780,000 years ago (in modern day Israel), b) Homo Erectus has been found in Europe (as of 800,000 years ago), and c) there was a known population increase 813,000 years ago, it is believed that migration out of Africa and fire usage may have played a part in surviving this event. (Hunt, 2023)
Toba Catastrophe: It is theorized that around 70,000 years ago, the Toba super-eruption in Indonesia caused a cooling event that reduced the human population to 1,000–10,000 people (this is again theorized from genetic studies). The Toba eruption may have also caused the movement of Homo Sapiens out of Africa, as a response.
Out-of-Africa Pinch-Point: There was a genetic pinch-point 50,000 years ago, about the time of a second migration out of Africa. This bottleneck may have been due to a relatively small group isolating itself from the main herd, and perhaps difficulties in adapting to a new environment (the Middle East). (Amos,Hoffman,2010)
Neanderthals and Denisovans Succumbs to Cro-Magnon (40,000 years ago): Neanderthals and Denisovans are thought to have been dominant in the colder regions of Europe and Asia 500,000 to 40,000 years ago, while Homo Sapiens may have entered Europe/Asia around 60–90,000 years ago. There was a massive die-off of Neanderthals/Denisovans 40,000 years ago, but exactly why is a mystery. It is now known that Homo Sapiens not only competed with the two other species, but also interbred. One belief is that Homo Sapiens lived in warmer regions, and survived a glacial period of that era, while the others did not. Other believe that Homo Sapiens out-competed the others for territory and food, and perhaps both theories are true. In any case, Homo Sapiens emerged with better genetics (and methods) with which to survive the cold. These may have included more robust immune systems, adaptations to altitude, better shelter (caves) and clothing (skins and furs). (Blakemore,2023), (Salopek,nd)
Agricultural Diseases (7,000 years ago): The Neolithic Period introduced agriculture, animal husbandry, and regional conquest (think ag-village pillaging men on horses here). This became a large pinch-point due to a) the introduction of genetic adaptations to elements of grain and milk (ie gluten and lactose), b) the sudden mingling of animal diseases (ie influenzas from birds, brucellosis, listeria, anthrax from cattle, salmonella, e coli from all of them), and c) The likelihood of being killed, your farm stolen, your wife raped, your children sold into slavery. Sadly, no sooner did people learn to feed large groups, than others learned to feed-off -people-that-fed-large-groups. It is theorized that this genocidal trend may have resulted in a kind of male-dominated “harem” society, with perhaps a 17:1 female to male ratio (called the “Neolithic Y-Chromosome Bottleneck”). The result was that almost all European males have a common male ancestor from this era, with a much more divergent female ancestry. Besides the startling realization that “great-grandpa may have been ‘Zlog the Impaler’”, there may have been a simultaneous adaption to ag and animal products (positive), with an enormous loss of genetic diversity (negative…possibly re-introducing some genetic abnormalities, like hemophilia). (Starr,2018)
Civic/Public Health Diseases (1,000–3,000 years ago): There are certain diseases associated with close human proximity (arising in cities, from things like polluted water sources and close human contact). Prior to the time of Christ, cities were relatively few and far between. But then agglomerations like the Greek, Roman and Han Dynasty Empires began to herd people into smaller areas. Famous “Plagues” were the Hittite Plague of 1330 BC (Tularemia), Plague of Athens, 430 BC (Typhus or Typhoid Fever), Northern Greece Plague of 412 BC (Influenza), Antonine Plague of 165 BC (Smallpox), Jian’an Plague of 217 AD (Typhoid Fever), Plague of Cyprian, 249 AD (Smallpox), and Plague of Justinian 541 AD (Bubonic Plague), for which there were massive fatalities. There was also the backdrop of human contact diseases such as leprosy and tuberculosis, which were less transmissible but deadly nevertheless. The evolutionary response to Bubonic Plague (and other infectious diseases) may have been a survival advantage to rural populations with better hygiene (and possibly religious communities).
Intercontinental Transfer Diseases (500 years ago): The Black Death (1346–51 AD) was caused by Bubonic Plague, and perhaps the most devastating pinch-point in modern history (killing 30–50% of all Europeans). The bacterium Yersinia pestis that was responsible was native to the Steppes, and thought to have been carried by flea-infected rats carried on ships. This was a time of increased contact between Europe and Asia (along with an increase in crowded cities), so an epidemic was waiting to happen. Several other bubonic plague outbreaks occurred in Europe (and elsewhere) in the next few hundred years, but public health (including better control of garbage and rats), and quarantine measures improved to minimize outbreaks. It is believed also that survivors may have had resistance to the disease related to the ERAP2 gene (learned from examining exhumed bodies of victims). There may also be people resistant to flea bites. As in the Civic diseases above, the Black Death forced a higher degree of hygiene upon cities, along with better quarantining and hospitalization. Like the recent Covid epidemic, diseases of this magnitude overwhelmed limited “hospitals” at the time (usually just a small portion of a local church or monastery). (Clunk,Chang,Beau,Elli,Varlik,et al,2022), (umaine.edu,nd)
Colonial Conquest and related Diseases (300–500 years ago): Certainly a pinch-point for indigenous populations, the epidemic of colonial conquest beginning in the 16th Century (by war and disease) had devastating effects. One scientific study estimates that 95% of Native Americans were killed by European infectious diseases (first Smallpox, then influenza, measles, and other agricultural diseases, for which Native Americans had few immunities). There is controversy, since Tuberculosis, Leptospirosis, syphilis, and salmonella (Cocoliztli) were known to have already been in the New World. It is possible that increased interactions triggered by Europeans (to previously isolated communities) helped transmit these diseases, but in any case there was a massive Native American die-off. This epidemic has even persisted into modern times, with Native Americans having less resistance to metabolic diseases (diabetes, heart disease, auto-immune disease, cancers, caused by the ag-heavy “Western Diet”). Evolutionary adaptations may have included dietary changes and intermarriage. (Ehrenpreis and Ehrenpreis,2022),(Browne,Lock,Walker,Egan,Backholer,et al,2020)
Alcoholic Diseases (300 years ago): Prior to 1700, most of the World had not been introduced to hard liquor (gin, whiskey, vodka, rum, brandy, tequila, flavored liquors), and only the Old World had known beer (the common people) and wine (mostly the wealthy and clergy). It is assumed that Old World people had developed some resistance to alcohol prior to hard liquor, since beer and wine had been used as a kind of grain/grape/water preservative and medicine since the advent of agriculture perhaps 7,000 years prior. Though the genetics of alcoholism may be complex, it is now known that two genes are involved in alcohol tolerance, ADH1B and ALDH2, with studies ongoing for GABRA2, CHRM2, KCNJ6, and AUTS2. Researchers acknowledge that environmental factors are also in play, but family history is known to be an alcoholism predictor. In any case, whereas wine and beer were previously used in moderation (either as part of a sensible diet or in short supply), hard liquor became a life-threatening and home-wrecking game-changer. When alcohol (mostly in the form of hard liquor) was introduced to indigenous populations (who had not developed any genetic resistance), it became a devastating epidemic. It is estimated that 12% of Native American deaths are alcohol related (3 times the occurrence in other populations). In addition to being directly life-threatening, hard liquor (and its successor, narcotics), is known to devastate family ties, leading to an additional “death by dereliction” epidemic. Survivors would appear to have evolved either the genetics of alcohol/drug resistance, or methods of coping without. (Edenberg,Foroud,2013),(NBC News,2008),(Vallee,2015)
Increased selection for urbanization, male nurturing and intelligence (50–100 years ago and ongoing): A massive modern phenomenon that may be developing another population funnel (almost without our knowledge), may be population decline due to global urbanization, with a subset of females choosing more intelligent and nurturing mates. Though at first glance one would point to the genocidal aspects of World Wars I and II, these events are relatively minor in terms of population decline. The shift from the robust, dominant rural male to the intelligent, nurturing urban male essentially reflects a large increase in female power and selection ability (related to the Red Queen Hypothesis). Since the world has grown “smaller” (many countries connected by flights of only a few hours), women have an unprecedented ability to “shop” for suitable males, often ones who can get the best jobs (now white collar, college-ed jobs) and help with domesticity, thereby freeing the female to become more versatile. This doesn’t mean that hunky athletic guys are not desirable, simply that they are more likely to become a) The philandering “first child” father, or b) A rather reluctant, hunky-nurturing male or c) All of the above. Another factor favoring the nurturing/less-procreating male is the invention of antibiotics and vaccines in the 1950s, giving weaker adolescents survival parity. In any case, population growth is plummeting in many parts of the world, especially in developed regions. (Martinez-Ruiz,Knell,2017)
Environmental Degradation (100 years in the future?): Unless we do some major adapting in the next 100 years, we may suffer severe population decline due to the environmental degradation of a) Climate and b) Habitat. Climate adaptations may involve a massive conversion to renewable energy, sustainable agriculture, relocations, and geoengineering. Habitat adaptations may include large habitat restorations, human population relocations, husbandry of threatened species, and wilderness set-asides. Humans may even evolve improved adaptations to heat and related diseases.
Organized Religion May have Conferred a Survival Advantage: Say what you will about the rise of “big church” in the last 3,000 years, but it may have given adherents a survival advantage in the areas of cleanliness, alcohol avoidance, rural living, family/community loyalty. Remember that the first hospitals grew out of church institutions.
Conclusions: Are you ready for the next great human die-off? Relax! In the long-run its good for us! A new adage for all this may be a kind of warped Nietzscheism, “That which doesn’t eradicate your species makes you stronger”! The modern human can thank their ancestors for adaptations to cold, fire, animal furs, Big Macs, alcohol, diseases, and happier females (Woo-hoo! PARTY!!!), but the eerie hangover might be…what is the next thing waiting for us, and will we adapt?
