Humanity’s First Epochal Event(s?): Growing our Brains and Controlling Fire – Part 2.
A plausible series of events, where fire came first and Acheulean industry second, is that the Homo erecti that migrated to East and Southeast Asia did not have Acheulean tools, but the primitive Oldowan toolset, and the most remote ones never used Acheulean tools. I consider it quite possible that early Homo erecti migrated from Africa (and maybe even an earlier protohuman, if the “hobbits” were descended from habilines or australopiths) wielding fire. Cooking came with it, and hundreds of thousands of years later, those Homo erecti that stayed home in cosmopolitan Africa invented a new level of technology, Acheulean tools, and that culture never made it to the far hinterland of East Asia. Some have speculated that those East Asian erecti used bamboo more than stone, which would not be preserved for study today, or that as they moved east, they collectively forgot how to make Acheulean tools. I think that the likelier explanation is that they never had Acheulean tools, meaning that they migrated before they were invented, but they brought fire with them, which was the essential technology.
The Homo erecti that arrived in East Asia and the islands off of Southeast Asia existed, with virtually no changes evident in their anatomy or technology, for more than 1.5 million years, to only disappear about when Homo sapiens arrived. Similar to tarsiers finding refuge in the islands off of Southeast Asia, those Homo erecti at the far end of the “known” world seem to have lived like country bumpkins for well over a million years without any outside disturbances or benefits from their cosmopolitan homeland. The foregoing is largely my speculation on the issue, which could collapse like a house of cards with the Next Great Finding, but I doubt it is far from the mark.
Growing the human brain was about more than energy. There is speculation that meat protein helped human evolutionary brain development, and there is also evidence that oils help, and there are surely nutritional requirements besides calories, but calories comprise the vast majority of nutrition. About 80% of what is called human nutrition consists of calories. If animals can get enough energy, the other dietary constraints are usually minor issues.
Apes make poor carnivores and are all adapted for eating fruit as their staple, and fruit is the ideal human food. The dietary shift to meat, likely out of necessity, came with a price. If humans get more than half of their calories from protein, they will die from protein poisoning. Chimpanzees get about ten percent of their calories from protein today, which is about the same level that humans seem to need.
Also, the rise of the human brain was not only about size, even if the human brain turns out to “only” be a linearly-scaled primate brain. The human cerebral cortex is four times the size of a chimp’s, and the cerebral cortex is considered to be where all higher human brain functions originate. For all the influences of using hands, tools, cooking, and the like, they largely only laid the foundation for the cerebral cortex to grow. At this stage, the mystic might say that the growing cerebral cortex allowed for the human brain to host a more sophisticated consciousness, which originates in other dimensions, which is a question largely unanswerable by today’s mainstream science, although Black Science probably has some pretty good ideas about the answers. As with mainstream scientists, I will not attempt to address that question, at least in this part of the essay. In the final analysis, the cerebral cortex’s growth is what made humans radically different from any other land animal in Earth’s history. Cetaceans may have similar levels of brain functioning, perhaps even greater, but they cannot manipulate their environments like humans can, and they cannot make fires. Humans are significantly juvenilized when compared to chimps, for instance, where humans retained traits of chimp infants. An infant chimps’ flat face appears far closer to a human’s than an adult chimp’s does. That juvenilization is partly why humans are far weaker, physically, than other great apes. As the human line increasingly relied on its brain, it lost even more of its brawn.
In summary, becoming bipedal had great portent for evolving protohumans, and the suspicion is very strong among scientists that it led to feedback loops where tool use became advanced, which allowed for a richer diet, which helped lead to larger and more complex brains, which led to more advanced thinking and behaviors, which led to more advanced tools, which led to more acquired energy, better protection, and larger brains, and so it went. But the control of fire was the watershed event. While better tools improved the viability of early humans, nothing on Earth could challenge fire-wielding humans. With the control of fire, humans never had to worry again about being preyed on, not as a threat to species viability, except by other humans. Fire was eventually used for offense instead of only defense, of course.
Until now, I have used the word “epoch” in this essay as geologists do, to denote timeframes smaller than periods. But in describing the rise of humanity, I use “epochal” to mean gigantic events, where the human condition before and after the events became so radically different that the two times were like different geological epochs, when the radical changes following the events are considered. I consider making stone tools, growing the protohuman brain, and the control of fire to be the human journey’s first epochal events. In fact, those events led to human existence. They were all likely related, and probably tightly related, and with the current uncertainty I have made them all aspects of the same event. They could arguably be split, but the energy advantages of stone tools and fire surely contributed to the expanding human brain, and the expanding human brain led to those inventions and more, in mutually-reinforcing feedback loops. Again, scientists are only certain that two things exist: energy and consciousness. Those interacted to produce humanity’s first epochal event(s).
Stone tools and the control of fire had energy consequences to the human line far above all other effects. Whether they happened within a few hundred thousand years of each other, or were separated by more than a million years, they were the key technical/cultural/social events in early humanity’s ability to survive on Earth and expand its range to eventually cover the planet.
If habilines began to control fire two mya, one thing is certain: the australopithecine Tesla who banged the first rocks together that fashioned a stone tool, and who was able to continue doing it and eventually taught others, probably via active demonstration or their observation, could not have imagined that his/her invention would lead to a relatively giant descendant (or cousin of a descendant) that slept on the ground, controlled fire, and would quickly migrate to the ends of Earth, traversing distances that were incomprehensible in australo-Tesla’s time. That relatively quick series of innovations, never before seen on Earth, gave birth to a creature that would have simply been unrecognizable to that australopithecine Tesla, some kind of magical creature. There have only been a few subsequent epochal events in the human journey, and like the first one(s), they were all energy events above all else, and were all dependent on humans gaining the social organization and technological prowess that enabled them to exploit a new energy source. And each time, the human reality after the epochal event was unimaginable to the humans who lived immediately before it. Also, the events and their aftermaths became far more dramatic each time, in shrinking the event’s timeframe and the time to the next epochal event, and the increase in energy levels used.
Did the control of fire lead to Homo erectus, as Wrangham thinks? Or did Homo erectus merely use it to begin dominating the world? Was cooking the seminal event in the appearance of humans? Those questions may not be definitively answered in my lifetime, and led to the somewhat uncertain title of this chapter. Highly transformative developments coincided with the appearance and dispersal of Homo erectus, which was a dramatic break from all that came before - biologically, technically, and culturally - which strongly implies great cognitive enhancements. I believe that the control of fire and cooking would leave deep cultural and biological impacts on the human journey, and that Homo erectus barely changed during its nearly two-million year tenure on Earth, both in biology and in Acheulean artifacts, leads me to favor Wrangham’s hypothesis, at least until the Next Big Finding. Just as Einstein said that every theory is killed by a fact and that his theories would one day become obsolete, but that their best parts would survive in the new theories, I believe that significant aspects of Wrangham’s hypothesis will live on in successor hypotheses. I am already seeing other researchers follow Wrangham’s lead, and I will follow that situation with great interest.
From the initial appearance of Homo erectus about 2.0-1.9 mya, Europe was periodically buried under the ice sheets that began growing and receding when the first stone tools were made, so Homo erectus tended to appear and disappear in Europe. The fact that humans evolved and spread during an ice age has led to competing hypotheses about many aspects of humanity’s rise. While the ice age began about 2.6-2.5 mya, and there have been seventeen identified episodes of advancing and retreating ice sheets, particularly in North America and northern Eurasia, the early ones were not as severe, and they did not achieve clockwork-like regularity until the past million years. But even though they were “regular” on the geologic time scale, driven by Milankovitch cycles, there would have been nothing “regular” about them to evolving humans. When ice sheets advanced, global climate became cooler and dryer; rainforests shrank and deserts grew. Human adaptations to those changes, which could even be discerned in one human lifetime, must have had profound impacts on the human journey. Works such as William Calvin’s A Brain for All Seasons explore such issues. In short, humans had to readily adapt to rapidly changing conditions, and rapid adaptation would have had selective effects on burgeoning human intelligence and problem-solving ability; those that could adapt, survived.
Although our species, Homo sapiens (named Homo sapiens sapiens if we consider that Neanderthals and an early human are subspecies of Homo sapiens, but I will use Homo sapiens in this essay to denote today’s humans), is the only survivor of the past several million years of human-line evolution, many of our cousins and ancestors were recognizably human. When did language begin. When did speech begin? They certainly predated the appearance of Homo sapiens. All great apes have readily learned sign language, and even when monkeys chatter, the same parts of their brains that control human language are used, and there is plenty of evidence that great ape vocalizations can denote objects and other ideas. The communicative abilities of crows can be hard to believe. Becoming bipedal created those neck/skull changes that began to form the structures need for human speech. If fossils are sufficiently preserved, important anatomical features can provide key evidence for human abilities and behaviors. Turkana Boy, for instance, had his inner ear, which is responsible for balance, preserved well enough so that it provided more evidence that he did not spend time in trees (it is larger in primates that regularly climb). Similarly the outer and middle ear of Homo heidelbergensis, which succeeded Homo erectus, apparently enabled keener hearing that its predecessors, which may have reflected the beginnings of spoken language. There is strong evidence that Neanderthals were capable of using spoken language. As with many other human traits, the potential for language seems to have existed with monkeys (even in dinosaurs), and just kept developing more sophistication over the millions of years, with structural and cognitive changes interacting, as human language developed into today’s version.
While many traits that led to human dominance of Earth can be discerned in our distant ancestors, a pile of baggage also came with the deal. All great ape societies but bonobos are male dominated, and the most marginal macaque will quickly become patriotic cannon fodder when his society is attacked. The traits almost always arose from economic costs and benefits, which were always rooted in energy. How bonobos, also called pygmy chimpanzees, became the only great ape species that is not male-dominated is primarily an economic tale.
The bonobos’ scientific name is Pan paniscus, and they live in the range in red in this image, and the other colors represent ranges of other chimp species. Bonobos are separated from all other chimp species by the Congo River, which forms the north, east, and west borders of the bonobos’ range. When the current ice age began 2.6-2.5 mya, the current bonobo range had a huge drought and the rainforest temporarily disappeared south of the Congo. Gorillas are masters of the rainforest, and when the rainforest south of the Congo first disappeared, gorillas left and never came back. Humans are the only great apes that can swim, so the Congo was an impenetrable barrier for chimps and gorillas.
Chimpanzee social organization has male and female hierarchies, with societies of up to 120 members. Fruit trees form the center of a chimp band’s territory, where females forage with their offspring, and the males form foraging parties that patrol the territorial perimeter. Chimps have foraging parties of less than ten members, with numbers ranging between two and nine, and the party size fluctuates rapidly. That is because chimps have to walk kilometers between food sources each day, largely fruit trees, and the varying harvests cannot reliably support larger groups. In general, the larger a territory, the faster that chimps breed, as they have more available energy.
Bonobos have an average partly size of about 17, and party sizes are consistent. How can they have such large and stable foraging parties while no other chimps can? In short, they eat gorilla food. Because gorillas no longer live south of the Congo, the young leaves and herb stems not available to chimps where gorillas live make for nice bonobo snacks as they travel. Since the biomass concentration of gorillas and chimps is nearly the same where their ranges overlap, it meant that bonobos had twice the food supply that chimps did. Bonobos also evolved to better eat gorilla foods, and larger parties put females on a more equal footing with males. Bonobos, both males and females, did not tolerate the alpha male model of other chimp societies, where they dominated everybody.
One chimpanzee and gorilla behavior that can be difficult to comprehend, mentally and emotionally, is male murder of infants. If a chimp or gorilla encounters an infant that he knows he did not sire, he will kill it if he can. Gorillas have a potentate-harem social organization, and when a male matures he is usually ejected from that gorilla society, but might become subordinate to the silverback patriarch (some troupes have more than one dominant silverback, and even up to seven silverbacks in one troupe has been observed). Unsatisfied male gorillas can try to unseat a silverback to steal his harem, and if successful, the new potentate will kill all the infants he can. The average female gorilla will lose an infant to murder by a male in her lifetime. In chimp society, when a female is sexually receptive she will mate with all males in the troupe, especially the dominant ones, so every important male thinks that the child might be his, and thus will not kill it. That strategy has been nicknamed, “Who’s Your Daddy?” If a silverback dies, either from natural causes or murder by rivals, or chimps murder the males of a rival band, the infants of the dead males will all be killed. And the next activity tends to boggle people’s minds: the females who lost their infants will then mate with the killers. That behavior is not confined to great apes: lions and bears also do it. While humans cannot not imagine a woman subsequently mating with her child’s killer, it is standard behavior in those species and provides agonizing evidence of the Selfish Gene Hypothesis. A male chimp or gorilla will not invest time and energy in raising offspring that are not his. Killing them makes the female come into season, and she has a primordial desire to produce offspring. Female chimps and gorillas need protection from other males, and a male strong enough to kill her mate gets the spoils, including her, and she will then mate with the killer and bear his young, and can stay mated for life. Female chimps will kill each other’s infants sometimes, as they play their own dominance games, but mating with the killers of their offspring boggles human minds and makes Darwin’s “war of nature” observations difficult to deny. Male orangutans will not kill infants that they did not sire, but orangutan females are constantly under threat of being raped by non-dominant males (called unflanged).
But bonobos are the only non-human African great ape exception to infanticide, and are also the only great ape species that does not sexually coerce females, humans included. The reason seems to be the social organization that arose from a plentiful food supply that allowed for larger groups where females were no longer vulnerable to male violence. Many behaviors within and between bonobo bands are unknown with chimps. A male bonobo will remain with his mother for his entire life, and male bonobos do not vie for dominance. Instead, bonobos have a sexuality that no other animal on Earth has remotely achieved. They settle nearly everything with sex. Female on female is common, particularly when bands meet, but anything goes in bonobo society, with the sole exception of mothers and sons, as the aversion to inbreeding is baked very deeply in animals, and it is also responsible for the human incest taboo. Bonobo societies are peaceful and seem to live by the slogan, “Make love, not war.” But it started with their economy, when their primary and dominant competitor moved away. In recent studies, the only bonobo sexual coercion observed is females coercing males, which is also rare. A likely influence on ending infanticide is that female bonobos, like humans, conceal their ovulation, so males are not going to suddenly compete to be the father. And since virtually all bonobos have sex all the time, there is no way for bonobos to determine paternity.
Humans took a different path 2.5 mya. There are generally two schools of thought regarding the appearance of Homo sapiens among scientists: one is called the Multiregional Model, and the other is called the “Out of Africa” Model. In their essence, the Multiregional Model had those Homo erectus migrants eventually evolving into today’s races, and the “Out of Africa” Model had humans evolve in Africa and then migrate across the world, replacing/displacing all other members of the Homo genus. The rise of molecular biology and DNA testing has largely resolved the issue in favor of the “Out of Africa” Model. There is also a variety of intermediate views and variations of each hypothesis, generally relating to the invaders mating with the natives, even if they could be classified as separate species. For instance, Neanderthal DNA is part of the human genome, which reflects interbreeding. Since Neanderthals were largely confined to Europe and what became the Fertile Crescent, and the migration of the original Homo sapiens was from Africa, sub-Saharan Africans possess less Neanderthal DNA than any other humans. Africans also have the most genetic divergence, reflecting the idea that humans have lived longer in African than anywhere else. There is virtually no doubt that the first Homo sapiens evolved in Africa.
While Acheulean hand axes are rather beautiful, anthropologist have lamented the “boring million years” that existed after Acheulean culture first appeared about 1.7 mya. It seems that not much was going on, anatomically or technologically, with the human line, from the first appearance of Acheulean culture to about a half million years ago. There is evidence of Acheulean culture spreading in waves across Asia, never quite reaching those in East Asia in what became their refugia, but Acheulean tools were even made by a likely Homo sapiens subspecies less than 200 kya. The Acheulean hand axe is the longest-lived technology in the human journey.
The nexus of Europe, Asia, and Africa has been the site of great migrations, conflicts, extinctions, innovations, and the like, all the way to today, beginning when Asian mammals likely drove half of European mammals to extinction 34 mya, to the invasion of Africa by Asian mammals 18 mya, to the ferment of Miocene apes in and around Africa as they migrated outward then back home, between 16.5 mya and nine mya. The “friction” between collisions of animal assemblages and human cultures, as well as the geographic and climactic variation in that nexus region, not only gave rise to humanity, but human civilization also first appeared in the region and is at the heart of the world’s attention and woes today. As mentioned previously, advancing and retreating ice sheets made Europe a difficult place for the human line to colonize, and they sporadically appeared and disappeared for more than a million years, clear up until this current interglacial period called the Holocene. But Homo erectus began appearing in Southern Europe about 1.5 mya. There were three basic routes to Europe. The easiest would have been largely overland, crossing today’s Turkey to get into Southern Europe around today’s Greece. The other two routes had to cross the Mediterranean Sea, one across Sicily to today’s Italy, and the other across the Strait of Gibraltar to today’s Spain. Sites have been discovered that show early humans using all three routes. In the mountains of Spain is the earliest evidence of the human line in Europe, dating as far back as 1.2 mya. The remains in that cave also show the first signs of human cannibalism. Those cannibals are also thought to be part of the human line, evolved from erectus and called Homo antecessor today. Today, anthropologists are pretty sure that Homo antecessor was a human ancestor and gave rise to Homo heidelbergensis, at least as sure as any of the early human ancestral relationships are. Chimps have also engaged in cannibalism, so this may be another very old primate behavior. With the recent advances in human DNA studies, the human genome provides evidence that all early human societies engaged in cannibalism, possibly as a ritual of eating rivals vanquished by violence.
Homo heidelbergensis fossils and artefacts are prevalent in Africa, Europe, and West Asia, and they may have lived from 1.3 mya to 200 kya, for another long-lived species. They may have been the first humans to bury their dead. In his human-line narrative, it is evident that species times overlap, where one ancestral species coexisted with its probable descendant for hundreds of thousands of years. From the perspective of evolutionary theory, there is nothing unusual about it. From a review of how speciation is thought to happen, it is apparent that genetically-isolated populations can adapt to new environments and eventually become new species, while ancestral and sibling species can continue thriving, just as parents rarely die upon producing offspring. The tree of life on Earth has many branches, and while all branches will eventually end, new twigs from the same branch can grow while the original branch continues growing. Stephen Jay Gould suggested that a transition to a new species averages about 15-20 thousand years. And that is under the “natural” effects of geography, climate, and animals trying to survive. But the human line has changed all that. While animals make nests, burrows, and other structures that enhance their ability to survive, humans began making radically-different environments that are called “artificial” today, and the first artificial environments were campfires surrounded by Homo erecti or close relatives trying to stay safe, warm, and well-fed. When the human line invented fire, they not only created the first dramatically artificial environments, they no longer lived in “harmony” with nature. They could not only use fire to help conquer the world, they also introduced “artificial” variables into human evolution, and the first may well have been the transition to being ground-dwelling and the changes that derived from eating cooked food. Humans introduced radically-new variables to evolution never seen before on Earth.
Over the years, I have become familiar with what is called Creation science, ET interventionist ideas, and other arguments that not only make the case that humans are highly unique, but that human evolution was so different than what came before it that it must have reflected God’s hand or ET intervention. What they fail to take into account, in my opinion, is the rapid evolution of humans that humans are responsible for, in ways that this essay will explore later. While there may be some accuracy in their perspectives, their explanations are not needed to explain how humanity has evolved.
Humans are unique in many ways, although a healthy behavior amongst scientists is stating that humanity is “just another species.” There is even an acronym used in scientific circles to emphasize our mundane status, which is no better or worse than any other organism. Humans are different, but using it to justify our status bestride Earth is egocentric, and the humility of “just another species” scientists is very needed in our world today.
During that boring million years, Homo erectus changed from hunted into hunter. They did not dominate their biomes, but they were also likely respected by local predators, and feared by what they could hunt with their primitive weapons. At what stage big cats and other megafauna in Africa learned to avoid Homo erectus and its descendants is not clear, but it likely happened, and is thought by most scientists today to be why Africa retained its megafauna, and to a lesser extent Eurasia, when the other continents quickly lost them soon after humans appeared, which is a subject for the next chapter. But an early indicator of what likely happened, repeatedly, in the coming rise and dominance of humanity, is when Homo erectus first made it to Flores Island about 900 kya (scientists have found tools but no human fossils), perhaps by rafting: a pygmy elephant, a giant tortoise, and a giant lizard all quickly went extinct. Today, it looks like once the invaders made it to Flores Island they stayed and either eventually forgot how to get off or came to the island by an “accidental” migration as so many other species have hopped the continents. Those invaders eventually became island-dwarfed and lived on Flores for the nearly the next million years, and went extinct soon after Homo sapiens arrived.
The closer we get to humanity, the less our ancestry is doubted among scientists, and there is virtual certainty that Homo heidelbergensis is humanity’s direct ancestor. Its brain was nearly the size of modern humans, and they inherited Acheulean tools from their ancestors and used them for hundreds of thousands of years. But there is evidence that somewhere around 500 kya that began to change; there is evidence of heidelbergensis using stone-tipped spears that long ago in today’s South Africa. Wooden throwing spears were recently discovered in today’s Germany, along with butchered horses, dated to about 400 kya. Scientists today are very confident that Homo heidelbergensis is also the direct ancestor of Homo neanderthalensis, with the split beginning around 500 kya. The range of Homo heidelbergensis was Africa, West Asia, and Europe, but the advancing and retreating ice sheets of Eurasia, Europe in particular, kept driving Homo heidelbergensis southward, and during one of the retreats, it seems like the ancestors of Neanderthals stayed. Neanderthals became a cold-adapted species that specialized in hunting the animals of the cold lands near the ice sheets. As the evidence shows scientists today, life was a brutal proposition in humanity’s early days, and it was particularly brutal for Neanderthals. They probably could not throw very well and relied on ambush predation. Scientists have studied the bones of Neanderthals and compared their injuries to those of rodeo riders, but a recent study cast some doubt on that, partly in light of recent evidence that Neanderthals may have also developed wooden throwing spears. But whether Neanderthals had to stab their prey in close quarters or eventually learned to throw weapons at them, the studies of early human bones describe a very harsh existence, with broken bones regular events, and that is for survivors of the traumas.
Neanderthals invented more sophisticated stone tools about 300 kya, for the first major advance in more than a million years, and their toolset is called Mousterian, or Mode 3. Neanderthals had the largest brains ever measured in the human line, and they seem to have also invented the practice of burying the dead and placing grave goods with them, but they may have inherited burial practices from their Homo heidelbergensis ancestors. As with their ancestors, they cooked and ate vegetables. As with their ancestors, they carved flesh from their corpses, in either the practice of cannibalism or a funerary practice. Neanderthals seem to be a regional variation of humans, adapted to the environments near the ice sheets, and the fact that they interbred with Homo sapiens has caused some scientists to classify them as Homo sapiens neanderthalensis. If they did not become a truly separate species, they were slowly speciating as they adapted to their ice age environment. Neanderthals built shelters, may have drawn cave paintings, and engaged in plenty of activities that put them on par with humans of the time. There seems to be little reason for calling them “primitive” when comparing them to Homo sapiens. The last Neanderthals died out about 30 kya, about the same time that Cro-Magnon humans arrived in the region.
To revisit the Neanderthal split from Homo heidelbergensis about 500 kya, that Homo heidelbergensis line stayed in West Asia and Africa. With evidence of stone-tipped spears being made 500 kya, some scientists place the beginning of the Middle Stone Age at about 500 kya. Stone tools have been dated using a relatively new tool called thermoluminescence dating, which works for stone tools that were heated by fires. For dating artifacts before the appearance of behaviorally modern humans about 50 kya, carbon-14 dating will not work, but other tests have been used quite successfully. Neanderthals came to dominate Europe and today’s Middle East, and while the home of Homo heidelbergensis was Africa, it ranged into Europe and West Asia. Whether Homo heidelbergensis existed for only about a half million years or a million is controversial today, but what is not very controversial is that it is the direct ancestor of Neanderthals and Homo sapiens, with the first members of our species appearing in Africa about 200 kya, and there is evidence that other descendants of Homo heidelbergensis may have existed, with a possible descendant discovered in Siberia. As with the discovery of the “hobbits” of Flores Island, it will not be surprising if scientists find a few more “splinter” species that branched off and died out about the time that behaviorally-modern humans appeared and spread across Africa and Eurasia.
When Homo sapiens first appeared about 200 kya, about the same time that Homo heidelbergensis disappeared from the fossil record, it was in Africa, East Africa in particular. That possible human subspecies or intermediate species between Homo heidelbergensis and Homo sapiens lived in today’s Ethiopia about 160 kya, and there is evidence of Homo sapiens in today’s Morocco about 160 kya. From proconsul to Ardi, Lucy, Turkana Boy, and Homo sapiens, East Africa, particularly around Lake Victoria and the Horn of Africa, was the place to evolve.
The advancing and retreating ice sheets likely had major impacts on events in those times. Milankovitch cycles have 26,000, 41,000, and 100,000-year oscillations, among others, related to Earth’s orientation to the Sun, and the 100,000 year effect is the weakest, but for reasons still rather obscure, it has been the tipping point for the advancing and retreating ice sheets of the past million years. The pattern for the past million years has been creeping glaciation that oscillates, with the glaciations reaching their maximum before they rapidly retreat and Earth has a warm respite that lasts for 10-20 thousand years, before the ice sheets begin to grow again, with another 100,000 years before the next interglacial period. The most extreme glaciation during the current ice age happened between 475 kya and 425 kya. Neanderthals seem to have become permanently separated from their Homo heidelbergensis kin with the growth of ice sheets about 300 kya, and between 250 and 200 kya there were two glacial events that finally ended about 200 kya, which roughly coincided with the final exit of Homo heidelbergensis and the appearance of either Homo sapiens or that possible transitional species. The previous interglacial period began 130 kya and ended 114 kya, and it appears that Homo sapiens left Africa for the first time about then, with evidence found in a cave in today’s Israel. When ice sheets advanced, the Neanderthals retreated southward, and one controversial area is the overlap of Neanderthals and Homo sapiens in Israel during the last glacial period. Did Neanderthals wipe out those first Homo sapiens migrants from Africa? Did they interbreed?
Whatever the case may be, it appears clear that the human population in Africa and Neanderthal population in Europe and the Middle East was isolated for tens of thousands of years, perhaps well more than 100,000 years, and humans used a toolkit similar to the Neanderthals’ until something happened between 70 and 50 kya. Just what happened is a matter of great controversy, and in recent years, several disciplines have converged on the issue and is drawing a pretty clear picture today. Some key areas shedding light have been global DNA studies, linguistics partnering with evolutionary theory, and brain studies. Nicolas Wade’s Before the Dawn, published in 2006, has surveyed the new findings and syntheses between those disciplines, among others. In the past generation, as DNA sequencing has been applied to many areas, a startling picture of the human journey has emerged. As discussed previously, mitochondria retained some of their DNA, probably for flexible power generation. For animals that reproduce sexually, the mother’s mitochondria are passed to her offspring, while virtually none comes from the father, if any. Geneticists can measure mutations in mitochondrial DNA and approximate when two different animals shared a common ancestor, whether they belong to the same species or not. Similarly, with nuclear DNA, the Y chromosome produces a male mammal, and mutations in the Y chromosome can also be analyzed by geneticists and can also estimate when two men shared the same ancestor. As discussed previously, putting absolute dates on DNA results has been problematic, but scientists have been working hard at aligning DNA results with fossil dates, which are considered far more reliable, and they have been resolving some of the limitations. But if the timing can be suspect with such analyses, there is far more confidence that descent relationships are valid. Human DNA testing is a burgeoning business, used for everything from freeing prisoners falsely convicted to determining paternity to examining the genetic heritage of the sitting U.S. president’s wife.
The picture emerging from global DNA testing is that all humans on Earth today are descended from a founder population that lived in East Africa, again near the Horn of Africa, around 50 kya. Geneticists think that the founder population may have only been about 5,000 people, and of that population, a few hundred humans at most left Africa about 50 kya, and they conquered the world. If any people ever lived up to Genesis’s instructions to subdue Earth, it would have been them. It may have been because they were the first primates to master language.
Re: WADE FRAZIER : A Healed Planet
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