This is taken from my book The Emergence and Nature of Human History, Volume One. The section of the book from which this is taken is a chronology of the emergence of consciousness. The chronology employs Carl Sagan's device of condensing the Universe's age down to one year, with the Big Bang occurring on 1 January. The section also measures time through the use of an imaginary timeline one million meters in length. In this scale of time, all of the events here began about 2 and one-half minutes ago and within 4 meters of the end of the line.
The chapter is very lengthy, so I will publish Part Two in the middle of tomorrow night.
I had always wondered how modern humans came to populate the surface of the Earth. This is what I found out
THE DIASPORA OF MODERN CONSCIOUSNESS: HOMO SAPIENS SPREADS THROUGHOUT THE WORLD
FROM ABOUT 11:57:30 PM, 31 DECEMBER; ABOUT 999,996 METERS UP THE LINE
Many of the last remnants of sapiens passed hundreds of centuries in their southern African redoubt before some of their members began venturing northward. Other small groups of sapiens huddled together in eastern Africa. The brave ones that began pushing into the unknown world to the north were beginning a journey that continues to this very day. They had embarked, unknowingly, on the settlement of the Earth’s landmasses, and what they experienced, what they suffered, what they learned, and what they created during that epic adventure spread human consciousness to every corner of the planet. They were the product of an astonishing sequence of emergences, although these events were unknown to them, and they carried within themselves the physical heritage of the Universe itself, although that extraordinary reality was concealed by their ordinary lives. They saw the world with the same eyes we do. They confronted its challenges with the same kind of minds we possess. We are their inheritors, living in a kind of world they could not possibly have anticipated, and experiencing lives the contours of which they could never have imagined. But it was they who laid the foundations of that world, and it was they who made those lives possible.
Models of Human Evolution
Three major schools of thought concerning the evolution of modern humans and their radiation across the planet’s surface have emerged within the scientific community. They are:
The Replacement Model, which argues that African Homo sapiens, the earliest examples of which, as we saw, appeared about 200,000 years ago, replaced the various regional populations of early humans such as the Neanderthals. Also known as The Recent Out of Africa Model, this is the dominant (but not universally accepted) hypothesis in paleoanthropology.
The Regional (or Multi-Regional)Continuity Model, which contends that modern humans evolved independently out of erectus in various areas, maintaining gene flow across the eastern hemisphere sufficient to prevent extensive speciation.
The Assimilation Model, which argues that the human line can be traced to Africa but various human types sometimes interbred with each other, creating in a sense a human hybrid. This model is a kind of synthesis of the first two.
Genetic Evidence of the African Origin of Modern Humans
Attempts to construct a chronology of the settlement of the world by modern humans rest on two bases. The first of these is genetic evidence, based on such factors as an analysis of mitochondrial DNA (mtDNA) sequences in various populations. (MtDNA is passed down solely through females; ova contain great numbers of mitochondria, sperm practically none.) The longer humans have occupied a region, the more time there has been for the mtDNA of various human populations to diversify. Research has found that mtDNA sequences show the greatest level of diversification in Africa, which means that modern humans must have evolved there first, making Africans the oldest anatomically modern human population in the world.1 Other research supports this conclusion. Analysis of Y chromosome DNA, heritable only through males, (see below) places the population ancestral to modern humans in Africa around 200,000 years ago. It would also appear that modern European and Asian groups are strongly linked to Ethiopian populations that may have expanded out of Africa beginning 60,000 years ago.2
One of the main groups of modern humans that migrated out of Africa, around 60,000 years ago, was probably a subgroup of a larger population. It appears that there was a serious bottleneck, i.e., a reduction in the breeding population, within this subgroup. Estimates of this migratory group’s population range from about 1,800 females (with an unspecified but presumably similar-sized group of males) to a group containing about 3,000 individuals in total, to another estimate of about 4,500.3 Why do bottlenecks matter? Because they restrict the size of the gene pool. One researcher points out, however, that there could have been several small subpopulations scattered throughout Africa from which migrants emerged, which would have produced the same genetic effect. He also notes the evidence supporting the hypothesis that this migratory group was a minority of the African population that existed 80,000-50,000 ybp.4
But whether one believes that successful out-of-Africa migratory groups were drawn from a single African population or several smaller ones, the genetic evidence is compelling: the level of heterozygosity—the extent to which different alleles of genes exist in a given population—declines in humans as a factor of distance from Africa. Genetic drift in the small human populations that established themselves in various regions outside of Africa probably acted to reduce their genetic diversity.5 Just as tellingly, studies of phenotypic variability give us powerful evidence as well. A massive study of human skull-types from around the world shows a decrease in physical variability as populations become more distant from east Africa. Plotted on maps, it correlates with the decline in genetic variability to a degree that is almost startling. The study also places the zone of human origin in an area ranging from southern to eastern Africa, with some minor boundary variations depending on whether we are considering the genetic or the phenotypic evidence.6 Of course, there can be local subpopulations that exhibit more heterozygosity than the larger population of which they are a part, and research on DNA microsatellites—repeating sequences of nucleotides of varying lengths—reveals this. Yet such research also indicates that in general the length of microsatellites varies according to distance from Africa in a predictable way.7
There are those who have contended that erectus populations in China interbred with later versions of humans, creating a hybrid, and laying the foundations of the Chinese people. But the research of Professor Li Jin and his colleagues leads to a different conclusion. These researchers conducted a major genetic study that encompassed 28 distinct populations, of various ethnicities, within China and Taiwan. While the researchers say that it is possible that modern humans evolved independently in China, there is no genetic evidence whatsoever to demonstrate this. East Asians are ultimately of African origin. Southern Chinese people may be the direct descendants of African sapiens populations which migrated to southeast Asia. Northern Chinese individuals may be descended from Altaic populations which in turn had a southeast Asian origin.8
So, the genetic evidence strongly indicates an African origin of the modern human species, or Anatomically Modern Humans (AMH) as paleoanthropologists call us. Can we be even more specific about the identity of our ancestors? In trying to answer this question, we begin by noting that the great advantage of using mtDNA and Y chromosomal DNA to analyze our ancestry is that these are the only two parts of the human genome that do not get shuffled by recombination during the reproductive process. These two pieces of genetic uniqueness have been used by scientists to analyze the population directly ancestral to AMH.9 What do they reveal?
In tracing the descent of modern humans, many researchers will refer to a prehistoric woman who is thought to have lived in Africa at the dawn of Homo sapiens, and who apparently has a genetic relationship to every member of the human community. The mtDNA of everyone alive today has been traced to her. This woman has been dubbed “Mitochondrial Eve”. Some even say (erroneously) that this woman is the “Mother” of modern humanity. This is a fundamental misunderstanding. Former Harvard immunology instructor John Kimball explains:
Computer analysis produced many possible family trees by which the present-day [mtDNA] sequences could be derived ultimately from a single ancestral sequence. Because of the maternal inheritance of mtDNA, this work was interpreted as showing that all present mtDNA is derived from a single ancestral mtDNA belonging to a woman who lived in Africa some 200,000 years ago. She was nicknamed "Mitochondrial Eve", the mother of us all…Some of the implications from these data are more dramatic than is justified. One woman living 200,000 years ago was not the mother of us all. She may well have existed, but was only one member of a population living then.
[It should be noted here that some researchers think Mitochondrial Eve existed about 150,000 years ago, while others think 190,000 ybp is more probable.]
Kimball explains why “Eve” is not the mother of us all by use of an example from modern history. Porphyria is a group of genetically-inherited disorders that affect either the skin or the nervous system. Kimball explains that the gene for porphyria in the South African population today is traceable to two Dutch settlers who arrived in southern Africa in the 1680s. But this doesn’t mean that these two people alone are the founders of the group of South African porphyria sufferers. Each of these porphyria sufferers could trace his or her genetic problems to a number of different couples that lived in the late 17th century. The survival of the genes inherited from one couple was a chance event. The implications for the “Eve” question are clear:
Because of the restricted maternal inheritance of mtDNA, every time a couple descended from the population to which Eve belonged failed to have any daughters, another line of mtDNA would have died out. By chance alone, Eve's mtDNA eventually was the only one left. This outcome is similar to the operation of genetic drift in neutral alleles of nuclear genes: in due course a given allele reaches a gene frequency of 100% or disappears entirely.10 [Emphasis in the original.]In short, the mtDNA present in modern humans could, if things had gone differently, have come from someone else in Eve’s group. It did not necessarily have to come from Eve herself. Tracing this mtDNA helps confirm that the modern human line did indeed originate in Africa around 200,000 years ago, not that we are all descended from one woman. It is also worth noting that Eve is related to all of us in this trait alone. She was not the founder of the whole AMH genome. (See below.) Most DNA is found in the nucleus, not the mitochondria.
Y Chromosomal Adam
There seems to be evidence that all modern men can trace their descent to a single male, but one that lived many tens of thousands of years after the women of Eve’s group. The evidence comes from Y chromosomal DNA. The Y chromosome consists of a much longer sequence of nucleotides than mtDNA, about 50 million compared to about 16,000, yet it is a highly traceable genetic marker. Its key genes are not, as we have noted, subject to recombination, and hence are passed on intact. Populations of living males throughout the world have been studied and compared to help us analyze the origins of the Y chromosome. Spencer Wells, a geneticist who has researched human origins very extensively, explains that the polymorphisms (variations in certain nucleotide sequences from population to population) along the Y chromosome can be traced across time in a manner similar to that in which mtDNA is traced. The study of the polymorphisms in Y chromosomal DNA tells us that the original split in it, the oldest traceable divergence, occurred in Africa, confirming that continent’s status as the home of anatomically modern humans. It is his conclusion that the male whose Y chromosomal DNA is now found in all of the billions of living males lived in eastern Africa around 59,000 years ago, although this date is simply the most probable one, the range of possibilities being between 40,000 and 140,000 ybp.11 As Wells puts it,
[At around 60,000 ybp] (w)e simply lose the signal from our genes at that stage, as all of the genetic diversity present today coalesces to a single ancestor. What is clearly implied by the data, however, is that all modern human genetic diversity found around the world was in Africa around 60,000 years ago.12However, a study published in 2011 challenges these findings. According to this research, which is based on very extensive sampling, Y chromosomal Adam emerged much earlier, at about 142,000 ybp, and not in east Africa but somewhere in central to northwest Africa. Moreover, the scientists conducting this study place the earliest east African Y chromosomal haplogroup (a population that contains the descendants of an individual that first exhibited a particular polymorphism) at about 105,000 ybp.13 These findings appear to some observers to be more congruent with the archeological data that have been uncovered regarding Homo sapiens settlement patterns. In truth, it must be said that the issue is not yet settled, but it appears that the more recent data have caused a reassessment of such issues as population movements and gene flow within the African continent and how mutational frequencies are calculated.
Mitochondrial Eve (at whatever date she existed), and Y chromosomal Adam (whenever he existed) are the Most Recent Common Ancestors (MRCA) for those traits. They are important—but not definitive. Obviously, they are not the only ancestors, and equally obviously, they were not the only female/male alive in their time. Further, just because they are the MRCAs for mtDNA and Y chromosomal DNA, it does not mean that every trait in humans today comes from their DNA.
Mitochondrial Eve existed many tens of thousands of years before Y chromosomal Adam, in any set of estimates. What accounts for this? One anthropologist explains it like this:
…it would appear that male population histories have more restrictions than do female histories. This accords with what we know about human reproductive patterns. Males vary more than females in their reproductive output. Some males have far more offspring than others, and many males have no offspring. Each female is likely to have a nearer to average number of offspring. This would cause apparent bottlenecks in the male lineage that would not appear in female-only DNA.14It is at these bottlenecks that genetic opportunities arise or are eliminated. The wide divergence between male and female mating and breeding patterns may also tell us important things about the relative geographical mobility of males compared to females, and the nature of gender roles in the Africa of 100-150,000 ybp.
A Small Number of Ancestors, A Multitude of Relatives
In considering our ancestry, we need to remember how the coalescence process works. In coalescent theory, as we move back in time particular genetic traits will be found in a narrower and narrower population, until they are found only in a single individual. So as we go back in time, we see that we share more and more genetic ancestors with other humans. And, naturally, the number of humans alive in the past was far less than it is now. Therefore, the pool of possible ancestors narrows—coalesces—as we go back. Obviously a great many variables affect the way in which particular traits are distributed. Inheritance does not proceed in neat, chronologically regular sequences.
We also need to consider the way in which our ancestors, hypothetically, increase geometrically in number as we trace them back through the generations. We each have two (biological) parents, four grandparents, eight great-grandparents, and so on. If we start with our parents and count them as step one, by the time we go back twenty steps, we would each have 1,048,576 great (x 18) grandparents. At step 30, we would each have 1,073,741,824 great (x 28) grandparents. If we assume that a generation may be arbitrarily defined as 20 years, step 30 would take us back to the early 1400s. Since there were not one billion people alive in the entire world in the early 1400s, it is clearly impossible for each of us to have had a unique and distinct set of ancestors. We are obviously all related to each other, we obviously all share a great many ancestors. We are an enormous and very extended family. Where does that extended family really begin?
If it were possible to reliably trace the origins of every section of chromosome in the human genome, any particular sequence of nucleotides, we would find, as we noted, that each section is ultimately traceable to a single person. So how many individuals are believed to have contributed to the genome of anatomically modern humans? Researchers in the early 2000s estimated that the total number of such individuals, the people who contributed all the DNA found in every human being alive in the world today, was about 86,000, two of whom were Mitochondrial Eve and Y chromosomal Adam.15 This number is fewer than the number of people living today in Hastings, UK, or Ghorashal, Bangladesh, or Rafaela, Argentina.16 If this figure is correct, it is this set of humans, living at diverse times in the past, who are the true ancestors of the family of anatomically modern humans.
Evidence of Genetic Flow Between Sapiens and Other Species
Once Homo sapiens left Africa and encountered other species of humans, did they interbreed successfully with them? Most paleoanthropologists have, in the past, ruled out the possibility of such breeding. But fairly recent and intriguing evidence may indicate otherwise. In 2010 a major analysis of the Neanderthal (or Neandertal) genome was announced, based on the sequencing of Neandertal DNA found in three bones ranging in age from about 38,000 to about 45,000 years. The most striking of the findings:
One model for modern human origins suggests that all present-day humans trace all their ancestry back to a small African population that expanded and replaced archaic forms of humans without admixture. Our analysis of the Neandertal genome may not be compatible with this view because Neandertals are on average closer to individuals in Eurasia than to individuals in Africa. Furthermore, individuals in Eurasia today carry regions in their genome that are closely related to those in Neandertals and distant from other present-day humans. The data suggest that between 1 and 4% of the genomes of people in Eurasia are derived from Neandertals. Thus, while the Neandertal genome presents a challenge to the simplest version of an “out-of-Africa” model for modern human origins, it continues to support the view that the vast majority of genetic variants that exist at appreciable frequencies outside Africa came from Africa with the spread of anatomically modern humans.17The researchers go on to say that individuals in east Asia and Papua New Guinea have just as close a genetic relationship to Neanderthals as do Europeans, meaning that the gene flow between Neanderthals and modern humans must have taken place before the divergence of Europeans, Chinese, and inhabitants of New Guinea. It is most likely that this intermixing of human types took place in the Middle East, where Neanderthals existed until around 50,000 ybp.18 If there was indeed interbreeding between AMH and Neanderthals, we may legitimately ask if the Neanderthals were truly a separate species—Homo neanderthalensis—or a subspecies of AMH, Homo sapiens neanderthalensis. There is as yet no consensus on this, but the discovery of Neanderthal DNA in our genome is challenging our definitions of speciation.
Extensive analysis has revealed that Neanderthals and AMH seem to have shared a common ancestor 800,000 years ago, and that the ancestors of AMH and Neanderthals split from each other about 270,000 to 440,000 ybp. MtDNA sequences from Neanderthals have been recovered as well, and they indicate that all Neanderthals shared a common mtDNA ancestor who lived about 100,000 ybp. We and the Neanderthals in turn can trace our ancestry to a “Mitochondrial Eve” living about 500,000 years ago.19
Other significant discoveries have come from Denisova Cave, in southern Siberia’s Altai Mountains. In 2010, DNA from a finger bone found in the cave was sequenced. The bone is dated at 30,000-50,000 ybp. The human from which this DNA was obtained appears to have shared a common origin with Neanderthals, but it does not appear to have been part of a Neanderthal-Eurasian genetic exchange. Interestingly, Denisovan DNA has been found to comprise between 4 and 6% of the genome of the modern Melanesian population [a group of Pacific islanders]. Further, the discovery of a morphologically unique Denisovan tooth, one that shares no derived features in common with AMH or Neanderthals, strongly suggests that Denisovans evolved as a distinct group.20
The geographical range of the Denisovans has not yet been ascertained. They may have lived in eastern Asia at the time the Neanderthals lived in western Eurasia. It is striking that there are Denisovan genes in Melanesians but none in the Mongolians and Han Chinese who live much closer to the Altai Mountains than do Pacific islanders. This would argue for a Denisovan presence far from southern Siberia, but just where or when this was is not clear. It appears that Neanderthals contributed more to the genome of the Eurasians than the Denisovans did. The Neanderthals and the Denisovans may be thought of as the western and eastern branches of the archaic humans who preceded sapiens in Europe and Asia. There are some who might call the easterners Homo denisova, but as yet no such formal taxonomic designation has been made. Needless to say, many more Denisovan specimens will be required for a full assessment of their place in our phylogeny.21
Of course, we do not know with any degree of certainty the specific ways in which this Neanderthal and Denisovan DNA manifests itself in non-Africans. There is also the issue of migration of humans into Africa from other regions, a sort of “return to the homeland”, one which would have had the effect of creating genetic diversity in certain African subpopulations.
Archeological Evidence of the African Origin of Modern Humans
The second basis on which the Recent Out of Africa model rests is the archeological evidence, in the form of the remains of Homo sapiens themselves and the presence of their tools in various regions. Since tools are a key indicator of the progress of humans across the planet’s surface, it may be useful at this point to explain the terminology used by researchers in tracing the development of technology. It is also important to note that different human cultures usually reached these stages at widely differing times, as we will see.
Paleolithic describes the oldest human tool-making traditions. Otherwise known as the Old Stone Age, the Paleolithic period encompasses more than 99% of the time that has passed since the first stone tools were made. From Lower (the oldest period) to Middle to Upper (the most recent period), it stretches all the way from perhaps as early as 2.5 million ybp to about 12,000 to 10,000 ybp, depending on whose definitions we accept. The tool-making traditions within the Paleolithic range chronologically from the first Oldowan-style tools through the Acheulian tool industries to the method of producing stone flakes for cutting known as the Levallois technique, which helped lay the basis of the era of more specialized tools known as the Mousterian and a still-more advanced Upper Paleolithic tool-making tradition, the Aurignacian. Then, in relatively rapid succession (by archeological standards), the Paleolithic produced the Gravettian, Solutrean, and Magdelanian tool-making industries. Each stage is characterized by not just distinct kinds of tools but by evidence of increasingly sophisticated manufacturing techniques. When we trace the history of the Paleolithic period, we are also tracing how the increasingly advanced brains of successive kinds of humans dealt with the challenges confronting them, and how those brains in turn were shaped by the solutions they devised.
Mesolithic describes the stage of tool manufacture characterized by the growth of smaller, more specialized, more diverse, and more sophisticated tools. Otherwise known as the Middle Stone Age, it represents the transition between the hunting-gathering societies of the last great age of glaciation and the first organized farming. Depending on how it is defined, it arose either 10,000 to 12,000 ybp and was giving way to the next era by 7,000 to 5,000 ybp.
Neolithic describes the most advanced stone age cultures, the New Stone Age. Neolithic cultures were the ones beginning to make the transition to systematic plant cultivation and animal husbandry. The end of the Neolithic (in various regions) was definitively reached when metallurgy became widespread. The earliest age of metal tools was the Chalcolithic, or Copper Age. It was a major milestone in a culture’s development whenever metal tools became widespread.
The people migrating out of Africa were generally possessors of middle Paleolithic technology, and when researchers find evidence of such tools in an area, it is significant.
The chronology of the human migration from Africa is being extensively researched. It appears that there was not one single large migratory event. Rather, there may have been intermittent migrations (although a surge seems to have taken place 60,000 ybp). It is possible that many small groups attempted to cross the Middle East, and there is evidence of sapiens occupation of the Arabian peninsula more than 100,000 years ago. (See below) Wells has argued, however, that Arabia might have been a traditional area of sapiens occupation very early on, and not necessarily a migration route.
What was causing the waves of human migration out of eastern Africa? Climatic factors may have played a significant role. A detailed study has revealed that there were major periods of aridity in Africa between 135,000 and 75,000 ybp. Core samples taken from Lake Malawi (bordered by modern-day Malawi, Tanzania, and Mozambique), Lake Tanganyika (bordered by modern-day Burundi, Democratic Republic of the Congo, Tanzania, and Zambia), and Lake Bosumtwi (in Ghana) indicate severe, periodic reductions of water levels during this era. Lake Malawi may have lost as much as 95% of its volume at times, and Lake Bosumtwi appears to have been completely desiccated in some eras. Precipitation in the regions of these three lakes may have been reduced in the range of 60-65% during these periods of low lake volumes.22 It cannot be stated definitively that it was these times of terrible drought that drove humans toward the northwest, but the data at least point to the possibility.
Surprisingly, perhaps, humans may have found welcoming conditions in the Arabian Peninsula. The climatic and topographical conditions of Arabia have not always been hostile to human migration. There seem to have been prolonged rainy phases between 135,000 to 120,000 ybp and between 82,000 and 78,000 ybp. During these periods vegetation would have been abundant. It was during a rainy period between major glaciation events that some researchers believe that AMH from Africa first ventured into the Middle East. The evidence is striking. Tools found at the Jebel Faya site, in the modern United Arab Emirates, suggest a long human habitation in the Arabian Peninsula. The oldest tools resemble those of the late Middle Paleolithic period of northeastern Africa. The earliest human habitation at Jebel Faya is thought to have been established by 125,000 ybp. The Arabian evidence is seen by some researchers as an indication that humans from eastern Africa had two routes into the Middle East. The northern route, sometimes called the northern gate, took humans along the Nile and then into the Levant. The southern route, which these scientists believe Jebel Faya and other sites in the south of the peninsula to be evidence of, would have begun at the narrow straits at the lower tip of the Red Sea. Genetic evidence appears to bolster this contention.23 As we will see, tool assemblages in other regions also reflect African tool making traditions.
In tracing the history of sapiens’ world-wide migration, we will find no physical remains of sapiens older than those from Africa. There have been claims by some observers that teeth discovered at Qesem Cave near Tel Aviv, Israel, dated to between 200,000 and 400,000 ybp, are of sapiens origin, but the discoverers of these teeth have made no such sweeping claim, and are in fact cautious about their interpretation.24 So until such time as more solid evidence is presented, the argument that AMH first evolved in the Middle East cannot be supported.
Therefore, it appears that African-descended Homo sapiens did indeed ultimately replace the Neanderthals, Denisovans, and whatever remnants of erectus may have remained at the time sapiens was spreading throughout the eastern hemisphere. However, it also appears that there was some gene flow between sapiens and the non-sapiens humans of western Eurasia, a genetic presence that exists in every contemporary non-African. (Such gene flow, as we have noted, may cause us to revise our definitions of what constitutes a species.) So while the Recent Out of Africa Model appears to be basically correct, perhaps a variant of the Assimilation Model is the most accurate picture we have. Further, the time scale of the ROA Model is still being elucidated, as we will see, and it is unwise, at this point, to assert that human migrations have been dated with anything like complete accuracy. So with this caveat in mind, we will attempt to summarize the wanderings and settlements of Homo sapiens on the outer crust of this planet, always aware that our estimates are subject to revision.
Chronological Overview of Sapiens Migration
Homo sapiens probably first emerged in Ethiopia around 200,000 ybp. Spreading climatic disaster wiped out many of its members, and forced others to flee southward. The survivors took refuge in far southern Africa from about 164,000 to about 35,000 ybp. (There is evidence, however, that a small remnant of sapiens remained in eastern Africa.) At about the time climatic conditions were improving (around 123,000 ybp) or perhaps somewhat earlier, groups of sapiens began to push northward again. In general, it is thought that waves of modern humans migrated out of northeast/east Africa beginning perhaps as early as 125,000 ybp.
There were two “gates” out of Africa, one through the Levant, and one across the narrowest point of the Red Sea and into southern Arabia. (There is as yet no evidence that the third possible “gate”, across the Strait of Gibraltar, was used.) The route through the Levant seems to have been the most-traveled one. The evidence suggests there were definitely Homo sapiens in southwestern Asia by 100,000 ybp. In the homeland, Africa, groups of sapiens had established themselves in present day Namibia by 90,000 to 80,000 ybp, and the various migrations of sapiens within Africa had reached the western region of the continent by perhaps 50,000 ybp. Central Africa was occupied by 60,000 ybp.
Groups of sapiens are thought to have headed east by following the shoreline of the Indian Ocean, (others may have traveled by a more inland path), and they may have reached what is now India by 74,000 ybp, although this figure is in dispute. Somewhere between 67,000 and 50,000 ybp, sapiens established itself in southeastern Asia, and there is evidence that sapiens inhabited Australia as early as 45-55,000 ybp, depending on the accepted estimates. The status of sapiens in China is a matter of great controversy, as we will see. There are Chinese paleontologists who claim there were modern humans in China as early as 110,000 ybp, and others even claim AMH habitation as early as 200,000 ybp, a highly disputed contention. Most researchers, while reserving final judgment, think that sapiens reached China between 60,000 and 40,000 ybp.
Modern humans may have reached the Philippines and New Guinea by about 50,000 years ago. There appear to have been sapiens groups in Europe as early as 45,000 ybp, and by 40,000 ybp they appear to have been firmly established in the northwestern part of the continent. Most sapiens in Europe would be driven out later by devastating glaciation (see below), and the continent was then repopulated. Sapiens established a presence in Japan as early as 38,000 ybp and small groups of sapiens were occupying northeastern Asia by about 35-30,000 years ago. Groups of sapiens crossed the (temporary) land bridge into the Americas perhaps as early as 20,000 ybp, and by 7,000 years ago groups of AMH were in Tierra del Fuego, at the southern tip of South America. Finally, the last regions of the Earth to be peopled were New Zealand, Polynesia (which includes Hawaii), and the rest of the various islands of the Pacific.
Did the various groups that ventured outside of Africa prior to 60,000-70,000 ybp survive, or were they biological dead-ends? Were only the groups of humans who left Africa after 60,000 years ago our direct ancestors? We will examine the evidence from each region of the Earth more closely, and attempt to find some answers, however tentative, to these questions.
Before we begin our brief regional survey, however, we must take cognizance of the impact of huge climatic/environmental events on the spread of modern humans and their ability to survive in various regions.
Episodes of Glaciation and Their Impact on Anatomically Modern Humans
We have already noted several periods of extensive glaciation in the Earth’s geological history, the most dramatic of which was the Cryogenian Era. The period in which humans were evolving and spreading, the Pleistocene Epoch, has often been called “The Ice Age” because of the frequency with which glaciers covered much of the Earth’s landmasses. It is not yet clear how many distinct cold and warm periods there were in the Pleistocene. At one time it was thought that there had been a handful of extended glacial events, perhaps 4-6 major episodes in Europe and North America, but recent research on sediments at the bottom of the world ocean indicates there may have been as many as 52 glacial/interglacial periods over the last 2.6 million years.25 Glaciers did not expand everywhere uniformly. Different regions of the world experienced glacial periods at different times, although there were large events that encompassed much of the northern hemisphere and certain regions such as New Zealand in the far southern hemisphere. The impact of glaciation on the world’s landscapes and life forms was dramatic. In the words of one group of climate researchers, this was the world during the last glacial maximum 18,000 ybp:
Many parts of the Northern Hemisphere that are densely populated today were frozen wastes: glaciers reached New York and Berlin, and the ground beneath London and Paris was permanently frozen. Ice sheets over 3 km thick covered much of North America and Scandinavia. Winds blowing down from the ice sheets reached speeds of 300 km per hour. Much of Western Europe was largely treeless with a tundra-like landscape. Much of the northern part of the North Atlantic Ocean was frozen although the Norwegian Sea remained seasonally ice free. Sea ice extended down to the latitude of the British Isles, and floating ice and large icebergs, even during the summer months, would have been common between Ireland and Newfoundland and would occasionally have been seen off the Portuguese coast.26The basic cause of these climatic fluctuations was discovered by an astronomer named Milutin Milankovich. Milankovich’s hypothesis was that if summer temperatures in the high latitudes (60° to 80° north) are low enough, they are insufficient to clear away all the snow cover in those regions. If these low summer temperatures persist over enough years, snow fields begin to grow into glaciers. A change in the tilt of the Earth’s rotational axis [the precession of the axis] contributes to this process.27 Although other scientists dismissed these ideas when they were first proposed in the 1920s and 1930s, evidence gathered from the oceans since that time has confirmed Milankovich’s views.
These waxing and waning periods of glaciation profoundly affected the world’s Pleistocene human communities. The numbers of humans alive at any given time were, as we have noted, extremely low by modern standards, and these communities were highly vulnerable to changes in the natural environment. Human evolution itself was spurred on by the shrinking of the forests and expansions of grassland in Africa, events caused by glacially-induced climate change. The changes in the flora and fauna of eastern Africa rewarded those animals that were able to move themselves on the ground efficiently. Glacier-driven climate change caused Homo sapiens’ retreat toward southern Africa, as we noted in the previous chapter.
In the northern regions of the world, in areas several of which sapiens had long been firmly established, the impact was much more direct. Europe was largely depopulated by the last great period of glaciation, as was much of North America and northeastern Asia. There are researchers who contend that Europe and northern Asia were not completely stripped of their human populations, although specific areas almost certainly were. The adaptation to cave dwelling may have been extensive at this time, and there is evidence of human habitation in severe European climates. The Late Pleistocene hunters of the north also exploited the large animal life that evolved during the colder periods of the Earth’s history, such as mammoth and bear. The hunting of such animals may in fact have had significant consequences for the social evolution of the human communities that exploited them.
The advancing ice absorbed so much seawater that the level of the world ocean sank precipitously on occasion, allowing for the emergence of ordinarily submerged “bridges” of land. Declines in sea level of 400-500 feet exposed many such bridges, which humans often exploited,28 such as the connection between northeastern Asia and northwestern North America that allowed for the flow of those humans who became the Native Americans. Additionally, huge inland lakes, such as the Great Lakes in North America, were created, and throughout the northern hemisphere the landscape reveals the boulders and other debris left by glaciation. Finally, it was during the retreat of the last great glacial epoch that a wave of human migration repopulated much of the world. Climatic changes allowed for the spread of particular kinds of grasses, particularly in the Middle East, which humans learned to cultivate—a phenomenon that was to have enormous consequences, as we will see.
Disaster at Mt. Toba
Approximately 74,000 ybp, there was a massive volcanic eruption at Mt. Toba, on the island of Sumatra in what is now Indonesia. The eruption produced 675 cubic miles of ash, an astonishing amount. India was completely covered by it, and approximately 4% of the entire Earth’s surface [about 20,000,000 square kilometers, or about 7.7 million square miles] was covered in ash. Sulfuric acid residues from Mt. Toba’s cataclysm have even been found as far away as Greenland. The huge ash cloud from the explosion, and the massive concentration of sulfur dioxide aerosols in the atmosphere, must have reflected a great deal of solar radiation back into space. As a consequence, the explosion appears to have immediately plunged the Earth into a period of semi-winter that may have lasted 10 years, and temperatures at this time may have plunged worldwide an average of 18 degrees F. Some researchers believe that given the harsh effects of the much smaller explosion at Mt. Tambora in 1815, when the whole world’s climate was affected for two years, the Mt. Toba eruption, which was 50 times larger, may have had a catastrophic impact.29 In fact, some scientists contend that the Mt. Toba eruption may have affected the Earth’s climate for more than a thousand years. This figure has been disputed by those using different climate models. Those in disagreement argue that the aerosolized sulfur dioxide from the explosion would have dissipated much sooner than a millennium. Further, they argue, there is evidence that the extent of the initial temperature drops was not as severe as originally believed.30
An argument has been made that Mt. Toba inflicted enormous destruction on the human communities alive at that time, reducing the human population severely and creating a genetic bottleneck. However, archaeological evidence from India, the region most heavily affected by the eruption, seems to indicate strong cultural continuity in the region’s population. Specifically, it appears that there was already a cooling trend in India’s climate 74,000 ybp, and the humans living there appear to have already been making adaptations to it. The eruption appears to have inflicted substantial damage to vegetation, but within a few decades plant life may have recovered completely. Undoubtedly, any human populations on Sumatra (perhaps the remnants of Homo erectus) must have suffered severe losses. But the human population of India, employing the technology of Middle Stone Age Africa, appears to have survived the Mt. Toba cataclysm, although it almost certainly must have endured a very rough period. And there is a possibility that those humans were members of Homo sapiens. (See below.)31
Modern Humans Spread Throughout Africa
A major study in 2009 confirmed the primacy of Africa in the genetic history of AMH. More significantly, by studying correlations between genetic diversity and the distribution of ethnic groups (and hence linguistic diversity) in the various regions of the continent, it identified the places where migration within Africa and migrations out of Africa began:
The geographic origin for the expansion of modern humans was inferred…from the correlation between genetic diversity and geographic position of populations. Both the point of origin of human migration and waypoint for the out-of-Africa migration were optimized to fit a linear relationship between genetic diversity and geographic distance This analysis indicates that modern human migration originated in southwestern Africa, at 12.5°E and 17.5°S, near the coastal border of Namibia and Angola, corresponding to the current San homeland, with the waypoint in northeast Africa at 37.5°E, 22.5°N near the midpoint of the Red Sea. However, the geographic distribution of genetic diversity in modern populations may not reflect the distribution of those populations in the past, although our waypoint analysis is consistent with other studies suggesting a northeast African origin of migration of modern humans out of Africa.32It can therefore be said that some of the “oldest”, most diverse modern human DNA on the planet is in the Khoisan, or Bushmen, people of southwestern Africa, Khoisan being a designation that covers a wide variety of subgroups. Members of the Khoisan population are more genetically different from each other than Europeans and Asians are from each other.33 We may surmise, therefore, that when humans began moving out of their southern African refuge that the first groups of them headed northwest.
A team of researchers, using genetic data gathered from a variety of African and Middle Eastern sources, offers a somewhat different view. It has concluded that there was a split in the original Homo sapiens population at least 140,000 ybp, and the Khoisan may have evolved as an independent subgroup. These scientists further hypothesize that the other independent subgroup was a small population of eastern African sapiens. In this scenario sapiens from southern Africa eventually migrated north and interbred with this population. It was this population, they surmise, from which the earliest Out-of-Africa migrants were drawn. It was also this population, they believe, whose descendants spread to northwestern and western Africa. From this west African group, in turn, Bantu populations pushed their way southward a few thousand years ago.34 The issue is still an open one, but given the very small populations of human groups earlier than 100,000 ybp, the survival of an eastern African sapiens population, even in the harsh conditions of the era, has evidentiary support.
Other evidence points to the survival of sapiens in eastern Africa. An analysis of African mtDNA genomes has found haplogroups that occur only in the southern and eastern regions of the continent. Tanzania was found to have a high level of genetic diversity (as were the Khoisan people and the Bakola Pygmies of present-day Cameroon). The eastern African sapiens may have been a significant source not just of Out-of-Africa migration but also migration within Africa. Tanzania is home to representatives of every major African language group, and it may be the origin of many African haplogroups. Indeed, these researchers speculate that the Khoisan population itself may be descended from these eastern African sapiens, although additional evidence is needed in relation to this hypothesis. Further, the Tanzanian mtDNA appears to indicate a significant level of “back migration”, groups of humans who originated in Africa, migrated from the continent, and whose descendants eventually returned to the “homeland”.35
In regard to the peopling of central Africa, we must also rely chiefly on genetic and linguistic evidence, since the highly acidic soil of equatorial Africa hinders the process of fossilization. Based on such evidence, it appears that hunter-gatherer Pygmies first became differentiated from what would eventually become farming populations some 60,000 years ago. It also appears that there was a split between the Eastern and Western Pygmies about 20,000 ybp, coinciding with the onset of the last glacial maximum and the reduction in forest land in Africa. There seems, however, to have been continued gene flow between the two Pygmy populations despite this split.36
Overall, it seems that the largest period of migration within Africa was between 80,000 and 50,000 ybp, probably driven by major changes in the environment, particularly decreases in rainfall ranging up to 50%. There may have been a sharp increase in the quality of hunting technology during this period as well. The necessity of adapting to a more challenging environment may also have led to the emergence of more complex forms of social and economic organization among the central African peoples.37
Finally, there is the possibility that relict populations of pre-modern humans survived in Africa until a surprisingly recent time. Two crania discovered at Iwo Eleru, Nigeria, and dated to about 13,000 ybp, show identifiably “archaic” traits, ones more consistent with Neanderthal-like humans or even later members of erectus. It is therefore possible that a subpopulation of non-modern humans lived in an isolated genetic pocket, well after AMH had come to dominate west Africa.38
Modern Humans in the Levant and Other Regions of Western Asia
Human specimens from the Middle Paleolithic era have been uncovered in many places in Israel and elsewhere in the Levant. The caves at Qafzeh and Skhul (at Mt. Carmel) have been particularly revealing. Qafzeh is the older of the two sites, with various dating methods indicating human occupation in the 100,000 ybp range. Skhul appears to have been occupied about 92,000 years ago or so.39 Exploration at these two caves has yielded up the remains of 23 individuals, including children, who are, according to some researchers, closer to Homo sapiens in their physical characteristics than they are to Neanderthals.40 However, a vigorous dissent to this position has been offered by a team of researchers that includes Milford H. Wolpoff, one of the leading advocates of the multi-regional model of human evolution. These scientists contend that the human specimens found in the Levant are not distinctly AMH, that they appear to be a sapiens-Neanderthal hybrid, and that the evidence seems to point in the direction of extensive interbreeding during the 60,000 years the two forms of humans lived together in western Asia.41 As we have already noted, many researchers believe that the parts of the non-African genome that are Neanderthal in origin must have come from the time the two varieties of humans were both present in the Middle East.
We can say with some confidence that the first true community of Homo sapiens to live outside of Africa was in the western regions of Asia. There are controversies revolving around such issues as the level of cultural development of the early AMH types in the region and the manner in which they survived (involving such matters as tool sophistication, hunting, and the extent of scavenging activities).42 Further, there are unresolved questions regarding the continuity of these early communities (especially Jebel Faya in the UAE), and whether the earliest migrants had a significant impact on the populations that later dispersed to other regions of the world. Sapiens in western Asia may have died out, and the region may have been repopulated beginning about 50,000 ybp. It is possible, however, that there has been continuous AMH presence in western Asia for more than a thousand centuries, and that this region served as the biological and cultural nexus between Africa and the rest of the world.43
Modern Humans in South Asia
It is now thought that many humans made their way into South Asia by following the coastline of the Indian Ocean, surviving through foraging. (There are places along the coastline, however, that would have forced migrants inland.) The deltas of the Indus River in the west and Ganges-Brahmaputra Rivers in the east would have formed natural barriers, ones largely confining migratory human groups to the southern part of the subcontinent. Yet those same rivers also provided pathways into the interior and gathering places for the animals pursued by hunters.44
As we saw above, some scientists are of the opinion that those in India who survived the Mt. Toba explosion may have been sapiens. This view is grounded in the belief that the technology of the time and the adaptability of the population in the face of disaster must have been the product of sapiens mental abilities. Tool discoveries made in Andhra Pradesh, which indicate possible sapiens presence there 74,000 ybp, are intriguing. But this view has been challenged on several grounds. There are researchers who argue that the available genetic evidence suggests that sapiens groups made their way into India via the southern route (going initially through the Arabian peninsula) and arrived in the subcontinent between 70,000 and 45,000 ybp, depending on which analysis one accepts. Even the earliest estimate finds the Mt. Toba eruption occurring well before the arrival of AMH. Further, researchers point out that there is no dramatic change in technology evident in discoveries of Middle Paleolithic tools in India, and that it cannot be determined with any certainty which kind of hominins made them. Nor was there any upsurge in the use of symbolism in the period before 70,000 ybp, as one might expect from an influx of sapiens.45
Important finds of sapiens or sapiens-like specimens in south Asia include the hominid remains found at Darra-I-Kur in northeastern Afghanistan, dated to about 30,000 ybp and possessing both AMH and Neanderthal-like traits. There are remains of definite AMH character that have been recovered in Maharashtra state, in India, which are being interpreted cautiously because of their indeterminate age. Then there is Narmada Man (which may actually have been a female), a calvaria (supplemented by some post-cranial material) from the Narmada Valley of India. This specimen was once thought to have been a member of erectus but it is now increasingly thought of as very early sapiens from the late Middle Pleistocene. And there are a number of sapiens finds on Sri Lanka, the oldest of which is dated from at least 34,000 ybp.46
South Asia played an important part in the story of human dispersal across the planet. It was a crossroad for those pushing eastward, and the genetic evidence indicates strong links between Africa, the subcontinent’s population, and southeast Asia. Moreover, it was in the Indian subcontinent that much of the later diversity of the human species may have been formed. There is a great deal of archeological information on the tool industries of south Asia, but the number of human fossils found in the region is relatively low, so our assessments must necessarily be cautious ones. Still, we may infer sapiens occupation of south Asia perhaps as early as 70,000 ybp, and the region became one of the chief centers of AMH culture.47
Modern Humans in China
The question of the earliest Homo sapiens in China has been fraught with controversy, as we have seen already. Among the most important recent finds are those discovered in Tianyuan Cave at Zhoukoudian. Some 34 pieces of human skeleton have been recovered there, consisting of partial cranial and post-cranial remains and some teeth. These remains have been dated at 42,000–39,000 ybp, and are among the oldest specimens in China of what the researchers who analyzed them call Early Modern Humans. Intriguingly, the bones seem to show a mixture of derived and somewhat more “archaic” features, especially in the size of the teeth and the fingers. The scientists analyzing these specimens believe these unusual features to be indicative of possible gene flow between this variety of human and even earlier modern human populations in eastern Asia [although the genetic studies do not as yet seem to support this contention].48
Perhaps the most significant—and controversial—Homo sapiens find in China is from Liujiang in Guangxi province, in southern China. Specifically, it is a skull discovered in sediments in Tongtianyan Cave. The skull clearly possesses all the typical morphological features of a contemporary Homo sapiens. The cranial capacity is actually greater than that of the modern median size. The issue lies in the dating of the find. A study from 2002 concluded that the sediments in which the skull may have been embedded were between 111,000 and 139,000 years old. However, the actual stratigraphic layer from which the skull came is not known (it was discovered in 1958 by a group of farmers in the area), and researchers estimate it could be anywhere from 68,000 to 153,000 years old.49
These findings have been strongly contested. The uncertainty surrounding the dating of the find, the uncertainty about the layer in which it was originally embedded, and the evidence from other Late Pleistocene Chinese sites all cast doubt on the purported extreme age of the Liujiang specimen. One group of researchers quite frankly calls these claims “weak”. This group says that the Liujiang find may be 67,000 years old, but they are careful to put a question mark after the figure.50
The more general issue is that despite the fact that more than 40 Late Pleistocene hominid sites have been discovered in China, the remains found in them are often fragmentary, and most of them are less than 30,000 years old. Recently, an important new find was made at Huanglong Cave, in central China, that might clarify some of the issues surrounding the colonization of east Asia by AMH, as well as illustrating some of the challenges confronting researchers in this field. Seven human teeth have been discovered there, six from adults ranging in age from 20-45 and one from a person younger than 20. Various dating techniques, some of which focus on faunal remains found in the fossil-yielding sediments, have yielded a wide range of dates, the oldest of which is around 100,000 ybp and the youngest of which is 44,180-34,780 years. The difficulty lies in the geological complexity of the cave, and the wide range of dates argues for caution in interpretation of the finds. Nevertheless, the teeth strongly resemble those of Homo sapiens, and help establish a minimum date at which AMH occupied central China.51
There is also considerable controversy surrounding the human remains discovered at Zhirendong (Zhiren Cave), in southern China. There are paleoanthropologists who contend that these specimens, two molars and part of a mandible dated at around 100,000 ybp, are AMH, and therefore indicative of a much earlier Homo sapiens presence in China than is currently accepted. The mandible shows both derived and robust (more archaic) features, and in the eyes of the researchers studying it, raises important issues about the possible interbreeding of archaic and modern humans in China. These remains predate by over 60,000 years the next oldest specimens from the region.52 It should be noted, however, that some researchers urge caution in the interpretation of these finds, citing their ambiguous nature, and as always in paleontology, many more specimens are needed before a definitive judgment about the earliest presence of Homo sapiens in China can be made.
The debate about AMH in China is sometimes clouded by the assertions of certain Chinese researchers that Homo sapiens established itself very early in the history of the species, even earlier than our evidence of AMH occupation of western Asia shows, interbred with archaic forms of humans, and produced a biologically distinct and unique human form, the modern Chinese. We must treat these contentions with great care, always mindful that we cannot let our research be influenced by national pride and claims of uniqueness in the human community. The evidence is clear: the Chinese, as is the case with all other humans, are ultimately of African origin. There is the chance that there was gene flow between Chinese sapiens and more archaic human types, but the evidence supporting this intermixing is still ambiguous and incomplete.
Modern Humans in Southeast Asia, Australia, and Oceania
Southeast Asia has presented a major challenge to researchers studying the migration of Homo sapiens across the planet Earth’s surface. Although Indonesia was home to some of the earliest examples of Homo erectus, and although erectus probably survived there longer than anywhere else, examples of Homo sapiens have been hard to find. Relatively few southeast Asian specimens from the crucial period of 100,000 to 25,000 ybp have been recovered.
One of the oldest purported hominid finds in southeast Asia is a small metatarsal bone found in Callao Cave, located in northern Luzon in the Philippines. Dated at a minimum of 67,000 ybp and dubbed “Callao Man”, the bone’s physical features indicate that it was from a member of the genus Homo, and its diminutive size may fall into the range of Homo sapiens groups known to be of small physique. However, the specimen is more gracile than a similar bone from Homo habilis, and more specimens of a similar nature will be needed before a definitive judgment about the bone’s significance can be made. At the very least, however, it shows that hominids in the region knew how to use watercraft more than 60,000 years ago.53
The most significant archeological site in the Philippines, and one of the most important in all of southeast Asia, is located at Tabon Cave, on the southwest coast of Palawan Island. Layers in the cave that were definitely occupied by humans have been dated from 30,500 ybp to 9000, and an extensive stone tool industry has been uncovered as well. A sapiens frontal bone dated at 16,500 years ± 2000 has been confirmed, and other cranial specimens, a mastoid process and a fragment of occipital bone, have been recovered as well. Ten post-cranial remains have also been unearthed, including limb, foot, and vertebral bones. One of the limb bones, a tibia, could be as old as 58,000 years, although this is the maximum age. The tibia’s mean date is around 47,000 ybp. The various bones found in Tabon Cave are probably from several individuals, and may even represent different sapiens varieties.54
Another of the most important regions for the study of sapiens, and prehistory in general in southeast Asia, is the Gunung Sewu area of Java, in Indonesia. Some 130 prehistoric sites have been identified in the region, and more are being uncovered. A great many tools have been discovered there as well, ranging from Paleolithic to Neolithic in nature, and parts of the area seem to have been occupied by hominids at least 180,000 years ago. Caves that show evidence of human habitation in the Gunung Sewu region have been dated to as old as 45,000 ybp, among the oldest in southeast Asia. Other habitation caves have been dated from 33,000 all the way to 800 ybp. The pattern of cave habitation is consistent with the first Homo sapiens occupation of the area, estimated to have been about 40,000 ybp.55
One of the other important hominid sites in Indonesia is at Ngandong, in central Java. Although the chief remains in the Ngandong area appear to be Homo erectus, there are some researchers who see evidence of erectus-sapiens transitional specimens, and they contend, on the basis of careful morphological analysis, that the sapiens-like hominids of the Ngandong area are ancestral to sapiens discovered in southeastern Australia.56
On mainland southeast Asia, evidence of the presence of sapiens is fairly sparse. Stone tools from Tham Lod, in northwestern Thailand, have been dated to about 40,000 ybp, but the earliest actual human specimen recovered was found at Moh Khiew, in Thailand’s part of the Malay Peninsula. It is a fairly well-preserved human skeleton dated at around 25,800 ybp. The specimen appears to be more similar to Melanesian and Australian Aboriginal human populations than human remains found in such locales as Vietnam, and the group of which this human was a part may not have contributed much to later populations in the mainland region. The Late Pleistocene southeastern Asian populations were hunters and foragers, and in contrast to hominins from the Middle Pleistocene of the mainland, they left an extensive stone tool record.57
Among the most unusual finds that has been made in southeast Asia recently is the discovery on Flores Island, in Indonesia, of the remains of what may have been a diminutive human type, nicknamed, “Hobbits” by some. Designated (controversially) as Homo floresiensis by certain scientists, the initial discovery was of a partial adult female human skeleton dated at 18,000 ybp. It was only about a meter in height and its estimated brain size was 380cc. It was designated as LB1. Several other specimens have been uncovered since the initial discovery. These hominids had a stone tool industry, and it does not appear as if they were microcephalic, as was once speculated. The scientific debate about the Flores hominids has not yet been resolved, but it does not appear as if they were a variety of sapiens. Their origin is as yet indeterminate, and they may have been a relict erectus-derived population.58
In Australia, the question of the earliest habitation by AMH centers around the evidence of sapiens occupation at Lake Mungo, in the western region of New South Wales. The evidence of human habitation in the area has been intensively analyzed and debated. The most spectacular find at the site is known as Mungo III, a buried, fully articulated sapiens skeleton discovered in 1974. There is also evidence that the world’s first known cremation took place at the site as well, a burial known as Mungo I, discovered in 1969. At one time it was thought that the two burials were widely separated in time and that Mungo III might be more than 60,000 years old. But it now appears that a consensus is emerging that the two burials occurred roughly in the same era, and that Mungo III is therefore somewhere around 40,000 years old. The evidence further shows that modern humans occupied the site perhaps 50,000 years ago. Hundreds of their artefacts have been found at the site. Mungo III has yielded something else as well: the oldest known mtDNA has been extracted from it.59
Finally, it appears that modern humans may have established themselves on the Huon Peninsula, on the northern coast of New Guinea, as early as 40,000 years ago. Humans definitely seem to have been living in a rock shelter at Lachitu, New Guinea about 35,000 ybp. [Given the fact that humans were in southern Australia about 50,000 ybp, we may surmise that modern humans were in New Guinea earlier than 40,000 ybp.] Human migration into New Guinea would have been facilitated by declines in the level of the world ocean caused by glaciation, since such declines linked New Guinea to other landmasses. Based on tools found there, humans also appear to have established themselves in the northern Solomon islands by 28,000 years ago and also seem to have been present in the Bismarck Archipelago by 20,000 years ago.60
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