Litnet

Beste Cornelius,

In die Bybel lees 'n mens van 'n vloed wat tot die uitwissing van die ganse menslike geslag gelei het en bevat Genesis 5 ook die name van mense wat voor die groot watervloed geleef het. Slegs Noag en sy mense oorleef dit en hieruit sal dan alle mense op aarde hul oorsprong vind.

Dat die mens wel getref is met rampe wat hul feitlik  uitgewis het is waar.Vulkaniese uitbarstings gevolg deur ystydperke het 'n ernstige bedreiging gevorm en die mense poel dus ook die genetiese materiaal drasties verminder soos blyk uit:

Extract from "Journal of Human Evolution" Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans. by Professor Stanley H. Ambrose, Department of Anthropology, University Of Illinois, Urbana, USA Extract from "Journal of Human Evolution" [1998] 34, 623-651

 The last glacial period was preceded by 1000 years of the coldest temperatures of the Late Pleistocene, apparently caused by the eruption of the Mount Toba volcano. The six year long volcanic winter and 1000-year-long instant Ice Age that followed Mount Toba's eruption may have decimated Modern Man's entire population.

Genetic evidence suggests that Human population size fell to about 10,000 adults between 50 and 100 thousand years ago. The survivors from this global catastrophy would have found refuge in isolated tropical pockets, mainly in Equatorial Africa.

 Populations living in Europe and northern China would have been completely eliminated by the reduction of the summer temperatures by as much as 12 degrees centigrade. Volcanic winter and instant Ice Age may help resolve the central but unstated paradox of the recent African origin of Humankind: if we are all so recently "Out of Africa", why do we not all look more African?

Because the volcanic winter and instant Ice Age would have reduced populations levels low enough for founder effects, genetic drift and local adaptations to produce rapid changes in the surviving populations, causing the peoples of the world to look so different today.

In other words, Toba may have caused Modern Races to differentiate abruptly only 70,000 years ago, rather than gradually over one million years. Volcanic Winter The Mount Toba eruption is dated to approximately 71,000 years ago. Volcanic ash from Mount Toba can be traced north-west across India, where a widespread terrestrial marker bed exists of primary and reworked airfall ash, in beds that are commonly 1 to 3, and occasionally 6 meters [18 feet] thick. Tambora, the largest known historic eruption, displaced 20 cubic kilometres of ash.

Mount Toba produced 800 cubic kilometres.* It was therefore forty times larger than the largest eruption of the last two centuries and apparently the second largest known explosive eruption over the last 450 million years. Volcanic Winter, and Differentiation of Modern Humans Mount Toba's eruption is marked by a 6 year period during which the largest amount of volcanic sulphur was deposited in the past 110,000 years.

 This dramatic event was followed by 1000 years of the lowest ice core oxygen isotope ratios of the last glacial period. In other words, for 1000 years immediately following the eruption, the earth witnessed temperatures colder than during the Last Glacial Maximum at 18-21,000 years ago.

 For the volcanic aerosols to be effectively distributed around the earth, the plume from the volcanic eruptions must reach the stratosphere, a height greater than 17 kilometres. Mount Toba's plume probably reached twice this height. Most solar energy falls at low latitudes between the Tropics of Cancer and Capricorn, so eruptions that happen near the Equator cause much more substantial cooling due to the reflection of solar energy.

Toba lies 2 degrees north of the Equator, on the Island Sumatra. The reduction in atmospheric visibility due to volcanic ash and dust particles is relatively short-lived, about three to six months. Longer-term global climatic cooling is caused by the highly reflective sulphuric acid haze, which stays suspended in the upper atmosphere for several years.

Ice core evidence implicates Mount Toba as the cause of coldest millennium of the late Pleistocene. It shows that this eruption injected more sulphur that remained in the atmosphere fo a longer time [six years] than any other volcanic eruption in the last 110,000 years.

This may have caused nearly complete deforestation of southeast Asia, and at the same time to have lowered sea surface temperatures by 3 to 3.5 degrees centigrade for several years. If Tambora caused the " The year without a summer" in 1816, Mount Toba could have been responsible for six years of relentless volcanic winter, thus causing a massive deforestation, a disastrous famine for all living creatures, and a near extinction of Humankind.

The Volcanic Winter/Weak Garden of Eden model proposed in this paper. Population subdivision due to dispersal within African and other continents during the early Late Pleistocene is followed by bottlenecks caused by volcanic winter, resulting from the eruption of Toba, 71 ka.

The bottleneck may have lasted either 1000 years, during the hyper-cold stadial period between Dansgaard-Oeschlger events 19 and 20, or 10ka, during oxygen isotope stage 4. Population bottlenecks and releases are both sychronous.

More individuals survived in Africa because tropical refugia were largest there, resulting in greater genetic diversity in Africa. Blombos Cave : 77,000 years old Small and portable, this red ochre stone is engraved with what must be "tally" marks.

 It is one of two such stones recently found in the Blombos Cave in South Africa and have been dated as being 77,000 years old, making them the oldest form of recorded counting ever found. The stone is worn which probably indicated that it wasconstantly handled over a period of time, how long is impossible to tell.

It looks as though the stone has been reused at least once before as the lighter marks appear to have been erased rather than worn away naturally. If the dating is accurate this stone was used 5000 years before the Mount Toba eruption of 71,000 years ago. The evidence from the Toba eruption indicates that the world's population of Modern Man was reduced to a total of around 10,000 adults."

Die groot watervloed wat in die Bybel beskryf  word vind volgens die Joodse jaartelling plaas in 1658 (2102 B C E). Dit is dus 'n gebeurtenis wat plaasvind jare na die tydperk waarin die mens amper uitgewis is. Die skrywers van Genesis was dus nie bewus daarvan dat daar wel groepies mense oorgebly het  soos bv in die suidpunt van Afrika en dat volgens hul waarneming die hele menslike ras, behalwe Noag en sy mense in die groot watervloed uitgewis is .

Beste Cornelius,

Die debat oor die oorsprong van die mens woed nog steeds onverpoos voort. Hier is 'n paar artikels oor die onderwerp. Google die opskrifte vir prentjies ens.

Origins of Modern Humans: Multiregional or Out of Africa?

Donald Johanson
 Article highlights :There are two theories about the origin of modern humans: 1) they arose in one place — Africa and 2) pre-modern humans migrated from Africa to become modern humans in other parts of the world.

 Most evidence points to the first theory because: fossils of modern-like humans are found in Africa stone tools and other artifacts support African origin.DNA studies suggest a founding population in Africa

( May 2001- Lucy is the common name of an Australopithecus afarensis specimen discovered in 1974 in Ethiopia. Lucy is estimated to have lived 3.2 million years ago. Cleveland Natural History Museum, photo by Andrew.)

 Around 30,000 years ago humans were anatomically and behaviorally similar throughout the world. One of the most hotly debated issues in paleoanthropology (the study of human origins) focuses on the origins of modern humans, Homo sapiens.9,10,3,6,13,15,14

Roughly 100,000 years ago, the Old World was occupied by a morphologically diverse group of hominids. In Africa and the Middle East there was Homo sapiens; in Asia, Homo erectus; and in Europe, Homo neanderthalensis.

However, by 30,000 years ago this taxonomic diversity vanished and humans everywhere had evolved into the anatomically and behaviorally modern form. The nature of this transformation is the focus of great deliberation between two schools of thought: one that stresses multiregional continuity and the other that suggests a single origin for modern humans.

Understanding the issue Multiregional theory:

 homo erectus left Africa 2 mya to become homo sapiens in different parts of the world. The Multiregional Continuity Model15 contends that after Homo erectus left Africa and dispersed into other portions of the Old World, regional populations slowly evolved into modern humans.

 This model contains the following components:
(i)some level of gene flow between geographically separated populations prevented speciation, after the dispersal
(ii) all living humans derive from the species Homo erectus that left Africa nearly two million-years-ago

(iii)natural selection in regional populations, ever since their original dispersal, is responsible for the regional variants (sometimes called races) we see today

(iv)the emergence of Homo sapiens was not restricted to any one area, but was a phenomenon that occurred throughout the entire geographic range where humans lived

 In contrast, the Out of Africa Model13 asserts that modern humans evolved relatively recently in Africa, migrated into Eurasia and replaced all populations which had descended from Homo erectus.

Critical to this model are the following tenets:

(i)Out of Africa theory: homo sapiens arose in Africa and migrated to other parts of the world to replace other hominid species, including homo erectus.

(ii)after Homo erectus migrated out of Africa the different populations became reproductively isolated, evolving independently, and in some cases like the Neanderthals, into separate species.

(iii)Homo sapiens arose in one place, probably Africa (geographically this includes the Middle East)

(iv)Homo sapiens ultimately migrated out of Africa and replaced all other human populations, without interbreeding

(v)modern human variation is a relatively recent phenomenon

The multiregional view posits that genes from all human populations of the Old World flowed between different regions and by mixing together, contributed to what we see today as fully modern humans.

The replacement hypothesis suggests that the genes in fully modern humans all came out of Africa. As these peoples migrated they replaced all other human populations with little or no interbreeding.

To understand this controversy, the anatomical, archaeological, and genetic evidence needs to be evaluated.

Anatomical evidence
 Sometime prior to 1 million years ago early hominids, sometimes referred to as Homo ergaster, exited Africa and dispersed into other parts of the Old World. Living in disparate geographical areas their morphology became diversified through the processes of genetic drift and natural selection.

 In Asia these hominids evolved into Peking Man and Java Man, collectively referred to as Homo erectus
.In Europe and western Asia they evolved into the Neanderthals. Neanderthals lived in quasi isolation in Europe during a long, relatively cool period that even included glaciations.

Neanderthals are distinguished by a unique set of anatomical features, including:
(i) a large, long, low cranial vault with a well-developed double-arched brow ridge
(ii)a massive facial skeleton with a very projecting mid-face, backward sloping cheeks, and large nasal aperture, with large nasal sinuses
(iii)an oddly shaped occipital region of the skull with a bulge or bun molars with enlarged pulp chambers, and large, often very heavily worn incisors
(iv)a mandible lacking a chin and possessing a large gap behind the last molar
(v) a massive thorax, and relatively short forearms and lower legs although short in stature they possessed robustly built skeletons with thick walled limb bones
(vi) long clavicles and very wide scapulas

Homo sapiens is a separate species from Neanderthals and other hominids By 130,000 years ago, following a prolonged period of independent evolution in Europe, Neanderthals were so anatomically distinct that they are best classified as a separate species — Homo neanderthalensis.

This is a classic example of geographic isolation leading to a speciation event. In contrast, at roughly the same time, in Africa, a body plan essentially like our own had appeared. While these early Homo sapiens were anatomically modern they were not behaviorally modern.

It is significant that modern anatomy evolved prior to modern behavior. These early sapiens were characterized by:
(i)a cranial vault with a vertical forehead, rounded occipital and reduced brow ridge
(ii)a reduced facial skeleton lacking a projecting mid-face
(ii)a lower jaw sporting a china more modern, less robustly built skeleton

Hence, the anatomical and paleogeographic evidence suggests that Neanderthals and early modern humans had been isolated from one another and were evolving separately into two distinct species. Archaeological evidence
Very interestingly, while Neanderthals and early Homo sapiens were distinguished from one another by a suite of obvious anatomical features, archaeologically they were very similar. Hominids of the Middle Stone Age of Africa (H. sapiens) and their contemporary Middle Paleolithic Neanderthals of Europe had artifact assemblages characterized as follows:
 (i)little variation in stone tool types, with a preponderance of flake tools that are difficult to sort into discrete categories
(ii)over long periods of time and wide geographical distances there was general similarity in tool kits

(iii)a virtual lack of tools fashioned out of bone, antler or ivory
(iv)burials lacked grave goods and signs of ritual or ceremony
(v)hunting was usually limited to less dangerous species and evidence for fishing is absent
(vi)population densities were apparently low
(vii)no evidence of living structures exist and fireplaces are rudimentary

Homo sapiens exhibited technological skills around 50,000 years ago.
(i) evidence for art or decoration is also lacking

The archaeological picture changed dramatically around 40-50,000 years ago with the appearance of behaviorally modern humans. This was an abrupt and dramatic change in subsistence patterns, tools and symbolic expression. The stunning change in cultural adaptation was not merely a quantitative one, but one that represented a significant departure from all earlier human behavior, reflecting a major qualitative transformation. It was literally a “creative explosion” which exhibited the “technological ingenuity, social formations, and ideological complexity of historic hunter-gatherers.”7 This human revolution is precisely what made us who we are today.

 The appearance of fully modern behavior apparently occurred in Africa earlier than anywhere else in the Old World, but spread very quickly, due to population movements into other geographical regions. The Upper Paleolithic lifestyle, as it was called, was based essentially on hunting and gathering. So successful was this cultural adaptation that until roughly 11,000 years ago, hominids worldwide were subsisting essentially as hunter-gatherers.

 In the Upper Paleolithic of Eurasia, or the Late Stone Age as it is called in Africa, the archaeological signature stands in strong contrast to that of the Middle Paleolithic/Middle Stone Age. It was characterized by significant innovation:
(i)a remarkable diversity in stone tool type
(ii)stool types showed significant change over time and space
artifacts were regularly fashioned out of bone, antler and ivory, in addition to stonestone
(iii)artifacts were made primarily on blades and were easily classified into discrete categories, presumably reflecting specialized use
(iv)burials were accompanied by ritual or ceremony and contained a rich diversity of grave goods
(v)living structures and well-designed fireplaces were constructed

(vi)hunting of dangerous animal species and fishing occurred regularly higher population densities
(vii)abundant and elaborate art as well as items of personal adornment were widespread
(viii)raw materials such as flint and shells were traded over some distances

Homo sapiens of the Upper Paleolithic/Late Stone Age was quintessentially modern in appearance and behavior. Precisely how this transformation occurred is not well understood, but it apparently was restricted to Homo sapiens and did not occur in Neanderthals. Some archaeologists invoke a behavioral explanation for the change. For example, Soffer11 suggests that changes in social relations, such as development of the nuclear family, played a key role in bringing about the transformation. Social or biological changes may account for “smarter” hominids.

 Klein7, on the other hand, proffers the notion that it was probably a biological change brought about by mutations that played the key role in the emergence of behaviorally modern humans. His biologically based explanation implies that a major neural reorganization of the brain resulted in a significant enhancement in the manner in which the brain processed information.

This is a difficult hypothesis to test since brains do not fossilize. But it is significant that no changes are seen in the shape of the skulls between earlier and later Homo sapiens. It can only be surmised from the archaeological record, which contains abundant evidence for ritual and art, that these Upper Paleolithic/Late Stone Age peoples possessed language abilities equivalent to our own. For many anthropologists this represents the final evolutionary leap to full modernity.

Shortly after fully modern humans entered Europe, roughly 40,000 years ago, the Neanderthals began a fairly rapid decline, culminating in their disappearance roughly 30,000 years ago. Neanderthals were apparently no match for the technologically advanced fully modern humans who invaded Europe and evidence for interbreeding of these two types of hominids is equivocal.

Genetic evidence
 Investigation of the patterns of genetic variation in modern human populations supports the view that the origin of Homo sapiens is the result of a recent event that is consistent with the Out of Africa Model.

(i) Studies of contemporary DNA, especially mitochondrial DNA (mtDNA) which occurs only in the cellular organelles called mitochondria, reveal that humans are astonishingly homogeneous, with relatively little genetic variation.1,5

(ii)The high degree of similarity between human populations stands in strong contrast to the condition seen in our closest living relatives, the chimpanzees.2 In fact, there is significantly more genetic variation between two individual chimpanzees drawn from the same population than there is between two humans drawn randomly from a single population. Furthermore, genetic variation between populations of chimpanzees is enormously greater than differences between European, Asian and African human populations.

 Africans display higher genetic variation than other populations, supporting the idea that they were the first modern humans.

(i)In support of an African origin for Homo sapiens the work of Cann and Wilson1 has demonstrated that the highest level of genetic variation in mtDNA occurs in African populations. This implies that Homo sapiens arose first in Africa and has therefore had a longer period of time to accumulate genetic diversity. Using the genetic distance between African populations and others as a measure of time, they furthermore suggested that Homo sapiens arose between 100,000 and 400,000 years ago in Africa.

(ii)The low amount of genetic variation in modern human populations suggests that our origins may reflect a relatively small founding population for Homo sapiens. Analysis of mtDNA by Rogers and Harpending12 supports the view that a small population of Homo sapiens, numbering perhaps only 10,000 to 50,000 people, left Africa somewhere between 50,000 and 100,000 years ago

(iii).Scientists recently succeeded in extracting DNA from several Neanderthal skeletons.8 After careful analysis of particularly the mtDNA, but now also some nuclear DNA, it is apparent that Neanderthal DNA is very distinct from our own. In assessing the degree of difference between DNA in Neanderthals and modern humans, the authors suggest that these two lineages have been separated for more than 400,000 years.

Although in its infancy, such genetic studies support the view that Neanderthals did not interbreed with Homo sapiens who migrated into Europe. It is, therefore, highly likely that modern humans do not carry Neanderthal genes in their DNA.

Additional considerations
The chronology in the Middle East does not support the Multiregional Model where Neanderthals and anatomically modern humans overlapped for a long period of time.

 (i)Cave sites in Israel, most notably Qafzeh and Skhul date to nearly 100,000 years and contain skeletons of anatomically modern humans. Furthermore, Neanderthal remains are known from sites such as the 110,000-year-old Tabun cave, which predates the earliest Homo sapiens by about 10,000 years in the region.

Neanderthals and modern humans coexisted in some parts of the world for thousands of years.

(ii)The presence of Neanderthals at two other caves in Israel, Amud and Kebara, dated to roughly 55,000 years means that Neanderthals and Homo sapiens overlapped in this region for at least 55,000 years. Therefore, if Homo sapiens were in this region for some 55,000 years prior to the disappearance of the Neanderthals, there is no reason to assume that Neanderthals evolved into modern humans

(ii).Archaeological evidence from Europe suggests that Neanderthals may have survived in the Iberian Peninsula until perhaps as recently as 30,000 to 35,000 years ago. Fully modern humans first appear in Europe at around 35,000-40,000 years ago, bringing with them an Upper Paleolithic tool tradition referred to as the Aurignacian. Hence, Neanderthals and fully modern humans may have overlapped for as much as 10,000 years in Europe. Again, with fully modern humans on the scene, it is not necessary to have Neanderthals evolve into modern humans, further bolstering the view that humans replaced Neanderthals.

Neanderthals probably did not breed with modern humans but they borrowed some of their tools and skills

  (i)The situation in southern France is, however, not quite as clear. Here, at several sites, dating to roughly 40,000 years there is evidence of an archaeological industry called the Châtelperronian that contains elements of Middle and Upper Paleolithic artifacts. Hominids from these sites are clearly Neanderthals, sparking speculation that the Châtel perronian is an example of Neanderthals mimicking the culture of modern humans. The lack of anatomical intermediates at these sites, suggests that if Neanderthals did encounter and borrow some technology from Homo sapiens, they did not interbreed.

(ii)A potential 24,500-year-old Neanderthal/sapiens hybrid was announced from the site of Lagar Velho, Portugal.4 This 4-year-old has a short, squat body like a Neanderthal, but possesses an anatomically modern skull. There are a number of problems with interpreting this find as a Neanderthal/sapiens hybrid.14 First of all, as a hybrid it should have a mixture of traits throughout its body and not possess the body of a Neanderthal and skull of a modern human. For example, if we look at hybrids of lions and tigers they do not possess the head of one species and the body of the other, but exhibit a morphological mixture of the two species. Secondly, and more importantly, acceptance of this specimen as a hybrid would suggest that Neanderthal traits had been retained for some 6,000 to 10,000 years after Neanderthals went extinct, which is highly unlikely. This is theoretically unlikely since Neanderthal traits would have been genetically swamped by the Homo sapiens genes over such a protracted period of time.

(iii) Proponents of the Multiregional Model, such as Milford Wolpoff, cite evidence in Asia of regional continuity. They see an evolutionary link between ancient Homo erectus in Java right through to Australian aborigines. A possible problem with this view is that recent dating of late surviving Homo erectus in Indonesia suggests that they survived here until 50,000 years ago, which is potentially when fully modern humans may have arrived in the region from Africa

.(iv)China may contain the best evidence for supporting the Multiregional Model. Here there are discoveries of a couple of skulls dated to roughly 100,000 years ago that seem to possess a mixture of classic Homo erectus and Homo sapiens traits. Better geological dating and more complete specimens are needed to more fully assess this possibility.

Conclusion
 For the moment, the majority of anatomical, archaeological and genetic evidence gives credence to the view that fully modern humans are a relatively recent evolutionary phenomenon. The current best explanation for the beginning of modern humans is the Out of Africa Model that postulates a single, African origin for Homo sapiens. The major neurological and cultural innovations that characterized the appearance of fully modern humans has proven to be remarkably successful, culminating in our dominance of the planet at the expense of all earlier hominid populations.

Paleoanthropologist Donald C. Johanson, is professor of anthropology and Director of the Institute of Human Origins at Arizona State University. He is best known for his discovery of “Lucy”, a 3.2 million-year old Australopithecus afarensis skeleton he found in 1974 in Ethiopia.

His books include Lucy: The Beginnings of Humankind and, most recently, From Lucy to Language. Dr. Johanson hosted the Emmy-nominated NOVA television series In Search of Human Origins.

Article references (Sien asb oorspronklike artikel)
  author glossary
 Gene flow - the flow of genes from one population to another.
Genetic drift - the change of gene frequency from one generation to another caused by the cumulative effects of random fluctuations, rather than by natural selection.
Mitochondrial DNA - the DNA found only in the mitochondria (the powerhouses of the cell) and inherited only from the mother.
Morphology - the scientific study of the form and structure of organisms.
Paleoanthropology - the study of human origins, the study of the fossil and cultural remains of extinct human ancestors.
Taxonomy - the classification of organisms into groups according to their relationships and the ordering of these groups into a hierarchical arrangement.

 Dit is interessant om daar op te Let dat navorsers van die Max Planck institute bevind het dat :

  Neandertals made the first specialized bone tools in Europe Edited by Erik Trinkaus, Washington University, St. Louis, MO, and approved May 22, 2013 (received for review February 12, 2013)

 Abstract :
"Modern humans replaced Neandertals ∼40,000 y ago. Close to the time of replacement, Neandertals show behaviors similar to those of the modern humans arriving into Europe, including the use of specialized bone tools, body ornaments, and small blades. It is highly debated whether these modern behaviors developed before or as a result of contact with modern humans. Here we report the identification of a type of specialized bone tool, lissoir, previously only associated with modern humans. The microwear preserved on one of these lissoir is consistent with the use of lissoir in modern times to obtain supple, lustrous, and more impermeable hides. These tools are from a Neandertal context proceeding the replacement period and are the oldest specialized bone tools in Europe. As such, they are either a demonstration of independent invention by Neandertals or an indication that modern humans started influencing European Neandertals much earlier than previously believed. Because these finds clearly predate the oldest known age for the use of similar objects in Europe by anatomically modern humans, they could also  be evidence for cultural diffusion from Neandertals to modern humans."

Ander navorsing.

 Denisovan DNA suggests a dark complexion and interbreeding ww.nhm.ac.uk/about-us/news/2012/august/denisovan-dna-suggests-a-dark-complexion-and-interbreeding113697.html 

 31 August 2012 Replica of the finger bone fragment from the ancient Denisovan human who lived about 75,000 years ago. Scientists have obtained its complete genome. © Max Planck Institute for Evolutionary
(sien foto in artikel)

Anthropology Scientists have reconstructed the whole genetic code, or genome, of a group of ancient humans called Denisovans. They interbred with our species and the DNA results suggest they had dark hair, eyes, and skin, the journal Science reports.

 In 2010, scientists from the Max Planck Institute in Germany announced the new human group based on DNA evidence from a finger bone fossil found in Denisova Cave in the Altai Mountains, Siberia.

 That first DNA was obtained from mitochondria, tiny power structures in each human cell that contain their own DNA. Now, many of the same team have used a new approach and have sequenced chromosomal DNA (the DNA of the cell nucleus which contains most genes) from the same finger bone fossil.

'They were able to reconstruct the whole genome to a quality matching that obtained for living humans,' says Professor Chris Stringer, human origins expert at the Natural History Museum. 'The higher quality genome not only provides greater confidence about previous conclusions, but also adds many details about the Denisovans, and how modern humans may have differed from them,' adds Stringer.

Skull of Homo heidelbergensis, the ancient human species that may be the ancestor of the mystery Denisovan human. (sien oorspronklike artikel)

'The research confirms that the Denisovans were related to the Neanderthals, and that many present-day Australasians have Denisovan DNA from an ancient interbreeding event.'

Some theories place Denisovans, along with Neanderthals and modern humans, as the descendents of the ancient human Homo heidelbergensis who lived about 500,000 years ago.

 Potential biological differences
 By comparing the genomes of Denisovans, apes, Neanderthals and different modern human populations, the team could identify DNA segments unique to these different groups.

 This may help shed light on potential biological differences between modern humans and the Neanderthal and Denisovan populations they replaced, Stringer says. 

For example, in modern humans, unique segments were associated with brain function and nervous system development, as well as diseases affecting the skin and eyes.

'Perhaps some of the skin and eye-related ones reflect resistance to diseases in the African homeland of modern humans, but the brain-related ones hint at possible enhancements in brain structure and function in our species.'

Two Neanderthal interbreeding events?
Skull of a Neanderthal, Homo neanderthalensis (sien oorspronklike artikel vir prentjie)

The Denisovan genome also reveals more clues about Denisovan and Neanderthal interbreeding with modern humans. Until now, evidence suggested that after modern humans dispersed from Africa about 60,000 years ago, there was a single interbreeding event with Neanderthals. '

Previous research suggested that all recent populations originating from outside of Africa had received about the same amount of Neanderthal input, implying a single early hybridisation event somewhere like the Middle East,' says Stringer.

 However, the results of this study show that the Neanderthal genetic input to modern human populations outside of Africa varies. 'This suggests that, overall, Europeans have less Neanderthal DNA (about 1%) than populations to the east (1.7%),' explains Stringer. '

This might imply changes in the proportions after interbreeding took place, or that there was more than one interbreeding event.'

 Denisovan interbreeding confirmation

The team found that the Denisovan genetic input in Australasian populations averaged about 3%. 'This supports the idea that Denisovans must have been present in south east Asia, where the hypothesised interbreeding with the ancestors of present-day Australasians occurred, as well as in Siberia,' says Stringer.

Low genetic diversity
 Our genes often come in different variants, such as those for skin colour or eye colour and a large population will generally hold more variation than a small population. But, the Denisovan DNA results showed very low diversity, much less than a single modern human would show, says Stringer.

 'This is surprising because the previous mitochondrial DNA research had suggested relatively high diversity, and interbreeding with the ancestors of Australasians (who are thought to have passed through southern Asia rather than Siberia) implied that the Denisovans were widespread in Asia, also leading to the expectation of a large and diverse population.'

'The surprisingly low genetic diversity of the Denisovans may indicate, as with Neanderthals to the west, that the core territory of the Denisovans was well to the south, and that they only expanded to regions like the Altai during brief warm intervals, and in small numbers.'

Other physical features
 Apart from the genetic evidence of a dark complexion, Stringer says we need to find out more about what the Denisovans looked like physically. 'This will require the recovery of ancient DNA from more complete fossils, perhaps in Denisova Cave itself, or from specimens in regions like China,’ he says.

'The genome does not tell us how big their brains or brow ridges were, if they had chins, or how tall and robust they were. Hence we need to have Denisovan DNA from more complete fossils to link the genome to morphology'.

 Function of shared DNA
Stringer says that further research should also help explain what function, if any, the Denisovan and Neanderthal DNA has in the modern humans that hold it.
More interbreeding
Finally, there is an issue that perhaps cannot be addressed properly until higher quality reconstructions of Neanderthal genomes also become available, says Stringer. If modern humans interbred successfully with both Neanderthals and Denisovans, did Neanderthals and Denisovans interbreed?

Stringer thinks this is likely. 'It seems highly probable that they did, given that they co-existed in Eurasia for hundreds of millennia, and Denisova cave itself has evidence of Neanderthal DNA in a fossil foot bone.'

Stringer concludes, 'Recognition of such interbreeding will inevitably complicate the untangling of the relationships between these ancient groups of humans, and their contributions to people today.'     

Dit is dus duidelik dat heel wat navorsing nodig is, maar dat navorsing tans meer die teorie
'Out of Africa' ondersteun.

Beste Chris en Cornelius,

Beste Cornelius,