Posted on 09/05/2001 5:05:20 PM PDT by sarcasm
Part 1: The debate
Over recent years, there has been a loud debate within palaeoanthropology over the origins of anatomically modern humans, or AMH. Opinions have polarized into two camps: Multiregional Evolution, or MRE, and Out-of-Africa, or OOA.
The former group of anthropologists, including Milford Wolpoff and Loring Brace, argue that ever since members of the genus Homo first spread out of Africa, probably before 1 million years ago (mya), we have all been members of one species. The many different populations of humans were all subject to natural selection, and gradually evolved along similar lines.
These different populations may have passed through different grades, so that at 1.0 mya they were all Homo erectus, while at 0.5 mya they were all Homo sapiens. But they never divided into two or more species because there was always sufficient gene flow across Eurasia to maintain genetic continuity.
The latter group, including vocal proponents Chris Stringer and Ian Tattersall, argue that all living humans are descended from an African population that lived within the last 200 thousand years (kya). They argue that earlier, non-African hominids belong to distinct species, such as Homo neanderthalensis, and that they have left no trace in the modern gene pool.
In Europe, in particular, OOA supporters see a strong discontinuity between Neanderthals and AMH. They believe that the physical and cultural differences between the two, and their apparent coexistence for several millennia, are evidence for a species-level distinction. Neanderthals were out-competed and replaced by moderns. Some even believe that there may have been genocidal warfare between the two.
In both Europe and Asia, MRE supporters point to evidence for continuity in particular morphological traits from earlier populations to later ones. They agree that modern Europeans do not look particularly similar to Neanderthals, but believe that they appear more so than non-Europeans do. Similarly, they see persistence of other skeletal traits from Javan Homo erectus through modern Australian Aborigines.
Some anthropologists take an intermediate position, arguing that there was a population movement out of Africa but that these migrants interbred with older local populations. They see the intermediate morphology of skeletons such as Lagar Velho 1 as a sign of hybridization.
Single origin supporters see the same remains (primarily skulls) differently. They argue that there are no clear regional continuities, and that any that do exist can be explained by parallel adaptation to the same environment. Instead, they see all AMH skeletal remains as fundamentally similar to those found in sub-Saharan Africa at sites such as Klasies River Mouth at 120 kya.
Genetic evidence has slowly mounted to support the OOA case. Humans exhibit far less genetic variation than any of our cousins do, despite our visible differences in phenotype. This indicates shared recent ancestry, and many estimates have placed that ancestry after 200 kya. But any reconstruction based purely on modern genetic variation is just that, a reconstruction, and does not prove that all of our common ancestry is that recent.
Recently, mitochondrial DNA from three Neanderthal specimens has been analyzed. The three individuals were all quite distinct from all known modern sequences, which provided support for their non-ancestral status. Judging from the popular press, these studies were the final nail in MRE's coffin.
That tone changed dramatically last week, when news stories appeared about two different studies that counter the genetic and skeletal evidence for OOA. While neither of these studies proves MRE to be true, they suggest that the actual picture is far more complicated than many OOA supporters admit.
Part 2: New evidence
The first study appears this week in the Proceedings of the National Academy of Sciences. Gregory Adcock and colleagues present mtDNA sequences from ten ancient Australian skeletons. Six of these individuals are very robust morphologically and come from Kow Swamp, dating to 8-15 kya, and three are more gracile and date to sometime after 10 kya. The tenth, Lake Mungo 3, is also gracile, and is significantly older than the others. The authors accept a date that has been proposed elsewhere of 62,000 kya; others argue that 20 kya is more accurate.
The gracile skeletons are well within the range of variation of contemporary Australian Aborigines. The robust individuals are not, and some anthropologists have previously argued that the two groups represent two different ancient migrations to the continent, whose descendants fused into modern Aborigines. Others have disputed this model, arguing that the apparent variation is the result of sexual dimorphism, poor preservation, pathology, and inadequate dating. The mtDNA samples from the two groups could not be distinguished from each other or from modern Aboriginal samples, which supports either argument. All samples fit within the broader pattern of modern mtDNA variation that has been taken to support the OOA model.
All, that is, save Lake Mungo 3, the oldest of the skeletons (whether or not one accepts 60 kya). The mtDNA from this individual is distinct from that of all living humans. It is not as distinct as the three Neanderthal sequences, but it clearly can trace its ancestry back well beyond the other known modern haplotypes. Genetically, it is highly unlikely that the maternal ancestry of this individual can be traced back to Africa within the past 200,000 years.
What does this mean? Despite some press reports, it does not mean that we are all descended from Australians. It does mean that not all anatomically modern humans can trace their ancestry to a recent African origin. If an individual who is morpologically indistinguishable from modern Australians has an extinct mtDNA haplotype, other individuals with extinct haplotypes, like the Neanderthals, cannot be excluded from modern human ancestry on mtDNA grounds alone.
On a broader scale, it suggests that the limited variation in modern human mtDNA may be the result of either genetic drift, which over time has caused other mtDNA lineages to go extinct, or natural selection in favor of one particular type of mtDNA for some unknown reason. In either case, modern mtDNA variation does not necessarily tell us a thing about ancient population history.
The second study appeared last Friday in Science. In it, Milford Wolpoff and colleages examined the morphology of one early skull from Australia, Willandra Lakes 50, and two from Mladec, Czech Republic. These are some of the earliest and most complete skulls that everyone agrees are anatomically modern.
They compared these skulls to those which MRE and OOA supporters might consider ancestral to them: The Australian skull to crania from Ngandong, Java, and a variety of sites in the Near East and Africa, and the Mladec skulls to European Neanderthals as well as male crania from Qafzeh and Skhul in Israel. If the replacement model is true, then WLH-50 should be more similar to the Levantine and African specimens than to those from Ngandong, while the Mladec crania should be more similar to Skhul and Qafzeh than to classic Neanderthals.
To perform these comparisons they scored 16 non-metric traits on WLH-50 and 30 on Mladec, and compared presence/absence of each trait to each other skull. They found that WLH-50 was more similar to 6 of the 7 Ngandong skulls than it was to any from Africa or the Near East. Mladec 5 was most similar to three Near Eastern skulls, but Mladec 6 was more akin to the Neanderthals.
Although the sample sizes of both individuals and traits were small, statistical tests indicated that the recent African origin hypothesis was not proven. That is, from this data the more recent anatomically modern humans were no more closely related to earlier "AMH" specimens than they were to "archaic" specimens, whether Neanderthal or Javan.
The conclusion that these two studies most clearly point to is that the complete replacement theory is probably an overstatement. Reality was a bit messier. Yes, there may have been extensive gene flow out of Africa within the past 100,000 years. But this was not the expansion of a genocidal new species. Different regions had their own population histories: In some areas, earlier populations may well have left no descendants, while in other places, resident and immigrant populations did mix.
They also highlight how little we still know about the process. Morphological and genetic studies of more well dated fossils from throughout the Old World are needed before we can pin down the details of the transformation to modernity.
However, it is the ancient practice of humanity to "trade daughters" among and between tribes.
Then there's always the "wondering male hunting party" - no doubt it has an effect. But it's still the female side that is relocated from one group to another. Over time gene combinations that first appeared in Siberia ended up in Kenya. No one had to travel the distance. All they had to do was trade daughters from one tribe to another, whether as captives or wives, or maybe as just "good friends", and next thing you know "Eve" is in Kenya.
Our supposed "nearest simian relatives", the chimps, are also reported to trade the girls.
If these 'people' were modern humans, they had to have been able to speak. Languages seem to be a much more accurate way to trace geopgaphic origins than by using a remarkably few skulls - or more accurately, skull fragments, ie: a few teeth and a piece of jawbone - to reconstruct an entire society of humanlike sub-species.
I think what this article is trying to avoid, and not very well, is that if someone is to believe in MRE they MUST, by definition, believe that not ALL humans are equally evolved. There is no practical way to avoid coming to the conclusion, that if we did not all spring from one evolutionary root, then some of us are more or less evolved than others.
The truth hurts, IF you are an evolutionist!
Just wandering,
Mungo Man could be African: scientists.)
By Richard Macey
Scientists expressed caution yesterday over claims by Australian researchers that cast doubt over the theory that modern man emerged from Africa.
Dr Alan Thorne, an anthropologist with the Australian National University, scored headlines around the globe with findings suggesting that modern humans evolved everywhere.
His claims are based on DNA recovered from the skeleton of Mungo Man, who lived and died about 60,000 years ago near South Australia's Lake Mungo.
That makes the DNA about 32,000 years older than any human DNA found before.
Mungo Man, said to have been physically similar to people living today, had one significant difference. Within his DNA, the scientists found a gene that Dr Thorne described as "unlike any alive today".
The scientists argue that had Mungo Man descended from modern humans flowing out of Africa, his genetic line should have also flowed on, rather than become extinct.
They believe the discovery backs the theory of "regional continuity" that says modern man evolved around the world as people interbred.
They argue that Mungo Man's ancient gene, responsible for supplying energy to the brain, probably became extinct as his descendants mingled with new arrivals.
Scientists around the world lauded the team's success in extracting 60,000-year-old DNA.
But Dr Peter Underhill from California's Stanford University said Mungo Man's ancestors "could have originated in Africa".
"It doesn't mean out of Africa is kaput," he said. "The problem with such ancient DNA is such specimens are few and far between ... it would be nice to see it reproduced independently elsewhere.''
The Australian Museum's head of evolutionary biology, Dr Don Colgan, said there could be another theory on why Mungo Man's gene had become extinct: "Maybe if you looked hard you might find it. It's still one individual."
In April 1999, the discovery of a human skeleton from Lagar Velho in Portugal was announced in the media, followed by a scientific paper a couple of months later (Duarte et al. 1999).
The skeleton is of a young boy, about 4 years in age, who was deliberately buried about 24,500 years ago. According to the paper's authors, which included Neandertal expert Erik Trinkaus, the skeleton contains a mixture of features from both modern humans and Neandertals, and is best explained as being a hybrid.
And because it is dated to be at least 4,000 years more recent than the last known Neandertals, they consider it to be not the result of a direct interbreeding, but the descendant of a hybrid population which persisted for thousands of years.
If true, this would strongly support the claim that Neandertals should be considered a subspecies of modern humans (Homo sapiens neanderthalensis), rather than a separate species, Homo neanderthalensis.
I wonder why recient migrations always seem to be from east to west
This is true. Descendants of this group include Libertaranus Flaccidus, Geekus Wallflowerus, and Startrekus Virginus.
There was another group- "the wandering male hunting party"whose descendants include Bubbus Hillbillus, Lechus Buttofuccus, and the African offshoot, Jexxus Jaksonus.
Indo-European got started in the westernmost part of the Eurasean plains. The words in different Indo-European languages that are related do not fit in with the geography, animals, ect. of Anatolia, but they do fit southern Russia. Now, the actual Indo-European people are mostly descended from Anatolian farmers, but the language was imposed by conquering horsemen.
Indo-European Languages, the most widely spoken family of languages in the world, containing the following subfamilies: Albanian, Armenian, Baltic, Celtic, Germanic, Greek, Indo-Iranian, Italic (including the Romance languages), Slavic, and two extinct subfamilies, Anatolian (including Hittite) and Tocharian. About 1.6 billion people speak Indo-European languages today.
II. Establishment of the Family
Proof that these highly diverse languages are members of a single family was largely accumulated during a 50-year period around the turn of the 19th century. The extensive Sanskrit and ancient Greek literatures (older than those of any other Indo-European language except the then-undeciphered Hittite) preserved characteristics of the basic Indo-European forms and pointed to the existence of a common parent language. By 1800 the close relationship between Sanskrit, ancient Greek, and Latin had been demonstrated. Hindu grammarians had systematically classified the formative elements of their ancient language. To their studies were added extensive grammatical and phonetic comparisons of European languages. Further studies led to specific conclusions about the sounds and grammar of the assumed parent language (called Proto-Indo-European), the reconstruction of that hypothetical language, and estimates about when it began to break up into separate languages. (By 2000 BC, for example, Greek, Hittite, and Sanskrit were distinct languages, but the differences among them are such that the original tongue must have been fairly unified about a millennium earlier, or about 3000 BC.) The decipherment of Hittite texts (identified as Indo-European in 1915) and the discovery of Tocharian in the 1890s (spoken in medieval Eastern Turkistan, and identified as Indo-European in 1908) added new insights into the development of the family and the probable character of Proto-Indo-European.
The early Indo-European studies established many principles basic to comparative linguistics. One of the most important of these was that the sounds of related languages correspond to one another in predictable ways under specified conditions (see Grimm's Law and Verner's Law for examples). According to one such pattern, in some Indo-European subfamilies—Albanian, Armenian, Indo-Iranian, Slavic, and (partially) Baltic—certain presumed q sounds of Proto-Indo-European became sibilants such as s and s (an sh sound). The common example of this pattern is the Avestan (ancient Iranian) word satem ("100"), as opposed to the Latin word centum ("100," pronounced "kentum"). Formerly, the Indo-European languages were routinely characterized as belonging either to a Western (centum) or an Eastern (satem) division. Most linguists, however, no longer automatically divide the family in two in this way, partly because they wish to avoid implying that the family underwent an early split into two major branches, and partly because this trait, although prominent, is only one of several significant patterns that cut across different subfamilies.
III. Evolution
In general the evolution of the Indo-European languages displays a progressive decay of inflection. Thus, Proto-Indo-European seems to have been highly inflected, as are ancient languages such as Sanskrit, Avestan, and classical Greek; in contrast, comparatively modern languages, such as English, French, and Persian, have moved toward an analytic system (using prepositional phrases and auxiliary verbs). In large part the decay of inflection was a result of the loss of the final syllables of many words over time, so that modern Indo-European words are often much shorter than the ancestral Proto-Indo-European words. Many languages also developed new forms and grammatical distinctions. Changes in the meanings of individual words have been extensive.
IV. Ancient Culture
The original meanings of only a limited number of hypothetical Proto-Indo-European words can be stated with much certainty; derivatives of these words occur with consistent meanings in most Indo-European languages. This small vocabulary suggests a New Stone Age or perhaps an early metal-using culture with farmers and domestic animals. The identity and location of this culture have been the object of much speculation. Archaeological discoveries in the 1960s, however, suggest the prehistoric Kurgan culture. Located in the steppes west of the Ural Mountains between 5000 and 3000 BC, this culture had diffused as far as eastern Europe and northern Iran by about 2000 BC.
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