Homo Longi Were Probably Denisovans

Homo longi ("Dragon men") the new species identification temporarily assigned to a Chinese specimen with a mix of archaic and modern features was probably one of a fairly heterogeneous species of hominin known genetically as Denisovans after the cave in Siberia where their DNA was first characterized. They were the predominant post-Homo erectus hominin of Asia and modern Papuans and Australian aborigines have particularly high level of Denisovan admixture which is present at trace levels in other Asians and in the indigenous peoples of the Americas. 

Their facial structure, although not necessarily their stature or build, resembles the typical artistic depiction of J.R.R. Tolkien's dwarves. An artist's impression of this archaic hominin previously known only from teeth and DNA is as follows:

 

Background and Analysis

The images above (via John Hawks) capture the big picture of archaic hominins. As Razib Khan explains, setting the background:

In 2010, genomes recovered from ancient remains of “archaic hominins” in Eurasia turned out to have genetic matches in many modern humans. . . . we had to get used to the new reality that a solid 2-3% of the ancestry of all humans outside Africa is Neanderthal. About 5% of the ancestry of Melanesian groups, like the Papuans of New Guinea, actually comes from a previously unimagined new human lineage discovered in Denisova cave, in Siberia of all places. . . . Trace, but detectable (0.2% or so), levels of “Denisovan” ancestry are found across South, Southeast, and East Asia (as well as among indigenous people of the Americas). Similarly, trace but detectable levels of Neanderthal ancestry actually appear in most African populations. And, though we have no ancient genomes to make the triumphant ID, a great deal of circumstantial DNA evidence indicates that many African groups harbor silent “archaic” lineages equivalent to Neanderthals and Denisovans. We call them “ghost” populations. We know they’re there in the genomes, but we have no fossils to identify them with. . . . an Israeli group has a paper out in Science on a human population discovered there which seems to resemble Neanderthals and dates to 120,000 to 140,000 years ago. . . .

Neanderthals, Denisovans, and modern humans are just the main actors in the plotline of our species’ recent origins. Today on our planet there is just one human species, but this is an exceptional moment. For most of the past few million years there were many human species. Up until 50,000 years ago in the Southeast Asian islands of Flores and Luzon, we see strong evidence of very specialized species of small humans, the pygmy Hobbits and Homo luzonensis. They are different not only from each other, but from modern humans, Denisovans and Neanderthals. In Africa, there were almost certainly very different human populations which over time were absorbed, just as the Denisovans and Neanderthals were. Homo naledi in South Africa almost certainly persisted down to the period of the rise of modern humans on the continent, 200,000 years ago.

Finally, a great deal of circumstantial archaeological and genetic evidence is accumulating that some earlier African lineages related to modern humans expanded out into eastern Eurasia before our own expansion. Artifacts in China and Sumatra dating to before 60,000 years ago seem suspiciously modern, and genetic analysis of Siberian Neanderthals dating to 120,000 years ago suggests admixture from populations related to modern humans. It is still possible that Homo longi descends from one of these early populations. Only DNA can establish this for a fact, but most older fossil remains do not yield genetic material, and this skull is old enough that only perfect conditions would have yielded DNA.

Ancient hominins from China ca. 200,000 to 100,000 years ago with a mix of archaic and modern features were probably Denisovans. John Hawks calls them "H. antecessor groups with the Jinniushan-Dali-Harbin-Xiahe clade." 

A new published journal article describes a specimen skull from these archaic hominins and puts them in context. Morphologically, it is closer to modern humans than to Neanderthals, although Denisovan DNA is shares a clade closer to Neanderthals than to modern humans (within the clade that all three share), and this is likely what this specimen is (although we don't have DNA to confirm it). It is akin to several other roughly contemporaneous sets of remains from Asia:

Razib Khan has this commentary:

Some researchers want to call “Dragon Man” Homo longi (龙, pronounced lóng, being Chinese for dragon), a new human species, and assert its features mean it is more closely related to modern humans than Neanderthals. This is particularly true of the Chinese researchers, in whom I can’t help but sense a drive to establish precedence for China as one of the major hearths of modern humans.*

Paleoanthropologists outside of China seem more inclined to believe that “Dragon Man” is actually the paradigm-busting species we have only known definitively from genomics: Denisovans. This faction points out that “Dragon Man” had massive teeth, just like a confirmed Denisovan jaw discovered in Tibet in 2019 (ancient-protein analysis indicated it was Denisovan). So why do others disagree? Because the skull is so intact they performed an evolutionary analysis of its relationships, using a full suite of characteristics (unfortunately the find did not yield DNA). On that inferred family tree, Homo longi lies closer to modern humans. In contrast, we know from genomics that Denisovans are more closely related to Neanderthals than they are to modern humans.

My bet is that Homo longi and Denisovans are one and the same. Or, more precisely, Homo longi is one of the many Denisovan lineages. 

. . .

The best genetic work indicates that Denisovans were not one homogeneous lineage, as seems to have been the case with Neanderthals, but a diverse group that were strikingly differentiated. The Denisovan ancestry in modern populations varies considerably in relatedness to the genome sequences from Denisova cave. It is clear that the Denisovan ancestry in Papuans is very different from the Siberian Denisovan sequences. The most geographically distant Denisovan groups, those in Siberia and those from on the far edge of Southeast Asia into Wallacea, were likely far more genetically different from each other than Khoisan are from the rest of humanity. Depending on the assumptions you set your “molecular clock” with, the most distant Denisovan lineages probably separated into distinct populations from each other 200,000 to 400,000 years before their extinction.

John Hawks states in a Tweet:

Now, we have learned a few things from DNA and ancient proteins. H. antecessor is a sister of the Neandertal-Denisovan-modern clade. Neandertals, today's humans, and Denisovans share common ancestors around 700,000 years ago. Neandertals and Denisovans were related.

I agree that the Homo longi remains are probably Denisovans. 

The main new article is Xijun Ni, "Massive cranium from Harbin in northeastern China establishes a new Middle Pleistocene human lineage" The Innovation (June 25, 2021) (open access).

Very Early Sky Burials?

John Hawks observes a new hypothesis about the death rituals of a very early Neolithic village, which are called "sky burial" where similar rituals are still practiced, for example, by Zoroastrians and Tibetan Buddhists, the first of which is a faith vital in historic times near the archaeological site in question. 

The archaeological site of Çatalhöyük, in present-day Turkey, is one of the most significant early Neolithic villages to have been excavated. It was occupied between around 7100 and 6000 BC, and at its height was occupied by more than 3500 people. An array of human skeletal remains have been found at the site. . . .  Marin Pilloud and coworkers in 2016 published a paper suggesting that the Çatalhöyük bodies were possibly defleshed by vultures. A brief excerpt from the conclusion gives the gist of their argument:

"The burial practices at Çatalhöyük (i.e., removal of cephalic extremity, limb removal, tight flexion) as observed in the archaeological record are often consistent with some manner of flesh removal prior to interment. It seems possible based on current forensic experimental work that the people of Çatalhöyük may have employed vulture excarnation prior to interment. Based on human studies, vultures are unlikely to leave marks on the bone that would be visible 9000 years later."

It’s an interesting concept. The paper goes into some of the symbolic meanings of vultures and the possibility that bodies were exposed on the roofs of residences for vultures to approach.

Were Classic SW Asian Neanderthals Admixed?

John Hawks (whom I am fated to miss every time he is in Denver to give a talk), has published a timely new survey of the state of knowledge in multiple disciplines regarding Neanderthals in light of new scientific developments.

The New Genetic Developments

The most profound development has been the sequencing of ancient DNA samples. He notes, in a decidedly glass half empty response to a near miracle of modern technology that "the genetic data from Neandertal skeletal remains are sparse, with fewer than two dozen mtDNA sequences (Dalen et al., 2012), and only six specimens with substantial nuclear DNA information (Green et al., 2010)." We also have a few nuclear genomes from the Denisova Cave in the Altai Mountain area of Russia.

Genetic data collected from modern populations have disclosed that all ancestrally non-African modern populations show a low percentage of Neanderthal admixture that can be confirmed by direct comparison with the ancient genomes. Likewise, Papuans, Australian aborigines, and populations derived from them, have significant Denisovan admixture in addition to their Neanderthal admixture that can be confirmed by direct comparison to ancient Denisovan genomes. A few of the oldest ancient nuclear DNA samples from Europe, most recently in the case of Otzi the Iceman, have likewise revealed distinctive Neanderthal DNA admixture patterns.

We have no ancient genomes to use as comparison samples from Africa. But, the same statistical methods that suggested that there might be ancient hominin ancestry where direct comparison later confirmed Neanderthal and Denisova admixture in modern genomes has also detected traces of ancient hominin admixture with at least one or two ancient hominin species in Africa that survives today in some Central African Pygmies and Southern African Khoi-san peoples, who are sometimes described as "Paleoafrican" because their uniparental genetic lineages are more basal in the phylogeny of modern human genetics than any others on earth.

The New Archaelogical Developments

There has also been a steady stream of new archaeological evidence from new excavations. The most notable of these has been discovery of a new ancient hominin species, Homo Florenesis sometimes called "Hobbits," over the objections of J.R.R. Tolkien estate, on the island of Flores in Indonesia, very close to the place where Denosivan genetic admixture starts to appear in indigenous populations.

Other important finds have been the discovery of the first post-Toba explosion, pre-Australian and Papuan settlement modern human remains in a cave in the Southeast Asia highland of Zomia, a correction to the dating of the youngest Homo Erectus specimen in Indonesia making it a pre-Toba eruption specimen, the discovery of Neanderthal remains not far from the Denisova Cave, clarification of the sequencing and dating of Neanderthal occupations and subsequent modern human occupations of sites in Europe, and the discovery of the use of a few technological techniques by Neanderthals in Europe that had not previously been documented.

Among other things, the improved dating has shown the arrival of modern humans in Europe to have been a more rapid colonization than had previously been assumed. This has also permitted a more nuanced analysis of the relationship between the arrival of modern humans in Europe, the decline of Neanderthals in Europe, and contemporaneous major volcanic eruptions and climate developments.

New archaeological excavations in Arabia that have just started to become available to member of the public have pushed back the earlier orthodoxy about when modern humans emerged from Africa finding distinctively modern human relics in inland Arabia more than 100,000 years ago with a clear affinity to contemporaneous Nuba complex modern human relics in Africa.

Hawks On Neanderthal Types

Much of Hawks paper simply summarizes some of these new developments, but the really powerful addition that his paper makes is in its revisiting of physical anthropology subtyping of Neanderthals skeletal remains that had culminated in a paper by Howell in 1957. The remainder of the paper then begins to fit these subtypes into a narrative in the context of the other evidence.

Howell distinguished Neanderthal remains by era, roughly speaking those before and after 100,000 years ago (the former being "early" and the latter "classical") and by region, with Southwest Asian instances being distinct from those to the North on a North-South axis, and other distinctions emerging in his study and later ones on an East-West axis in Eurasia.

Hawks makes this key observation on page 6 of the paper:

A problematic aspect of the idea of Levantine Neandertals is that the very features that distinguish them from European Neandertals tend to align them with modern humans. For example, the Amud skeleton has stature and limb proportions that set it apart from European Neandertals, but that fall within the range of variability of the Skhul and Qafzeh skeletal remains. Trinkaus (1995) considered the Near East, including Shanidar and the Levantine samples, to include two forms of hominins: “late archaic” and “modern” forms. He argued that the late archaic forms in the Near East have no close connection to European Neandertals, and that similar features reflect mosaicism or generalized archaic morphology in both evolving populations.

Several workers after Howell added the concept of a north-south axis of Neandertal diversification within Europe. Rosas and colleagues (2006) noted that southern Neandertals tend to have increased heights of the lower face and broader faces than the northern sample of Neandertals within Europe. Because the line separating north and south must run along the very long east-west axis of Europe, there are many possible ways to divide the continent into northern and southern samples.

Connecting The Dots

Hawks pulls his punches and refrains from sweeping conclusions, ending his paper with the simple observation that the genetic evidence and archaeological evidence alike indicate that there were several distinct subtypes of Neanderthals in space and time whose categorization has still to be worked out.

But, being the fool who rushes in where angels fear to tread, it isn't hard for me or anyone else familiar with the data to connect the dots.

The emerging genetic evidence suggests that modern human-Neanderthal hybridization probably took place after the Out of Africa event but well before the Upper Paleolithic revolution with Southwest Asia as a prime candidate for the location of this event, as that is where first contact must have taken place and the modern human range did not extend to Europe or further than India for much of that time period.

The obvious conclusion to jump to would be that the similarity of "classic" era Southwest Asian physical skeletal remains to modern humans, relative to Neanderthals elsewhere and from earlier eras, would be that these similarities are due to the impact of modern human-Neanderthal admixture on the Neanderthal populations of the Southwest Asia.

Likewise, an obvious conclusion to jump to that few professional anthropologists have committed to stating forthrightly, is that the post-Mousterian technological cultures of the Neanderthals may have been the product of the increased capabilities of admixed Neanderthals in those communities relative to their pure Neanderthal predecessor.

Hawks has instead advanced the hypothesis that Neanderthals were more fully within the range of modern human variation than they are given credit for being and were more human-like in general than previously assumed. His public comments lean towards the notion that Neanderthals were more of a subspecies of Homo Sapiens than a separate hominin species.

But, personally, I am more inclined to interpret the evidence of behavioral modernity and morphological similarity between Neanderthals and modern humans, not as much as a sign of convergent evolution or close evolutionary relationships, as it is a manifestation of highly influential admixture with modern humans. Indeed, in Southwest Asia and toward the end of the period of Neanderthal and modern human cohabitation of Europe, Neanderthals may have been more admixed with us than we were with them.

Reference

John Hawks, "Dynamics of genetic and morphological variability within Neanderthals" 90 Journal of Anthropological Sciences 1-17 (2012).

John Hawks In Boulder On Friday

John Hawks will be giving a talk in Boulder, Colorado at 4:00 p.m. this Friday on the Neanderthal genome.  Health and workload permitting, I plan to go and then to blog on the talk here.

John Hawks on Andrew Lawler On Steven Pinker

Is human "progress" real in the sense that there is a secular trend towards reduced violence?

This is the core premise of Steven Pinker's book The Better Angels of Our Nature: Why Violence Has Declined. A recent issue of the journal Science contains a collection of articles on human conflict including a critique of Pinker by Andrew Lawler from the point of view of ethnographers of primative societies. Lawler notes that "biological anthropologists and archaeologists . . . find the data too weak to support such sweeping claims and add that the statistical averaging done by Pinker and Gat erases the enormous variation in small-scale societies."

Upper Paleolithic era physical and evoluationary anthropologist John Hawks takes on this debate concluding that:

My oversimplified view of matters is that Pinker abstracts a single latent variable from the data on violence and aggression: violence appears to decrease as social complexity and hierarchy increase. The anthropologists here are arguing for a more complex, and possibly cyclical, relationship in which other factors besides social complexity are important. George Milner's example:

He cites the example of the Hopewell culture of the 1st through 5th centuries C.E. in eastern North America, which appears to have been “socially permeable,” allowing traders to safely transport obsidian from sources in what is today Wyoming as far east as Ohio. Such ease of movement would have been unthinkable before and after that era, when violence between groups was more common. The interesting question, Milner says, is what changed. “To see this from a solely Hobbesian viewpoint misses the real story,” he adds. “We want to know why people switch from peace to war and back again.”

Rousseau was wrong. The Pleistocene was never a peaceful state of nature.

Hobbes is too simplistic. Violence in human societies is multidimensional and we perceive it differently depending on its cultural motivation. This is why every discussion of Pinker's thesis (including Lawler's) begins by acknowledging the industrial-scale warfare and mass killing of the 20th century. Such events mean something different than big-city crime. Pinker's generalization is correct, but why it is correct depends on how the social uses of violence have changed over time. Hunter-gatherer groups often used violence, in ways that varied among groups and across time to maintain sometimes-elaborate systems of social control. Pinker's generalization is incomplete, and its incompleteness may be explained by the multidimensionality of violence in human societies.

Like Hawks, I'm not sold in Lawler's critique of Pinker. Pinker may not have the whole story, but he has at least an important part of it right.

There may be enormous variation in the levels of violence in small scale societies. But, given the relatively short time periods of any ethnographic data in small populations that inherently leaves room for considerable sampling error, averaging to mitigate against mere random variation is a necessary evil.

Also, the Hopewell example cited itself can quite plausibly be explained by the social complexity thesis ad the heart of what Hawks gleans from Pinker.

An emerging narrative of modern era Mississippian culture depicts the Hopewell situation as likely involving the rise and fall of a pre-Columbian New World empire and not simply a decentralized archaeological culture. Hence, the existence of trade networks when it thrived is comparable to the Pax Romana experienced at the same time in Europe, the Middle East and North Africa.

Indeed, given the increasing indications that longer term climate trends are a major driver of the rise and fall of empires and civilization, it is likely that the Roman and Hopewell parallels in the same error are not mere coincidences but represent a period of favorable climate in which independent Old World and New World empires thrive as a result and because of their success are able to maintain peace over large geographic areas sufficient for trade in ways not possible before they arose or after they fell. The largest city in the Hopewell culture, near modern day Saint Louis, Missouri, was on the same order of magnitude as ancient Rome in population at its peak.

If some of the most notable exceptions to the rule, like the Hopewell case, turn out to be cases that aren't actually exceptions but are instead insufficiently understood episodes of history, then the case for Pinker's thesis grows quite a bit stronger vis-a-vis his critics.

John Hawks To Give Talk In Denver Today

Eminent Neanderthal scholar and blogger John Hawks is giving a presentation on Neanderthal DNA at the Denver Museum of Nature and Science tonight at 7 p.m., which is really exciting, except that I have to work and can't go. :(

So very not fair.

Anyway, welcome to Denver. Perhaps, he will have a chance to connect with our resident expert on the subject, Julien Riel-Salvatore. It looks like he will also give a presentation at the University of Colorado Denver on Friday afternoon.