Neandertal Teeth 450Ky Old Found in Italy

The Smithsonian is reporting that excavations in Italy have uncovered teeth dated to 450 thousand years ago that have Neandertal characteristics.

A fossil tooth study published today in the journal PLOS ONE analyzes some of the oldest human remains ever found on the Italian Peninsula. The teeth, which are some 450,000 years old, have some telltale features of the Neanderthal lineage of ancient humans. Dating back to the Middle Pleistocene, the fossils help to fill in gaps in an intriguingly complex part of the hominid family tree.

The species Homo neanderthalensis shares an unknown common ancestor with our own species, Homo sapiens, but it’s unclear exactly when the lineages diverged. Homo sapiens evolved perhaps 300,000 years ago, according to the fossil record, while Neanderthals’ evolutionary timeline has proven even trickier to pin down. Some genetic studies suggest that their lineage split from our own as long as 650,000 years ago, but the oldest definitive fossil evidence for Neanderthals extends back only about 400,000 years.

Conventional wisdom is that Neandertals emerged around 200 thousand years ago, in Europe. The Atapuerca Sima de Los Huesos remains, which show pre-Neandertal characteristics, are about the same age as the Italian remains. It has been suggested that Homo heidelbergensis is the common ancestor to both Neandertals and modern humans but this is far from clear. The genetics suggests that Neandertals and modern humans split around 600 thousand years ago but interacted as recently as 60 to 70 thousand years ago and interbred.Modern Europeans have between 3 and 6% Neandertal genes. 

This pushes back the origins of Neandertals and further muddies the picture of when and where these groups were and how they interacted.  More puzzle pieces. 

New DNA Analysis Allows for Greater Understanding of Modern Human Prehistory

From Science Daily:

A University of Utah-led team developed a new method for analyzing DNA sequence data to reconstruct the early history of the archaic human populations. They revealed an evolutionary story that contradicts conventional wisdom about modern humans, Neanderthals and Denisovans.

The study¹ found that the Neanderthal-Denisovan lineage nearly went extinct after separating from modern humans. Just 300 generations later, Neanderthals and Denisovans diverged from each other around 744,000 years ago. Then, the global Neanderthal population grew to tens of thousands of individuals living in fragmented, isolated populations scattered across Eurasia.

"This hypothesis is against conventional wisdom, but it makes more sense than the conventional wisdom." said Alan Rogers, professor in the Department of Anthropology and lead author of the study that will publish online on August 7, 2017 in the Proceedings of the National Academy of Sciences.

As the authors note, there is mounting evidence of a migration from Africa to Europe, likely by way of the Strait of Gibraltar, in which Acheulean stone tools are introduced by a group which became known as Homo heidelbergensis.  This group, subsequently, split, likely gave rise to the Neandertals  and the Denisovans a bit later.  Then, a second wave of migrations around 90 to 100 ky happened, during which there was hybridization between Neandertals, moderns and Denisovans.

We live in a time where we now have the genomes of archaic Africans, Eurasians, Neandertals, Denisovans and early moderns and can compare them using site pattern analysis.  These authors found that

• In contrast to previous studies, this one indicates that Neandertal population size was large, on the order of tens of thousands of people, in isolated populations
• The split between the Neandertals and Denisovans was early, on the order of 744 thousand years ago.  
• By the time you find these hominins in the fossil record, they had already split from the Denisovans, which explains why the Atapuerca Sima De Los Huesos hominins resemble Neandertals more than Denisovans.
• Therefore, Neandertal features are thought to have emerged over a long period of time in Europe. 

This analysis will help us rethink our understanding of the fossil material from Gran Dolina, which now likely represents a population from which both the Denisovans and Neandertals split.  This makes sense, given the general, non-derived nature of the fossil material from there.  Things are slowly (maybe?) falling into place.

¹Alan R. Rogers, Ryan J. Bohlender, and Chad D. Huff. Early history of Neanderthals and Denisovans. PNAS, August 2017 DOI: 10.1073/pnas.1706426114

New Investigations at the Sima de los Huesos Cave in Atapuerca: Kind of Neandertal and Kind of Not

Science Daily is reporting on a new paper in Science, about the conclusions drawn from the largest single cache of human remains in one place in Europe, the Sima de los Huesos cave, near Atapuerca, in Spain.  They write:

“With the skulls we found," co-author Ignacio Martínez, Professor of Paleontology at the University of Alcalá, added, "it was possible to characterize the cranial morphology of a human population of the European Middle Pleistocene for the first time.”

About 400 to 500 thousand years ago, in the heart of the Pleistocene, archaic humans split off from other groups of that period living in Africa and East Asia, ultimately settling in Eurasia, where they evolved characteristics that would come to define the Neandertal lineage. Several hundred thousand years after that, modern humans -- who had evolved in Africa -- settled in Eurasia, too. They interbred with Neandertals, but even then showed signs of reproductive incompatibility. Because of this, modern humans eventually replaced Neandertals.

This is the hybrid depression that I mentioned a few posts back.  This model fits the genetics information that was summarized by Dennis Venema in his BioLogos post on palaeogenomics from a few weeks ago.  It still also fits with the idea that modern humans swamped a Neandertal genome that was already subject to selective disadvantage.  Consequently, by around 27-29 ky BP, the last populations of Neandertals are, perhaps represented by Zafarraya, a late surviving Neandertal from the very southern coast of Spain. The idea that this Neandertal represents a refugium has been kicked around for decades. Critically, the earliest moderns in Central Europe predate this “last neandertal” by between five and nine thousand years and the evidence from Lagar Velho, in Portugal, indicates that hybridization was occurring as late as this. 

Oldest Human DNA Recovered

Using the fossil material from the Sima de Los Huesos cave, at the Spanish site of Atapuerca, geneticists have recovered DNA.   From the National Geographic story by Karl Gruber:

Analysis of the bones challenges conventional thinking about the geographical spread of our ancient cousins, the early human species called Neanderthals and Denisovans. Until now, these sister families of early humans were thought to have resided in prehistoric Europe and Siberia, respectively. (See also: "The New Age of Exploration.")

But paleontologists write in a new study that the bones of what they thought were European Neanderthals appear genetically closer to the Siberian Denisovans, as shown by maternally inherited "mitochondrial" DNA found in a fossil thighbone uncovered at Spain's Sima de los Huesos cave.

"The fact that they show a mitochondrial genome sequence similar to that of Denisovans is irritating," says Matthias Meyer of Germany's Max Planck Institute for Evolutionary Anthropology in Leipzig, lead author of the study, published Wednesday in Nature.

"Our results suggest that the evolutionary history of Neanderthals and Denisovans may be very complicated and possibly involved mixing between different archaic human groups," he said.

Although the report argues that the Atapuerca remains show a greater similarity to Denisovans than Neandertals, we already know that modern Europeans and East Asians have Neandertal genes in them, indicating that admixture was occurring.  Milford Wolpoff has been arguing for decades that archaic Homo sapiens represents a polytypic species that has genetic ties to modern human groups in different parts of the Old World.  While it certainly appears that Neandertals were distinctive, this information, in conjunction with various studies (here and here) of the Denisovans and African archaics indicates that this model may be the more correct one. 

Lost in the shuffle, however, is that the ability to recover this DNA is an astounding feat of science and portends for great advances in human palaeontology in the future. 

Study: Neandertal Speech and Language Abilities Like Modern Humans

Science Daily has a story on Neandertal speech.  Work by Dan Didiu and Stephen Levinson suggests that Neandertals and modern humans share a common ancestry with regard to the use of language.  Science Daily writes:

Dediu and Levinson review all these strands of literature and argue that essentially modern language and speech are an ancient feature of our lineage dating back at least to the most recent ancestor we shared with the Neandertals and the Denisovans (another form of humanity known mostly from their genome). Their interpretation of the intrinsically ambiguous and scant evidence goes against the scenario usually assumed by most language scientists, namely that of a sudden and recent emergence of modernity, presumably due to a single -- or very few -- genetic mutations. This pushes back the origins of modern language by a factor of 10 from the often-cited 50 or so thousand years, to around a million years ago -- somewhere between the origins of our genus, Homo, some 1.8 million years ago, and the emergence of Homo heidelbergensis. This reassessment of the evidence goes against a saltationist scenario where a single catastrophic mutation in a single individual would suddenly give rise to language, and suggests that a gradual accumulation of biological and cultural innovations is much more plausible..

I am still a bit “iffy” on the whole “common ancestor of modern humans and Neandertals” thing since some are trying to argue for a common ancestor based on the material from the Gran Dolina, in Spain, and it sure as all get out looks like modern humans originated in Northeast Africa at, or near, Herto. I have a tendency to think that there was a good deal of panmixia throughout Europe and north Africa.  Otherwise, we are required to believe that there was a species split at H. antecessor into what became modern humans (how'd they get to north Africa?) on one side and Neandertals on the other and that, some 700 to 720 thousand years later, emerging moderns and Neandertals encountered one another and interbred.  That is overly simplistic, I am sure but it seems far-fetched.  It seems easier to argue that the H. antecessor material represents an archaic Homo sapiens population that was the precursor (or something like it was) to later archaics, such as Petralona and Atapuerca, out of which Neandertals came.  Then the Neandertals interbred with the north-moving moderns and somewhere in there, the Denisova population split off.  The panmixia in Europe, western Asia and Russia explains why moderns have both Neandertal and Denisovan genes, along with the modern genes that originated in North Africa.  Subsequent swamping of the archaic genome led to the demise of both the Neandertals and Denisovans.   

Fossil Data and Genetic Data More Concurrent Than Thought

It is now coming out that the “clocks” that are used to calculate mutation rates are badly calibrated. Ewen Callaway of Nature writes:

Geneticists have previously estimated mutation rates by comparing the human genome with the sequences of other primates. On the basis of species-divergence dates gleaned—ironically—from fossil evidence, they concluded that in human DNA, each letter mutates once every billion years. “It’s a suspiciously round number,” says Linda Vigilant, a molecular anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The suspicion turned out to be justified.

Now it seems that the clock is off by half. This means that a bunch of divergence dates can be recalculated. One is particular is mentioned:

Take the 400,000–600,000-year-old Sima de Los Huesos site in Atapuerca, Spain, which yielded bones attributed to Homo heidelbergensis, the direct ancestors of Neanderthals. Genetic studies have suggested that earlier ancestors of Neanderthals split from the branch leading to modern humans much more recently, just 270,000–435,000 years ago. A slowed molecular clock pushes this back to a more comfortable 600,000 years ago.

It isn't a magic bullet, there are still some kinks to be worked out but it has remarkable potential for getting a handle on when the Denisova genome might have arisen.It might also give us a believable figure for the LCA of apes and humans since the current, 5 million year date is plainly not so.

Middle Pleistocene Hominin Height

Science Daily has a story on work being done with the material from the Sima de los Huesos cave at Atapuerca. 27 complete long bones have been discovered there and from these, it has been possible to estimate the height of Homo heidelbergensis. Science Daily writes:

The results suggest that both men and women in the Sima de los Huesos population were on average slightly higher than Neanderthal men and women. "Neither can be described as being short and both are placed in the medium and above-medium height categories. But, both species featured tall individuals," assured the experts.

The height of these two species is similar to that of modern day population of mid-latitudes, like in the case of Central Europe and the Mediterranean.

The humans who arrived in Europe during the Upper Palaeolithic era, Cro-Magnons or anatomically modern humans, replaced the Neanderthal populations. They were significantly taller than other human species and their average height for both sexes was higher, falling in the very tall individual category.

Height remained the same for some 2 million years.

We know from the remains at Turkana that, at least for some individuals, height close to that of modern humans had been achieved by 1.3 million years ago.This probably reflects (amongst other things) a massive increase in protein in the diet, which would come about by increased hunting, something present in late African Homo ergaster. More pieces of the puzzle.

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“Oh, My Aching Back!”

Researchers working with human fossil material between 400 and 500 thousand years ago, from the Sima de Los Huesos, have discovered a Homo heidelbergensis individual that had some serious back issues. Susan Uzel of Cambridge News reports:

Found among the bones of around 28 people at a site called Sima de los Huesos – “pit of bones” – in northern Spain, the lumbar spine was reconstructed from fragments discovered by scientists from the Centro Mixto de Evolución Humana in Burgos.

The lumbar spine comes from the same man as a pelvis found in 1994. It is thought he was aged 45, and lived more than half a million years ago.

The way in which the bones developed and the way they changed due to wear and tear show he was likely to have suffered severe back pain.

Dr Gomez-Olivencia said: “It appears that we are looking at the spine of a man who had several different problems, including inversion of the curvature of the back, spondylolisthesis, and Baastrup disease – which are associated with pain today.”

Homo heidelbergensis were nomadic hunter gatherers, relying on animals such as red deer for food, and a damaged spine would have made hunting impossible.

This is not so unusual. With bipedalism comes all sorts of issues with the back. We put an incredible amount of strain on the lower vertebrae, which often causes herniation of the discs. As we get larger and heavier (read: fatter), these get exacerbated.

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