Primitive yet recent jawbone from Taiwan; Penghu 1

An article published in Nature Communicatons on Jan. 27, 2015 describes a mandible belonging to an archaic Homo species from Taiwan, known as Penghu 1. The bone, a lower jawbone with some teeth is remarkable because it displays robust primitive features which do not appear in other contemporary hominids. It is recenty yet primitive.

The authors propose that Penghu 1 is a survivor of "multiple evolutionary lineages among archaic hominins before the arrival of modern humans in the region." [1]

There is a growing body of evidence showing that Asia was not a dead end for human evolution, the notion that H. erectus settled there after leaving Africa and died out or was replaced by modern Humans 50 kya is being refuted by new findings.

The age of Penghu 1's remains is a bit uncertain: "younger than 450 ka, and most likely 10-70 ka or 130-190 ka." [1], which is very recent for primitve features and definitively too primitive to be H. sapiens.

The interesting part is that Penghu 1 is a mossaic of Chinese, Asian and non-Asian archaic jawbones. It is very similar to the Hexian remains (found in China, 590 mi - 950 km north of the Penghu 1 site), which have been placed within the H. erectus line and have been dated to 400 - 150 ka (there is controversy about this date). So this opens the door to some possible link between H. erectus and the Penghu 1 man.

Penghu 1 lacks some features found in Eurasian Neanderthals (so it is not derived from Neanderthals meandering across Asia into Taiwan).

What is remarkable is the survival until such recent dates of teeth that are so large, and set in thick mandibles. This is a very primitive trait. But how does Penghu 1 fit into our ancestral family treee? The authors suggest that:

Several different models can be proposed to explain this situation. First, such morphology may be primitive retention from earlier Asian Homo. Because H. erectus mandibles from the terminal Early or early Middle Pleistocene of Java and China had already acquired thinner corpus and smaller molars, this hypothesis implies the presence of another longstanding Homo lineage in Asia that continued from the Early Pleistocene.
Otherwise, there may have been a migration of robust-jawed Homo from Africa, possibly bringing along Acheulean stone tool technology around the terminal Early Pleistocene, who later evolved some unique morphology locally. Both hypotheses cast doubt on the traditional view that H. erectus was the sole hominin species on the Asian continent in the Early to early Middle Pleistocene... [1]

In other words their hypothesis 1 suggests that an "earlier Asian Homo" had thick jaws and big molars and that these archaic features were inherited by a later group that descended from these primitive Homos (that is what "primitive retention" means: they retained an archaic feature). This means that this archaic lineage survived and was contemporary with the smaller jawed H. erectus that coexisted with Penghu 1.

While hypothesis 2, proposes that some thick jawed Africans bearing Acheulean toolage, reached Asia in the final stages of the Early Pleistocene (which ended 781 kya), and that they evolved separately from the extant and contemporary H. erectus that were already living there, and who had more gracile jaws.

In the first case mentioned above, Who was this ancient Asian? Perhaps some surviving H. habilis? that left Africa before H. erectus? and survived until recently?

In the second case, which African group used Acheulean toolage and migrated out of Africa 780 kya? This was later than the wave of H. erectus that peopled Asia. Did these more recent heavy jawed Africans cross Asia to Taiwan through H. erectus populated China? We can rule out H. heidelbergensis because the paper says that Penghu 1 "1 lacks a suit of uniquely derived morphology of west Eurasian H. neanderthalensis (and in part its Middle Pleistocene predecessor, ‘H. heidelbergensis’)." [1]. So who is the ancestor?

The authors point out that "Figure 7b also suggests that Penghu 1 is similar to ‘Denisovans’14 in M2 crown size; however, a direct comparison is not possible as there are no mandibles and mandibular teeth associated with this enigmatic Siberian hominin" [1], suggesting similarities with Denisovans...

Sources

Chang, C.-H. et al. The first archaic Homo from Taiwan. Nat. Commun. 6:6037 doi: 10.1038/ncomms7037 (2015).

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Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2014 by Austin Whittall © 

Epigenetics, a new twist to inheritance

During a recent trip abroad, to kill the long hours of flight time, I bought a Scientific American -something I have done for the last 15 years, I always buy a Sci Am. when I fly. And besides a very intersting though probably far fetched article on the origin of our universe as the outcome of a stellar implosion in a four dimensional universe that lies beyond ours... I read an article on epigenetics.

I had never imagined that stress and chemicals can alter the switching-on and off of our genes without modifying our genetic code. The article proved that it can happen and in consequence, be a powerfull force driving evolution, one that is not recorded in our DNA.

Among the factors mentiones are, of course, the harmful chemicals and pesticides (DDT for instance) generated by our modern society. Pollutants cause mice to pass on disorders to their descent, not only their direct offspring but also to their great-great-grand-pups. And this without any trace in DNA changes.

Hunger and other causes of stress also alter the actions of genes. And this is intersting, because environmental factors, naturally occuring ones could impact on the inhibition or activation of our genes and be driving forces behind the evolution of species. The article summarizes this as follows:

If the environment can sometimes directly produce longterm, transgenerational changes in gene activity without first altering the DNA coding sequence, then the classical view of evolution ... wil have to be expanded.
... Epigenetic changes appear to occur 1,000 times more frequently [than advantageous genetic mutations]... Natural selection would then pick the best adapted among them to thrive and carry on - genome, epigenome, and all.

I am still pondering over this thought, because it does have direct impact in Human evolution: starving and stressed humans would have been very common during most of mankind's history (beasts and natural events causing famine, illness and death). And this would have prompted subgroups a and b of population A to survive while subroups c to n died out. All of them had the same DNA but a and b had some genes activated which gave them the edge and they survived...

How does this impact on the "molecular clock"?

Further Reading
A New Kind of Inheritance, Michael K. Skinner, pp. 45-51. Scientific American, Aug. 2014 vol 311, No. 2.

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Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2014 by Austin Whittall © 

Homo Erectus and a recent admixture with modern humans

January is mid Summer in Argentina, holiday season so I have taken some time off to read and relax. And as usual I found an interesting article: Alan R. Rogers and Ryan J. Bohlender Bias in Estimators of Archaic Admixture, 23.Dec.2014. I will not bore you with the technical matters, I will go straight to the point:

Rogers and Bohlender take a look at the methods and assumptions used in estimating admixture of ancient humans (Denisovans and Neanderthals) in modern H. sapiens. They noticed that these methods "are sensitive to “ghost” admixture, which occurs when a population receives archaic DNA from sources not acknowledged by the statistical model". They detail different estimators and take the cases of Europeans and Melanesians for Neanderthal and Denisovan admixture to check their hypothesis.

They do find that " Such comparisons indicate that archaic gene flow into Europe came primarily from Neanderthals and support the view that archaic populations were much smaller than those of early modern humans, which supports their theory but, when it comes to Melanesians: they expose an inconsistency, and point out that "Although this inconsistency may be a statistical artifact,it could also result from an incorrectly specified model. For example, Homo erectus may have contributed genes to populations of Denisovans (Prüfer et al., 2014, p. 48) or to modern humans in Melanesia (Mendez et al., 2012)."

This is a very interesting conclusion, I don't recall having read anyone suggest that H. erectus mingled with Denisovans or with modern Humans in Melanesia... but it is, and always has been the best explanation.

How did the genes of a group of Denisovans living in Altai get into the lineages of a coast-hugging migration Out Of Africa on its way to Melanesia? If the ancestors of Melanesians did not cross the Himalaya and other mountain ranges to reach Altai then the Denisovans had to do the same, in the opposite direction... and this does not sound reasonable.

The simple explanation: a group of humans (H. erectus) who have been living in South East Asia and China for over one million years were the common link between Denisovans and Melanesians. They were directly in the path of the migrating humans. Ergo they admixed, humans and erectus.

And this is exactly what I suggested over a year ago in my post of Dec. 21, 2013 Denisovans interbred with Homo erectus after reading Prüfer et al. paper.

I had not seen, however, the other paper mentioned by Rogers and Bohlender:

Mendez, F. L., Watkins, J. C., Hammer, M. F., 2012. Global genetic variation at OAS1 provides evidence of archaic admixture in Melanesian populations. Molecular Biology and Evolution 29 (6),1513–1520.)

So I looked it up and read it, and to my surprise, they (Mendez, Watkins and Hammer) reached the same conclusion outlined above:

Another unanswered question concerns how gene flow occurred given the large geographic distance between the Denisova archeological site in the Altai Mountains and the likely route of migration of Melanesian ancestors. It is unclear whether individuals carrying Denisova-like sequences in the Altai region contributed directly or shared some genetic variation with the population that contributed to the ancestry of Melanesians.

Then they try to identify the source: " we suggest that the archaic ancestor contributing the deep lineage to Melanesians and the specimen from Denisova were members of genetically differentiated populations. Interestingly, the coalescent time of the human reference and deep lineage of 3.3 Ma is much older than the population divergence time of ∼0.3 Ma for humans and Denisova suggested by Reich et al. (2010).... These observations present the intriguing possibility that this deeply diverged region of OAS1 may have introgressed into the common ancestor of Denisova and Melanesians via admixture with an unsampled hominin group, such as Homo erectus. In fact, the introgression of a more archaic form into the ancestors of Denisova was also considered by Reich et al. (2010) to explain some archaic morphological features of the Denisova molar. However, without DNA from this “ghost” population or evidence from other loci showing a similar pattern of extreme haplotype differentiation, such a scenario is speculative.".

So what we need is DNA from H. erectus, for comparison, something which may be very unlikely, but who know, maybe a relatively recent H. erectus fossil may be found with viable DNA for sequencing... After all if the H. floresiensis survived until 17 kya, maybe H. erectus did so too... after all, they had to be there, in person, to introgress with humans.

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Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2015 by Austin Whittall © 

Very odd teeth found in China

First of all, my best wishes for 2015!.

Today I read an article that led me to a paper (Hominin teeth from the early Late Pleistocene site of Xujiayao, Northern China, by Song Xing, María Martinón-Torres, Jose María Bermúdez de Castro, Xiujie Wu1 and Wu Liu. Article first published online: 20 OCT 2014. DOI: 10.1002/ajpa.22641) which is very interesting.

The Abstract (paper is behind a paywall) is:

ABSTRACT
It is generally accepted that from the late Middle to the early Late Pleistocene (∼340–90 ka BP), Neanderthals were occupying Europe and Western Asia, whereas anatomically modern humans were present in the African continent. In contrast, the paucity of hominin fossil evidence from East Asia from this period impedes a complete evolutionary picture of the genus Homo, as well as assessment of the possible contribution of or interaction with Asian hominins in the evolution of Homo sapiens and Homo neanderthalensis. Here we present a comparative study of a hominin dental sample recovered from the Xujiayao site, in Northern China, attributed to the early Late Pleistocene (MIS 5 to 4). Our dental study reveals a mosaic of primitive and derived dental features for the Xujiayao hominins that can be summarized as follows: i) they are different from archaic and recent modern humans, ii) they present some features that are common but not exclusive to the Neanderthal lineage, and iii) they retain some primitive conformations classically found in East Asian Early and Middle Pleistocene hominins despite their young geological age. Thus, our study evinces the existence in China of a population of unclear taxonomic status with regard to other contemporary populations such as H. sapiens and H. neanderthalensis. The morphological and metric studies of the Xujiayao teeth expand the variability known for early Late Pleistocene hominin fossils and suggest the possibility that a primitive hominin lineage may have survived late into the Late Pleistocene in China.

In other words they compared some teeth from the Xujiayao site in Northern China and found that it combines modern and archaic traits, some are also found among the Neanderthals and even some older traits found among earlier Asian hominins (maybe H. erectus).

The clean cut theory of a recent Out Of Africa into a world free of more primitive relatives has changed considerably over the last few years. I am glad to see that Neanderthals are found furhter and further east from their purported European Homeland, and that Homo erectus may not have vanished into nothingness before H. sapiens evolved.

It is likely that H. erectus mixed with Neanderthals and moder Humans, as recent findings have shown, they were intelligent beings, with symbolic representations (i.e. the engreaved sea shell found recently). They had everything that is necessary to survive in Asia until modern times, and who knows, perhaps moved north and east, into America.

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Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2014 by Austin Whittall ©