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Friday, August 3, 2018

Windows of Opportunity for the early peopling of America over the last 800 Ky


Windows for the crossing of the Beringia landbridge into America from Asia have existed many times before the latest one (at the end of the last Ice Age) during which supposedly modern humans finally entered America around 16,000 years ago.


Animals have crossed to and fro between Asia and America (horses, black bears, caribou and camels went west into Asia while bison, mammoths, moose and elk moved east into America) during the last 8 million years. So why couldn't our more distant human relatives (H. habilis, H. erectus, Neanderthal or Denisovan) do the same thing?


The following chart from History of Earth's Climate 5. - Cenozoic II - Pleistocene at www.dandebat.dk, shows how the sea level rose and dropped over tha last 800,000 years. As you can see, during the interglacial periods -like the current one- ice melted and the sea levels rose (zero meter is the present sea level), but when the ice caps grew during the ice ages and glaciers advanced, water was moved from sea to continental ice sheets and therefore sea level dropped by over 120 meters or approx. 360 feet. More than enough to dry out Beringia and allow the land bridge to link America and Asia.


The red arrows show the dates these bridges formed: 140, 340, 630 and 720 thousand years ago. And the blue arrow shows the most recent event, the that is the "accepted" date for the entry of humans into America.


Actually the arrows point at the "lowest" sea levels but to cross Beringia only a drop of 60 meters is needed so there were plenty more "windows" and these lasted for quite a long time (see this map for an undersea level contour of Beringia).


sea level chart ice ages

Sea Level variations over the last 800 ky

The fact is that humans existed 140 kya, and perhaps even 340 kya. Neanderthals lived between 630 and 140 kya. Densiovans are a mystery but we may assume the same dates as those of the Neanderthals. Homo erectus on any date earlier than 340 kya.


So we should consider these dates as "windows of opportunity" for the first humans to reach America.



Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2018 by Austin Whittall © 

Short Stature evolved twice on Flores Island


A Report (Evolutionary history and adaptation of a human pygmy population of Flores Island, Indonesia by Serena Tucci et al. Science 03 Aug 2018, Vol. 361, Issue 6401, pp. 511-516.DOI: 10.1126/science.aar8486) tells us that the pygmy-sized Hobbits of Flores island evolved their own short stature independently from the small-sized Homo sapiens that live nowadays in Flores (pygmies).


The background is (quote from the magazine):


"The genetics of human short stature
Flores Island in Indonesia has a long history of hominin occupation, including by the extinct Homo floresiensis and a more recent settlement by modern humans. Furthermore, Flores has an extant population of pygmy humans, and H. floresiensis exhibited a diminutive adult size relative to other hominins. Tucci et al. examined genetic variation among 32 individuals, including 10 sequenced genomes, from a population of pygmies living close to the cave where H. floresiensis remains were discovered. These individuals exhibit signatures of polygenic selection explaining the short stature and have genomic content from both Neanderthals and Denisovans, but no additional archaic lineages. Thus, restricted height is under selection at this location and has evolved independently at least twice in hominins.
"


Twice because it evolved once in Pygmies in Flores and again (or rather before) in the H. floresiensis.


The Abstract tells us the following:


"Flores Island, Indonesia, was inhabited by the small-bodied hominin species Homo floresiensis, which has an unknown evolutionary relationship to modern humans. This island is also home to an extant human pygmy population. Here we describe genome-scale single-nucleotide polymorphism data and whole-genome sequences from a contemporary human pygmy population living on Flores near the cave where H. floresiensis was found. The genomes of Flores pygmies reveal a complex history of admixture with Denisovans and Neanderthals but no evidence for gene flow with other archaic hominins. Modern individuals bear the signatures of recent positive selection encompassing the FADS (fatty acid desaturase) gene cluster, likely related to diet, and polygenic selection acting on standing variation that contributed to their short-stature phenotype. Thus, multiple independent instances of hominin insular dwarfism occurred on Flores."


So the pygmy population that is now living on the island has Denisovan and Neanderthal admixture -but no additional archaic lineages. The latter is interesting. Maybe this has been concluded as the only genetic components are that of Denisovans, H. sapiens and Neanderthals.


But, as a BBC News article points out today: "Unfortunately, the wet and tropical conditions on Flores mean that all efforts to isolate hobbit DNA have so far failed. Dr Serena Tucci told the BBC: "Like many other scientists, it is my dream to find ancient DNA from the Hobbit. No DNA was recovered in the original Hobbit fossils, but DNA methods have improved markedly in the last few years.".


So no genetic comparison was made between both short statured groups.



Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2018 by Austin Whittall © 

Wednesday, August 1, 2018

45 KY old African teeth from Magubike with Neanderthal and H. erectus traits...


This paper Middle Stone Age human teeth from Magubike rockshelter, Iringa Region, Tanzania, by Pamela R. Willoughby, Tim Compton, Silvia M. Bello, Pastory M. Bushozi, Anne R. Skinner and Chris B. Stringer. Published: July 31, 2018https://doi.org/10.1371/journal.pone.0200530, discusses human teeth found in Africa:


They are significant because they come from Tanzania (the Magubike rockshelter) and are apparently fom Middle Stone Age (MSA) deposits dated and a "conservative estimate of their minimum age is 45,000 years" according to the paper.


As we all know, finding human remains in this part of Africa, especially those from the Middle Stone Age (which took place between 320,000 and 30,000 years ago) is a very rare event.


The authors try to find similarities between these ancient teeth and the San people (the San are always mentioned because they are assumed to be a "relict" of the original Homo sapiens that left Africa, the "oldest" extant humans, the "most diversified" members of our species.


And they say so, albeit cautiously, in this paper: "... a number of characteristics in the Magubike teeth suggest possible San affinities.".


But as we go into the details, it seems that these teeth are indeed quite unique, and, in my opinion, not at all like those of the San people:


Quoting the authors: (bold is mine)


"In summary, the Magubike teeth have the characteristics typical of African sub-Saharan Homo sapiens Holocene teeth, but aspects of the morphology of the upper canine and third premolar are atypical for the African mid/late Pleistocene sample. However, this may be at least partly due to its North African bias. Certain traits present ― e.g. the root shape of the lateral incisor and canine, and the presence of a cingulum pit on the lateral incisor ― are rare or absent in the comparative samples. Traits specific to Homo heidelbergensis / archaic Homo sapiens and Aterian teeth are not present. Despite their large size, there is some suggestion of San affinities, though this interpretation must be very tentative, being based on a single individual."


The interesting part is the similarity with Neanderthal and Homo erectus features: (again bold is mine)


"... The pronounced buccal vertical curvature of the canine root found at Magubike is seen in early teeth, Homo erectus and Neanderthal [22, 47], but not in samples of early modern Homo sapiens (Skhūl and Qafzeh) or European Upper Palaeolithic Homo sapiens[48].
In recent teeth, the buccal surface is usually straight or has a mild curvature [49]. The few canine roots that could be observed in the Kenyan early Holocene sample, and the two in the Gwisho sample, are straight, and in the mid/late Pleistocene sample only the Broken Hill canine has similar curvature to that of the Magubike canine.
"


In other words it is not found among early modern Homo sapiens, only in Neanderthals and H. erectus. The authors continue, finding some examples of curvature in recent African samples (7% of them - a low figure) which may have come from out of African migrants in more recent times...:


"However, four instances were found in the recent sub-Saharan East/South African sample (7%). Similarly, the incomplete root of the Magubike lateral incisor has pronounced buccal vertical curvature in contrast to the more evenly tapered form of recent teeth [50]. A lateral incisor of this form occurs at the Klasies River Main site [51] and in one of four in the Gwisho sample, but in just one out of seventy-five in the recent East/South African sample."


As we see in the preceden paragraph, there are yet more morphological traits that are not at all related to modern African samples.


And the authors admit the teeth's unusual uniqueness very clearly:


"The six Magubike teeth are differentiated from African archaic Homo sapiens / Homo heidelbergensis and Aterian teeth in terms of size and the lack of morphological traits that could be associated with these groups. They are also differentiated from the Kenyan early Holocene and Gwisho samples and more recent teeth in terms of the relative size of the incisors, the incisor crown heights, the relative crown heights of the two premolars, and the long premolar roots. However, the morphological evidence is contradictory, principally in relation to the canine having traits that are rare or absent in the African mid/late Pleistocene sample, though this may be partly due to the small size of this sample and its North African bias."


They attribute this to the small sample size and its "North African bias"


But why try to find them similar to San teeth? Well, orthodoxy requires it: oldest African remains of a Homo sapiens and "oldest" extant humans (SAN) "must" be related:


"Small bodied individuals recovered from East African LSA sites have often been described as having “Khoisanoid affinities”, implying an assumed connection with the small bodied people of South Africa, including the San [75]. There are also still people in northern Tanzania today whose languages are often related to Khoisan (the Hadzabe and Sandawe), implying some possible past connections with southern African peoples [78]."


But what if... the teeth resemble Homo erectus and Neanderthal teeth because these migrated INTO AFRICA? As we can see they don't resemble the African teeth of that time or those of early Modern Homo Sapiens...



Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2018 by Austin Whittall ©