molar size hominins

New study of molar size regulation in hominins

New study of molar size regulation in hominins

The Dental Anthropology Group at the CENIEH has tested the inhibitory cascade model to see whether it explains the size relationships and differences in shape between the different kinds of teeth, in the molar sample from the individuals identified at the Sima de los Huesos site in the Sierra de Atapuerca.
Mandíbula AT-1 de la Sima de los Huesos. Credits: Mario Modesto

The molar size relationship is one of the peculiar characteristics of the different species of hominins and various theories have been proposed to account for this, as well as the differences in shape between the different kinds of teeth (incisors, canines, premolars and molars). The latest theory, called the inhibitory cascade model, arose out of experiments with mice embryos, and in 2016 it was applied theoretically to fossil hominins, with satisfactory results.

It appeared that all hominins satisfy the inhibitory cascade model. In a paper by the Dental Anthropology Group at the Centro Nacional de Investigación sobre la evolución Humana (CENIEH), published recently in the Journal of Anatomy, this model was tested on the molar sample from the individuals identified at the Sima de los Huesos site, situated in the Sierra de Atapuerca (Burgos).

The results match the model generated in mice extraordinarily well, thus confirming the theory's utility once more. “Nevertheless, our conclusions have brought out an anomaly in the model, when it is applied to the oldest species of the genus Homo”, explains José María Bermúdez de Castro, Paleobiology Program Coordinator at the CENIEH and lead author of this work.

Increasing and decreasing patterns

In the genera Ardipithecus, Australopithecus and Paranthropus, as well as in Homo habilis, the size pattern is increasing and fits the premises of the inhibitory cascade model perfectly. The same thing happens in Homo sapiens, except that the pattern is decreasing, with the first molar larger than the second, which in turn is bigger than the third one (wisdom tooth).

Application of the inhibitory cascade model had led to the assumption that the switch from increasing to decreasing pattern would have arisen a little under two million years ago, perhaps coinciding with the transition between the genera Australopithecus and Homo. “However, in our work we noticed that this change could have required at least a million years to take place”, states Bermúdez de Castro.

The hominins from the Sima de los Huesos, which are around 430,000 years old, are a good example of that transition, whereas most specimens of Homo ergaster, Homo erectus, Homo antecessor and Homo heidelbergensis, as well as other species, do not fit the inhibitory cascade model. “Our idea is to continue our research to determine which genetic mechanisms lie behind this anomaly in the model”, says Bermúdez de Castro.

Full bibliographic information

Bermúdez de Castro et al. 2020. Testing the inhibitory cascade model in the Middle Pleistocene Sima de los Huesos (Sierra de Atapuerca, Spain) hominin sample. Journal of Anatomy. DOI: 10.1111/joa.13292
Press release from CENIEH.

First exhaustive analysis of use-wear traces on basalt tools from Olduvai

First exhaustive analysis of use-wear traces on basalt tools from Olduvai

The CENIEH leads an experimental study of the possible uses for tools made from basalts at Olduvai Gorge (Tanzania), by analyzing the relationships between the petrological characteristics of this raw material and the formation of use-wear traces
basalt tools Olduvai
Beta vulgaris processing during the experimental basalt program/P. Bello-Alonso

The Centro Nacional de Investigación sobre la Evolución humana (CENIEH) has participated in an experimental study published recently in the journal Archaeological and Anthropological Sciences, on the possible uses of tools fashioned from basalts, volcanic rocks that are highly abundant at the Olduvai Gorge sites in Tanzania, through the first exhaustive analysis of the relationships between the petrological characteristics of this raw material and the formation of use-wear traces.

In addition to providing elements of great significance for interpreting human behavior at Olduvai Gorge, the results of this research led by the archaeologist Patricia Bello-Alonso furnish a model which will enable comparative studies for lithic industry assemblages in volcanic rocks from different archaeological and geological contexts to be conducted.

“The results we have obtained are a fundamental resource for analyzing the ways stone tools were used at the archaeological sites located in Beds I and II, in general, and at the Thiongo Korongo (TK) site in particular as, in this area, volcanic rocks are one of the key raw materials for the technological and, therefore, evolutionary development of the different hominin groups that occupied Olduvai more than two million years ago”, explains Bello-Alonso.

Reference Collection

The main objective of the research, in which the Museo de Ciencia Naturales and the Instituto de Evolución Humana en África in Madrid also participated, was to determine how traces are formed in basalts at both the macro and micro scales, to enable their use to be identified. To do so, non-retouched flakes were employed and a wide variety of organic materials was worked upon: animal carcasses, tubers, wood, grass, cane and fresh bone.

“Carrying out these operations has allowed us to compile an experimental reference collection for greater understanding of the role played by the internal and chemical structure of basalts in the formation and development of use-wear traces”, she adds.

This multidisciplinary study, financed by the Ministerio de Ciencia, Innovación y Universidades (HAR2013-45246-C3-2-P and HAR2017-82463-C4-2-P), under the auspices of The Olduvai Paleonthropology and Paleoecology Project (TOPPP) on the Acheulean site of TK, led by the researchers Joaquín Panera and Manuel Santonja, was conducted at the Prehistoric Technology and Archaeology Laboratory of the CENIEH and the Emiliano Aguirre camp, at Olduvai Gorge itself.

Full bibliographic information

Bello-Alonso, P., Rios-Garaizar, J., Panera, J., Martín-Perea, D.M., Rubio-Jara, S., Pérez-González, A., Rojas-Mendoza, R., Domínguez-Rodrigo, M., Baquedano, E., y Santonja, M. Experimental approaches to the development of use-wear traces on volcanic rocks: basalts. Archaeol Anthropol Sci 12, 128 (2020). https://doi.org/10.1007/s12520-020-01058-6.
Press release from CENIEH on the basalt tools from Olduvai.

The settlement of Europe could be the result of several immigration waves by a single population

The settlement of Europe could be the result of several immigration waves by a single population

The CENIEH conducts the morphological and metric analysis of the lower molars in the mandible from Montmaurin-La Niche (France) using micro-computed tomography, to study the origin of the Neanderthals.
settlement Europe immigration population
Montmaurin-La Niche mandible/M. Martínez de Pinillos

The Dental Anthropology Group of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), in collaboration with the paleoanthropologist Amélie Vialet of the Muséum National d’Histoire Naturelle (MNHN) in Paris, has just published a detailed external and internal study of the molars in the mandible from the French site of Montmaurin-La Niche in the Journal of Human Evolution, whose results strengthen the hypothesis that the settlement of Europe could have been the result of several waves of migration at different times by a common source population.

The aim in this paper, led by the researchers Marina Martínez de Pinillos (CENIEH) and Laura Martín-Francés (CENIEH and PACEA-University of Bordeaux), is to shed light on the origin of the Neanderthals. The latest data obtained from paleontological and geomorphological studies place the Montmaurin-La Niche mandible in a chronologically intermediate position between the fossils of the Middle Pleistocene and the Neanderthals.

The micro-computed axial tomography (microCT) technique has enabled the molars in this mandible to be compared with the external and internal structures of over 400 other molars from the European, Asian and African Pleistocene and Holocene.

This exhaustive metric and morphological analysis has revealed that, while the mandible is more closely related to African and Eurasian populations from the Early and Middle Pleistocene, the enamel and dentine morphology and pulp cavity proportions are similar to those in Neanderthals. “Nevertheless, the absolute and relative enamel thickness values (2D and 3D) show greater affinity with those exhibited by certain Early Pleistocene hominins”, says Martínez de Pinillos.

Possible hybridization

Over recent decades, finds of human fossil remains from the European Middle Pleistocene have prompted the debate on the evolutionary scenario of the genus Homo on that continent to be reopened. “The great variability we find among the European Middle Pleistocene fossils cannot be ignored in studying human evolution on our continent”, states Martín-Francés.

This variability in European Middle Pleistocene populations could indicate different migrations at different times and/or fragmentation of the population, thought it might also be due to possible hybridization between residents and new settlers.

Montmaurin-La Niche mandible/M. Martínez de Pinillos

Full bibliographic information

Martínez de Pinillos, M., Martín-Francés, L., Bermúdez de Castro, J. M., García-Campos, C., Modesto-Mata, M., Martinón-Torres, M., & Vialet, A. (2020). Inner morphological and metric characterization of the molar remains from the Montmaurin-La Niche mandible: the Neanderthal signal. Journal of Human Evolution, 145, 102739. doi: 10.1016/j.jhevol.2019.102739.
Press release on the settlement of Europe due to immigration waves from a common source population from CENIEH

molars Sima de los Huesos

The molars from Sima de los Huesos site share dental tissue traits with Homo antecessor and Neanderthals

The molars from Sima de los Huesos site share dental tissue traits with Homo antecessor and Neanderthals

The Dental Anthropology Group from CENIEH publishes a paper in PLOS ONE in which microscopy and micro-computed tomography are used to study the dental tissues in molars from European Middle Pleistocene individuals found at this site in Atapuerca, and compares these with species from the fossil record and modern humans
Distribution of enamel thickness in a lower molar from Sima de los Huesos compared with H. antecessor, Tighenif specimen and modern human. Credits: Martín-Francés et al.

The Dental Anthropology Group of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) has published a paper this week in the journal PLOS ONE which marks another step forward in characterizing the individuals from the Sima de los Huesos site (Atapuerca, Burgos, Spain) and their relationship with Neanderthals and Homo antecessor, and helps to clarify the evolutionary steps that led to the dentition characteristic of Late Pleistocene hominins.

In this paper, whose lead author is the researcher Laura Martín-Francés (CENIEH and PACEA-University of Bordeaux), the dental tissues in the molars of the European Middle Pleistocene individuals found at Sima de los Huesos are analyzed, and compared with species in the fossil record and modern humans.

To conduct this comparative study, micro-computed tomography (mCT) and high-resolution images were used to examine the internal structure of 72 upper and lower molars from this site at Atapuerca, and these were contrasted against another 500 molars belonging to species from the genus Homo, extinct and extant, from Africa, Asia and Europe.

In the entire fossil record analyzed, only the Neanderthals present a unique structural pattern in molar tissues (enamel thickness, percentage of tissues and their distribution in the crown) which, in addition, they do not share with any other species. “In comparison with that record and with modern humans, Neanderthals had thin enamel, with a higher proportion of dentine and a more disperse distribution pattern”, says Martín-Francés.

It has been possible to determine that the molars from the Sima de los Huesos individuals had thick enamel and that, therefore, they do not share this trait with Neanderthals. Nevertheless, the two groups do share the same tissue distribution pattern.

“The results suggest that even though the complex of typically Neanderthal traits appeared later, certain aspects of the Neanderthal molar structure were already present in the hominins from Sima de los Huesos. In earlier work, we had identified this same pattern in Homo antecessor, another of the species recovered at Atapuerca”, adds Martín-Francés.

The Sima de los Huesos population, related genetically to the Neanderthals, represents a unique opportunity to study the appearance of the “typical” structural pattern of Neanderthal molar tissue.

Distribution of enamel thickness in an upper molar from Sima de los Huesos compared with H. antecessor, Neanderthal and modern human. Credits: Martín-Francés et al.

Full bibliographic information

Martín-Francés, L., Martinón-Torres, M., Martínez de Pinillos, M., García-Campos, C., Zanolli, C., Bayle, P., Modesto-Mata, M., Arsuaga, J. L., & Bermúdez de Castro, J. M. (2020). Crown tissue proportions and enamel thickness distribution in the Middle Pleistocene hominin molars from Sima de los Huesos (SH) population (Atapuerca, Spain). PLoS ONE, 15(6), e0233281. doi: 10.1371/journal.pone.0233281.
Press release from CENIEH

Two new extinct primate species are found in the Ethiopia site of Gona

Two new extinct primate species are found in the Ethiopia site of Gona

Sileshi Semaw from CENIEH participated in a study about large series of fossil cercopithecid primates named Pliopapio alemui and Kuseracolobus aramisi, two different species dated between 4.8 and 4.3 million years ago
Gona primate Pliopapio alemui and Kuseracolobus aramisi
Maxillae of Kuseracolobus aramisi from Gona

Sileshi Semaw from the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), is coauthor of a paper published in the Journal of Human Evolution about a large series of fossil cercopithecid primates named Pliopapio alemui and Kuseracolobus aramisi, two different new primate species dated between 4.8 and 4.3 million years ago known only from Gona and the Middle Awash study area in Ethiopia.

Mandibles of Kuseracolobus aramisi from Gona

The fossil discoveries include upper jaws, mandibles and postcrania found from deposits that also yielded Ardipithecus ramidus, a hominin species first identified in the Middle Awash study area located to the south of Gona. Based on abundance of various animal species, including monkeys, the ancient environment in which Ardipithecus ramidus lived was argued to be in a closed habitat with forests.

In addition to providing important information on the biological evolution of monkeys, these fossil discoveries provide critical information about the ancient environment in which Ardipithecus ramidus lived. Remarkably, differences in relative abundance of these fossil monkeys showed that at Gona Ardipithecus ramidus lived in open wooded habitats, which is different from the closed forested habitat documented in the Middle Awash.

“Therefore, our study shows environmental differences in the areas inhabited by Ardipithecus ramidus, one of the earliest hominins that lived at Gona and in the Middle Awash 4.5 million years ago,” says Sileshi Semaw.

A site of Ardipithecus

Gona is one of the two palaeoanthropological sites in Africa where the hominin species known as Ardipithecus ramidus) has been discovered. Ardipithecus ramidus is among the earliest bipedal hominin species (walking on two feet) that lived in East Africa. Only two other hominin species known as Ardipithecus kaddaba (dated to 6.0 million years ago) and Sahelanthropus tchadensis (from Tchad in Central Africa dated to 7.0 million years ago) are older than Ardipithecus ramidus. Also Ardipithecus kadabba, dated to more than 6.0 million years ago, has also been discovered at Gona.

Full bibliographic information

Frost, S. R., Simpson, S. W., Levin, N. E., Quade, J., Rogers, M. J., & Semaw, S. (2020). Fossil Cercopithecidae from the Early Pliocene Sagantole formation at Gona, Ethiopia. Journal of Human Evolution, 144, 102789. doi: 10.1016/j.jhevol.2020.102789.
Press release from CENIEH

giant ostrich Crimean cave

Bird three times larger than ostrich discovered in Crimean cave

Bird three times larger than ostrich discovered in Crimean cave

First evidence that giant ostrich-like birds once roamed Europe

giant ostrich Crimean cave
PaleoArt of the bird discovered in a Crimean cave. It weighed three times the largest living bird, the common ostrich. Credit: Andrey Atuchin

A surprise discovery in a Crimean cave suggests that early Europeans lived alongside some of the largest ever known birds, according to new research published in the Journal of Vertebrate Paleontology.

It was previously thought that such gigantism in birds only ever existed on the islands of Madagascar and New Zealand as well as Australia. The newly-discovered specimen, discovered in the Taurida Cave on the northern coast of the Black Sea, suggests a bird as giant as the Madagascan elephant bird or New Zealand moa. It may have been a source of meat, bones, feathers and eggshell for early humans.

"When I first felt the weight of the bird whose thigh bone I was holding in my hand, I thought it must be a Malagasy elephant bird fossil because no birds of this size have ever been reported from Europe. However, the structure of the bone unexpectedly told a different story," says lead author Dr Nikita Zelenkov from the Russian Academy of Sciences.

"We don't have enough data yet to say whether it was most closely related to ostriches or to other birds, but we estimate it weighed about 450kg. This formidable weight is nearly double the largest moa, three times the largest living bird, the common ostrich, and nearly as much as an adult polar bear."

It is the first time a bird of such size has been reported from anywhere in the northern hemisphere. Although the species was previously known, no one ever tried to calculate the size of this animal. The flightless bird, attributed to the species Pachystruthio dmanisensis, was probably at least 3.5 metres tall and would have towered above early humans. It may have been flightless but it was also fast.

While elephant birds were hampered by their great size when it came to speed, the femur of the current bird was relatively long and slim, suggesting it was a better runner. The femur is comparable to modern ostriches as well as smaller species of moa and terror birds. Speed may have been essential to the bird's survival. Alongside its bones, palaeontologists found fossils of highly-specialised, massive carnivores from the Ice Age. They included giant cheetah, giant hyenas and sabre-toothed cats, which were able to prey on mammoths.

Other fossils discovered alongside the specimen, such as bison, help date it to 1.5 to 2 million years ago. A similar range of fossils was discovered at an archaeological site in the town of Dmanisi in Georgia, the oldest hominin site outside Africa. Although previously neglected by science, this suggests the giant bird may have been typical of the animals found at the time when the first hominins arrived in Europe. The authors suggest it reached the Black Sea region via the Southern Caucasus and Turkey.

The body mass of the bird was reconstructed using calculations from several formulae, based on measurements from the femur bone. Applying these formulae, the body mass of the bird was estimated to be around 450kg. Such gigantism may have originally evolved in response to the environment, which was increasingly arid as the Pleistocene epoch approached. Animals with a larger body mass have lower metabolic demands and can therefore make use of less nutritious food growing in open steppes.

"The Taurida cave network was only discovered last summer when a new motorway was being built. Last year, mammoth remains were unearthed and there may be much more to that the site will teach us about Europe's distant past," says Zelenkov.

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Oldest flaked stone tools point to the repeated invention of stone tools

Oldest flaked stone tools point to the repeated invention of stone tools

stone tools
A large green artifact found in situ at the Bokol Dora site. Right: Image of the same artifact and a three dimensional model of the same artifact. Credit: David R. Braun

A new archaeological site discovered by an international and local team of scientists working in Ethiopia shows that the origins of stone tool production are older than 2.58 million years ago. Previously, the oldest evidence for systematic stone tool production and use was 2.58 to 2.55 million years ago.

Analysis by the researchers of early stone age sites, published this week in the Proceedings of the National Academy of Sciences, suggests that stone tools may have been invented many times in many ways before becoming an essential part of the human lineage.

The excavation site, known as Bokol Dora 1 or BD 1, is close to the 2013 discovery of the oldest fossil attributed to our genus Homo discovered at Ledi-Geraru in the Afar region of northeastern Ethiopia. The fossil, a jaw bone, dates to about 2.78 million years ago, some 200,000 years before the then oldest flaked stone tools. The Ledi-Geraru team has been working for the last five years to find out if there is a connection between the origins of our genus and the origins of systematic stone tool manufacture.

A significant step forward in this search was uncovered when Arizona State University geologist Christopher Campisano saw sharp-edged stone tools sticking out of the sediments on a steep, eroded slope.

Archaeologists from the Max Planck Institute, and the Ethiopian Authority for Research and the Conservation of Cultural Heritage as well as geologists from University of Algarve study the sediments at the Bokol Dora site. Stones were placed on the contact surface during the excavation to preserve the fragile stratigraphic contacts. Credit: Erin DiMaggio

"At first we found several artifacts lying on the surface, but we didn't know what sediments they were coming from," says Campisano. "But when I peered over the edge of a small cliff, I saw rocks sticking out from the mudstone face. I scaled up from the bottom using my rock hammer and found two nice stone tools starting to weather out."

It took several years to excavate through meters of sediments by hand before exposing an archaeological layer of animal bones and hundreds of small pieces of chipped stone representing the earliest evidence of our direct ancestors making and using stone knives. The site records a wealth of information about how and when humans began to use stone tools.

Preservation of the artifacts comes from originally being buried close to a water source.

"Looking at the sediments under a microscope, we could see that the site was exposed only for a very short time. These tools were dropped by early humans at the edge of a water source and then quickly buried. The site then stayed that way for millions of years," noted geoarchaeologist Vera Aldeias of the Interdisciplinary Center for Archaeology and Behavioral Evolution at the University of Algarve, Portugal.

Kaye Reed, who studies the site's ecology, is director of the Ledi-Geraru Research Project and a research associate with Arizona State University's Institute of Human Origins along with Campisano, notes that the animals found with these tools were similar to those found only a few kilometers away with the earliest Homo fossils.

Blade Engda of the University of Poitiers lifts an artifact from 2.6 million year old sediment exposing an imprint of the artifact on the ancient surface below. Credit: David R. Braun

"The early humans that made these stone tools lived in a totally different habitat than 'Lucy' did," says Reed. "Lucy" is the nickname for an older species of hominin known as Australopithecus afarensis, which was discovered at the site of Hadar, Ethiopia, about 45 kilometers southwest of the new BD 1 site. "The habitat changed from one of shrubland with occasional trees and riverine forests to open grasslands with few trees. Even the fossil giraffes were eating grass!"

In addition to dating a volcanic ash several meters below the site, project geologists analyzed the magnetic signature of the site's sediments. Over the Earth's history, its magnetic polarity has reversed at intervals that can be identified. Other earlier archaeological sites near the age of BD 1 are in "reversed" polarity sediments. The BD 1 site is in "normal" polarity sediments. The reversal from "normal" to "reversed" happened at about 2.58 million years ago, geologists knew that BD 1 was older than all the previously known sites.

The recent discovery of older hammering or "percussive" stone tools in Kenya dated to 3.3 million years ago, described as "Lomekwian," and butchered bones in Ethiopia shows the deep history of our ancestors making and using tools. However, recent discoveries of tools made by chimpanzees and monkeys have challenged "technological ape" ideas of human origins.

Archaeologists working at the BD 1 site wondered how their new stone tool discovery fit into this increasingly complex picture. What they found was that not only were these new tools the oldest artifacts yet ascribed to the "Oldowan," a technology originally named after finds from Olduvai Gorge in Tanzania, but also were distinct from tools made by chimpanzees, monkeys or even earlier human ancestors.

"We expected to see some indication of an evolution from the Lomekwian to these earliest Oldowan tools. Yet when we looked closely at the patterns, there was very little connection to what is known from older archaeological sites or to the tools modern primates are making," said Will Archer of the Max Planck Institute for Evolutionary Anthropology in Leipzig and the University of Cape Town.

The major differences appear to be the ability for our ancestors to systematically chip off smaller sharp-edged tools from larger nodules of stone. Chimpanzees and monkeys generally use tools for percussive activities, to hammer and bash food items like nuts and shellfish, which seems to have been the case with the 3.3 million year old Lomekwian tools as well.

Something changed by 2.6 million years ago, and our ancestors became more accurate and skilled at striking the edge of stones to make tools. The BD 1 artifacts captures this shift.

It appears that this shift in tool making occurred around the same time that our ancestor's teeth began to change. This can be seen in the Homo jaw from Ledi-Geraru. As our ancestors began to process food prior to eating using using stone tools, we start to see a reduction in the size of their teeth. Our technology and biology were intimately intertwined even as early as 2.6 million years ago.

The lack of clear connections with earlier stone tool technology suggests that tool use was invented multiple times in the past.

David Braun, an archaeologist with George Washington University and the lead author on the paper, noted, "Given that primate species throughout the world routinely use stone hammers to forage for new resources, it seems very possible that throughout Africa many different human ancestors found new ways of using stone artifacts to extract resources from their environment. If our hypothesis is correct then we would expect to find some type of continuity in artifact form after 2.6 million years ago, but not prior to this time period. We need to find more sites."

By 2.6 million years ago, there appears to be a long-term investment in tool use as part of the human condition.

Continued field investigations at the Ledi-Geraru project area are already producing more insights into the patterns of behavior in our earliest ancestors. New sites have already been found, and the Ledi-Geraru team will begin excavating them this year.

###

This research was supported by the United States National Science Foundation and the John Templeton Foundation.

This research, "Earliest known Oldowan artifacts at >2.58 Ma from Ledi-Geraru, Ethiopia, highlight early technological diversity," is published in the Proceedings of the National Academy of Sciences.

 

Press release from the Arizona State University


Unexpected potential paths for the spread of Homo Sapiens across Asia in Late Pleistocene

Humans used northern migration routes to reach eastern Asia

New article suggests wetter climates may have allowed Homo sapiens to expand across the deserts of Central Asia by 50-30,000 years ago

 

Northern and Central Asia have been neglected in studies of early human migration, with deserts and mountains being considered uncompromising barriers. However, a new study by an international team argues that humans may have moved through these extreme settings in the past under wetter conditions. We must now reconsider where we look for the earliest traces of our species in northern Asia, as well as the zones of potential interaction with other hominins such as Neanderthals and Denisovans.

Archaeologists and palaeoanthropologists are increasingly interested in discovering the environments facing the earliest members of our species, Homo sapiens, as it moved into new parts of Eurasia in the Late Pleistocene (125,000-12,000 years ago). Much attention has focused on a 'southern' route around the Indian Ocean, with Northern and Central Asia being somewhat neglected. However, in a paper published in PLOS ONE, scientists of the Max Planck Institute for the History of Human Science in Jena, Germany, and colleagues at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China, argue that climate change may have made this a particularly dynamic region of hominin dispersal, interaction, and adaptation, and a crucial corridor for movement.

'Heading North' Out of Africa and into Asia

"Archaeological discussions of the migration routes of Pleistocene Homo sapiens have often focused on a 'coastal' route from Africa to Australia, skirting around India and Southeast Asia," says Professor Michael Petraglia of the Max Planck Institute for the Science of Human History, a co-author of the new study. "In the context of northern Asia, a route into Siberia has been preferred, avoiding deserts such as the Gobi." Yet over the past ten years, a variety of evidence has emerged that has suggested that areas considered inhospitable today might not have always been so in the past.

"Our previous work in Saudi Arabia, and work in the Thar Desert of India, has been key in highlighting that survey work in previously neglected regions can yield new insights into human routes and adaptations," says Petraglia. Indeed, if Homo sapiens could cross what is now the Arabian Deserts then what would have stopped it crossing other currently arid regions such as the Gobi Desert, the Junggar Basin, and the Taklamakan Desert at different points in the past? Similarly, the Altai Mountains, the Tien Shan and the Tibetan Plateau represent a potentially new high altitude window into human evolution, especially given the recent Denisovan findings from Denisova Cave in Russia and at the Baishiya Karst Cave in China.

Nevertheless, traditional research areas, a density of archaeological sites, and assumptions about the persistence of environmental 'extremes' in the past has led to a focus on Siberia, rather than the potential for interior routes of human movement across northern Asia.

A "Green Gobi"?

The sand dunes of Mongol Els jutting out of the steppe in Mongolia. Many of these desert barriers only appeared after the Last Glacial Maximum (~20,000 years ago). Credit: Nils Vanwezer

Indeed, palaeoclimatic research in Central Asia has increasingly accumulated evidence of past lake extents, past records of changing precipitation amounts, and changing glacial extents in mountain regions, which suggest that environments could have varied dramatically in this part of the world over the course of the Pleistocene. However, the dating of many of these environmental transitions has remained broad in scale, and these records have not yet been incorporated into archaeological discussions of human arrival in northern and Central Asia.

"We factored in climate records and geographical features into GIS models for glacials (periods during which the polar ice caps were at their greatest extent) and interstadials (periods during the retreat of these ice caps) to test whether the direction of past human movement would vary, based on the presence of these environmental barriers," says Nils Vanwezer, PhD student at the Max Planck Institute for the Science of Human History and a joint lead-author of the study.

"We found that while during 'glacial' conditions humans would indeed likely have been forced to travel via a northern arc through southern Siberia, during wetter conditions a number of alternative pathways would have been possible, including across a 'green' Gobi Desert," he continues. Comparisons with the available palaeoenvironmental records confirm that local and regional conditions would have been very different in these parts of Asia in the past, making these 'route' models a definite possibility for human movement.

Where did you come from, where did you go?

Ancient lake landforms around Biger Nuur, Mongolia, which is evidence of larger lake sizes in the past. Credit: Nils Vanwezer

"We should emphasize that these routes are not 'real', definite pathways of Pleistocene human movement. However, they do suggest that we should look for human presence, migration, and interaction with other hominins in new parts of Asia that have been neglected as static voids of archaeology," says Dr. Patrick Roberts also of the Max Planck Institute for the Science of Human History, co-author of the study. "Given what we are increasingly discovering about the flexibility of our species, it would be of no surprise if we were to find early Homo sapiens in the middle of modern deserts or mountainous glacial sheets."

"These models will stimulate new survey and fieldwork in previously forgotten regions of northern and Central Asia," says Professor Nicole Boivin, Director of the Department of Archaeology at the Max Planck Institute for the Science of Human History, and co-author of the study. "Our next task is to undertake this work, which we will be doing in the next few years with an aim to test these new potential models of human arrival in these parts of Asia."

 

Press release from the Max Planck Institute for the Science of Human History / Max-Planck-Instituts für Menschheitsgeschichte

 

Homo sapiens may have had several routes of dispersal across Asia in the Late Pleistocene

A new model identifies unexpected potential paths for the spread of human culture and technology

Eastern Asia Central Homo Sapiens migrations
Illustrated dispersal routes from the results of the Least Cost Path analysis: The three routes from the "wet" simulations and the single route from the "dry" simulation are presented together in conjunction with palaeoclimatic extents (glaciers and palaeolakes). Sites: 4. Obi-Rakhmat, 5. Shugnou, 8. Denisova, 9. Ust-Karakol, 10. Kara-Tenesh, 11. Kara-Bom, 12. Luotuoshi, 14. Gouxi, 15. Lenghu 1, 17. Chikhen Agui, 18. Tsagaan Agui, 19. Tolbor 4, 20. Kharganyn Gol 5, 21. Orkhon 1 & 7, 22. Makarovo 4, 23. Kandabaevo, 24. Varvarina Gora, 25. Tolbaga, 27. Shuidonggou 1, 28. Shuidonggou 9, 42. Yushuwan, 70. Shibazhan (75075). I. 'Altai' Route, II. 'Tian Shan' Route, III. 'Tarim' Route, IV. "Revised Overland' Route. Base map raster is from naturalearthdata.com. Credit: Li et al, 2019

Homo sapiens may have had a variety of routes to choose from while dispersing across Asia during the Late Pleistocene Epoch, according to a study released May 29, 2019 in the open-access journal PLOS ONE by Feng Li of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and colleagues.

After leaving Africa, Homo sapiens dispersed across the Asian continent during the Late Pleistocene, but it isn't known exactly what routes our species followed. Most models assume that the Gobi Desert and Altai Mountain chains of North and Central Asia formed impassable barriers on the way to the east, so archaeological exploration has tended to neglect those regions in favor of seemingly more likely paths farther north and south.

In this study, Li and colleagues use Geographic Information Systems (GIS) software alongside archaeological and paleoclimate data to reconstruct the conditions of North and Central Asia over the Late Pleistocene and to identify possible routes of travel. Their data suggest that the desert and mountain regions were likely impassable during cold and dry glacial periods, but that during warmer and wetter interglacial times it would have been possible for human populations to traverse these regions via at least three routes following ancient lake and river systems.

The authors caution that these data do not demonstrate definite routes of dispersal and that more detailed models should be constructed to test these results. However, these models do identify specific routes that may be good candidates for future archaeological exploration. Understanding the timing and tempo of Homo sapiens dispersal across Asia will be crucial for determining how culture and technology spread and developed, as well as how our species interacted with our extinct cousins, the Neanderthals and Denisovans.

Roberts adds: "Our modelling of the available geographic and past climate data suggest that archaeologists and anthropologists should look for early human presence, migration, and interaction with other hominins in new parts of Asia that have been neglected as static voids. Given what we are increasingly discovering about the flexibility of our species, it would be of no surprise if we were to find early Homo sapiens in the middle of modern deserts or mountainous glacial sheets all across Asia. Indeed, it may be here that the key to our species' uniqueness lies".

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Citation: Li F, Vanwezer N, Boivin N, Gao X, Ott F, Petraglia M, et al. (2019) Heading north: Late Pleistocene environments and human dispersals in central and eastern Asia. PLoS ONE 14(5): e0216433. https://doi.org/10.1371/journal.pone.0216433

Funding: This study was funded by Max-Planck-Gesellschaft (DE) to Nicole Boivin, Strategic Priority Research Program of Chinese Academy of Sciences grant XDB26000000 to Feng Li, and Youth Innovation Promotion Association of the Chinese Academy of Sciences grant 2017102 to Feng Li. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

 

Press release from the Public Library of Sciences


Neanderthals and modern humans diverged at least 800,000 years ago

Neanderthals and modern humans diverged at least 800,000 years ago

Neanderthals and modern humans diverged at least 800,000 years ago, substantially earlier than indicated by most DNA-based estimates, according to new research by a UCL academic.

Neanderthals diverged teeth
Dental morphology. Credit: Aida Gómez-Robles

The research, published in Science Advances, analysed dental evolutionary rates across different hominin species, focusing on early Neanderthals. It shows that the teeth of hominins from Sima de los Huesos, Spain - ancestors of the Neanderthals - diverged from the modern human lineage earlier than previously assumed.

Sima de los Huesos is a cave site in Atapuerca Mountains, Spain, where archaeologists have recovered fossils of almost 30 people. Previous studies date the site to around 430,000 years ago (Middle Pleistocene), making it one of the oldest and largest collections of human remains discovered to date.

Dr Aida Gomez-Robles (UCL Anthropology), said: "Any divergence time between Neanderthals and modern humans younger than 800,000 years ago would have entailed an unexpectedly fast dental evolution in the early Neanderthals from Sima de los Huesos."

"There are different factors that could potentially explain these results, including strong selection to change the teeth of these hominins or their isolation from other Neanderthals found in mainland Europe. However, the simplest explanation is that the divergence between Neanderthals and modern humans was older than 800,000 years. This would make the evolutionary rates of the early Neanderthals from Sima de los Huesos roughly comparable to those found in other species."

Modern humans share a common ancestor with Neanderthals, the extinct species that were our closest prehistoric relatives. However, the details on when and how they diverged are a matter of intense debate within the anthropological community.

Ancient DNA analyses have generally indicated that both lineages diverged around 300,000 to 500,000 years ago, which has strongly influenced the interpretation of the hominin fossil record.

This divergence time, however, is not compatible with the anatomical and genetic Neanderthal similarities observed in the hominins from Sima de los Huesos. The Sima fossils are considered likely Neanderthal ancestors based on both anatomical features and DNA analysis.

Dr Gomez-Robles said: "Sima de los Huesos hominins are characterised by very small posterior teeth (premolars and molars) that show multiple similarities with classic Neanderthals. It is likely that the small and Neanderthal-looking teeth of these hominins evolved from the larger and more primitive teeth present in the last common ancestor of Neanderthals and modern humans."

Dental shape has evolved at very similar rates across all hominin species, including those with very expanded and very reduced teeth. This new study examined the time at which Neanderthals and modern humans should have diverged to make the evolutionary rate of the early Neanderthals from Sima de los Huesos similar to those observed in other hominins.

The research used quantitative data to measure the evolution of dental shape across hominin species assuming different divergent times between Neanderthals and modern humans, and accounting for the uncertainty about the evolutionary relationships between different hominin species.

"The Sima people's teeth are very different from those that we would expect to find in their last common ancestral species with modern humans, suggesting that they evolved separately over a long period of time to develop such stark differences."

The study has significant implications for the identification of Homo sapiens last common ancestral species with Neanderthals, as it allows ruling out all the groups postdating 800,000 year ago.

Neanderthals diverged teeth
Hominin teeth. Credit: Aida Gómez-Robles

Press release from University College London


Denisovans Tibetan Plateau Baishiya Karst Cave Xiahe mandible

First hominins on the Tibetan Plateau were Denisovans

First hominins on the Tibetan Plateau were Denisovans

Denisovan mandible likely represents the earliest hominin fossil on the Tibetan Plateau

Denisovans Tibetan Plateau Baishiya Karst Cave Xiahe mandible
The Xiahe mandible, only represented by its right half, was found in 1980 in Baishiya Karst Cave. Credit: © Dongju Zhang, Lanzhou University

So far Denisovans were only known from a small collection of fossil fragments from Denisova Cave in Siberia. A research team led by Fahu Chen from the Institute of Tibetan Plateau Research, CAS, Dongju Zhang from Lanzhou University and Jean-Jacques Hublin from the Max Planck Institute for Evolutionary Anthropology now describes a 160,000-year-old hominin mandible from Xiahe in China. Using ancient protein analysis the researchers found that the mandible’s owner belonged to a population that was closely related to the Denisovans from Siberia. This population occupied the Tibetan Plateau in the Middle Pleistocene and was adapted to this low-oxygen environment long before Homo sapiens arrived in the region.

Denisovans - an extinct sister group of Neandertals - were discovered in 2010, when a research team led by Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) sequenced the genome of a fossil finger bone found at Denisova Cave in Russia and showed that it belonged to a hominin group that was genetically distinct from Neandertals. "Traces of Denisovan DNA are found in present-day Asian, Australian and Melanesian populations, suggesting that these ancient hominins may have once been widespread," says Jean-Jacques Hublin, director of the Department of Human Evolution at the MPI-EVA. "Yet so far the only fossils representing this ancient hominin group were identified at Denisova Cave."

Mandible from Baishiya Karst Cave

In their new study, the researchers now describe a hominin lower mandible that was found on the Tibetan Plateau in Baishiya Karst Cave in Xiahe, China. The fossil was originally discovered in 1980 by a local monk who donated it to the 6th Gung-Thang Living Buddha who then passed it on to Lanzhou University. Since 2010, researchers Fahu Chen and Dongju Zhang from Lanzhou University have been studying the area of the discovery and the cave site from where the mandible originated. In 2016, they initiated a collaboration with the Department of Human Evolution at the MPI-EVA and have since been jointly analysing the fossil.

While the researchers could not find any traces of DNA preserved in this fossil, they managed to extract proteins from one of the molars, which they then analysed applying ancient protein analysis. "The ancient proteins in the mandible are highly degraded and clearly distinguishable from modern proteins that may contaminate a sample," says Frido Welker of the MPI-EVA and the University of Copenhagen. "Our protein analysis shows that the Xiahe mandible belonged to a hominin population that was closely related to the Denisovans from Denisova Cave."

Primitive shape and large molars

The researchers found the mandible to be well-preserved. Its robust primitive shape and the very large molars still attached to it suggest that this mandible once belonged to a Middle Pleistocene hominin sharing anatomical features with Neandertals and specimens from the Denisova Cave. Attached to the mandible was a heavy carbonate crust, and by applying U-series dating to the crust the researchers found that the Xiahe mandible is at least 160,000 years old. Chuan-Chou Shen from the Department of Geosciences at National Taiwan University, who conducted the dating, says: "This minimum age equals that of the oldest specimens from the Denisova Cave".

"The Xiahe mandible likely represents the earliest hominin fossil on the Tibetan Plateau," says Fahu Chen, director of the Institute of Tibetan Research, CAS. These people had already adapted to living in this high-altitude low-oxygen environment long before Homo sapiens even arrived in the region. Previous genetic studies found present-day Himalayan populations to carry the EPAS1 allele in their genome, passed on to them by Denisovans, which helps them to adapt to their specific environment.

"Archaic hominins occupied the Tibetan Plateau in the Middle Pleistocene and successfully adapted to high-altitude low-oxygen environments long before the regional arrival of modern Homo sapiens," says Dongju Zhang. According to Hublin, similarities with other Chinese specimens confirm the presence of Denisovans among the current Asian fossil record. "Our analyses pave the way towards a better understanding of the evolutionary history of Middle Pleistocene hominins in East Asia."

 

 

Press release from the Max Planck Institute for Evolutionary Anthropology / Max-Planck-Institut für evolutionäre Anthropologie in Leipzig 

Tibetan plateau first occupied by middle Pleistocene Denisovans

Baishiya Karst Cave
Fieldwork in the Baishiya Karst Cave and surrounding regions. Credit: ITP

The Tibetan Plateau, as Earth's "Third Pole," was reported to be first occupied by modern humans probably armed with blade technology as early as 40 ka BP. However, no earlier hominin groups had been found or reported on the Tibetan Plateau until a recent study was published by Chinese researchers.

A joint research team led by CHEN Fahu from the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences and ZHANG Dongju from the Lanzhou University reported their studies on a human mandible found in Xiahe, on the Northeastern Tibetan Plateau. The findings were published in Nature.

The researchers found that the mandible came from an individual who belonged to a population closely related to the Denisovans first found in Siberia. This population occupied the Tibetan Plateau in the Middle Pleistocene and adapted to this low-oxygen environment long before the arrival of modern Homo sapiens in the region.

So far, Denisovans are only known from a small collection of fossil fragments from Denisova Cave in Siberia. Traces of Denisovan DNA are found in present-day Asian, Australian and Melanesian populations, suggesting that these ancient hominins may have once been widespread.

This study confirms for the first time that Denisovans not only lived in East Asia but also on the high-altitude Tibetan Plateau. It also indicates that the previously found possible introgression of Denisovan DNA (EPAS1) into modern Tibetans and Sherpas, who mainly live on the high-altitude Tibetan Plateau and surrounding regions today, is probably derived or inherited locally on Tibetan Plateau from Xiahe hominin represented by this Xiahe mandible.

The reported Xiahe mandible was found on the Tibetan Plateau in the Baishiya Karst Cave in Xiahe, China. Researchers managed to extract collagen from one of the molars, which they then analysed using ancient protein analysis. Ancient protein data showed that the Xiahe mandible belonged to a hominin population closely related to the Denisovans from Denisova Cave.

The robust primitive shape of the mandible and the very large molars still attached to it suggest that this mandible once belonged to a Middle Pleistocene hominin sharing anatomical features with Neandertals and specimens from the Denisova Cave.

Attached to the mandible was a heavy carbonate crust. By applying U-series dating to the crust, the researchers found that the Xiahe mandible is at least 160,000 years old, representing a minimum age of human presence on the Tibetan Plateau.

The similarities between the Xiahe mandible and other Chinese specimens confirm the presence of Denisovans among the current Asian fossil record. The current study paves the way towards a better understanding of the evolutionary history of Middle Pleistocene hominins in East Asia.

 

Press release from the Chinese Academy of Sciences