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.

The temporal lobes of Homo erectus were proportionally smaller than in H. sapiens

The temporal lobes of Homo erectus were proportionally smaller than in H. sapiens

The CENIEH has contributed to a paleoneurological study published in the journal Quaternary International, on the brain of Homo erectus, which analyzes its temporal lobes and compares these with other species like H. ergaster and H. sapiens
temporal lobes erectus sapiens ergaster
Pearson at al.

Emiliano Bruner, a paleoneurologist at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has participated in a study published in the journal Quaternary International, on the anatomy of the temporal lobes in the brain of Homo erectus, which establishes that they were proportionally smaller than in modern humans.

In H. sapiens, the temporal lobes are relatively more highly developed than in other primates, although little is known about their anatomy in extinct human species, because they are housed in a very delicate region of the cranium known as the middle cranial fossa, which is often not conserved in fossil individuals.

An earlier study by the same team had shown that the size of the middle cranial fossa can be used to deduce the volume of the temporal lobes. In this new study, three anatomical diameters were analyzed in fossils of H. erectus and H. ergaster, and compared with the corresponding measurements for 51 modern humans. The results suggest that both fossil species had temporal lobes proportionally smaller than in humans today.

Moreover, “The Asiatic individuals, namely Homo erectus, had larger temporal lobes than in the African ones, Homo ergaster, although the scanty fossil record does not allow us to tell whether this is due to chance or a paleoneurological difference between the two species”, says Bruner.

As the temporal lobe is a brain region involved in the integration of many cognitive functions, such as memory, the emotions, hearing, social relations and language, any change in their sizes or proportions is of transcendent importance, as this could reveal variations in the development of their neurons or their connections, and therefore in the cognitive functions associated to this region of the cerebral cortex.

This study has been conducted by Alannah Pearson, a doctoral student of Emiliano Bruner at the Australian National University in Canberra (Australia), in collaboration with Professor David Polly, of Indiana University (USA).

 

Full bibliographic information

Pearson, A., Polly, P. D., & Bruner, E. (2020). Temporal lobe evolution in Javanese Homo erectus and African Homo ergaster: inferences from the cranial base. Quaternary International (0). doi: 10.1016/j.quaint.2020.07.048.

 

Press release from CENIEH


cultura muerte neandertales humanos modernos Nohemi Sala culture death neanderthals humans

Does the culture of death predate the Neanderthals and modern humans?

Does the culture of death predate the Neanderthals and modern humans?

The CENIEH researcher Nohemi Sala has been awarded 1.5 million euros by the European Research Council through an ERC-Starting Grant, to scour the fossil record for the roots and evolution of our ancestors' funerary behavior.

cultura muerte neandertales humanos modernos Nohemi Sala
Nohemi Sala, ERC-Starting Grant proyect IP.Credits: N. Sala

All societies existing today possess some kind of funerary culture, and this is one of the behaviors that takes us closest to how complex the human mind is. However, the emergence of this behavior is one of the most controversial topics in the field of human evolution. When did our ancestors start to acquire a culture of death? How was this behavior manifested over time and space? Did this practice appear independently in different species?

There are different ways to tackle these questions, and the more specific one of whether the culture ofdeath precedes Neanderthals and anatomically modern humans. To date, analyses in Paleolithic archaeology have centered on the archaeological context: that is, whether skeletons are preserved completely, the existence of a grave cut or whether objects that could be interpreted as symbolic elements or grave goods are present. This vision restricts funerary behavior almost exclusively to burials, something that was exceptionally rare before the Late Pleistocene, which began 127,000 years ago.

Thus, there is a need to find new methodological approaches so that what has been preserved up to our own time is right at the center: human bones. The European fossil record is a fundamental source of information due to the abundance of fossil skeletons. This is where forensic taphonomy, a discipline that can help to shed light on fundamental issues in this field, comes in. Applying this would be something like carrying out “autopsies” of human fossils to try to learn how they died and, above all, what happened to the remains of the individual between death and modern excavation.

This line of research has crystallized in a project entitled DEATHREVOL. The roots and evolution of the culture-of-death. A taphonomic research of the European Paleolithic record, which has been selected to receive financing under the European Union's Horizon 2020 Research and Innovation program, and which will be conducted over the next five years at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH).

“This is the first large-scale project centering on an exhaustive taphonomic study of the European fossil record”, explains the CENIEH taphonomy specialist Sala, a member of the Atapuerca research team and a researcher under the Juan de la Cierva-Incorporación program, who has obtained 1.5 million euros in funding for this project submitted to the 2020 call.

Carrying this out will require the participation of a large team of academics and a network of methods which include taphonomic analyses, virtual reconstructions for forensic analyses, studying spatial distribution patterns, the overall relations between different sites and mathematical models to interconnect the broad spectrum of data compiled.

Highly competitive projects

The European Research Council (ERC) projects known as “Starting Grants” are aimed at early-career researchers with post-doctoral experience of between 2 and 7 years, who have an outstanding research record and submit an excellent scientific project on the frontiers of knowledge. These are considered the most prestigious awards in the sphere of European research and, therefore, are highly competitive.

In the 2020 call, 436 researchers from 25 countries in the European Union and associated countries were selected, and 23 of the projects will be conducted at Spanish research centers. Of these 23, four are in the field of humanities and only one is centered on Paleoanthropology.

 

Press release from CENIEH on the Starting Grant for the research about the culture of death preceding Neanderthals and modern humans.


Unprecedented 3D reconstruction of pre-Columbian crania from the Caribbean and South America

Unprecedented 3D reconstruction of pre-Columbian crania from the Caribbean and South America

The CENIEH Digital Mapping and 3D Analysis Laboratory has participated in the reconstruction of 13 crania from an exceptional collection at The Montané Anthropological Museum in Cuba
3D reconstruction pre-Columbian crania
Crania with oblique tabular deformation. Credits: G. Rangel de Lázaro et al

Alfonso Benito Calvo, head of the Digital Mapping and 3D Analysis Laboratory at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) has participated in the 3D reconstructions of a representative selection of 13 pre-Columbian human crania specifically from Cuba and Peru, which are part of the osteological collection of the The Montané Anthropological Museum in Cuba.

The sample studied comprised crania with tabular oblique artificial deformation, annular deformation, and undeformed specimens. The 3D models generated were used to produce prints and 3D animated videos.

The deformed and undeformed crania were digitized with the Artec Space Spider structured blue light scanner, which created three-dimensional models based on the real samples. The resulting 3D models were used to produce 3D printed replicas and animated videos. “These 3D models of the Cuban pre-Columbian skulls have been made with microns precision,” says Alfonso Benito.

The 3D reconstruction of the crania will allow its precise systematic investigation and dissemination in different audiovisual media and online platforms, and they are also a perfect means to publicize the associated intangible resources, such as the experiences, rites and stories that surround these crania.

This study lead by Gizéh Rangel-de Lázaro (Natural History Museum in London and IPHES-URV) is published in the journal Virtual Archaeology Reviewwith the collaboration of researchers from CENIEH, University of Valladolid and The Montané Anthropological Museum in Cuba.

Full bibliographic information

Rangel de Lázaro, G., Martínez-Fernández, A., Rangel-Rivero, A., & Benito-Calvo, A. (2020). Shedding light on pre-Columbian crania collections through state of the art 3D scanning techniques. Virtual Archaeology Review (0). doi: 10.4995/var.2021.13742.
Press release on 3D reconstruction of pre-Columbian crania from CENIEH

Amud 9 neandertal

Amud 9 is shown to be a Neandertal woman weighing 60 kg who lived in the Late Pleistocene

Amud 9 is shown to be a Neandertal woman weighing 60 kg who lived in the Late Pleistocene

The CENIEH researcher Adrián Pablos co-leads a paper on the morphology of a foot found at Amud Cave in Israel, establishing that this fossil known as Amud 9 can be taxonomically attributed as Neandertal, and obtaining this individual's sex, weight and height.
Amud 9 neandertal
Fósiles de Amud 9. Credits: Osborjn M. Pearson y Adrián Pablos

Adrián Pablos, a scientist at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), co-leads a paper published in PaleoAnthropology, the official journal of the PaleoAnthropology Society, looking at the morphology and anatomy of a partial foot recovered over 25 years ago at Amud Cave (Israel), which confirms that the individual Amud 9 was a Neandertal woman from the Late Pleistocene, with a stature of some 160-166 cm and weight of 60 kg.

Over the course of several excavations conducted in the twentieth century at Amud Cave, remains of at least 15 Neandertals were found. A systematic and detailed study of one of these individuals, Amud 9, has found that the fossil possesses the traits usually associated with Neanderthals in the different elements of the foot, tarsals, metatarsals and phalanges, which differ from those of modern humans, both fossil and recent.

“Most of these traits are related to the typical, exceptional robustness of the postcranial skeleton, that is, from the neck down, observed in the majority of Neandertals”, explains Pablos.

Sex, weight and height

Sex, weight and height estimates in fossil populations are normally based on the dimensions of the large leg bones. However, in the case of Amud 9, only a fragment of tibia, the talus or ankle bone, one metatarsal or instep bone, and several phalanges are conserved.

As no long leg bones have been found, the researchers applied different mathematical estimates based upon the foot bones, thus obtaining an approximation to important paleobiological parameters.

“Knowing parameters such as the body size and sex of this individual helps us learn a bit more about what the Neandertals were like”, he says.

The participants in this paper, entitled A partial Neandertal foot from the Late Middle Paleolithic of Amud Cave, Israel, are researchers from Spain (the CENIEH), the United States (University of New Mexico and Arizona State University), and Israel (Tel Aviv University and The Hebrew University of Jerusalem).

Full bibliographic information

Pearson, O.M., Pablos, A., Rak, Y., Hovers, E., 2020. A partial Neandertal foot from the Late Middle Paleolithic of Amud cave, Israel. PaleoAnthropology 2020, 98-125. http://paleoanthro.org/media/journal/content/PA20200098.pdf.
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

Georadar reveals the unknown parts of the Sierra de Atapuerca caves

Georadar reveals the unknown parts of the Sierra de Atapuerca caves

The CENIEH has participated in a study led by Lucía Bermejo, in which this geophysical method was used to define the bottom part of the caves in the Trinchera del Ferrocarril sites
georadar Sierra de Atapuerca
GPR in Trinchera del Ferrocarril (Atapuerca). Credits: Miguel Ángel Martín

An international team of researchers from the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) and the University of Denver has managed to define the bottom part of the caves in the Trinchera del Ferrocarril sites (Cueva Peluda, Sima del Elefante, Galería and Gran Dolina), using georadar, revealing the unknown parts of these caves in the Sierra de Atapuerca (Burgos, Spain).

This non-invasive geophysical method, also known as ground penetrating radar (GPR), widely employed in archaeology because it is rapid and easy to apply, enables structures buried at different depths to be discovered. However, using it to study caves is usually discarded because the clayey sediments that fill them, being highly conductive, attenuate the radar signal, thus limiting its penetration capacity.

“Nevertheless, in our case this characteristic has served for studying the lower part of these caves, because we have been able to clearly distinguish the walls from the conduits, and from the sediments that fill them”, states Bermejo, lead author of this study, which was published recently in the journal Geomorphology.

It was possible to constrain the caves' depth by drilling two mechanical boreholes with core recovery, which have identified up to 17 meters of terrigenous fillings, such as in the case of the Galería site. Moreover, different types of sediments were discernible, thanks to which a possible conduit full of fluvial sediments was recorded, which would connect the lower level of Cueva Peluda with the lower part of Sima del Elefante.

Trinchera del Ferrocarril caves (Atapuerca). Credits: L. Bermejo et al

Quarrying activity

On the other hand, the information provided by the georadar and historical photographs have made it possible to establish how far the impact of the quarrying activity that took place at the Trinchera until the 1970s extended.

This activity was especially intensive between Cueva del Compresor, situated opposite the Galería site, and Gran Dolina, and it produced rubble fills up to 4 meters thick in the areas most impacted.

“All these data will help to optimize strategies for future excavations, as in this study it has been possible to identify the best preserved zones”, concludes Bermejo.

Full bibliographic information

Bermejo, L., Ortega, A. I., Parés, J. M., Campaña, I., Bermúdez de Castro, J. M., Carbonell, E., & Conyers, L. B. (2020). Karst features interpretation using ground-penetrating radar: A case study from the Sierra de Atapuerca, Spain. Geomorphology (0), 107311. doi: 10.1016/j.geomorph.2020.107311
Press release from CENIEH

Drones enable the first detailed mapping of the High Plateaus Basin in the Moroccan Atlas

Drones enable the first detailed mapping of the High Plateaus Basin in the Moroccan Atlas

The CENIEH has used this technology to assess how the landscape of this area in the Atlas chain has evolved, which is key to understanding human evolution in North Africa during the Quaternary

drones Atlas
Alfonso Benito driving the drones. Credits: M.G:Chacón (IPHES)

The Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) has led a paper just published in the Journal of Maps, according to which, with the help of drones, it has been possible to obtain high-resolution aerial images and topographies, fundamental to compiling the first detailed map of the High Plateaus Basin, a region in Eastern Morocco key to understanding human evolution in North Africa during the Quaternary.

“We used the drones from our Digital Mapping and 3D Analysis Laboratory to analyze how the landscape in this intramountain basin in the Atlas chain has evolved, and thus distinguish the different geological formations”, says the lead author of this work, Alfonso Benito Calvo, head of the Geomorphology and Formation Processes line of research at CENIEH.

In the zone studied, there are abundant geological materials on great plains marked by fluvial channels which led finally to the formation of shallow lakes and wetlands. From that moment, deep valleys began to be incised, leaving fluvial terraces and buttes, formed under arid conditions with frequent climatic changes.

“Numerous archaeological remains of different chronologies are preserved today in this geological record, indicating the great potential of the region for studying the archaeological history of North Africa from the Pliocene to the present day”, states Benito Calvo.

This work was conducted under the auspices of a Spanish-Moroccan project, directed by the IPHES (Instituto Catalán de Paleoecología Humana y Evolución Social), in Tarragona, and Mohammed I University (Oujda, Morocco), and has institutional support from the local and regional authorities of the Moroccan province of Jerada,  the Fundación Palarq and the Ministerio de Cultura y Deporte.

Aerial photo of Gara Soultana, in the valley of El Haï river. Credits: Alfonso Benito Calvo

Full bibliographic information

Benito-Calvo, A., Haddoumi, H., Aouraghe, H., Oujaa, A., Chacón, M. G., & Sala-Ramos, R. (2020). Geomorphological analysis using small unmanned aerial vehicles and submeter GNSS (Gara Soultana butte, High Plateaus Basin, Eastern Morocco). Journal of Maps, 16(2), 459-467. doi: 10.1080/17445647.2020.1773329.

Press release 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