The shoulders of 'Homo antecessor' and modern humans are similar

The shoulders of 'Homo antecessor' and modern humans are similar

The CENIEH has published a paper in the journal Scientific Reports which concludes that Homo antecessor had a shoulder development analogous to that in H. sapiens, although its growth was faster
Homo antecessor shoulders
Homo antecessor scapulae. Credits: D. Garcia Martínez et al

The shape of our shoulders was already present in the Lower Pleistocene, according to a pioneering study published today in the journal Scientific Reports, carried out by Daniel García Martínez and José María Bermúdez de Castro, paleoanthropologists at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), in collaboration with David Green of Campbell University (USA).

Studying the shoulder (technically known as the "shoulder girdle") furnishes information on points significant for human evolution such as locomotion, body shape, the possibility of climbing with ease or the ability to launch objects like stones or spears with high accuracy.

The authors of this work were able to study for the first time shoulder growth and development in the species Homo antecessor, dated to 850,000 years old, using tools from virtual anthropology and 3D geometric morphometry. The results show that the course of development of the shoulder in this species was very similar to that in H. sapiens, although the growth might have been faster.

Almost one million years ago, our evolution had already attained almost all the biomechanical capacities characterizing the shoulder in modern humans, and it had definitively parted ways from the abilities still then retained by the more archaic species of the human phylogeny, including climbing with great agility.

 To verify the changes undergone by this part of our anatomy, we need a flat bone: the shoulder blade or scapula. But, as the authors of this study state, “The fossil record of our phylogeny contains barely a handful of these highly delicate bones, which has posed enormous difficulties to studying the growth and development of the shoulders during human evolution”.

Two key fossils

By good luck, at level TD6 of the Gran Dolina site, situated in the Sierra de Atapuerca (Burgos), two scapulae have been conserved: one from a child and the other from an individual of age equivalent to a modern adolescent. These fossils were recovered during the excavation in the first decade of the twenty-first century and belonged to the species H. antecessor.

“In an earlier study of these two fossils, it had been noticed that the morphology of the scapulae was similar to our own. But until now, the growth and development model for the shoulders had remained unknown, and this work has now allowed us to check that our shoulder girdle bones have undergone modifications in accordance with different capacities”, says Bermúdez de Castro.

Comparative study

With the scant information available, it was known that the scapulae of Australopithecus species were similar in some ways to those of chimpanzees or gorillas but were different from our own. “We know that the development of our most archaic ancestors was very similar to that of the anthropoid apes, and the morphology of their shoulders shows that they still retained the capacity to climb with ease. We, on the contrary, have lost this ability”, explains García Martínez.

Comparative of scapulae. Credits: D.García Martínez et al

To determine when our anatomical peculiarities arose, in addition to virtual anthropology and 3D geometric morphometry, the researchers used complex statistical methods to study the development of the shoulder girdle in the species H. antecessor, comparing it with other species from the Pliocene and Lower Pleistocene, such as Australopithecus sediba and A. afarensis. A very broad sample from H. sapiens and chimpanzees (Pan troglodytes) was also used.

“This study shows that although there exist slight morphological differences between the scapulae of H. antecessor and H. sapiens, the former were much more similar to modern humans, to H. erectus and even to Australopithecus than to chimpanzees”, comments García Martínez.

With regard to how the scapulae grew, it was also seen that this was very different from what happens in chimpanzees, and comparable with H. sapiens. “However, it is true that the data seem to point to growth being more rapid in H. antecessor, as highlighted by the CENIEH research team on the basis of dental evidence”, emphasizes Bermúdez de Castro.

This paper lays the foundations for how the shoulder girdle developed in Lower Pleistocene species, and opens the door to new research studying shoulder development in fossil species, as it may become possible to expand the timeframe and study this development even in Pliocene species like the genus Australopithecus.

Full bibliographic information

García-Martínez, D., Green, D., Bermúdez de Castro, J.M. 2021. Evolutionary development of the Homo antecessor scapulae (Gran Dolina site, Atapuerca) suggests a modern-like development for Lower Pleistocene Homo. Scientific Reports. DOI: 10.1038/s41598-021-83039

 

Press release from CENIEH


A study proposes the low genetic diversity of the Neanderthals as the principal cause of their extinction

New data support the theory of low genetic diversity of Neanderthals as the main cause of their extinction

Atles (Kr.98) recovered from the Krapina site that presents the anatomical variant known as Unclosed Transverse Foramen

What caused the disappearance of Homo neanderthalensis, a species that apparently had as many capabilities as Homo sapiens? There are several theories that try to explain it: climate, competition with Homo sapiens, low genetic diversity... A study in which the Universitat de València is participating analyses the first cervical vertebra of several Neanderthals and confirms that the genetic diversity of the population was low, which made it difficult for them to adapt to possible changes in the environment and, therefore, to survive. The research has been published in the Journal of Anatomy.

Professor Juan Alberto Sanchis Gimeno, from the Department of Human Anatomy and Embryology of the Faculty of Medicine and Dentistry of the Universitat de València; the National Museum of Natural Sciences (MNCN-CSIC), and the National Centre for Research on Human Evolution (CENIEH) have participated in the study. Three vertebrae from the Krapina site (Croatia) have been analysed and material from other sites has been reviewed.

Neanderthals inhabited the European continent until barely 30,000 years ago and their disappearance remains a mystery. In order to know their genetic diversity, work has been done to decipher their genome, but also to analyze different anatomical characteristics of the fossil record of the species. "In this study we have focused on the anatomical variants of the first cervical vertebra, known as the atlas. The anatomical variants of this vertebra have a high relationship with genetic diversity: the higher the prevalence of this type of anatomical variants, the lower the population genetic diversity", explains MNCN researcher Carlos A. Palancar.

In Homo sapiens the anatomical variants of the atlas have been widely studied in recent years. In the case of modern humans, the atlas shows some of the different anatomical variants in almost 30% of cases. "However, probably due to the poor preservation of this cervical vertebra and the little material recovered in the fossil record, the atlas of Neanderthals have hardly been observed under this magnifying glass," says Juan Alberto Sanchis Gimeno, a researcher at the Universitat de València.

Recently, researchers from the MNCN Paleonanthropology Group determined the presence of different anatomical variants in the atlases of the Neandertals from the El Sidrón site (Asturias). In order to confirm the high prevalence of anatomical variants of this species, they thoroughly analyzed the fossil atlases of the Neandertals from the Krapina site (Croatia). "Krapina is a site of about 130,000 years old, compared to about 50,000 years old in El Sidrón. It is the site from which the largest number of Neanderthal remains have been recovered, which makes it a sample of special interest in the analysis of the genetic diversity of this species since potentially all the individuals belonged to the same population," points out Daniel García-Martínez, researcher at the CENIEH.

The study of the anatomy of the three atlases recovered in this site has revealed the presence of anatomical variants in two of them (66%). One of them, known as Unclosed Transverse Foramen, UTF, has a prevalence of only 10% in modern humans. "Checking the presence of these anatomical variants in Krapina, together with the review of other atlases presented to the scientific community that have not been analyzed under this perspective until now and that yield similar data (more than 50%), suggests that the number of variants in Neanderthals is significantly higher than that of current humans," says Palancar.

"These data support the theory that their genetic diversity was very low and confirm that this could be one of the causes of their disappearance," concludes MNCN researcher Markus Bastir.

Press release from Asociación RUVID; Source: Universidad de Valencia

A study proposes the low genetic diversity of the Neanderthals as the principal cause of their extinction

The CENIEH has participated in a paper published in the Journal of Anatomy on the first cervical vertebra, atlas, of several Neanderthals from the Krapina site (Croatia), which confirms that the genetic diversity of these populations was low

Neanderthals extinction
Atlas from Neanderthals found in Krapina site. Credits: Carlos A. Palancar et al

What caused the disappearance of Homo neanderthalensis, a species which apparently possessed as many capacities as Homo sapiens? There are several theories attempting to explain this: the climate, competition, low genetic diversity… Daniel Garcia Martínez, a researcher at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has participated in a study published in the Journal of Anatomy, on the first cervical vertebra of several Neanderthals, which confirms that the genetic diversity of the population was low, thus hampering their capacity to adapt to possible changes in their environment and, therefore, their survival.

The Neanderthals inhabited the European continent until barely 30,000 years ago, and their disappearance continues to be a mystery. Work to decipher their genome has been carried out to determine their genetic diversity, as have analyses of different anatomical characteristics in the fossil record of the species.

“We have centered on the anatomical variants of the first cervical vertebra, known as the atlas. The anatomical variants of this vertebra are tightly bound up with genetic diversity: the greater the prevalence of this kind of anatomical variant, the lower the population genetic diversity", explains Carlos A. Palancar, a researcher at the Museo Nacional de Ciencias Naturales.

In H. sapiens, the anatomical variants of the atlas have been extensively studied over recent years. With regard to modern humans, the atlas presents one or more of the different anatomical variations in almost 30% of cases.

El Sidrón

In this study, in which researchers from the Museo Nacional de Ciencias Naturales in Madrid (MNCN-CSIC) and the Universidad de Valencia also participated, three vertebrae from the Krapina site (Croatia) were analyzed, and the material from other sites such as El Sidrón (Asturias) was reviewed.

Recently, researchers from the Paleoanthropology Group at the MNCN determined the presence of different anatomical variants in the atlases from the El Sidrón Neanderthals. With the objective of confirming the high prevalence of these anatomical variants in the species, they conducted exhaustive analyses of the Neanderthal fossil atlases from Krapina.

“Krapina is a site around 130,000 years old, compared with the age of 50,000 or so for El Sidrón. This is the site from which the highest number of Neanderthal remains has been recovered, which makes these a sample of particular interest when analyzing the genetic diversity of this species, as all the individuals may potentially have belonged to the same population”, says García-Martínez.

Full bibliographic information

Palancar C.A., García-Martínez D., Radovčić D., et al. (2020) Krapina atlases suggest a high prevalence of anatomical variations in the first cervical vertebra of Neanderthals. Journal of Anatomy DOI: https://doi.org/10.1111/joa.13215
Press release from CENIEH

Cueva de los Toriles

Cueva de los Toriles site is dated to the Early-Middle Pleistocene by the presence of a primitive badger

Cueva de los Toriles site is dated to the Early-Middle Pleistocene by the presence of a primitive badger

The CENIEH has led a paper on this archaeological site located in Castilla-La Mancha (Spain), which makes clear its importance as one of the most significant enclaves with fossil remains from these chronologies in the southern Iberian plateau

Badger teeth. Credits: Daniel García Martínez

A team of researchers headed by Daniel Garcia Martínez, a paleoanthropologist at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has just published a paper in the Journal of Iberian Geology on some remains of a primitive badger found in the Cueva de los Toriles (Carrizosa, Ciudad Real, Spain) which have allowed it to be dated to the Early-Middle Pleistocene: this archaeological site could potentially be a singular enclave with fossil remains from the southern Iberian plateau in these chronologies.

Even though there is currently no exact dating for the sedimentary deposits at this site in La Mancha, the finding of two lower molars of a mustelid, attributed to the species Meles cf. thorali, a primitive badger, has enabled their potential age to be checked, because this extinct mustelid is principally found in sites around 1 million years old.

As Alberto Valenciano, a specialist in mustelids from the University of Cape Town, explains: “In accordance with the presence of this badger species in the cave, we can tentatively assume an age ranging from the Late Pliocene up to the Middle Pleistocene”. In addition, as García Martínez comments: “These chronologies would be consistent with certain lithic tools recovered from the site”.

A natural corridor

Studying the southern Iberian plateau is primordial to revealing the population and movement of fauna in the Iberian Peninsula, because it functions as a natural corridor connecting the Central System and Iberian Range to the north with the Baetic Ranges to the south.

Cueva de los Toriles
Cueva de los Toriles site. Credits: Danie García Martínez

In the southern Iberian plateau, there are far fewer Pleistocene sites than in the northern plateau, where sites of world importance such as Atapuerca (Burgos) are found, because the eminently agricultural use of the land has caused many open-air sites to be altered or vanish.

“And while it is true that certain sites well-known to archaeologists are found in Ciudad Real, such as Albalá or El Sotillo, these are rich in lithic remains but poor in fossils, something which does not happen at Cueva de los Toriles where remains of macromammals have also been found, which could help to fill the gaps in our knowledge about this region”, states García Martínez.

“This cave is also an important site because of the enduring human presence stretching back to prehistory which we are seeing in our first investigations. A major milestone in the archaeology of Castilla-La Mancha and the southern sub-plateau", says Pedro R. Moya Maleno, from the Universidad Complutense de Madrid.

 

Full bibliographic information

 

García-Martínez, D., Valenciano, A., Suárez-Bilbao, A., Palancar, C. A., Megía García, I., Moreno, D., Campaña, I., & Moya-Maleno, P. R. (2020). New remains of a primitive badger from Cueva de los Toriles (Carrizosa, Castilla-La Mancha, Iberian Peninsula) suggest a new quaternary locality in the southern Iberian plateau. Journal of Iberian Geology (0). doi: 10.1007/s41513-020-00127-y

Press release from CENIEH