New geological datings place the first European hominids in the south of the Iberian Peninsula 1.3 million years ago

One of the most important controversies about human evolution and expansion is when and by what route the first hominids arrived in Europe from the African continent. Now, geological dating techniques at the Orce sites (Baza basin, Granada, Spain) place the human remains found in this area as the oldest in Europe, at approximately 1.3 million years old. These results reinforce the hypothesis that humans arrived in Europe through the south of the Iberian Peninsula, through the Strait of Gibraltar, instead of returning to the Mediterranean via the Asian route. The study, led by Lluís Gibert, researcher and lecturer at the University of Barcelona's Faculty of Earth Sciences, has involved the participation of researchers from the Berkeley Geochronology Centre and Murray State University (United States).

Analysis of a new sampling area

The new dating has been based on the analysis of the paleomagnetism of an area of the Orce region, which has never been sampled before and which has been protected from the erosion that this basin has suffered over the years. This technique is a relative dating method based on the study of the inversion of the magnetic poles of the planet due to the internal dynamics of the Earth. These changes do not have a specific periodicity, but they are recorded in the minerals and make it possible to establish time periods from the different magnetic events.

These new data are very precise thanks to the long sedimentary sequence that outcrops in Orce. "The uniqueness of these sites is that they are stratified and within a very long sedimentary sequence, more than eighty metres long. Normally, the sites are found in caves or within very short stratigraphic sequences, which do not allow you to develop long palaeomagnetic sequences in which you can find different magnetic reversals," says Lluís Gibert.

The researchers have been able to identify a magnetic polarity sequence "with five magnetic events that allow them to place the three Orce sites with human presence between the Olduvai and Jaramillo subchron, that is, between 1.77 and 1.07 million years ago (Ma)," says the researcher. Subsequently, they have applied a statistical age model to accurately refine the chronology of the different stratigraphic levels with a margin of error of only 70,000 years. The result of this innovative methodology is that the oldest site with human presence in Europe would be Venta Micena with an age of 1.32 Ma, followed by Barranco León, with an age of 1.28 and finally Fuente Nueva 3, with an age of 1.23 Ma. "With these data, the other major site on the peninsula, the Sima del Elefante in Atapuerca, would be relegated to second place, far behind Orce, between 0.2 and 0.4 Ma more modern," adds the researcher.

Fauna underpins the antiquity of the site

To complete the dating, the study has also analyzed the fauna found at the different sites in Orce, as this is different depending on the period, and compared it with that found at other Early Pleistocene sites in other parts of Europe.

In this sense, the paper presents a detailed analysis of the micromammals and large mammals from all the Orce sites, carried out by the expert Robert Martin, based on the palaeontological collections stored at the Museum of the Catalan Institute of Palaeontology Miguel Crusafont (IPS) in Sabadell. "The results indicate that the small and large fauna of Orce is more primitive than, for example, that of the Sima del Elefante, where the evidence shows that the rodent Allophaiomys lavocati is more evolved than the Allophaiomys recovered from the Orce sites," Gibert explains.Another relevant indicator of the age of the Orce sites is the absence of the ancestors of the pigs. "These animals are considered to be Asian immigrants and have not been found in any European site between 1 and 1.5 Ma, while they have been found in the Sima del Elefante, supporting that the Orce fauna is older," explains the researcher.

Evidence pointing to passage through Gibraltar

This new dating would be added, according to the researcher, to other evidence that would tip the balance in favour of the colonization of Europe through the Strait of Gibraltar, rather than the alternative route: the return to the Mediterranean via Asia, such as "the existence of a lithic industry with similarities to that found in the north of the African continent and also the presence of remains of African fauna in the south of the peninsula, such as those of Hippopotamus, found in the sites of Orce, and those of Theropithecus oswaldi, an African primate similar to a baboon, found in the Victoria cave, a site near Cartagena (Murcia), non-existent anywhere else in Europe."

"We also defend the hypothesis -- adds the researcher -- that they arrived from Gibraltar because no older evidence has been found at any other site along the alternative route."

These new data are very precise thanks to the long sedimentary sequence that outcrops in Orce.

Similarity with hominids from the island of Flores

With these results, the researchers point to a "diachronism" between the oldest occupation of Asia, measuring 1.8 Ma, and the oldest occupation of Europe, which would be 1.3 Ma ago, so that African hominids would have arrived in southwestern Europe more than 0.5 Ma after leaving Africa for the first time about 2 Ma ago. "These differences in human expansion can be explained by the fact that Europe is isolated from Asia and Africa by biogeographical barriers that are difficult to overcome, both to the east (Bosphorus Strait, Dardanelles, Sea of Marmara) and to the west (Strait of Gibraltar). Humanity arrived in Europe when it had the necessary technology to cross maritime barriers, as happened before a million years ago on the island of Flores (Indonesia)," says Gibert. In this sense, the researcher adds that the Gibraltar route currently requires crossing up to fourteen kilometres of sea route, but "perhaps in the past this distance was shorter at certain times due to the high tectonic activity in this region and the fluctuations in sea level that favoured migrations."

"As cited in the paper -- he adds -- , we have identified other migrations of African fauna through Gibraltar at earlier times, 6.2 and 5.5 Ma ago when the Strait of Gibraltar was very narrow."

Human remains in Orce

A total of five human remains were found at the Orce sites since excavations began in 1982 by the palaeoanthropologist Josep Gibert. Firstly, two fragments of humerus bitten by hyenas were found at Venta Micena, as well as parts of a cranial fragment consisting of two parietals and an occipital, associated with an abundant Early Pleistocene fauna. The human provenance of these remains generated great controversy for years, although independent palaeoproteomic studies by the universities of Granada and San Francisco identified human proteins in the remains.

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Apes' inner ears could hide clues to evolutionary history of hominoids

Studying the inner ear of apes and humans could uncover new information on our species' evolutionary relationships, suggests a new study published today in eLife.

Humans, gorillas, chimpanzees, orangutans and gibbons all belong to a group known as the hominoids. This 'superfamily' also includes the immediate ancestors and close relatives of these species, but in many instances, the evolutionary relationships between these extinct ape species remain controversial. The new findings suggest that looking at the structure (or morphology) of the inner ears across hominoids as a whole could go some way to resolving this.

"Reconstructing the evolutionary history of apes and humans and determining the morphology of the last common ancestor from which they evolved are challenging tasks," explains lead author Alessandro Urciuoli, a researcher at the Institut Català de Paleontologia Miquel Crusafont (ICP) in Barcelona, Spain. "While DNA can help evolutionary biologists work out how living species are related to one another, fossils are typically the principle source of information for extinct species, although they must be used with caution."

The bony cavity that houses the inner ear, which is involved in balance and hearing and is fairly common in the fossil record, has proven useful for tracing the evolution of certain groups of mammals. But until now, no studies have explored whether this structure could provide insights into the evolutionary relatedness among living and extinct hominoids.

To address this, Urciuoli and his team used a 3D imaging technique to capture the complex shapes of the inner ear cavities of 27 species of monkeys and apes, including humans and the extinct ape Oreopithecus and fossil hominin Australopithecus. Their results confirmed that the shape of these structures most closely reflected the evolutionary relationships between the species and not, for example, how the animals moved.

The team next identified features of these bony chambers that were shared among several hominoid groups, and estimated how the inner ears of these groups' ancestors might have looked. Their findings for Australopithecus were consistent with this species being the most closely related to modern humans than other apes, while those for Oreopithecus supported the view that this was a much older species of ape related in some respects with other apes still alive today.

"Our work provides a testable hypothesis about inner ear evolution in apes and humans that should be subjected to further scrutiny based on the analysis of additional fossils, particularly for great apes that existed during the Miocene," says senior author David Alba, Director of the ICP. The Miocene period, which extends from about 23 to five million years ago, is when the evolutionary path to hominoids became distinct.

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Artificial intelligence applied to the genome identifies an unknown human ancestor

Genome sequencing

By combining deep learning algorithms and statistical methods, investigators from the Institute of Evolutionary Biology (IBE), the Centro Nacional de Análisis Genómico (CNAG-CRG) of the Centre for Genomic Regulation (CRG) and the Institute of Genomics at the University of Tartu have identified, in the genome of Asian individuals, the footprint of a new hominid who cross bred with its ancestors tens of thousands of years ago.

Modern human DNA computational analysis suggests that the extinct species was a hybrid of Neanderthals and Denisovans and cross bred with Out of Africa modern humans in Asia. This finding would explain that the hybrid found this summer in the caves of Denisova -- the offspring of a Neanderthal mother and a Denisovan father -- was not an isolated case, but rather was part of a more general introgression process.

The study, published in Nature Communications, uses deep learning for the first time ever to account for human evolution, paving the way for the application of this technology in other questions in biology, genomics and evolution.

Humans had descendants with an species that is unknown to us

One of the ways of distinguishing between two species is that while both of them may cross breed, they do not generally produce fertile descendants. However, this concept is much more complex when extinct species are involved. In fact, the story told by current human DNA blurs the lines of these limits, preserving fragments of hominids from other species, such as the Neanderthals and the Denisovans, who coexisted with modern humans more than 40,000 years ago in Eurasia.

Now, investigators of the Institute of Evolutionary Biology (IBE), the Centro Nacional de Análisis Genómico (CNAG-CRG) of the Centre for Genomic Regulation (CRG), and the University of Tartu have used deep learning algorithms to identify a new and hitherto-unknown ancestor of humans that would have interbred with modern humans tens of thousands of years ago. "About 80,000 years ago, the so-called Out of Africa occurred, when part of the human population, which already consisted of modern humans, abandoned the African continent and migrated to other continents, giving rise to all the current populations," explained Jaume Bertranpetit, principal investigator at the IBE and head of Department at the UPF. "We know that from that time onwards, modern humans cross bred with Neanderthals in all the continents, except Africa, and with the Denisovans in Oceania and probably in South-East Asia, although the evidence of cross-breeding with a third extinct species had not been confirmed with any certainty."

Deep learning: deciphering the keys to human evolution in ancient DNA

Hitherto, the existence of the third ancestor was only a theory that would explain the origin of some fragments of the current human genome (part of the team involved in this study had already posed the existence of the extinct hominid in a previous study). However, deep learning has made it possible to make the transition from DNA to the demographics of ancestral populations.

The problem the investigators had to contend with is that the demographic models they have analysed are much more complex than anything else considered to date and there were no statistic tools available to analyse them. Deep learning "is an algorithm that imitates the way in which the nervous system of mammals works, with different artificial neurons that specialise and learn to detect, in data, patterns that are important for performing a given task," stated Òscar Lao, principal investigator at the CNAG-CRG and an expert in this type of simulations. "We have used this property to get the algorithm to learn to predict human demographics using genomes obtained through hundreds of thousands of simulations. Whenever we run a simulation we are travelling along a possible path in the history of humankind. Of all simulations, deep learning allows us to observe what makes the ancestral puzzle fit together."

It is the first time that deep learning has been used successfully to explain human history, paving the way for this technology to be applied in other questions in biology, genomics and evolution.

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Where hominid brains are concerned, size doesn't matter

The recently-discovered species Homo naledi may have had a pint-sized brain, but that brain packed a big punch. New research by Ralph Holloway and colleagues -- that include researchers from the University of the Witwatersrand, Johannesburg, South Africa -- published in the Proceedings of the National Academy of Sciences examines the imprints of the brain upon the skulls of this species, called endocasts. The research highlights the humanlike shape of naledi's tiny brain, surprising scientists who studied the fossils. These findings draw further into question the long-held belief that human evolution was an inevitable march towards bigger, more complex brains.

The discovery of Homo naledi by Professor Lee Berger of Wits University and his team at the Rising Star caves in the Cradle of Human Kind in 2013 was one of the largest hominin discoveries ever made and hailed as one of the most significant hominid discoveries of the 21st Century. Berger and Professor John Hawkes who was also part of the original Rising Star team who made the naledi discovery, as well as Professor Heather Garvin from Des Moines University in the US, are associated with the Evolutionary Studies Institute (ESI), based at Wits University. They are all co-authors of the current study.

In 2017, geologists demonstrated that this species existed in southern Africa between 236,000 and 335,000 years ago -- potentially the same time that modern humans first emerged in Africa. This is a puzzle to scientists, who long held that there was only one species in Africa at this late time period -- Homo sapiens. How did this species exist alongside others with brains three times its size? The new study suggests that naledi's behavior may have reflected the shape and structure of the brain more than its size.

The researchers pieced together traces of Homo naledi's brain shape from an extraordinary collection of skull fragments and partial crania, from at least five adult individuals. One of these bore a very clear imprint of the convolutions on the surface of the brain's left frontal lobe. "This is the skull I've been waiting for my whole career," said lead author Ralph Holloway, of Columbia University.

The anatomy of naledi's frontal lobe was similar to humans, and very different from great apes. Naledi wasn't alone. Other members of our genus, from Homo erectus to Homo habilis and the small-brained "hobbits," Homo floresiensis, also share features of the frontal lobe with living humans. But earlier human relatives, like Australopithecus africanus, had a much more apelike shape in this part of the brain, suggesting that functional changes in this brain region emerged with Homo. "It's too soon to speculate about language or communication in Homo naledi," said coauthor Shawn Hurst, "but today human language relies upon this brain region."

The back of the brain also showed humanlike changes in naledi compared to more primitive hominins like Australopithecus. Human brains are usually asymmetrical, with the left brain displaced forward relative to the right. The team found signs of this asymmetry in one of the most complete naledi skull fragments. They also found hints that the visual area of the brain, in the back of the cortex, was relatively smaller in naledi than in chimpanzees -- another humanlike trait.

The small brains of Homo naledi raise new questions about the evolution of human brain size. Big brains were costly to human ancestors, and some species may have paid the costs with richer diets, hunting and gathering, and longer childhoods. But that scenario doesn't seem to work well for Homo naledi, which had hands well-suited for toolmaking, long legs, humanlike feet, and teeth suggesting a high-quality diet. According to study coauthor John Hawks, "Naledi's brain seems like one you might predict for Homo habilis, two million years ago. But habilis didn't have such a tiny brain -- naledi did."

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The First Adhesive Was Invented by Neanderthals 200,000 Years Ago

Reconstruction of the environment of a Neanderthal man in the mid-Paleolithic period (80,000 BC)

Neanderthals — early members of the genus Homo from Europe and Asia — have had such a lowly standing on the human family tree that the very word Neanderthal is often synonymous with archaic ways and ignorance.

Neanderthals, however, had big brains, complex societies, and tools so useful that some designs created for leatherworking are still in use today. Many researchers even believe that a true extinction of Neanderthals might not have occurred, but that these individuals instead were absorbed into what evolved to be current Homo sapiens. To this day, people of European and Asian heritage retain Neanderthal DNA.

Excavations over the past few decades have unearthed tar lumps and adhesive residues on stone tools at Neanderthal sites in Germany. Some anthropologists have claimed that adhesive production is a high-tech skill associated with anatomically modern humans, yet new research published in the journal Scientific Reports not only supports that Neanderthals invented adhesives, but also it explains how they probably achieved the feat.

“Right now, the oldest evidence we have points to Neanderthals inventing adhesives at least 200,000 years ago in Europe,” lead author Paul Kozowyk said.

Kozowyk, a researcher at Leiden University, and his team analyzed archaeological evidence for early tar production. They additionally conducted experiments based on Neanderthal know-how to determine how the early Eurasians managed to invent tar, an adhesive that helped to strengthen and waterproof bindings made of sinew, hide, or plant fibers used to attach bone or stone tools to handles. The technique, known as hafting with tar, was also extended to weapon production, such as improving spears employed for hunting.

The researchers propose as many as three tar production methods could have been developed by Neanderthals. The first, called "ash mound," required placing ambers and ash over a roll of birch bark tied with fresh wood fiber to keep it tight. The scientists determined that care must be taken to balance the ratio between embers and ash, which helps to keep oxygen out and promotes the production of tar that can then be scraped off the roll.

Experimentally produced birch bark tar dripping from a flint flake

The second method demonstrated by the researchers, "pit roll,” required placing hot embers directly on top of a birch bark roll placed over a pit, which produced tar.

The other method, “raised structure,” was the most sophisticated of all in the study. It involved putting a container made of birch bark in a pit. A loose roll of bark was then placed on organic mesh covering the pit. The researchers covered the bark with dirt and lit a fire over the entire mound. This technique, which required more wood, time, and set-up than the other methods, yielded the most tar.

“It's possible that all three methods we tested, or even some different methods, were used depending on the needs or requirements at the time,” Kozowyk said. “For example, a major service to a Neanderthal tool kit might have called for something like the raised structure to produce lots of tar for multiple tools.”

“On the other hand,” he added, “a small hunting camp requiring a quick repair may have only needed a small amount of tar, and then a simpler method would be much more practical. My personal favorite is the pit roll method, because it's simple, but still produced reasonable quantities of tar.”

Tar collected in a birch bark container from the "pit roll" experiment, a technique which uses glowing embers placed over a roll of bark in a small pit.

The earliest evidence so far for adhesive production by anatomically modern humans dates to around 70,000 years ago, according to the researchers. It is likely that members of Homo sapiens in Africa figured out how to create tar on their own — a case of independent invention — but scientists have not ruled out that they learned the birch bark tar production techniques from Neanderthals.

Tar has many possible functions. Kozowyk, though, said, “During the Paleolithic, it’s unlikely that tar was used for much more than hafting tools.”

“In historic times," he added, "tar was used to waterproof boats and ships, containers and to protect wooden buildings, so its use is not limited to hafting tools. But these require production on an industrial scale that is not seen until more recently.”

Placing materials in ceramic containers can help with tar production. There is no evidence that Neanderthals ever produced pottery, however.

“There was probably no need for pottery until quite recently — speaking on a scale including hundreds of thousands of years of human evolution — and even in most modern human hunter-gatherer societies, pottery is an exception,” Kozowyk explained.

Neanderthals and early anatomically modern humans might have instead crafted containers out of wood and plant fibers. But if they did, preservation of such items is so poor that there is no firm evidence of them dating to the times of the oldest tar production.

Neanderthals and anatomically modern humans diverged long before then. An emerging theory is that the divergence occurred at least 500,000 years ago, with each group evolving on its own path until interbreeding occurred. The latter mixing, as well as similarities among the groups, however, have many anthropologists believing that Neanderthals and other hominids, such as Denisovans, should be considered as Homo sapiens.

“I used to argue that ‘anatomically modern humans’ — including fossils that essentially look like us today — are the only group that should be called Homo sapiens,” Chris Stringer of the Natural History Museum in London said. “Now, I think that anatomically modern humans are only a sub-group within the species Homo sapiens, and that we should recognize the diversity of forms within early Homo sapiens, some of which probably went extinct.”

Approximately 0.3 ounces of birch bark tar produced using the "raised structure" technique being prepared for analysis in the lab

The jury is still out on what exactly happened to Neanderthals. Some researchers have suggested that anatomically modern humans killed them off, or — like early colonizers of the Americas infecting native populations — spread diseases for which Neanderthals had no immunity. Kozowyk shared his view.

“What happened to Neanderthals was probably the result of a number of complex processes including, but not necessarily limited to, interbreeding with some cultural interaction, competition in some form, and a low Neanderthal population that led to them eventually being genetically overrun by the arriving modern human populations,” he said. “But this also likely varied from one region to another.”

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