Cave That Housed Neandertals and Denisovans Challenges View of Cultural Evolution

Researchers have deduced which early human species occupied Denisova Cave and when, drawing surprising conclusions about who made the sophisticated artifacts found there

By Kate Wong on January 30, 2019


Deep in the Altai mountains of southern Siberia sits a very choice piece of real estate. It’s nothing so newfangled as a ski lodge or one of the traditional wood houses that dot the local countryside. Rather it’s a primeval limestone cave, called Denisova, that overlooks a rushing river and the surrounding forest. Multiple human species, or hominins, have sought shelter in this cave over the past 300,000 years, such is its allure. Artifacts, bits of bone and ancient DNA found in its chambers testify to the presence of these peoples. The site thus offers a rare window on a particularly fascinating period of human evolution, one in which other human species coexisted with our own kind.

Researchers have long wondered how these groups interacted and influenced one another culturally when they met up, and Denisova could be a key to answering this question. But figuring out which hominin species was present when at the cave and which artifacts they made has proved challenging. Now new efforts to date the remains from Denisova are at last bringing that picture into sharper focus. Two studies published in the January 31 Nature provide a time line of human occupation of the cave. The results raise intriguing questions about the origins of symbolism and certain technologies traditionally considered to be inventions of Homo sapiens alone.

Archaeologists have been unearthing artifacts from Denisova Cave since the 1980s. The site contains frustratingly little in the way of hominin fossils, however. Most of the bones from the site are mere scraps, too incomplete to assign to a particular species on the basis of their physical characteristics. But in the last decade researchers have managed to recover ancient DNA from some of these fossil bits and from sediments in the cave. The DNA shows both Neandertals and another archaic group known as the Denisovans hung out there. And last year a team reported they had retrieved DNA from what was apparently a hybrid individual who had a Neandertal mom and a Denisovan dad. But for all that scientists have been able to piece together about Denisova, the timing of hominin occupation of the site has remained uncertain, thanks to certain quirks of site formation and preservation as well as the limitations of various techniques used to date archaeological and fossil material.


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In the new studies, two groups of researchers obtained a raft of fresh dates for the stratigraphic levels of interest at the site using a combination of techniques. One group, led by Zenobia Jacobs and Bo Li of the University of Wollongong in Australia, used a method called optically stimulated luminescence to date sediments from the cave. The team also reconstructed the environmental conditions at the site between 300,000 and 20,000 years ago. In the second study, Katerina Douka of the Max Planck Institute for the Science of Human History in Germany, Thomas Higham of the University of Oxford and their colleagues used radiocarbon dating to ascertain the ages of artifacts spanning the transition from the simpler Middle Paleolithic material culture to the more elaborate Upper Paleolithic one. Most of the human fossils are too old for radiocarbon dating, which maxes out at around 50,000 years. So the team determined the so-called relative genetic ages of the human fossils from the site by comparing their DNA sequences with those obtained from other human fossils and counting the differences between them. Such mutations accumulate at a known rate in modern humans. Using that rate the researchers were able to convert the ancient DNA differences to time. Douka, Higham and their colleagues then fed all of the ages obtained from the radiocarbon and optically stimulated luminescence methods, along with timing data from the genetic studies and the stratigraphic layers themselves, into a statistical model that calculated the most probable ages for the human fossils.

The results of these studies reveal Denisovans and Neandertals occupied the cave intermittently from at least 200,000 until around 50,000 years ago during both cooler and warmer climate phases. Denisovans were the first of the two groups to move into the cave and the last to abandon it. They probably overlapped there around 120,000 years ago, and possibly at other times as well.

The time line hints at a tantalizing possibility for who made the early Upper Paleolithic artifacts at the site, which include animal tooth pendants, a stunning stone bracelet and a needle and other tools crafted from bone. The radiocarbon dates obtained from some of the pendants and bone tools put them at 43,000 to 49,000 years old. There are no known hominin remains of that age from the site—the youngest specimen is a Denisovan fossil that dates to between 52,000 and 76,000 years ago. Yet Douka, Higham and their colleagues think creators of these artifacts are likely to have been Denisovans. Neandertals appear to have checked out of the cave by around 80,000 years ago. A fossil from the site of Ust’ Ishim documents the presence of our species in western Siberia around 45,000 years ago, which is the right time for it to be the maker of these artifacts. But that site is hundreds of kilometers from Denisova. “Our Russian colleagues have rightfully argued that we have no modern human fossils at Denisova and no modern human DNA from Denisova sediments, so why invoke modern humans” to explain the onset of the Upper Paleolithic at the site, Douka says. “One might say that given [the Ust’ Ishim fossil], we should assume modern humans made the pendants and bone tools at Denisova, but we don’t have modern human fossils in the Altai at that time.” Higham adds: “It could be modern humans but the most parsimonious explanation for the moment is that it’s Denisovans.”

The suggestion Denisovans developed the Upper Paleolithic artifacts at the site bears on a hot topic in paleoanthropology: the origins of modern behavior and cognition. Once upon a time, archaeologists thought only H. sapiens made symbolic items such as jewelry and advanced technology such as standardized bone tools. Then discoveries in the 1970s ignited debate over whether Neandertals also might have invented such items. In recent years evidence has mounted in support of a more sophisticated Neandertal. For instance, last year researchers reported cave paintings in Spain pre-date the arrival of H. sapiens to the region by thousands of years and must therefore be Neandertals’ handiwork. Neandertals, however, are not the only archaic hominin species to show signs of advanced cognition: In 2015 archaeologists unveiled their discovery of a shell that was engraved with a geometric design some 500,000 years ago—long before the origin of modern humans or Neandertals—the implication being that an earlier human ancestor known from this time period, Homo erectus, must have been the designer.

Could Denisovans have independently developed modern cognitive capabilities, too? Archaeologist Francesco d’Errico of the University of Bordeaux in France, who was not involved in the new studies, contends the paucity of relevant archaeological material from the site and insufficient description of these remains “make it difficult to reach a firm conclusion.” But “I’m not against the idea,” he says. “I do not see why archaic hominins could have not invented personal ornamentation independently and repeatedly, and a lot of evidence from Europe is now supporting this view.”

Pendants made from animal teeth and tools fashioned from bone may have been manufactured by Denisovans. Credit: Katerina Douka

When a Neandertal Met a Denisovan, What Happened Was Only Human

Scientists describe the hybrid child of two starkly different human groups

By Richard Conniff on August 22, 2018

In a remarkable twist in the story line of early human evolution, scientists have announced the discovery of “Denisova 11”—a female who was at least 13 years old, lived more than 50,000 years ago and was a child of mixed parentage. Her parents were not just of different races, but two different and now-extinct early human types. Their exact taxonomic designations—whether they were separate species or subspecies—is still a matter of scientific debate. But the bottom line for Denisova 11 is that mom was a Neandertal and dad a Denisovan.

The research, published Wednesday in Nature, is the work of a team led by pioneering paleogeneticist Svante Pääbo at Max Planck Institute for Evolutionary Anthropology in Germany. He and his co-authors published the first description of the Denisovans in 2010, based on genetic evidence from one of the 2,000 or so bone fragments found in Denisova Cave in the Altai Mountains, where Siberia borders Mongolia and China. The new discovery is based on another bone fragment from that lot, a 2.5-centimeter-long fragment of what was a femur or humerus, from which the researchers extracted six DNA samples and then cloned them for detailed analysis.

Molecular dating indicates that Denisovans, who are so far known only from Denisova Cave, and Neandertals, known mainly from sites in Europe, diverged from each other almost 400,000 years ago. They coexisted, probably in relatively small populations scattered across the vast Eurasian landmass, until both became extinct some 30,000 to 40,000 years ago.

But the genetic evidence from Denisova 11 and other recent studies suggests that, on the occasions when they met, Denisovans and Neandertals commonly mated with each other—and with modern humans. Denisova 11’s father carried a small amount of Neandertal ancestry, the study notes, from “possibly as far back as 300 to 600 generations before his lifetime.”

Sharon Browning, a statistical geneticist at the University of Washington who was not involved in the research, praises the new study. “I’m really kind of blown away by it,” she says. “Just to catch the offspring of these two different groups is really remarkable.”

“It looks absolutely solid,” adds University of Utah population geneticist Alan Rogers, who also was not part of the work. “I think these guys, as usual, have done a great job.” Asked if Denisova 11 might have simply been the offspring of a mixed Neandertal–Denisovan population—rather than of a mother and father of two such starkly separate backgrounds—Rogers says, “I felt that their analysis made sense. I was convinced by that. It’s not surprising that the two species would mate, if they were together at the same place and time,” he adds. “But I don’t think we knew before now that they were together at the same place and time—and if they were, it raises the question of why they were so different.” That is, why didn’t they evolve into a single species?

“It’s a really interesting question,” says Harvard University geneticist David Reich, who did not take part in Pääbo’s study. “At Denisova Cave we are clearly looking at an area where these two groups washed across one another, within walking distance of the cave. But there must have been a lot of isolation, as well as mixture.” The hybrid offspring from such divergent populations, Reich says, may have experienced biological problems. Or they may have faced cultural bias, Pääbo notes, if people of mixed backgrounds were “not very well accepted in the cultures of that time.”

Even so, both Neandertals and Denisovans have persisted in the modern human genome. A small percentage of Neandertal ancestry is common in all modern human populations outside Africa; some Denisovan lineage is also common among people from east Asia and Oceania. Earlier this year a study led by Browning indicated the modern Denisovan inheritance derives from at least two separate populations, suggesting they were once dispersed far beyond the Denisova Cave. Pääbo says the next step for his laboratory will be extracting DNA from sediment in the Denisova Cave floors to determine “just when Neandertals were there, when Denisovans were there and when both were there together.”

The dream that scientists could document such interactions in the prehistory of humankind “used to seem impossible,” Reich says. “But now we are getting to witness the dream.”

Tomado de: https://www.scientificamerican.com/article/when-a-neandertal-fell-for-a-denisovan-what-happened-was-only-human/?utm_source=newsletter&utm_medium=email&utm_campaign=evolution&utm_content=link&utm_term=2018-08-27_featured-this-week&spMailingID=57255681&spUserID=MjUyMzM5OTAwODkS1&spJobID=1463668589&spReportId=MTQ2MzY2ODU4OQS2

¿Cómo cazaban los neandertales?

Unos huesos de hace 120.000 años revelan cómo se hacían los neandertales con sus presas: a dos

gamos los mataron clavándoles lanzas enérgicamente.

Nature Ecology & Evolution

Gracias a los yacimientos se sabe que los neandertales y sus predecesores preparaban lanzas de madera, pero no está claro cómo usaban esas armas: ¿las arrojaban a larga distancia, las clavaban a muy corta distancia o simplemente apartaban con ellas a otros animales de sus botines? Un equipo de investigadores, dirigido por Sabine Gaudzinski-Windheuser, ha encontrado ahora una respuesta. Según las lesiones que han encontrado en unos huesos de gamo de hace 120.000 años, un neandertal arrimado al animal le clavó la lanza y le perforó un agujero en la pelvis. En los de otro gamo han observado lesiones vertebrales que también se causaron con ese mismo tipo de ataque.

La investigadora (del Museo y Centro de Investigaciones Arqueológicas MONREPOS para la Evolución del Comportamiento Humano, en Neuwied, Renania-Palatinado, Alemania) y sus colaboradores lo cuentan en Nature Ecology and Evolution. Los huesos que han investigado se extrajeron en los años ochenta y noventa del siglo pasado junto a un pequeño lago cercano a Halle, en Sajonia-Anhalt, Alemania. Debió de haber allí un espeso bosque en el que presumiblemente los neandertales cazaban al acecho. Las presas estudiadas eran ejemplares de la subespecie hoy extinguida de gamo Dama dama geiselana.

Realizaron pruebas balísticas con los huesos, y de ellas dedujeron que las lesiones se produjeron muy probablemente con un impacto muy potente pero relativamente lento. Si hubiese sido causado por una lanza arrojada cabe suponer que se habrían visto unas señales diferentes.

Hasta ahora se han encontrado muy pocos yacimientos en los que se haya dado con indicios de cómo cazaban los seres humanos de tiempos remotos. La anatomía de los neandertales da a entender que no eran unos lanzadores especialmente hábiles, pero lo observado en los huesos del yacimiento sajón no quiere decir que no usaran nunca sus lanzas como proyectiles; es muy posible que en otras oportunidades sí lo hiciesen.

Jan Dönges / spektrum.de

Artículo traducido y adaptado por Investigación y Ciencia con permiso de Spektrum der Wissenschaft.

Referencia: «Evidence for close-range hunting by last interglacial Neanderthals», de Sabine Gaudzinski-Windheuser et al. en Nature Ecology and Evolution, publicado el 25 de junio de 2018.

Tomado de: 

Descubiertos en Marruecos los fósiles más antiguos de la especie humana

Hallazgos recientes hacen retroceder en 100.000 años el origen de Homo sapiens y apuntan a la compleja historia evolutiva de la humanidad, que habría tenido lugar en toda África.

Nature

Reconstrucción del cráneo del Homo sapiens más antiguo conocido hasta ahora, cuyos fósiles se han hallado en Jebel Irhoud (Marruecos). La reconstrucción se ha basado en la microtomografía computarizada de múltiples fósiles originales. Datados de hace 300.000 años, estos humanos ya presentaban un rostro similar al actual. Sin embargo, la morfología de su cavidad craneal (azul) indica que la forma del cerebro, y posiblemente también su función, evolucionaron dentro del propio linaje de Homo sapiens. [© Philipp Gunz, Instituto Max Planck de Antropología Evolutiva / CC-BY-SA 2.0]

Nuevos fósiles y herramientas de piedra descubiertos en el yacimiento arqueológico de Jebel Irhoud, en Marruecos, hacen retroceder los orígenes de nuestra especie unos 100.000 años y demuestran que hace unos 300.000 años tuvieron lugar en una gran parte de África cambios importantes en nuestra biología y comportamiento.

Un equipo internacional de investigadores dirigido por Jean-Jacques Hublin, del Instituto Max Planck de Antropología Evolutiva, en Leipzig, y Abdelouahed Ben-Ncer, del Instituto Nacional de Arqueología y Patrimonio, en Rabat, han descubierto huesos fósiles de Homo sapiens junto con herramientas de piedra y huesos de animales en Jebel Irhoud. Los hallazgos datan de hace unos 300.000 años y constituyen la prueba fósil más antigua de nuestra especie. Son 100.000 años más antiguos que los fósiles considerados hasta ahora los más antiguos de nuestra especie. Los descubrimientos, que se describen en dos artículos recién publicados en Nature, revelan la compleja historia evolutiva de la humanidad, que probablemente sucedió en todo el continente africano.

Los datos genéticos de los humanos actuales y de los restos fósiles apuntan al origen africano de nuestra especie, Homo sapiens. Con anterioridad, los fósiles más antiguos de Homo sapiens, datados de hace 195.000 años, se habían hallado en el yacimiento de Omo Kibish, en Etiopía. En Herto, también en Etiopía, se había descubierto otro fósil de nuestra especie de 160.000 años. Hasta ahora, la mayoría de los investigadores creían, pues, que todos los humanos actuales descendíamos de una población que vivió en el este de África hace unos 200.000 años, pero los nuevos datos revelan que Homo sapiens ya se había extendido antes por todo el continente africano, hace unos 300.000 años. «Mucho antes de su dispersión fuera de África, se produjo una dispersión dentro del continente», comenta Hublin.

El yacimiento de Jebel Irhoud era conocido desde la década de 1960 por sus fósiles humanos y sus artefactos de la Edad de Piedra Media. Sin embargo, la interpretación de los restos de los homininos había resultado complicada desde hacía tiempo por las persistentes incertidumbres que rodeaban su antigüedad. La nueva excavación, que comenzó en 2004, reveló nuevos fósiles de Homo sapiens, que aumentaron de seis a 22. Los restos corresponden a cráneos, dientes y huesos largos de al menos cinco individuos. Para establecer su cronología, los investigadores utilizaron el método de datación por termoluminiscencia de piedras talladas calentadas con fuego halladas en los mismos depósitos, lo que arrojó una antigüedadad de unos 300.000 años. También emplearon métodos mejorados de resonancia de espín electrónico para la datación de los fósiles y obtuvieron datos concordantes con esa edad.

Los cráneos de los humanos actuales se caracterizan por una combinación de rasgos que nos diferencian de otras epecies emperentadas con la nuestra: un rostro pequeño y grácil y una cavidad craneal globular. Los fósiles de Jebel Irhoud exhiben un rostro y dientes similares a los actuales, y también presentan una gran cavidad craneal, aunque de aspecto más arcaico. Hublin y su equipo utilizaron la novedosa técnica de microtomografía computarizada y análisis estadísticos para demostrar que la forma de la cara de los ejemplares de Jebel Irhoud resultaba casi indistinguible de la de los humanos actuales. «La forma interior de la cavidad craneal refleja la forma del cerebro», explica Philipp Gunz, del Instituto Max Planck de Antropología Evolutiva. «Nuestros hallazgos sugieren que la actual morfología facial de los humanos surgió al inicio de la historia evolutiva de nuestra especie, y que la forma del cerebro, y posiblemente también las funciones cerebrales, evolucionaron dentro del linaje de Homo sapiens», dice Gunz.

La morfología y la edad de los fósiles de Jebel Irhoud también corroboran la interpretación de un enigmático cráneo parcial hallado en Florisbad, en Sudáfrica, que se había atribuido a un representante primitivo de nuestra especie. Los fósiles más antiguos de Homo sapiens se han encontrado, pues, en todo el continente africano: Jebel Irhoud, Marruecos (300.000 años), Florisbad, Sudáfrica (260.000 años) y Omo Kibish, Etiopía (195.000 años). Ello indica la compleja historia evolutiva de nuestra especie, que tuvo lugar en todo el continente africano.

«El norte de África no se había tenido en cuenta desde hace mucho tiempo en los debates acerca del origen de nuestra especie. Ahora, los descubrimientos espectaculares de Jebel Irhoud demuestran las estrechas conexiones del Magreb con el resto del continente africano en el momento de la aparición de Homo sapiens», comenta Ben-Ncer.

Más información en Nature (1) y (2)

Fuente: Instituto Max Planck de Antropología Evolutiva

Tomado de: http://www.investigacionyciencia.es/noticias/descubiertos-en-marruecos-los-fsiles-ms-antiguos-de-la-especie-humana-15352?utm_source=boletin&utm_medium=email&utm_campaign=Del+3+al+9+de+junio