lunes, 21 de diciembre de 2015

El genoma más antiguo de África reescribe la historia de la evolución humana


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  • Publican en Science la secuenciación del genoma más antiguo del continente africano.
  • Los flujos migratorios desde Oriente Medio al cuerno de África influyeron de manera decisiva en la diversidad genética del continente.
evolución
Julius Kielaitis | Shutterstock
África es la cuna de la humanidad. El lugar que nos permite entender las raíces de la especie humana. Hasta el momento, sin embargo, ningún estudio había logrado secuenciar el genoma ancestral obtenido a partir de fósiles del continente. La razón era la inestabilidad de la propia molécula de ADN, que se veía afectada por las condiciones de temperatura y humedad. Una nueva investigación, publicada en Science, ha conseguido analizar por primera vez el genoma más antiguo encontrado en el continente, reescribiendo la historia de la evolución humana."Las cuevas de África pueden albergar ejemplares muy bien conservados, por lo que en el futuro se secuenciarán más muestras de ADN"
El esqueleto hallado en 2012 por John y Kathryn Arthur en la Cueva Mota de Etiopía puso sobre la pista a los investigadores. La excavación, situada a una altitud de 1.963 metros en el sudoeste del país, contaba con unas buenas condiciones de temperatura y humedad. Como explica Marcos Gallego a Hipertextual, "solo se ha secuenciado ADN antiguo durante los últimos 4-5 años, lo que significa que mientras mejoraba la técnica, se ha tendido a analizar muestras mejor conservadas".
El investigador, primer autor del artículo en Science, también apunta que "las cuevas de África pueden albergar ejemplares muy bien conservados, por lo que están seguros de que en el futuro se secuenciarán más muestras de ADN antiguo en este continente". En particular, el microclima de la excavación de Etiopía permitió preservar el ADN durante 4.500 años, la edad estimada de los restos de este varón adulto que, según los análisis genómicos, pudo tener ojos marrones y piel oscura.

Cómo las migraciones afectaron a la diversidad genética

Los rasgos físicos del individuo no son la característica más llamativa de los resultados de la secuenciación genómica. Según publican en la revista Science, el análisis del ADN ancestral ha permitido trazar con más precisión la historia de la evolución humana. Las migraciones desde Oriente Medio, en particular desde las regiones de Anatolia y Mesopotamia, podrían haber tenido un mayor impacto de lo que se pensaba anteriormente.El genoma de la Cueva Mota de Etiopía es el más antiguo hallado en el continente africano
La carencia de genomas tan antiguos como el de la Cueva Mota hacía que los científicos tuvieran que conformarse con el estudio de las poblaciones contemporáneas para comprender el "flujo genético" que había ocurrido en el continente africano. Por fortuna, la investigación hoy publicada nos ayuda a reconstruir con mayor detalle la evolución de nuestra especie. El hallazgo de estos fósiles permitió la extracción y secuenciación del ADN de la porción petrosa del hueso temporal del cráneo. Al comparar las 250.000 pares de bases analizadas con 40 poblaciones africanas y 81 europeas, los investigadores vieron que el ancestro de Mota estaba más relacionado con el grupo étnico de los Ari.
El estudio comparado demostró que el genoma de Mota carecía de entre el 4 y el 7% de regiones que se encontraban tanto en el grupo de los Ari como en el resto de poblaciones africanas evaluadas. ¿Qué ocurría con esas porciones de ADN? Según los resultados presentados, las secuencias genéticas eran más similares a las que presentaban agricultores del Neolítico que habían colonizado el continente europeo 4.000 años antes.
evolución
Cueva Mota de Etiopía, excavada por primera vez por Kathryn y John Arthur.
El descubrimiento del genoma más antiguo de África ha permitido, por tanto, trazar la importante influencia de los flujos migratorios sobre la diversidad genética del continente, y por ende, la propia historia de la evolución humana. Los datos también sugieren que aquellos primeros agricultores que volvieron a estas zonas etíopes pudieron contribuir de manera significativa en los cambios relacionados con la producción alimentaria en el cuerno de África.Los nuevos pobladores de Oriente Medio contribuyeron al éxito de la agricultura y la ganadería en África
Gallego comenta a Hipertextual que "se sabe que hubo pobladores de Oriente Medio que llegaron a Europa hace 8.000 años trayendo la agricultura y la ganadería". El estudio publicado ahora muestra que, entre 3.500-4.000 años después, hubo un episodio parecido, con el mismo origen, pero esta vez hacia África. En el continente ya existían granos y cereales antes de la migración, pero según explica Gallego, "la introducción de nuevos granos, cereales y animales por los nuevos pobladores procedentes de Oriente Medio contribuyó al éxito de la agricultura en África posteriormente".
Andrea Manica, del Departamento de Zoología de la Universidad de Cambridge, también apunta que "las olas migratorias hacia esta región del continente africano podrían haber supuesto hasta un 30% de la población que allí vivía". La investigadora se pregunta qué llevaría a aquellas poblaciones a volver de vuelta al cuerno de África. Aunque esta cuestión no ha podido ser resuelta, lo cierto es que el análisis de un único genoma ancestral ha permitido abrir una nueva ventana al pasado, profundizando en la historia de la evolución humana.
Por el momento, los científicos de la Universidad de Cambridge han descartado que los flujos migratorios se debieran a algún tipo de cambio climático. Las hipótesis se centran en las transfomaciones ocurridas en la producción agrícola, ya que las migraciones coincidieron en el tiempo con la llegada de cultivos como la cebada y el trigo a la región.La secuenciación del ADN muestra la importancia de los flujos migratorios sobre la diversidad genética
La secuenciación de este genoma ancestral es un hito importante en la investigación en biología. Marcos Gallego apunta que los análisis de ADN "no solo nos ayudarán a desenmarañar las complejas migraciones de la historia humana, sino también a estudiar cómo diferentes poblaciones se han adaptado de manera diferente a climas cambiantes". Así podremos entender, por ejemplo, la adaptación de los esquimales al frío, de los etíopes o pobladores del Himalaya a las alturas o incluso a determinadas enfermedades.
Pero el trabajo presentado en Science no es importante únicamente por sus aplicaciones para comprender la evolución humana, sino que también es un gran avance técnico. Como señala Sara Monzón, de la Unidad de Bioinformática del Instituto de Salud Carlos III, "la cobertura lograda en el estudio [de 12,5x] de las muestras es elevada teniendo en cuenta el origen de las mismas".
En el análisis común de un exoma (la región codificante del genoma), se suelen secuenciar con coberturas de 100x y de 20x en los genomas contemporáneos. "La fiabilidad técnica del trabajo, considerando la antigüedad del ADN, es todo un logro", apunta la científica. Un éxito que además nos permite conocer con más detalle nuestro propio origen, y volver la vista atrás hacia el pasado de la especie humana.

New species of human may have shared our caves – and beds



 New species of human may have shared our caves – and beds
As fire light flickered on the back of the cave, a group of people ate deer, porcupine and otter. Then a man solemnly took a large bone off the fire, broke it in half and sucked the bone marrow out. He then carefully painted the broken bone with red clay and buried it in the cave.
He observed this ritual because this bone belonged to another human species. One they shared not only the forest with, but also their beds.
This is the remarkable – though so far tentative – picture emerging from controversial discoveries from two caves in south-west China. If true, some think it could overturn our understanding of what it means to be human.
Among the discoveries appears to be a primitive human species, which most closely resembles the earliest human species, Homo habilis and Homo erectus.
But while these lived about 2 million years ago, this new species lived just 14,000 years ago, says Darren Curnoe of the University of New South Wales in Sydney, Australia, who lead the team behind the discoveries. This would make it the most recent human species to have gone extinct.
“If true, this would be rather spectacular and it would make the finds of truly global importance,” says Michael Petraglia at the University of Oxford, who wasn’t involved in the discoveries.
The work is excellent, he says, but is likely to leave many in the field unconvinced.

One of the most exciting pieces of evidence in the story is a hominin femur found in Muladong cave in south-west China, alongside other human and animal bones. It shows evidence of having been burned in a fire that was used for cooking other meat, and has marks consistent with it being butchered for consumption.
It has also been broken in a way that is often used to access the bone marrow.
Unusually, it had been painted with a red clay called ochre, something often associated with burial rituals. While many other bones were eaten in the cave, only the ones from human species were painted.
It’s hard to know if the bone was actually cannibalised by the H. sapiens whose remains have also been found in the area, Curnoe says, but all the evidence points towards that conclusion.
“We don’t know it was cannibalism,” he says. “We’ve got cut marks that would be consistent with butchering.”
 New species of human may have shared our caves – and beds
But things got interesting when the team tried to identify the bone. “Our work shows clearly that the femur resembles archaic humans,” Curnoe says. Yet the sediment the bone was found in dated to just 14,000 years ago.
The shaft of the bone is very narrow and it has a thin outer layer, yet the walls are reinforced in areas of high strain. There is also a notch where muscle would have joined the bone, which is much larger than in anatomically modern humans, and it faces more towards the back of the bone (see photo, above).
“These features suggest it walked differently,” says Curnoe. And judging by the size of the bone, Curnoe estimates the adult human would have weighed about 50 kilograms – much smaller than other known Ice Age humans.
“When you put all the evidence together the femur comes out quite clearly resembling the early members of Homo,” says Curnoe.
If confirmed, says Petraglia, this would change our understanding of human evolution.
 New species of human may have shared our caves – and beds
Besides Homo floresiensis, also known as “the Hobbit”, which was confined to an Indonesian island up to around 18,000 years ago, the most recent archaic humans were thought to be the Denisovans and Neanderthals, which became extinct quickly after H. sapiens came through their lands some 40,000 years ago.
“This turns that on its head,” says Curnoe. “Its young age shows that remarkably primitive-looking humans must have shared the landscape with very modern-looking people at a time when China’s earliest farming cultures were beginning to flourish.”
But some in the field have doubts that such a young bone can be from something so archaic.
“It is not an archaic human,” says Erik Trinkaus at Washington University in St Louis. Trinkaus thinks the differences in the bone are a result of natural variation within a population, not a new species.
Henry McHenry at the University of California, Davis, is more ambivalent. He says the femur looks very odd, but that it does seem to have similarities to very archaic humans.

The second cave

Further supporting evidence might come from Longlin cave, a few hundred kilometres north, where another stash of human bones, including an almost complete skull, were found – some as early as 1979. Curnoe and Ji Xueping at the Yunnan Institute of Cultural Relics and Archaeology in China re-analysed these bones and dug up more, describing them in 2012.
Curnoe and his colleagues analysed skull and facial bones and argue they belong to a hybrid of our own species and something more archaic – quite likely the creature that once walked on the now-painted femur. They have preliminarily dated that hybrid to just 10,500 years ago.
One of the less complete bones found at Maludong cave had been cut and had holes dug near the top of it, suggesting it was used as a vessel for carrying and drinking liquid.
What all this hints at, Curnoe and colleagues say, is that H. sapiens was mating with an archaic human species, possibly eating them, and using the hybrid offspring bones as tools.
But to back up these controversial claims, we will need DNA from these bones, says Petraglia.

DNA needed

“Ultimately, what we’d like is DNA evidence,” agrees Curnoe, “But so far we’ve had no luck.”
The burning of many of the bones and the tropical climate have degraded the DNA. He says technology has improved, though, and they will continue trying.
DNA could answer some of the thorniest questions raised by these findings. Is the archaic human they found the mysterious Denisovan, so far only known from a finger and a tooth found in a Siberian cave? Or is it a new species, suggesting a rich array of human species existed in Asia at this time? And do we carry any of their genes?
Curnoe says the discoveries point to a profound shift in our understanding of what it means to be human.
Adding to the now well-established interbreeding that occurred with our cousins the Neanderthals and Denisovans, we can no longer consider ourselves a single lineage that emerged from Africa.
“We had particular notions of our evolution: That we found ourselves evolving in isolation in Africa and quickly replaced all the other species that were around because we thought we were superior to them. And it happened very quickly, without question, and without biological interaction,” Curnoe says. “But the hybridisation story has turned that on its head.”
Journal reference: PLoS One, DOI: 10.1371/journal.pone.0143332
Read more:Denisovans: The lost humans who shared our world
Image information, from top: Reproduction of Homo sapiens hunting (Enigma Man A Stone Age Mystery © Vince Valitutti/Electric Pictures); Discovered femur compared with modern human femur (Darren Curnoe, Ji Xueping & Getty Images); The cave at Maludong (Ji Xueping & Darren Curnoe

lunes, 30 de noviembre de 2015

Evolución humana

video

lunes, 19 de octubre de 2015

The gaze that hinders expression

Autism: Altered connections between eye contact and facial mimicry -
It is not enough to observe what abilities are altered in those with autism, we also need to understand how each function interacts with the others. In fact, whereas in typical subjects, joint attention appears to facilitate facial mimicry (both are skills relevant for human social interaction), the opposite holds true for those with autism. That is what a new study, just published in Autism Research, suggests.
Empathy -- the ability to identify and understand other people's emotions -- has many components, some sophisticated and involving complex thought processes, others basic but essential nonetheless. The latter include joint attention -- which is activated by direct eye contact between two or more individuals, and allows them to focus their attention on the same object; and facial mimicry -- the tendency to reproduce on one's own face the expressions of emotion seen in others. Subjects suffering from autism have difficulty with both these abilities, but according to the new research, it is also important to study how these two functions interact.
"Empathy is an essential human trait in social relations," explains Sebastian Korb, a researcher at the International School for Advanced Studies (SISSA) in Trieste, Italy and one of the study authors. "According to embodied cognition theories, to better understand the facial expression of the person in front of us we reproduce the same expression on our face." This does not necessarily mean that if we see someone smiling we smile as well, even though this does happen sometimes. More often, however, the facial muscles involved in smiling are indeed activated, but so subtly that the movement is invisible to the naked eye.
The known difficulty autistic people have in interpreting other people's emotions could stem from reduced facial mimicry, since many studies have demonstrated that this function is defective in these subjects. Other studies have shown that joint attention is also impaired in autism, and this is another function that has huge relevance for social interaction. Nevertheless, the impairments in facial mimicry and joint attention in autism remain controversial and poorly understood. For this reason, "we believe the interaction between these two abilities deserves plenty of attention," explains Korb. "In our experiments, we saw that in persons with more pronounced autistic traits, joint attention tended to 'disturb' facial mimicry, whereas in normal subjects it facilitated it."

A question of interaction

It should be noted that the 62 subjects who took part in the experiment were not individuals with a clinical diagnosis of autism. Instead, researchers used a questionnaire measuring the autistic tendencies of normal persons. In fact, it has been demonstrated that everyone has more or less autistic traits, although in most cases these tend to be mild and therefore do not lead to a diagnosis.
During the experiment, the subjects interacted with an "avatar," a three-dimensional interactive face (in the sense that it responded to the subject's gazing behavior). At the beginning of each trial, the avatar looked down, but as soon as the subject's gaze (monitored by means of an eye-tracking system) moved towards the avatar's eye region, the avatar looked up and he could either make eye contact with the subject (condition of joint attention) or avert his gaze and look up (condition of no joint attention). Subsequently, the avatar shifted his gaze to focus on one of two objects to the side, while the eye-tracker recorded whether or not the subject's gaze followed that of the avatar. At that point, the avatar could either smile or make an expression of disgust. During the trial, the subject's facial mimicry was measured by facial electromyography (a method used for recording muscle activation).
"What we observed is that in conditions of joint attention and where the avatar smiled, the subjects with more pronounced autistic traits tended to show less activation of the major smile muscle, whereas those with milder or no autistic traits showed a much more amplified expressive response," explains Korb. "Individuals without autism tend to display a stronger empathic response (and facial mimicry) to persons with whom they have established eye contact and joint attention. However, if the subject has autistic tendencies then the eye contact can disturb and diminish facial mimicry."
"In order to understand both the mechanisms underlying normal social interaction and the altered processes involved in autism, it is therefore important to observe not only which functions are impaired but also how these functions work together," concludes Korb.

 face avatars used in autism research

Note: Material may have been edited for length and content. For further information, please contact the cited source.

SISSA medialab

Publication

Chakrabarti B et al. Spontaneous Facial Mimicry is Modulated by Joint Attention and Autistic Traits.   Autism Research, Published Online October 7 2015. doi: 10.1002/aur.1573

sábado, 17 de octubre de 2015

Así evolucionó el cuerpo humano


Los fósiles de Atapuerca revelan un nuevo modelo en la evolución del cuerpo humano: más corpulentos pero con menos cerebro.
 
evolucion-cuerpo VER GALERÍAPortadas históricas de la revista Nature

Un equipo de investigadores de diversos centros españoles, liderados por el Centro Mixto Universidad Complutense de Madrid y el Instituto de Salud Carlos III de Evolución y Comportamiento Humanos (España) ha examinado los fósiles de la Sima de los Huesos en el yacimiento de la Sierra de Atapuerca,añadiendo un nuevo modelo en la evolución del cuerpo humano, estableciéndose por tanto cuatro fases o etapas evolutivas.

Los científicos han analizado al detalle los fósiles -que son muchos- del esqueleto postcraneal (del cuello para abajo), datados en unos 430.000 añosy recuperados durante los últimos 20 años en este conocido yacimiento. Los resultados han posibilitado el establecimiento de cuatro grandes patrones sucesivos en nuestra evolución.

Las cuatro etapas en la evolución del cuerpo humano quedarían de la siguiente forma: primero, los ardipitecos (arborícola y ocasionalmente bípedo); luego, los australopitecos (bípedo pero con innegables capacidades arbóreas); posteriormente, la del humano “arcaico”(como el Homo erectus, ancho, robusto y con locomoción exclusivamente terrestre); y, por último, elhumano moderno (alto, estrecho y con esqueleto grácil).

Se ha realizado una investigación global del esqueleto (forma del cuerpo, peso, altura, dimorfismo del tamaño corporal) y un análisis detallado de cada parte anatómica para poder establecer la evolución de la forma del cuerpo en el género Homo que ahora se propone”, explica Carlos Lorenzo, coautor del estudio.

Según el estudio, que ha sido publicado en la revista Proceedings of the National Academy of Sciences (PNAS)los humanos de la Sima de los Huesos eran relativamente altos (1,63 metros) y con cuerpo musculoso y ancho (con un peso medio de 69-70 kgs) pero con menos masa cerebral que losneandertales.

viernes, 11 de septiembre de 2015

Homo naledi: New species of human ancestor discovered in South Africa

When an amateur caver and university geologist arrived at Lee Berger's house one night in late 2013 with a fragment of a fossil jawbone in hand, they broke out the beers and called National Geographic.
Berger, a professor at the University of the Witwatersrand in Johannesburg, South Africa, had unearthed some major finds before. But he knew he had something big on his hands.
What he didn't know at the time is that it would shake up our understanding of the progress of human evolution and even pose new questions about our identity.
Two years after they were tipped off by cavers plumbing the depths of the limestone tunnels in the Rising Star Cave outside Johannesburg, Berger and his team have discovered what they say is a new addition to our family tree.
The team is calling this new species of human relative "Homo naledi," and they say it appears to have buried its dead -- a behavior scientists previously thought was limited to humans.
Berger's team came up with the startling theory just days after reaching the place where the fossils -- consisting of infants, children, adults and elderly individuals -- were found, in a previously isolated chamber within the cave.
The team believes that the chamber, located 30 meters underground in the Cradle of Humanity world heritage site, was a burial ground -- and that Homo naledi could have used fire to light the way.
"There is no damage from predators, there is no sign of a catastrophe. We had to come to the inevitable conclusion that Homo naledi, a non-human species of hominid, was deliberately disposing of its dead in that dark chamber. Why, we don't know," Berger told CNN.
"Until the moment of discovery of 'naledi,' I would have probably said to you that it was our defining character. The idea of burial of the dead or ritualized body disposal is something utterly uniquely human."
Standing at the entrance to the cave this week, Berger said: "We have just encountered another species that perhaps thought about its own mortality, and went to great risk and effort to dispose of its dead in a deep, remote, chamber right behind us."
"It absolutely questions what makes us human. And I don't think we know anymore what does."
The first undisputed human burial dates to some 100,000 years ago, but because Berger's team hasn't yet been able to date naledi's fossils, they aren't clear how significant their theory is.
Berger tried to put the new find into perspective.
"This is like opening up Tutankhamen's tomb," he said. "It is that extreme and perhaps that influential in this stage of our history."

Almost human but not quite

Homo naledi is a strange mosaic of the ancient and the thoroughly modern.
Naledi's brain was no bigger than an orange, scientists say. Its hands are superficially human-like, but the finger bones are locked into a curve -- a trait that suggests climbing and tool-using capabilities.
Homo naledi was relatively big: it stood about 5 feet tall, had long legs, and its feet are almost identical to ours, suggesting it had the ability to walk long distances.
The braincase of a male Homo naledi is less than half the size of the modern human skull.
"Overall, Homo naledi looks like one of the most primitive members of our genus, but it also has some surprisingly human-like features, enough to warrant placing it in the genus Homo," says John Hawks of the University of Wisconsin-Madison, a senior author on the papers describing the new species that were published Thursday.
The scientists can make these claims, in part, because of the sheer scale of the find.
In the vault at the University of Witwatersrand, hundreds of priceless specimens lie in padded cases across the room.
So far they've unearthed more than 1,500 fossil remains in total -- the largest single hominin find yet revealed on the continent of Africa, the cradle of human evolution.

Underground astronauts

Gathering the fossils was dangerous work.
Berger, a National Geographic Explorer-in-Residence, was already well-known for his discovery of "Australopithecus sediba," another species of human ancestor, in 2008. But this expedition would face unique challenges.
The fossils were found at the end of a series of chambers and tight squeezes deep underground, some 90 meters (100 yards) from the cave entrance. To get there, scientists would have to squeeze through a 7-inch wide cave opening.
S
o Berger put out a call on social media for skinny scientists and cavers who could fit through the tiny chute and bring up the bones.
Within days Berger had dozens of responses, and he eventually selected a team of six "underground astronauts" -- all women -- to do the job.
Berger himself could not reach the chamber where the remains lay, but he followed all of the exploration on real-time monitors above ground and communicated with his team.
"It is the heart of exploration. What we are privileged enough to do is going into the next new unexplored spaces," says Berger.

A field of bones

In the first few days of the expedition, the biggest problem was knowing where to step.
"The first thing that you would see, especially in the early stages of the investigation, was just bones. Bone debris everywhere," says K. Lindsay Hunter, an American scientist and one of the "astronauts" on the Rising Star expeditions, which were conducted in November 2013 and March 2014.
Marina Elliott, another of Berger's astronauts, described the scene underground as "some of the most difficult and dangerous conditions ever encountered in the search for human origins."
Some scientists in this field spend an entire career finding one fragment to identify a possible new species. But early on, the team knew they had stumbled onto something extraordinary.
Initially, Berger thought that they might find no more than a single skeleton. But he says that almost all the bones they found -- besides a few rodent and bird remains that came into the cave much later -- were from Homo naledi.
"We found everything from infants to babies to toddlers to teens, young adults, old individuals. It is like nothing that we could have ever imagined," says Berger. "Homo naledi is already practically the best-known fossil member of our lineage."
The team claims to have uncovered remains of at some 15 distinct individuals, but say this is only the beginning.
"The chamber has not given up all its secrets," Berger says. "There are potentially hundreds if not thousands of remains of Homo naledi still down there."
Berger says their discovery raises haunting questions about our deep past, and about our very identity. Many mysteries remain, and other scientists may well challenge some of the team's controversial conclusions. But few will dispute that Homo naledi is truly significant.
Years of careful exploration lie ahead. "This was right under our nose," says Berger. "And we didn't see it. What else is out there?"

Descubren en Sudáfrica un nuevo antepasado del hombre: el Homo naledi


Hallazgo científico
Esta nueva especie del género humano tenía un pequeño cerebro y un cuerpo muy esbelto. La altura media era de 1,50 metros y pesaba unos 45 kilos. Sus pies no podrían distinguirse de los pies actuales.
Estoy feliz de presentarles a un nueva especie del género humano". Así abrió la conferencia de prensa Lee Berger, investigador de la universidad de Witwatersrand de Johannesburgo, para dar a conocer a una antigua especie humana que salió a la luz en una gruta de Sudáfrica donde fueron exhumadas las osamentas de 15 homínidos.
Mirá la FOTOGALERÍA en HD
Los fósiles fueron hallados en una cueva de difícil acceso en Maropeng, próximo a Johannesburgo, donde se encuentra el rico yacimiento arqueológico de la "Cuna de la humanidad", que forma parte del patrimonio mundial de la UNESCO.
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El hallazgo tiene dos años. Y entre 2013 y 2014 científicos exhumaron más de 1.550 huesos pertenecientes a al menos 15 individuos, incluidos bebés, adultos jóvenes y personas más mayores. Todos presentaban una morfología homogénea pero todavía no se pudo determinar la data.

Este descubrimiento "extraordinario", según el Museo de Historia Natural de Londres, supone la mayor muestra de fósiles de homínidos jamás exhumados en Africa.
La nueva especie fue bautizada Homo nadeli y clasificada dentro del género Homo al que pertenece el hombre moderno.
¿Cómo era el Homo naledi? "Tenía un cerebro minúsculo del tamaño de una naranja y un cuerpo muy esbelto", declaró John Hawks, investigador de la universidad de Wisconsin-Madison y autor de un artículo publicado el jueves en la revista científica eLife. Tenía una altura media de 1,5 metros y pesaba 45 kilos.
"Teniendo en cuenta que casi todos los huesos del cuerpo están representados en múltiples ocasiones, el Homo naledi es ya prácticamente el miembro fósil mejor conocido de nuestra estirpe", dijo Lee Berger, director de las dos expediciones que dieron con el descubrimiento.
Sus manos "permiten suponer que tenía la capacidad de manejar útiles", sus dedos estaban muy curvados, mientras que es "prácticamente imposible distinguir sus pies de los de un hombre moderno", precisa un comunicado conjunto de la universidad de Wits, la National Geographic Society y el ministerio sudafricano de Ciencia.
"Sus pies y sus largas piernas indican que estaba hecho para caminar durante mucho tiempo".
Leé también: Las preguntas que dispara el Homo naledi
Las osamentas exhumadas en Sudáfrica suponen un desafío para los investigadores. Complican un poco más el tablero de los homínidos, pues la especie descubierta presenta tanto características propias de los homínidos modernos como de los antiguos.
"Algunos aspectos del Homo naledi, como sus manos, sus muñecas y sus pies, están muy próximos a los del hombre moderno. Al mismo tiempo, su pequeño cerebro y la forma de la parte superior de su cuerpo son más próximos a los de un grupo prehumano llamado australopithecus", explicó el profesor Chris Stringer, del Museo de Historia Natural de Londres.
Este descubrimiento podría permitir conocer más sobre la transición, hace unos 2 millones de años, entre el australopithecus primitivo y el primate del género homo, nuestro antepasado directo.
"La mezcla de características del Homo naledi destaca una vez más la complejidad del árbol genealógico humano y la necesidad de llevar a cabo investigaciones más exhaustivas para comprender la historia y los orígenes últimos de nuestras especies", consideró Chris Stringer.