Evolución humana

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.

 

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

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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

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.

Sarah Romero

 

 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.

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.

Homo Naledi, el nuevo miembro de la familia. (AP)

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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.

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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.

Scientists Discover World's Oldest Stone Tools

Finds Challenge Ideas about Who Were the First Toolmakers

 

Sonia Harmand and Jason Lewis examine stone artifacts at the Lomekwi dig in Kenya. Credit: West Turkana Archaeological Project

Scientists working in the desert badlands of northwestern Kenya have found stone tools dating back 3.3 million years, long before the advent of modern humans, and by far the oldest such artifacts yet discovered. The tools, whose makers may or may not have been some sort of human ancestor, push the known date of such tools back by 700,000 years; they also may challenge the notion that our own most direct ancestors were the first to bang two rocks together to create a new technology.
The discovery is the first evidence that an even earlier group of proto-humans may have had the thinking abilities needed to figure out how to make sharp-edged tools. The stone tools mark “a new beginning to the known archaeological record,” say the authors of a new paper about the discovery, published today in the leading scientific journal Nature.
“The whole site’s surprising, it just rewrites the book on a lot of things that we thought were true,” said geologist Chris Lepre of the Lamont-Doherty Earth Observatory and Rutgers University, a co-author of the paper who precisely dated the artifacts.
The tools ”shed light on an unexpected and previously unknown period of hominin behavior and can tell us a lot about cognitive development in our ancestors that we can't understand from fossils alone,” said lead author Sonia Harmand, of the Turkana Basin Institute at Stony Brook University and the Université Paris Ouest Nanterre.
Hominins are a group of species that includes modern humans, Homo sapiens, and our closest evolutionary ancestors. Anthropologists long thought that our relatives in the genus Homo – the line leading directly to Homo sapiens – were the first to craft such stone tools. But researchers have been uncovering tantalizing clues that some other, earlier species of hominin, distant cousins, if you will, might have figured it out.

Chris Lepre from Lamont-Doherty Earth Observatory takes sediment samples to help date the age of the Lomekwi site. Credit: West Turkana Archaeological Project

The researchers do not know who made these oldest of tools. But earlier finds suggest a possible answer: The skull of a 3.3-million-year-old hominin, Kenyanthropus platytops, was found in 1999 about a kilometer from the tool site. A K. platyops tooth and a bone from a skull were discovered a few hundred meters away, and an as-yet unidentified tooth has been found about 100 meters away.
The precise family tree of modern humans is contentious, and so far, no one knows exactly how K. platyops relates to other hominin species. Kenyanthropus predates the earliest known Homo species by a half a million years. This species could have made the tools; or, the toolmaker could have been some other species from the same era, such as Australopithecus afarensis, or an as-yet undiscovered early type of Homo.
Lepre said a layer of volcanic ash below the tool site set a “floor” on the site’s age: It matched ash elsewhere that had been dated to about 3.3 million years ago, based on the ratio of argon isotopes in the material. To more sharply define the time period of the tools, Lepre and co-author and Lamont-Doherty colleague Dennis Kent examined magnetic minerals beneath, around and above the spots where the tools were found.
The Earth’s magnetic field periodically reverses itself, and the chronology of those changes is well documented going back millions of years. “We essentially have a magnetic tape recorder that records the magnetic field … the music of the outer core,” Kent said. By tracing the variations in the polarity of the samples, they dated the site to 3.33 million to 3.11 million years.
Another co-author, Rhonda Quinn of Seton Hall University, studied carbon isotopes in the soil, which along with animal fossils at the site allowed researchers to reconstruct the area’s vegetation. This led to another surprise: The area was at that time a partially wooded, shrubby environment. Conventional thinking has been that sophisticated tool-making came in response to a change in climate that led to the spread of broad savannah grasslands, and the consequent evolution of large groups of animals that could serve as a source of food for human ancestors.

The Lomekwi 3 dig sits in arid lands west of Lake Turkana in northwest Kenya. Credit: West Turkana Archaeological Project

One line of thinking is that hominins started knapping – banging one rock against another to make sharp-edged stones – so they could cut meat off of animal carcasses, said paper co-author Jason Lewis of the Turkana Basin Institute and Rutgers. But the size and markings of the newly discovered tools “suggest they were doing something different as well, especially if they were in a more wooded environment with access to various plant resources," Lewis said. The researchers think the tools could have been used for breaking open nuts or tubers, bashing open dead logs to get at insects inside, or maybe something not yet thought of.
“The capabilities of our ancestors and the environmental forces leading to early stone technology are a great scientific mystery,” said Richard Potts, director of the Human Origins Program at the Smithsonian’s National Museum of Natural History, who was not involved in the research. The newly dated tools “begin to lift the veil on that mystery, at an earlier time than expected,” he said.
Potts said he had examined the stone tools during a visit to Kenya in February.
“Researchers have thought there must be some way of flaking stone that preceded the simplest tools known until now,” he said. “Harmand’s team shows us just what this even simpler altering of rocks looked like before technology became a fundamental part of early human behavior.”
Ancient stone artifacts from East Africa were first uncovered at Olduvai Gorge in Tanzania in the mid-20th century, and those tools were later associated with fossil discoveries in the 1960s of the early human ancestor Homo habilis. That species has been dated to 2.1 million to 1.5 million years ago.

Photos of selected Lomekwi 3 stones accompanying the paper show both cores and flakes knapped from the cores that the authors say illustrate various techniques.

Subsequent finds have pushed back the dates of humans’ evolutionary ancestors, and of stone tools, raising questions about who first made that cognitive leap. The discovery of a partial lower jaw in the Afar region of Ethiopia, announced on March 4, pushes the fossil record for the genus Homo to 2.8 million years ago. Evidence from recent papers, the authors note, suggests that there is anatomical evidence that Homo had evolved into several distinct lines by 2 million years ago.
There is some evidence of more primitive tool use going back even before the new find. In 2009, researchers at Dikika, Ethiopia, dug up 3.39 million-year-old animal bones marked with slashes and other cut marks, evidence that someone used stones to trim flesh from bone and perhaps crush bones to get at the marrow inside. That is the earliest evidence of meat and marrow consumption by hominins. No tools were found at the site, so it’s unclear whether the marks were made with crafted tools or simply sharp-edged stones. The only hominin fossil remains in the area dating to that time are from Australopithecus afarensis.
The new find came about almost by accident: Harmand and Lewis said that on the morning of July 9, 2011, they had wandered off on the wrong path, and climbed a hill to scout a fresh route back to their intended track. They wrote that they “could feel that something was special about this particular place.” They fanned out and surveyed a nearby patch of craggy outcrops. “By teatime,” they wrote, “local Turkana tribesman Sammy Lokorodi had helped [us] spot what [we] had come searching for.”
By the end of the 2012 field season, excavations at the site, named Lomekwi 3, had uncovered 149 stone artifacts tied to tool-making, from stone cores and flakes to rocks used for hammering and others possibly used as anvils to strike on.
The researchers tried knapping stones themselves to better understand how the tools they found might have been made. They concluded that the techniques used “could represent a technological stage between a hypothetical pounding-oriented stone tool use by an earlier hominin and the flaking-oriented knapping behavior of [later] toolmakers.” Chimpanzees and other primates are known to use a stone to hammer open nuts atop another stone. But using a stone for multiple purposes, and using one to crack apart another into a sharper tool, is more advanced behavior.
The find also has implications for understanding the evolution of the human brain. The toolmaking required a level of hand motor control that suggests that changes in the brain and spinal tract needed for such activity could have occurred before 3.3 million years ago, the authors said.
“This is a momentous and well-researched discovery,” said paleoanthropologist Bernard Wood of George Washington University, who was not involved in the study. “I have seen some of these artifacts in the flesh, and I am convinced they were fashioned deliberately.” Wood said he found it intriguing to see how different the tools are from so-called Oldowan stone tools, which up to now have been considered the oldest and most primitive.
Lepre, who has been conducting fieldwork in eastern Africa for about 15 years, said he arrived at the dig site about a week after the discovery. The site is several hours’ drive on rough roads from the nearest town, located in a hot, dry landscape he said is reminiscent of Arizona and New Mexico. Lepre collected chunks of sediment from a series of depths and brought them back to Lamont-Doherty for analysis. He and Kent used a bandsaw to trim the samples into sugar cube-size blocks and inserted them into a magnetometer, which measured the polarity of tiny grains of the minerals hematite and magnetite contained in the sediment.
“The magnetics pretty much clinches that the age is something like 3.3 million years old,” said Kent, who also is a professor at Rutgers.
Earlier dating work by Lepre and Kent helped lead to another landmark paper in 2011: a study that suggested Homo erectus, another precursor to modern humans, was using more advanced tool-making methods 1.8 million years ago, at least 300,000 years earlier than previously thought.

Brasil establece la danza y el teatro como asignaturas obligatorias

Brasil crece como nación en pro de la danza y el teatro. La Comisión de Constitución y Justicia y Ciudadanía de la Cámara de Diputados, propone establecer como asignaturas obligatorias de educación básica de artes visuales, danza, música y teatro.

El texto propuesto viene a cambiar la Ley de Directrices y Bases de la Educación Nacional ya que en la actualidad, sólo se contempla su carácter de asignatura obligatoria para la educación musical.

La redacción de la norma cambia para tomar en cuenta a las directrices de diseño de la Resolución de la Junta de Educación Básica (CEB) del Consejo Nacional de Educación (CNE), que especifica los componentes curriculares de acuerdo a las áreas de conocimiento.

“El fomento de la enseñanza de estas lenguas artísticos proporciona tanto el desarrollo personal del individuo como la preservación de la cultura nacional”, dijo Molon.

Es de esperar que en nuestro país se pudiera imitar la medida, para fomentar y potenciar el arte en nuestros niños en estas disciplinas.