Un estudio compara la evolución de las capacidades visoespaciales en neandertales y humanos modernos

Un trabajo del Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) ha comparado en dos estudios la evolución de las capacidades visual y espacial de humanos modernos y neandertales, y ha constatado como estos últimos no ampliaron las áreas parietales dedicadas a estas funciones como lo hicieron los humanos modernos.

Además, las marcas en sus dientes denotan el uso habitual de la boca para manipular objetos con mayor frecuencia que cualquier población de 'Homo sapiens'.

El investigador Emiliano Bruner, autor de este trabajo, revisó en la revista 'Quaternary International' la importancia de la evolución de las áreas parietales en los homínidos, que radica en que estas áreas representan un nudo crucial para todas las funciones visoespaciales.

Éstas permiten integrar el cuerpo con el espacio y con los objetos, "incluyendo procesos a pequeña escala, como la manipulación, o a una escala más amplía, como la orientación", señala el investigador, que ha contado con la participación de Atsushi Iriki, del Riken Brain Institute de Tokio (Japón).

Al integrar antropología, paleontología, primatología y neurociencias, el trabajo pone en evidencia el papel de las funciones visoespaciales (capacidad para representar, analizar y manipular un objeto mentalmente) en la gestión de la relación entre cerebro, cuerpo y objetos.

"Los cambios en estas funciones podrían haber aumentado el nivel de integración entre nuestro cerebro y el ambiente externo, ampliando nuestras capacidades cognitivas, al disponer de elementos e informaciones del ambiente exterior, y no solo de los recursos de nuestro sistema nervioso", ha explicado a 'Sinc' Bruner.

INTEGRACIÓN ENTRE CEREBRO, CUERPO Y CULTURA MATERIAL

Además, el investigador también ha publicado otro estudio sobre las capacidades de integración visoespacial de neandertales y humanos modernos publicado en la revista 'Journal of Anthropological Sciences', que forma parte de la segunda parte de una serie de comentarios científicos acerca de unos posibles límites en la integración entre cerebro, cuerpo y cultura material en los neandertales.

"Las poblaciones neandertales no presentan una ampliación de las áreas parietales dedicadas a la integración visoespacial parecida a los humanos modernos, y al mismo tiempo muestran marcas en los dientes que denotan el uso habitual de la boca para manipular objetos, con una frecuencia y un grado mucho mayor que cualquier población de 'Homo sapiens'", ha explicado este experto.

Con esta hipótesis, Emiliano Bruner y la investigadora del IPHES de Tarragona Marina Lozano se cuestionan si el uso tan frecuente de los dientes, que podría considerarse "arriesgado" dada su importancia en la alimentación, pudo haber sido consecuencia de una capacidad de integración entre ojo y mano --compensada con la ayuda de la boca--, y entre cerebro y objeto menos especializada que en nuestra especie.

Tomado de: http://noticias.lainformacion.com/ciencia-y-tecnologia/paleontologia/un-estudio-compara-la-evolucion-de-las-capacidades-visoespaciales-en-neandertales-y-humanos-modernos_A0jnfEWYbCwdQMvTr15jh3/

Documental El origen del hombre y su evolución

Yale researchers map ‘switches’ that shaped the evolution of the human brain

Thousands of genetic “dimmer” switches, regions of DNA known as regulatory elements, were turned up high during human evolution in the developing cerebral cortex, according to new research from the Yale School of Medicine.

Unlike in rhesus monkeys and mice, these switches show increased activity in humans, where they may drive the expression of genes in the cerebral cortex, the region of the brain that is involved in conscious thought and language. This difference may explain why the structure and function of that part of the brain is so unique in humans compared to other mammals.

The research, led by James P. Noonan, Steven K. Reilly, and Jun Yin, is published March 6 in the journal Science.

In addition to creating a rich and detailed catalogue of human-specific changes in gene regulation, Noonan and his colleagues pinpointed several biological processes potentially guided by these regulatory elements that are crucial to human brain development.

“Building a more complex cortex likely involves several things: making more cells, modifying the functions of cortical areas, and changing the connections neurons make with each other. And the regulatory changes we found in humans are associated with those processes,” said Noonan, associate professor of genetics, an investigator with the Kavli Institute for Neuroscience, and senior author of the study. “This likely involves evolutionary modifications to cellular proliferation, cortical patterning, and other developmental processes that are generally well conserved across many species."

Scientists have become adept at comparing the genomes of different species to identify the DNA sequence changes that underlie those differences. But many human genes are very similar to those of other primates, which suggests that changes in the way genes are regulated — in addition to changes in the genes themselves — is what sets human biology apart.

Up to this point, however, it has been very challenging to measure those changes and figure out their impact, especially in the developing brain. The Yale researchers took advantage of new experimental and computational tools to identify active regulatory elements — those DNA sequences that switch genes on or off at specific times and in specific cell types — directly in the human cortex and to study their biological effects.

First, Noonan and his colleagues mapped active regulatory elements in the human genome during the first 12 weeks of cortical development by searching for specific biochemical, or “epigenetic” modifications. They did the same in the developing brains of rhesus monkeys and mice, then compared the three maps to identify those elements that showed greater activity in the developing human brain. They found several thousand regulatory elements that showed increased activity in human.

Next, they wanted to know the biological impact of those regulatory changes. The team turned to BrainSpan, a freely available digital atlas of gene expression in the brain throughout the human lifespan. (BrainSpan was led by Kavli Institute member Nenad Sestan at Yale, with contributions from Noonan and Pasko Rakic, a co-author on this study.) They used those data to identify groups of genes that showed coordinated expression in the cerebral cortex. They then overlaid the regulatory changes they had found with these groups of genes and identified several biological processes associated with a surprisingly high number of regulatory changes in humans.

“While we often think of the human brain as a highly innovative structure, it’s been surprising that so many of these regulatory elements seem to play a role in ancient processes important for building the cortex in all mammals, said first author Steven Reilly. “However, this is often a hallmark of evolution, tinkering with the tools available to produce new features and functions.”

Next, Noonan and colleagues plan to investigate the function of some of the regulatory changes they identified by introducing them into the mouse genome and studying their effects on mouse brain development.

Tomado de: http://news.yale.edu/2015/03/05/yale-researchers-map-switches-shaped-evolution-human-brain

World’s oldest butchery tools gave evolutionary edge to human communication

Two and a half million years ago, our hominin ancestors in the African savanna crafted rocks into shards that could slice apart a dead gazelle, zebra or other game animal. Over the next 700,000 years, this butchering technology spread throughout the continent and, it turns out, came to be a major evolutionary force, according to new research from UC Berkeley, the University of Liverpool and the University of St. Andrews, both in the UK.

Combining the tools of psychology, evolutionary biology and archaeology, scientists have found compelling evidence for the co-evolution of early Stone Age slaughtering tools and our ability to communicate and teach, shedding new light on the power of human culture to shape evolution.

Reported today (Jan.13) in the journal Nature Communications, the study is the largest to date to look at gene-culture co-evolution in the context of prehistoric Oldowan tools, the oldest-known cutting devices. It suggests communication among our earliest ancestors may be more complex than previously thought, with teaching and perhaps even a primitive proto-language occurring some 1.8 million years ago.

“Our findings suggest that stone tools weren’t just a product of human evolution, but actually drove it as well, creating the evolutionary advantage necessary for the development of modern human communication and teaching,” said Thomas Morgan, lead author of the study and a postdoctoral researcher in psychology at UC Berkeley.

Video by Phil Ebiner and Roxanne Makasdjian
“Our data show this process was ongoing two and a half million years ago, which allows us to consider a very drawn-out and gradual evolution of the modern human capacity for language and suggests simple ‘proto-languages’ might be older than we previously thought,” Morgan added.

Morgan and University of Liverpool archaeologist Natalie Uomini arrived at their conclusions by conducting a series of experiments in teaching contemporary humans the art of “Oldowan stone-knapping,” in which butchering “flakes” are created by hammering a hard rock against certain volcanic or glassy rocks, like basalt or flint (see video demonstration above).

Oldowan stone-knapping dates back to the Lower Paleolithic period in eastern Africa, and remained largely unchanged for 700,000 years until more sophisticated Acheulean hand-axes and cleavers, which marked the next generation of stone tool technology, came on the scene. It was practiced by some of our earliest ancestors, such as Homo habilis and the even olderAustralopithecus garhi, who walked on two legs, but whose facial features and brain size were closer to those of apes.

In testing five different ways to convey Oldowan stone-knapping skills to more than 180 college students, the researchers found that the demonstration that used spoken communication – versus imitation, non-verbal presentations or gestures – yielded the highest volume and quality of flakes in the least amount of time and with the least waste.

To measure the rate of transmission of the ancient butchery technology, and establish whether more complex communication such as language would get the best results, study volunteers were divided into five- or 10-member “learning chains.” The head of the chain received a knapping demonstration, the raw materials and five minutes to try their hand at it. That person then showed it to the next person in the chain, who in turn showed the next person, and so on. Their competence picked up significantly with verbal instruction.

“If someone is trying to learn a skill that has lots of subtlety to it, it helps to engage with a teacher and have them correct you,” Morgan said. “You learn so much faster when someone is telling you what to do.”

As for what the results mean for the Oldowan hominins: “They were probably not talking,” Morgan said. “These tools are the only tools they made for 700,000 years. So if people had language, they would have learned faster and developed newer technologies more rapidly.”

Without language, one can assume that a hominin version of, say, Steve Jobs would have been hard-pressed to pass on visionary ideas. Still, the seeds of language, teaching and learning were planted due to the demand for Oldowan tools, the study suggests, and at some point hominins got better at communicating, hence the advent of Acheulean hand-axes and cleavers some 1.7 million years ago.

“To sustain Acheulean technology, there must have been some kind of teaching, and maybe even a kind of language, going on, even just a simple proto-language using sounds or gestures for ‘yes’ or ‘no,’ or ‘here’ or ‘there,’” Morgan said.

Indeed, the data suggest that when the Oldowan stone-tool industry started, it was most likely not being taught, but communication methods to teach it were developed later.

“At some point they reached a threshold level of communication that allowed Acheulean hand axes to start being taught and spread around successfully and that almost certainly involved some sort of teaching and proto-type language,” Morgan said.

In addition to Morgan and Uomini, co-authors and researchers on the paper are Luke E. Rendell, Sally E. Street, Hannah M. Lewis, Catherine P. Cross, Cara Evans, Ronan Kearney, Andrew Whiten and Kevin N. Laland, all at the University of St. Andrews in Scotland, Ignacio de la Torre at University College London and Laura Chouinard-Thuly at McGill University in Canada.

Tomado de: http://newscenter.berkeley.edu/2015/01/13/stone-age-tools/