“Esta es la primera vez que se recupera un genoma completo de un individuo europeo antes del Neolítico”, ha explicado a la Agencia SINC Carles Lalueza-Fox, uno de los autores del estudio, investigador del Instituto de Biología Evolutiva del CSIC y la Universidad Pompeu Fabra. Entre las nuevas características encontradas están el tono oscuro de la piel y el color azul de los ojos. “Los europeos presentan variantes genéticas diferentes del resto de las poblaciones humanas, tienen algo especial, y en este listado de genes hemos encontrado bastantes sorpresas como la pigmentación de la piel y la mutación que provoca los ojos azules”.
Los científicos indican que antes de su estudio, se consideraba que la piel clara de los europeos provenía del Paleolítico Superior y que se había desarrollado durante 45.000 años. En cambio, el individuo estudiado, conocido como La Braña-1, todavía tiene en su genoma las variantes propias de los cazadores recolectores de África que oscurecen la piel. “La piel clara no es algo que se desarrolle con la llegada de los cromañones, sino que está relacionado con la llegada del Neolítico”, defiende Lalueza-Fox.
Pero lo más llamativo es que La Braña–1 poseía también la mutación que provoca los ojos azules en los humanos actuales. “Es chocante porque sabemos que son genes diferentes los del color de los ojos y la piel pero normalmente asumimos que se presentan conjuntamente. La combinación de pigmentación oscura y ojos azules no existe en la Europa actual. En EE UU hay algún actor que tiene un aspecto parecido pero sencillamente es porque sus progenitores son de continentes diferentes y han dado este genotipo. Aquí hablamos de individuos que genéticamente se agrupan con las poblaciones actuales del norte de Europa”.
Los científicos señalan que el objetivo de este estudio era observar cómo la llegada de la agricultura, la forma de vida más sedentaria, los cambios en la dieta y los patógenos asociados a los animales domésticos modelaron el genoma de las poblaciones europeas. "Somos el producto de las remodelaciones genéticas que tienen lugar con la llegada de la agricultura, a nivel de metabolismo y a nivel de dieta y de inmunidad", recuerda el investigador.
Esta investigación fue posible gracias al excelente estado de conservación que tenían los restos de homínidos localizados en el yacimiento de La Braña–Arintero descubierto en 2006. Estos fósiles se encontraban en una cueva a 1.500 metros de altura en una zona bastante fría de la cordillera cantábrica.
Según los investigadores, el individuo localizado en el yacimiento leonés tiene un ancestro en común con los pobladores del Paleolítico Superior que habitaron Mal'ta, en el lago siberiano de Baikal (Rusia), cuyo genoma fue recuperado hace unos meses., y Lalueza-Fox concluye:“Estos datos indican que existe una continuidad genética en las poblaciones del centro y oeste de Eurasia. Los resultados son coherentes y muy similares con los restos arqueológicos de otras excavaciones en europeas y rusas”.
The hunter-gatherers who inhabited Europe 7,000 years ago in the Mesolithic, had dark skin and blue eyes. So say Spanish and Danish scientists who first sequenced the complete genome of a European hominid found at the site of La Braña-Arintero in León (Spain). The paper, published online in Nature, helps us understand how were the habitants of the Old World in the prehistoric Mesolithic period (between the Paleolithic and the Neolithic 10,000 to 5,000 years ago) before the arrival of the agriculture and livestock.
"This is the first time a complete genome of a pre-Neolithic European individual has been recovered" said to SINC agency Carles Lalueza-Fox, one of the authors of the study and researcher at the Institute of Evolutionary Biology (CSIC) and the University Pompeu Fabra. Among the new found features are the dark skin tone and the blue eyes. "Europeans have genetic variants different from other human populations, they have have something special, and in this list of genes we found many surprise,s as the pigmentation of the skin and the mutation that causes blue eyes".
Scientists suggest that before their study, the predominant view was that the clear skin of Europeans came from the Upper Palaeolithic and had developed over 45,000 years. On the contrary, the studied subject, known as La Braña-1, still has in his own genome variants of African hunter-gatherers that darken the skin. "Light skin is not something developed with the arrival of the Cro-Magnon, but is related to the arrival of the Neolithic" argues Lalueza-Fox.
But most striking is that La Braña-1 also had the mutation that causes blue eyes in modern humans. "It's shocking because we know that genes of the color of the eyes and skin are different, but usually we assumed that occur together.The combination of dark pigmentation and blue eyes does not exist in Europe today. There is an Amercian actor that looks similar but is simply because their parents are from different continents and have given this genotype. Here we talk about individuals who genetically cluster with current populations of northern Europe".
The researchers point out that the aim of this study was to observe how the arrival of agriculture, a more sedentary life, the dietary changes and pathogens associated with domestic animals, forged the genome of European populations. "We are the product of genetic renovations taking place with the advent of agriculture, in terms of metabolism, diet and immunity level".
The research was possible thanks to the excellent conditions of the hominid remains, localized at the La Braña-Arintero site discovered in 2006. These fossils were found in a cave at 1,500 meters high in a pretty cool area of the Cantabrian Mountains.
According to the researchers, the individual found in the León reservoir have a common ancestor with Upper Paleolithic people who lived at Mal'ta in Siberia's Lake Baikal (Russia) and whose genome was recovered a few months ago. "These data indicate that there is a genetic continuity of populations in central and western Eurasia. The results are consistent and very similar to other European and Russian archaeological excavations" concludes Lalueza-Fox.
Tomado de/Taken from SINC
Resumen de la publicación/Abstract of the paper
Derived immune and ancestral pigmentation alleles in a 7,000-year-old Mesolithic European
I. Olalde, M.E. Allentoft, F. Sánchez-Quinto, G. Santpere, C.W.K. Chiang, M. DeGiorgio, J. Prado-Martinez, J.A. Rodríguez, S. Rasmussen, J. Quilez, O. Ramírez, U.M. Marigorta, M. Fernández-Callejo, M.E. Prada, J.M. Vidal Encinas, R. Nielsen, M. G. Netea, J. Novembre, R.A. Sturm, P. Sabeti, T. Marquès-Bonet, A. Navarro, E. Willerslev and C. Lalueza-Fox
Nature (2014) doi:10.1038/nature12960 Published online 26 January 2014
Abstract
Ancient genomic sequences have started to reveal the origin and the demographic impact of farmers from the Neolithic period spreading into Europe. The adoption of farming, stock breeding and sedentary societies during the Neolithic may have resulted in adaptive changes in genes associated with immunity and diet. However, the limited data available from earlier hunter-gatherers preclude an understanding of the selective processes associated with this crucial transition to agriculture in recent human evolution. Here we sequence an approximately 7,000-year-old Mesolithic skeleton discovered at the La Braña-Arintero site in León, Spain, to retrieve a complete pre-agricultural European human genome. Analysis of this genome in the context of other ancient samples suggests the existence of a common ancient genomic signature across western and central Eurasia from the Upper Paleolithic to the Mesolithic. The La Braña individual carries ancestral alleles in several skin pigmentation genes, suggesting that the light skin of modern Europeans was not yet ubiquitous in Mesolithic times. Moreover, we provide evidence that a significant number of derived, putatively adaptive variants associated with pathogen resistance in modern Europeans were already present in this hunter-gatherer.
