miércoles, 11 de enero de 2017

LAU geneticist leads revelatory research into Ice Age populations

New genetics research led by LAU professor Pierre Zalloua has confirmed the existence of isolated populations around the Black Sea and the Northern Levant during the Ice Age. Referred to as refugia, these populations lived apart from each other with no contact or inter-mixing for more than 25,000 years. "This allowed for distinct genetic signatures specific to each refugium to accumulate," the researcher explains.

Geneticist and Dean of Graduate Studies and Research Zalloua worked together with a team made up of members from New Zealand's University of Otago, Saint Joseph University in Lebanon, and technology company IBM, to collect and study new genetic data.

"Archeology indicates the existence of populations in certain areas, but it doesn't show that people were isolated," adds Zalloua.

Not only did his team confirm the existence of refugia, but they also traced their migration away from their isolation after the first ice melted some 15,000 years ago by mapping the genetic data against existing archaeological, paleontological, paleobotanical, and climate data [...] National News Agency

Expansions post-glaciaires en Asie du Sud-Ouest - Généalogie génétique 
Les changements du climat ont influencé drastiquement l'occupation de l'Asie du Sud-Ouest par l'homme moderne depuis sa première occupation sur les sites de Skhul et Qafzeh au Proche-Orient il y a environ 100.000 ans. Ces impacts climatiques sur les mouvements de population et sur le développement des différentes cultures ont été fortement débattus. Durant le dernier maximum glaciaire, les conditions ont poussé les populations à occuper différents refuges autour de la Méditerranée, la Mer Noire et le Sud de la péninsule Arabique. Ensuite, le réchauffement post-glaciaire et la révolution Néolithique ont permis l'expansion de ces différentes populations en Asie du Sud-Ouest...

Megafaunal extinction: Size was what killed woolly mammoths and sabre tooth cats

New research overturns the idea that more ecologically unique species are the most vulnerable.

Woolly mammoths, sabre-tooth tigers, the enormous armadillo-like Glyptodon and the fearsome dire wolves, as seen in Game of Thrones, all roamed the US and Canada in the past 50,000 years. They died in the megafaunal extinction in the Pleistocene period, and now scientists have dispelled an established theory of what factors made them vulnerable – it turns out that the animals' ecological uniqueness played no role in the extinctions.

Scientists have argued about why the extinctions happened, but not many have looked at how. A popular theory has been that the largest and most ecologically unique animals were the first to go. Now a study in the journal Proceedings of the Royal Society B finds otherwise. While size did affect whether an animal went extinct, their ecological uniqueness wasn't a factor.

"We didn't have data at a fine enough scale to ask this question before," study author Matt Davis of Aarhus University in Denmark told IBTimes UK. "We know we had woolly mammoths and things, but most of the time we didn't know exactly which species were around and when."

The key was trudging through a lot of books and museum collections to find the best dates for the extinctions of the North American megafauna, which hadn't been done on this scale. [...] ibtimes.co.uk

A research framework for tracing human migration events after 'out of Africa' origins

Map of the migration of humans out of Africa, based on mitochondrial DNA

As more DNA sequencing data continues to become available, including extinct hominids, a new human origins study has been performed that augments a trio of influential papers published in 2016 in the journal Nature.

The papers all confirmed the "Out of Africa" origins of modern humans, while disagreeing on the timing of when a more southern migration route (into Southeast Asia and Australia) may have occurred.

The new study, performed by geneticists at Harvard Medical School, provides an expanded framework for researchers to study human origins, drawing upon extensive DNA sampling —- 10 representative modern human populations and all archaic hominid DNA sequenced. After accounting for interbreeding events involving the archaic hominids, their model features a major eastern-western population split once modern humans left Africa, dating back to at least 45,000 years ago, with Australians and New Guineans inside the eastern group.

"We view our model as a detailed synthesis of existing data and a good basis for further work," said Mark Lipson, lead author on the paper from the Department of Genetics at Harvard Medical School. Lipson, along with colleague David Reich, of Harvard, the Broad Institute, and Howard Hughes Medical Institute, published the study in the advance online edition of the journal Molecular Biology and Evolution.[...] phys.org / Link 2 

What teeth reveal about the lives of modern humans

Book explores how scientists use teeth to study human evolution

When anthropologists of the future find our fossilized teeth, what will they be able to conclude about our lives?

Debbie Guatelli-Steinberg has an idea. She is a professor of anthropology at The Ohio State University who studies fossilized teeth to answer questions about the life history, growth, and diet of primates and our human ancestors, as well as the relationships between different species.

In a new book, What Teeth Reveal About Human Evolution (Cambridge University Press, 2016), she gives a broad overview of what scientists have learned about our ancestors from studying fossilized teeth.

As for the teeth of humans living today – well, it is a good thing we have modern dentistry.

“We have teeth that were adapted for eating a very different diet than the one we eat today, at least in Western societies,” Guatelli-Steinberg said.

In the book, she noted that 99 percent of humans’ evolutionary history was spent eating foods that were hunted or gathered. Our current diets of soft, processed and sugary foods are nothing like the diets for which our teeth are adapted. [...] The Ohio State University