human evolution

Early Humans Migrated From Africa Far Earlier Than Previously Thought, New Study Suggests

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The researchers cautioned that interbreeding between modern humans and other lineages of humans might influence the results of this new study. For example, instances of interbreeding with the now-extinct Denisovan lineage might have introduced ancient genes into certain modern human groups, perhaps making them look as if they left Africa earlier than they actually did.

“Our study did not specifically test for hybridization with archaic humans, and, of course, it is possible that such admixture could contribute to our results,” Harvati said. “We feel, however, that the very low levels of admixture that have been proposed are not sufficient to drive our findings.”

The researchers said continued fieldwork and genetic advancements might help confirm this model of multiple, relatively isolated waves of migration.

“The story of human evolution tends to be simplified,” Harvati said. “However, more complex models, such as multiple dispersals versus a single dispersal out of Africa, gain strength as more data and new methods become available.”

Waves and waves of hominids

Early Humans Migrated From Africa Far Earlier Than Previously Thought, New Study Suggests

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Footprints left behind by what may be one our first human ancestors to arrive in Britain have been discovered on a beach in Norfolk.

The preserved tracks, which consisted of 49 imprints in a soft sedimentary rock, are believed to be around 900,000 years old and could transform scientists understanding of how early humans moved around the world.

Anthropologists and evolutionary biologists from around the UK have been studying the tracks, and believe they may have been related to an extinct form of human ancestor known as Homo antecessor, or “Pioneer Man”.

The tracks include up to five different prints, indicating a group of both adults and children walked across the ancient wet estuary silt.

They are the earliest direct evidence of human ancestors in the area and may belong to some of the first ever Britons.

From their analysis of the prints, researchers believe the group were probably heading in a southerly direction over what would at the time have been an estuary surrounded by salt marsh and coniferous forest.

At the time Britain was connected to continental Europe by land and the site at Happisburgh would have been on the banks of a wide estuary several miles from the coast.

The estuary itself would have provided a rich array of plants, seaweed and shellfish. Fossils of mammoth, an extinct kind of horse and early forms of voles have also been found at the site Happisburgh.

The early humans could also have hunted or scavenged the grazing herds for meat.

The discovery of the footprints is particularly significant as there are few surviving tracks of human ancestors elsewhere in the world.

Scientists can glean large amounts of information about our ancestors, including the size of the groups they travelled in, how they walked, their size and weight.

The prints were discovered in deposits that have also revealed stone tools and fossilised bones dating to between 800,000 and one million years ago.

It is thought that the footprints may have belonged to a relative of a Homo antecessor – an extinct hominid species that may have been a common ancestor to both modern humans and Neanderthals, although such theories are still highly disputed.

Remains from Homo antecessor were discovered in the Atapuerca Mountains in Spain.

Professor Chris Stringer, an eminent anthropologist at the Natural History Museum in London who worked with the team, said: “The humans who made the Happisburgh footprints may well have been related to the people of similar antiquity fromi Atapuerca in Spain, assigned to the species Homo antecessor.

“These people were of a similar height to ourselves and were fully bipedal. They seem to have become extinct in Europe by 600,000 years ago and were perhaps replaced by the species Homo heidelbergensis.

“Neanderthals followed from about 400,000 years ago and eventually modern humans some 40,000 years ago.”

http://www.telegraph.co.uk/science/science-news/10623660/900000-year-old-footprints-of-earliest-northern-Europeans-discovered.html

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In one new study of 1000 human genomes, Sriram Sankararaman and David Reich of Harvard Medical School and colleagues found that Neanderthal DNA is most common in regions of the genome with the greatest genetic variability, making them a prime target for natural selection. While Neanderthal DNA may make up only 1.6 to 1.8 per cent of the Eurasian genome, it punches above its weight in terms of biological impact, says Reich (Nature, DOI: 10.1038/nature12961).

Joshua Akey and Ben Vernot of the University of Washington in Seattle have analysed the Neanderthal DNA in a further 665 humans (Science, DOI: 10.1126/science.1245938). Both their study and the Harvard one found a hotspot of Neanderthal ancestry in genes relating to keratin, a fibrous protein found in our hair, skin and nails.

One of the genes, BNC2, is involved in skin pigmentation. That implies that Eurasians owe their paler skins partly to Neanderthals. Light skin is an advantage at higher latitudes because it is more efficient at generating vitamin D from sunlight, so Neanderthal DNA may have helped modern humans to adapt to life outside Africa.

If so, the adaptation took thousands of years to become universal. A third study published this week describes a DNA analysis of one person who lived in Stone Age Europe about 7000 years ago – 40,000 years after any Neanderthal interbreeding. His genes suggest his skin was dark (Nature, doi.org/q74). It may be that the Neanderthal keratin affected early Eurasians’ hair instead, perhaps straightening it.

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Neanderthal DNA is irregularly spaced through the modern human genome rather than being fully mixed. That implies that interbreeding occurred very rarely. Sankararaman estimates it may have happened just four times.

http://www.newscientist.com/article/mg22129542.600-neanderthalhuman-sex-bred-light-skins-and-infertility.html
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After several failed attempts, they managed to reconstruct the man’s entire genome from DNA found in the root of a third molar. It is the first time researchers have obtained the complete genome of a modern European who lived before the Neolithic revolution.

The DNA threw up a series of surprises. When Lalueza-Fox looked at the genome, he found that rather than having light skin, the man had gene variants that tend to produce much darker skin. “This guy had to be darker than any modern European, but we don’t know how dark,” the scientist said.

Another surprise finding was that the man had blue eyes. That was unexpected, said Lalueza-Fox, because the mutation for blue eyes was thought to have arisen more recently than the mutations that cause lighter skin colour. The results suggest that blue eye colour came first in Europe, with the transition to lighter skin ongoing through Mesolithic times.

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The Spanish team went on to compare the genome of the hunter-gatherer to those of modern Europeans from different regions to see how they might be related. They found that the ancient DNA most closely matched the genetic makeup of people living in northern Europe, in particular Sweden and Finland.

The discovery of mutations that bolstered the immune system against bacteria and viruses suggests that the shift to a farming culture in Neolithic times did not drive all of the changes in immunity genes that Europeans carry today. At least some of those genetic changes have a history that stretches further back. “One thing we don’t know is what sort of pathogens were affecting these people,” said Lalueza-Fox.

Martin Jones, professor of archaeological science at Cambridge University, said the immunity genes were the most striking result. “There is a no doubt oversimplified grand narrative that the move from a hunter-gatherer lifestyle to settled farming was initially bad for our health. A number of factors contributed, particularly living closely together with other humans and animals, shrinking the food web, and crowding-out water supplies. The authors are drawing attention to the role of pathogens in pre-agricultural lives, and that is interesting.”

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Mounting evidence from genome analysis of archaic populations has indicated that the various hominin species mated with each other.

When Neanderthal and modern human populations crossed paths, they interbred too. The Neanderthal genome data confirms that there was “leakage of DNA” from these extinct hominins into modern humans.

“Neanderthals live on a little bit in people living outside Africa today,” Pääbo said, making up about two percent of the genome of all humans that don’t originate from Africa.

Collating the genetic material of two related hominin species — the Neanderthals and Denisovans — and comparing it with sequence data of 25 humans, the researchers have triangulated in on a section of the hominin genome that is unique to our species.

“It’s a definitive recipe if you like for making a modern human,” Pääbo said. “We can now start doing experiments to ask what is it that makes modern humans special.”

“There is also an interesting question of what, if anything, Neanderthal and Denisovan DNA may be doing in the people that have it today, and whether it has been of benefit or detriment to our species,” Chris Stringer, a paleoanthropologist at the Natural History Museum in London, who was unconnected with the work, wrote in a comment sent to press.

Further research into what those areas coded for may reveal why we, homo sapiens, lived on while Denisovans, Neanderthals, and scores of our hominin relatives vanished.

http://m.nbcnews.com/science/sex-siberian-neanderthal-incest-inter-species-action-2D11767012

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Stone tools discovered in this site confirm the continuity of human settlement in Europe, the researchers said.

The finding contradicts the theory of some researchers who believe Europe was populated in small waves without continuity by groups doomed to extinction because of their inability to adapt to new surroundings, they said in their statement.

“Even though they are very archaic tools, they reflect complex activities such as recovering animals that fell into the caves,” which functioned as traps, the statement said.

Researchers have also found the remains of a large bear which is an ancestor to the brown bear that exists today.

Various remains of this species were found at the site, as well as those of other animals such as rhinos, giant deer, bison and wild donkeys.

http://artdaily.com/news/64014/Archaeologists-find-1-4-million-year-old-flint-in-the-caves-of-Atapuerca-in-Spain-#.UfOLHKA_4m-[/url]

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