Ancient Humans, Dubbed 'Denisovans', Interbred with Us

Professor Chris Stringer: "It's nothing short of sensational - we didn't know how ancient people in China related to these other humans"

Scientists say an entirely separate type of human identified from bones in Siberia co-existed and interbred with our own species.

The ancient humans have been dubbed Denisovans after the caves in Siberia where their remains were found.

There is also evidence that this group was widespread in Eurasia.

A study in Nature journal shows that Denisovans co-existed with Neanderthals and interbred with our species - perhaps around 50,000 years ago.

An international group of researchers sequenced a complete genome from one of the ancient hominins (human-like creatures), based on nuclear DNA extracted from a finger bone. 'Sensational' find

According to the researchers, this provides confirmation there were at least four distinct types of human in existence when anatomically modern humans (Homo sapiens sapiens) first left their African homeland.

 

 DNA from a tooth (pictured) and a finger bone show the Denisovans were a distinct group 

Along with modern humans, scientists knew about the Neanderthals and a dwarf human species found on the Indonesian island of Flores nicknamed The Hobbit. To this list, experts must now add the Denisovans.

The implications of the finding have been described by Professor Chris Stringer of the Natural History Museum in London as "nothing short of sensational".

Scientists were able to analyse DNA from a tooth and from a finger bone excavated in the Denisova cave in southern Siberia. The individuals belonged to a genetically distinct group of humans that were distantly related to Neanderthals but even more distantly related to us.

The finding adds weight to the theory that a different kind of human could have existed in Eurasia at the same time as our species.

Researchers have had enigmatic fossil evidence to support this view but now they have some firm evidence from the genetic study carried out by Professor Svante Paabo of the Max Planck Institute in Leipzig, Germany.

"A species of early human living in Europe evolved," according to Professor Paabo.

"There was a western form that was the Neanderthal and an eastern form, the Denisovans."

The study shows that Denisovans interbred with the ancestors of the present day people of the Melanesian region north and north-east of Australia. Melanesian DNA comprises between 4% and 6% Denisovan DNA.

David Reich from the Harvard Medical School, who worked with Svante Paabo on the study, says that the fact that Denisovan genes ended up so far south suggests they were widespread across Eurasia: "These populations must have been spread across thousands and thousands of miles," he told BBC News.

One mystery is why the Denisovan genes are unique in modern Melanesians and are not found in other Eurasian groups that have so far been sampled. 'Fleeting encounter'

Professor Stringer believes it is because there may have been only a fleeting encounter as modern humans migrated through South-East Asia and then on to Melanesia.

 

The remains were excavated at a cave site in southern Siberia

"It could be just 50 Denisovans interbreeding with a thousand modern humans. That would be enough to produce this 5% of those archaic genes being transferred," he said.

"So the impact is there but the number of interbreeding events might have been quite small and quite rare."

No one knows when or how these humans disappeared but, according to Professor Paabo, it is very likely something to do with modern people because all the "archaic" humans, like Denisovans and Neanderthals disappeared sometime after Homo sapiens sapiens appeared on the scene.

"It is fascinating to see direct evidence that these archaic species did exist (alongside us) and it's only for the last few tens of thousands of years that is unique in our history that we are alone on this planet and we have no close relatives with us anymore," he said.

The study follows a paper published earlier this year by Professor Paabo and colleagues that showed there 

was interbreeding between modern humans and Neanderthals as theyemerged from Africa 60,000 years ago. 

Source: http://www.bbc.co.uk/

Author: radhite  Category: ancient,bones,do you know,feature,human,modification DNA,research,species

Professor Chris Stringer: "It's nothing short of sensational - we didn't know how ancient people in China related to these other humans"

Scientists say an entirely separate type of human identified from bones in Siberia co-existed and interbred with our own species.

The ancient humans have been dubbed Denisovans after the caves in Siberia where their remains were found.

There is also evidence that this group was widespread in Eurasia.

A study in Nature journal shows that Denisovans co-existed with Neanderthals and interbred with our species - perhaps around 50,000 years ago.

An international group of researchers sequenced a complete genome from one of the ancient hominins (human-like creatures), based on nuclear DNA extracted from a finger bone. 'Sensational' find

According to the researchers, this provides confirmation there were at least four distinct types of human in existence when anatomically modern humans (Homo sapiens sapiens) first left their African homeland.

 

 DNA from a tooth (pictured) and a finger bone show the Denisovans were a distinct group 

Along with modern humans, scientists knew about the Neanderthals and a dwarf human species found on the Indonesian island of Flores nicknamed The Hobbit. To this list, experts must now add the Denisovans.

The implications of the finding have been described by Professor Chris Stringer of the Natural History Museum in London as "nothing short of sensational".

Scientists were able to analyse DNA from a tooth and from a finger bone excavated in the Denisova cave in southern Siberia. The individuals belonged to a genetically distinct group of humans that were distantly related to Neanderthals but even more distantly related to us.

The finding adds weight to the theory that a different kind of human could have existed in Eurasia at the same time as our species.

Researchers have had enigmatic fossil evidence to support this view but now they have some firm evidence from the genetic study carried out by Professor Svante Paabo of the Max Planck Institute in Leipzig, Germany.

"A species of early human living in Europe evolved," according to Professor Paabo.

"There was a western form that was the Neanderthal and an eastern form, the Denisovans."

The study shows that Denisovans interbred with the ancestors of the present day people of the Melanesian region north and north-east of Australia. Melanesian DNA comprises between 4% and 6% Denisovan DNA.

David Reich from the Harvard Medical School, who worked with Svante Paabo on the study, says that the fact that Denisovan genes ended up so far south suggests they were widespread across Eurasia: "These populations must have been spread across thousands and thousands of miles," he told BBC News.

One mystery is why the Denisovan genes are unique in modern Melanesians and are not found in other Eurasian groups that have so far been sampled. 'Fleeting encounter'

Professor Stringer believes it is because there may have been only a fleeting encounter as modern humans migrated through South-East Asia and then on to Melanesia.

 

The remains were excavated at a cave site in southern Siberia

"It could be just 50 Denisovans interbreeding with a thousand modern humans. That would be enough to produce this 5% of those archaic genes being transferred," he said.

"So the impact is there but the number of interbreeding events might have been quite small and quite rare."

No one knows when or how these humans disappeared but, according to Professor Paabo, it is very likely something to do with modern people because all the "archaic" humans, like Denisovans and Neanderthals disappeared sometime after Homo sapiens sapiens appeared on the scene.

"It is fascinating to see direct evidence that these archaic species did exist (alongside us) and it's only for the last few tens of thousands of years that is unique in our history that we are alone on this planet and we have no close relatives with us anymore," he said.

The study follows a paper published earlier this year by Professor Paabo and colleagues that showed there 

was interbreeding between modern humans and Neanderthals as theyemerged from Africa 60,000 years ago. 

Source: http://www.bbc.co.uk/

Read More

Catatumbo Lightning, Drought extinguishes Venezuela's lightning phenomenon

Darkness rarely lasted long in the skies over Lake Maracaibo. An hour after dusk the show would begin: a lightning bolt, then another, and another, until the whole horizon flashed white.

Catatumbo lightning over Lake Maracaibo in Venezuela. Photograph: Vladimir Marcano

Electrical storms, product of a unique meteorological phenomenon, have lit up nights in this corner of Venezuela for thousands of years. Francis Drake abandoned a sneak attack on the city of Maracaibo in 1595 when lightning betrayed his ships to the Spanish garrison.

But now the lightning has vanished. A phenomenon that once unleashed up to 20,000 bolts a night stopped in late January. Not a single bolt has been seen since.

"This is unprecedented. In recorded history we have not had such a long stretch without lightning," said Erik Quiroga, an environmentalist and leading authority on the Relampago de Catatumbo, or Catatumbo Lightning.

The spectacle, one of the longest single displays of continuous lightning in the world, lasts up to nine hours a night. On average it is visible over 160 nights a year and from 400km away. Lightning bolts discharged from cloud to cloud strike 16 to 40 times a minute.

They can reach an intensity of 400,000 amps but are so high thunder is inaudible. There are similar phenomena in Colombia, Indonesia and Uganda but they do not last the whole night.

Fishermen in the village of Congo Mirador, a collection of wooden huts on stilts at the phenomenon's epicentre, are puzzled and anxious by its absence. "It has always been with us," said Edin Hernandez, 62. "It guides us at night, like a lighthouse. We miss it."

The celestial spectacular appears to be a casualty of the El Niño weather phenomenon, which has disrupted global weather patterns and caused a severe drought in Venezuela. Rain has all but disappeared, drying up rivers and disrupting the conditions that produce the lightning, whose causes remain unclear.

One theory links it to decomposing organic materials which release methane. Another links it to Andean winds blowing across marshes, generating low pressure and building up an electrical charge in the atmosphere.

The last time the phenomenon vanished was in 1906 after a catastrophic 8.8-magnitude earthquake off the coast of Ecuador and Colombia unleashed a tsunami. The lightning returned three weeks later.

Now it is five weeks and there is still no sign of the nocturnal flashes. "I look for it every night but there is nothing," said Francisca Hernandez, 28, a schoolteacher in Congo Mirador who monitors Lake Maracaibo's sky for researchers based in Caracas.

Some scientists believe the electrical storms help replenish the ozone layer. Others doubt that, saying the ozone they produce reaches only the tropospheric atmosphere.

The drought has also extinguished many man-made lights across Venezuela as the country relies largely on hydropower. Last month, the president, Hugo Chávez, declared an electricity emergency and said severe rationing, which has blacked out towns and cities, could last months. One state electricity company told workers to pray for rain.

Losing the lightning is a symbolic blow. In addition to warding off Drake's naval assault – an event celebrated in Lope de Vega's 1598 epic poem – it is credited with helping independence fighters defeat a Spanish fleet in 1823. The state of Zulia, which encompasses Lake Maracaibo, has a lightning bolt across its centre and refers to the phenomenon in its anthem.

Quiroga worries that when rains return the lightning may not recover its former glory. It was dwindling in frequency and force even before the drought, probably because deforestation and agriculture had clogged the Catatumbo river and several lagoons with silt.

"This is a unique gift and we are at risk of losing it," said Quiroga, who has led scientific teams to its epicentre. He has lobbied Venezuelan authorities to protect the area and the United Nations to recognise it as a world heritage site. A Unesco spokeswoman said there were no plans to do so because electrical storms did not have a "site".

Source :
guardian.co.uk

Author: radhite  Category: Catatumbo Lightning,do you know,feature,phenomenon,storm,venezuela

Darkness rarely lasted long in the skies over Lake Maracaibo. An hour after dusk the show would begin: a lightning bolt, then another, and another, until the whole horizon flashed white.

Catatumbo lightning over Lake Maracaibo in Venezuela. Photograph: Vladimir Marcano

Electrical storms, product of a unique meteorological phenomenon, have lit up nights in this corner of Venezuela for thousands of years. Francis Drake abandoned a sneak attack on the city of Maracaibo in 1595 when lightning betrayed his ships to the Spanish garrison.

But now the lightning has vanished. A phenomenon that once unleashed up to 20,000 bolts a night stopped in late January. Not a single bolt has been seen since.

"This is unprecedented. In recorded history we have not had such a long stretch without lightning," said Erik Quiroga, an environmentalist and leading authority on the Relampago de Catatumbo, or Catatumbo Lightning.

The spectacle, one of the longest single displays of continuous lightning in the world, lasts up to nine hours a night. On average it is visible over 160 nights a year and from 400km away. Lightning bolts discharged from cloud to cloud strike 16 to 40 times a minute.

They can reach an intensity of 400,000 amps but are so high thunder is inaudible. There are similar phenomena in Colombia, Indonesia and Uganda but they do not last the whole night.

Fishermen in the village of Congo Mirador, a collection of wooden huts on stilts at the phenomenon's epicentre, are puzzled and anxious by its absence. "It has always been with us," said Edin Hernandez, 62. "It guides us at night, like a lighthouse. We miss it."

The celestial spectacular appears to be a casualty of the El Niño weather phenomenon, which has disrupted global weather patterns and caused a severe drought in Venezuela. Rain has all but disappeared, drying up rivers and disrupting the conditions that produce the lightning, whose causes remain unclear.

One theory links it to decomposing organic materials which release methane. Another links it to Andean winds blowing across marshes, generating low pressure and building up an electrical charge in the atmosphere.

The last time the phenomenon vanished was in 1906 after a catastrophic 8.8-magnitude earthquake off the coast of Ecuador and Colombia unleashed a tsunami. The lightning returned three weeks later.

Now it is five weeks and there is still no sign of the nocturnal flashes. "I look for it every night but there is nothing," said Francisca Hernandez, 28, a schoolteacher in Congo Mirador who monitors Lake Maracaibo's sky for researchers based in Caracas.

Some scientists believe the electrical storms help replenish the ozone layer. Others doubt that, saying the ozone they produce reaches only the tropospheric atmosphere.

The drought has also extinguished many man-made lights across Venezuela as the country relies largely on hydropower. Last month, the president, Hugo Chávez, declared an electricity emergency and said severe rationing, which has blacked out towns and cities, could last months. One state electricity company told workers to pray for rain.

Losing the lightning is a symbolic blow. In addition to warding off Drake's naval assault – an event celebrated in Lope de Vega's 1598 epic poem – it is credited with helping independence fighters defeat a Spanish fleet in 1823. The state of Zulia, which encompasses Lake Maracaibo, has a lightning bolt across its centre and refers to the phenomenon in its anthem.

Quiroga worries that when rains return the lightning may not recover its former glory. It was dwindling in frequency and force even before the drought, probably because deforestation and agriculture had clogged the Catatumbo river and several lagoons with silt.

"This is a unique gift and we are at risk of losing it," said Quiroga, who has led scientific teams to its epicentre. He has lobbied Venezuelan authorities to protect the area and the United Nations to recognise it as a world heritage site. A Unesco spokeswoman said there were no plans to do so because electrical storms did not have a "site".

Source :
guardian.co.uk

Read More