Dormir recarga el cerebro

 

Alex Fernández Muerza

El sueño nos recarga las pilas y el cerebro

En las etapas iniciales del sueño, los niveles de energía aumentan de manera enorme en las regiones del cerebro activas durante las horas de vigilia, según una investigación publicada en el Journal of Neuroscience. Estos resultados sugieren que un aumento de la energía celular puede reponer los procesos del cerebro necesarios para su funcionamiento normal mientras se está despierto.
Los responsables del estudio, de la Escuela Médica de Harvard y el Sistema de Salud de Boston (EE.UU.), explican que ya se conocía que dormir es bueno para el cuerpo, pero hasta ahora no se habían descubierto los procesos biológicos involucrados en dicho proceso.
En concreto, los científicos midieron los niveles de trifosfato de adenosina (ATP), la energía de las células, en ratas. Los autores descubrieron que el sueño es necesario para el aumento de energía ATP, ya que si se mantenía a las ratas despiertas se impedía el incremento energético.

Why Bonobos Don’t Kill Each Other

A Conversation With Brian Hare and Vanessa Woods

By CLAUDIA DREIFUS

Published: July 2, 2010

 Brian Hare, an assistant professor at the Duke Institute for Brain Sciences at Duke University, and Vanessa Woods, a research scientist in the Department of Evolutionary Anthropology at Duke, do comparative studies on the cognitive development of bonobo apes, chimpanzees and humans. Ms. Woods, 33, a former journalist from Australia, has just published a book about their marriage and work, "Bonobo Handshake: A Memoir of Love and Adventure in the Congo." We spoke last month after they had appeared at the World Science Festival in New York City. An edited version of the conversation follows:

Q. VANESSA, YOU’RE NOT A TRAINED PRIMATOLOGIST. HOW DID YOU COME TO WORK WITH BONOBOS?
A. Vanessa: By a series of happy accidents. For much of my 20s, I didn’t know what I wanted to do with my life. So I went to Africa and did a little of everything. I worked with chimpanzees for a bit and then I did a little bit of filming and I worked a bit on children’s books.
When I met Brian in 2004, I was 27 and volunteering at a chimp sanctuary in Uganda. Brian was testing the chimpanzees’ capacity for cooperation and sharing.
Then Brian got invited to the Congo to perform the same experiments on bonobos, our other close ape relations. Would I come along as a helpmate? I hated the idea. My mother, the world’s biggest feminist, always said, “Never follow a man — do your own thing.” I knew almost nothing about bonobos. I thought: “Aren’t those the apes that have a lot of sex?”
Brian: That’s what most people know about bonobos: they have a lot of sex. That’s not what’s interesting about them. The No. 1 reason they are interesting is that they don’t kill each other. The question I was in Africa chasing was: why will a chimp get into a severe fight with another — perhaps kill or maim it — while a bonobo, in the same situation, won’t? I’m basically an anthropologist. And in looking at the psychological and social propensities of our close relatives, learning about their differences in behavior, maybe we’ll be able to make some inferences about what happened during human evolution.
Q. WHAT KINDS OF EXPERIMENTS DID YOU DO?
A. Brian: The type of experiments that developmental psychologists try on human subjects to see how they’d behave in certain situations. With the apes, I designed tests and games where they could obtain treats — apples, bananas — if they engaged in acts of cooperation.
The chimps, it turned out, would only cooperate if they were teamed up with others of equal status. If you put them with subordinate or superior status chimps, they became intolerant. When you had equal-status chimps together on a test, they were able to solve conflicts of interest, negotiate successfully and recruit collaborators. But when we changed one simple thing, we’d crush their ability to cooperate. We took separate piles of treats and combined them into one. Immediately, the chimpanzees started competing with each other and all cooperation fell apart.
Later, when we were in the Congo, we posed the same question to the bonobos. The piles of food were merged. No problem. Everyone shared. My doctoral thesis adviser at Harvard, Richard Wrangham, thinks this may be because chimpanzees evolved in a situation of food scarcity while bonobos developed in the giant salad bowl of the Congo basin where there was abundance.
Vanessa: Another thing: bonobos are matriarchal. If it’s usual for female chimps to get pushed around and battered by males, bonobo females run things. Once, while in the Congo, I witnessed Tatango, this young male bonobo, start to do what the chimps in Uganda regularly did: he went up to the alpha female, Mimi, and backhanded her across the face. She gave him the most withering look. Within seconds, five unrelated females chased him into the forest. Poor guy. They almost took his testicles off. After that, he never made another problem. Bonobo females seem to know that if they stick together, the males can’t dominate.
Brian’s gender was actually a problem when we first arrived in the Congo. He walked right up to the bonobos, did all these loud displays, which usually fascinates chimpanzees and makes them want to play with you. The male bonobos were terrified of Brian and the female ones would have nothing to do with him. I had to run the experiments because they seemed to accept me more easily. Once that became clear, my role became larger than that of a “helpmate.” With time, the work became mine, too.
Q. WHERE EXACTLY DID YOU PERFORM THESE EXPERIMENTS? I’M UNDER THE IMPRESSION THAT BONOBOS ARE DIFFICULT TO RESEARCH BECAUSE THEIR HABITAT IS IN THE WILDS OF THE CENTRAL AFRICAN RAIN FOREST.
A. Brian: Well, we went to the semiwild. There’s this amazing conservationist, Claudine Andre, who founded a sanctuary in Kinshasa for bonobos orphaned by the bush meat trade. She’d convinced the Congolese to let her use this 100-acre wood with lily ponds and forests that once had been a bucolic retreat for Mobutu Sese Seko.
Working with the orphans in the sanctuary, they were much more like wild animals than the captive bonobos one might study at a zoo. They were obviously much easier to see and interact with than animals in the forest.
Q. HAVE YOU FOUND ANSWERS TO THE SCIENTIFIC QUESTIONS YOU’VE BEEN ASKING?
A. Brian: Tentative answers. The research is ongoing. Some of the differences between chimps and bonobos have to do with what happens to them during their development. Essentially bonobos and chimps have similar behaviors as youngsters. Like bonobos, juvenile chimps are very tolerant, peaceful. When they go through puberty, they change. So what happens to adolescent bonobos? Nothing! They don’t change. Their levels of play, their levels of sharing and sex, it all keeps going. They are Peter Pans.
Q. HOW ENDANGERED ARE BONOBOS?
A. Vanessa: Very. There are probably about 10,000 remaining in the wild. Nobody really knows. It’s hard to get in there and count them all.
There’s very little agriculture in the Congo. And a lot of hunting. Bush meat is how people get their protein. And unfortunately, bonobos are really prized meat for hunters because they live in communities. If you’ve found one, you’ve found thirty that you can shoot and kill all at the same time. Of course, bonobos aren’t the answer to feeding the Congolese people. There are 68 million Congolese and 10,000 bonobos. The people need aid, some kind of agricultural program so that the farming becomes sustainable, and peace.

Clues of Britain’s First Humans

John Sibbick/AHOBs

Newly discovered artifacts and fossils indicate that early humans were living in northern Europe more than 780,000 years ago.

By NICHOLAS WADE

Published: July 7, 2010

The last time the British Museum claimed that the earliest known human was British, some 98 years ago, its evidence was the Piltdown skull, which the British archaeological establishment did not concede was a forgery until 1953.

Researchers from the British Museum and other institutions on Wednesday announced a more modest claim, that an eroding cliff in Norfolk, England, had yielded evidence of the earliest substantial record of the human presence in Northern Europe.
The discovery of 78 flint tools, more than 800,000 years old, shows that early humans, thought to survive only in warm, Mediterranean-style climates, could penetrate much colder regions and survive with a kit of crude tools.
The world at the time confronted serious climate change in the form of global cooling. It was the middle of the Pleistocene, the last great ice age that ended 10,000 years ago.
The dense Northern European forests of the Pleistocene ice age contained few animals or edible plants, but food would have been more abundant in the flood plain where the flint tools were found. Mammoth, red deer and elk grazed the grasslands, preyed upon by two species of saber-toothed tigers, the dirk-toothed cat and the scimitar-toothed cat.
Humans fit into this ecosystem in a very humble role, that of cleaning up after the giant hyenas that took over the bones left by the saber-toothed tigers.
But the hyenas were of great help to the team of British excavators, led by Simon A. Parfitt and Chris B. Stringer of the Natural History Museum and Nick M. Ashton of the British Museum.
Just above the layer where the flints were found, near the Norfolk village of Happisburgh (pronounced HAZE-bura) lay a hyena coprolite, the paleontologist’s term for a fossilized piece of dung. Pollen grains from the coprolite showed the area was once a grassland that covered a flood plain.
Flint flakes cannot be dated directly. Archaeologists must find clues to their age in the layers of material above and below a find. From fossil voles, of which one species replaced another at a known date, and from records of magnetism in rocks, the archaeologists estimate that the flints were made 780,000 to 990,000 years ago.
They further narrowed the date with the help of fossil beetles of a species that lived only in temperatures that are quite warm. The presence of this species suggests that the region was occupied during one of the two periods between glacial advances that occurred 950,000 and 840,000 years ago.
“Collectively, this evidence provides a strong case for the Happisburgh site as the oldest uncontested site of human occupation of Europe,” said Andrew P. Roberts, an expert on paleomagnetic dating at the Australian National University. The site is known to archaeologists as the Cromer Forest-bed Formation.
But Richard G. Klein, a paleoanthropologist at Stanford University, said he would like to see a better dated site closer to this age before accepting that early humans ranged so far north.
To prove that humans were present, such a site would ideally contain animal bones bearing the cut marks of stone tools. “I know this sets a high bar, and it may be an impractical standard to apply in the context of the Cromer Forest-bed, particularly where it is being exposed by wave erosion,” he said.
The makers of the flints would have been archaic humans, of a so far unknown species, whose ancestors left Africa at least a million years before the emergence of modern humans about 100,000 years ago.
Archaic humans have been documented in the Mediterranean area at this time, but their presence so far north is unexpected, said Ian Tattersall, an anthropologist at the American Museum of Natural History in New York. The new find “does tell us that hominids could tackle boreal forest environments with what seem to be pretty crude tool kits and it confirms they got that far north amazingly early,” he said.
The place where the flint tools were found lay on the ancestral banks of the Thames, which 900,000 years ago reached the sea 90 miles north of its present river mouth. It was joined just before its exit to the sea by the Bytham, now vanished, a river that drained central England. The estuary of these two ancient rivers lay to the north of a broad land corridor that then joined southeast England to continental Europe.
In 2005, 32 flint tools were excavated from the same site, but they were about 100,000 years younger. Probably all archaic humans were driven out of the British Isles during the Last Glacial Maximum, the last fling of the Pleistocene ice age, when the glaciers returned a final time some 20,000 years ago and made most of Europe uninhabitable except for refuges in Spain and southern France. The settlers who repopulated Europe after the glaciers’ retreat were modern humans who had first left the African cradle of humankind just 50,000 years ago.

Early humans ventured farther north than thought

AP – Palaeontologist Simon Parfitt shows a newly discovered fossil of hyena droppings found in a United Kingdom …

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By RAPHAEL G. SATTER, Associated Press Writer Raphael G. Satter, Associated Press Writer – Wed Jul 7, 7:04 pm ET

LONDON – Ancient man ventured into northern Europe far earlier than previously thought, settling on England's east coast more than 800,000 years ago, scientists said.
It had been assumed that humans — thought to have emerged from Africa around 1.75 million years ago — kept mostly to relatively warm tropical forests, steppes and Mediterranean areas as they spread across Eurasia.
But the discovery of a collection of flint tools some 135 miles (220 kilometers) northeast of London shows that quite early on man braved colder climes.
"What we found really undermines traditional views about how humans spread and reacted to climate change," said Simon Parfitt, a University College London researcher. "It just shows how little we know about the movement out of Africa."
About 75 flint tools have been found at the site near Happisburgh, a seaside hamlet in Norfolk, Parfitt and colleagues report in Thursday's issue of the journal Nature.
The researchers dated the artifacts to somewhere between 866,000 to 814,000 years ago or 970,000 to 936,000 years ago. That's at least 100,000 years before the earliest known date for British settlement, in nearby Pakefield.
Exactly what kind of humans made these tools is unknown.
"It is impossible to guess who those people were without fossil evidence," said Eric Delson, an anthropologist at Lehman College of the City University of New York, who was not involved in the research.
Mammoths and saber-toothed cats roamed the area at that time, and the River Thames flowed into the sea there — about 150 kilometers (90 miles) to the north of where its mouth is today. The climate was a little colder than now, at least during the winter.
The Natural History Museum's Chris Stringer, another of the paper's authors, said living in such an environment would have been challenging. Thick forests meant a poor supply of edible plants and dispersed prey. In the winter, there would be less daylight for hunting and foraging. Then, of course, there was the cold.
"For humans that have not long emerged from the tropic and the subtropics, that is something," Stringer said. "There's always been the view that that the cold was holding them back."
But the find suggests that it didn't. So how did these humans adapt? The researchers said the mix of a tidal river, marshes and coastline at the site might have helped, providing seaweed, tubers, and shellfish when prey was scarce.
"We could imagine these people exploiting the slow-flowing banks of the Thames, just as today," Stringer said.
Co-author Nick Ashton, with the British Museum in London, said there was still considerable uncertainty about how they adapted.
"Have they got effective clothing? Have they got effective shelters? Have they got controlled use of fire?" he said, adding that the find "provides more questions than answers."
Delson said that the discovery helped complete Europe's patchy prehistoric record.
"We don't know much, but we're increasing our knowledge of the earliest phases of what went on in Europe," he said. "It's one more piece of the puzzle."
Stringer, meanwhile, said he hoped more discoveries could be made along the coastline. He noted that he had already seen the chronology of human habitation in Britain pushed back, and then pushed back again.
"Now I'm thinking: 'Who knows, can we go back even further?'"
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Online:
http://www.nature.com/nature