Monday, November 23, 2009
Friday, November 20, 2009
Where did all the giant beavers go?
Credits to NPR
One of the great mysteries about North America is what killed off woolly mammoths and other exotic animals that roamed the land after the last ice age. Ideas have ranged from a comet impact and climate change to human hunters. A study published Friday in Science Magazine provides new clues about this — cleverly deduced from samples of a fungus that grew on the animals' dung.
After the end of the last ice age, North America was covered with large mammals even more diverse than we see in Africa today. Jacqueline Gill, a doctoral student at the University of Wisconsin in Madison, is fascinated by how North America came to have such diverse wildlife, and why those animals are all gone today. She says the continent was home to mammoths, mastodons, beavers the size of black bears, giant ground sloths, camels and horses, and predators like the American lion, the short-faced bear and the dire wolf.
"By about 11,000 years ago, we lose about half of the animals in North America larger than the size of a German shepherd, and that's a pretty big ecological event," Gill says.
There aren't enough bones left to determine in detail when exactly they all became extinct, but Gill and her colleagues hit upon a nifty method to track the abundance of grazing animals. The scientists study a certain species of fungus, spores of which end up in lake sediments that date back some 15,000 years.
"The spores from this fungus are preserved in the lake, and the fungus only grows on animal dung," Gill says.
When there were many large animals, there was lots of dung. When the animals went away, so did the dung and the fungus that lived on those droppings. So, by studying the amount of this fungus in various layers of lake sediment, Gill and her group have pieced together a timetable that helps resolve how and when these animals died out.
One of the long-held ideas had been that a climate shift caused a change in vegetation, and the new plant matter was no good for these grazing animals, so they starved.
Gill and company have disproved that, however, by putting a date on the animals' decline: It occurred more than 14,000 years ago.
"This happens before some of the widespread vegetation change that we see in the areas that we studied, which suggest to us that habitat loss is actually not a cause of the decline, but possibly a consequence," Gill says.
That is, the vegetation might have changed after the browsing animals disappeared and stopped munching on it.
The new dates also help eliminate other ideas that have been argued over the years. John Alroy at the University of California, Santa Barbara says it's clear that the extinctions couldn't have been caused by a cold snap called the Younger Dryas.
"These data show that the extinction happened well before that time, and there's also been a recent paper arguing that the extinction might have been caused by the impact of a comet, and that impact appears to have happened much, much later than the decline, at least [at] this location," Alroy says.
So what does that leave? Well, human beings were moving into North America at that time, so Alroy says this is more evidence that hunters played a key role in driving these large animals to extinction.
"Now, really the question is: Exactly what did humans do to cause this large extinction?" Alroy says.
Gill is interested in that question, too, because, she notes, human beings are now forcing another mass extinction as we reshape habitat around the world.
One of the great mysteries about North America is what killed off woolly mammoths and other exotic animals that roamed the land after the last ice age. Ideas have ranged from a comet impact and climate change to human hunters. A study published Friday in Science Magazine provides new clues about this — cleverly deduced from samples of a fungus that grew on the animals' dung.
After the end of the last ice age, North America was covered with large mammals even more diverse than we see in Africa today. Jacqueline Gill, a doctoral student at the University of Wisconsin in Madison, is fascinated by how North America came to have such diverse wildlife, and why those animals are all gone today. She says the continent was home to mammoths, mastodons, beavers the size of black bears, giant ground sloths, camels and horses, and predators like the American lion, the short-faced bear and the dire wolf.
"By about 11,000 years ago, we lose about half of the animals in North America larger than the size of a German shepherd, and that's a pretty big ecological event," Gill says.
There aren't enough bones left to determine in detail when exactly they all became extinct, but Gill and her colleagues hit upon a nifty method to track the abundance of grazing animals. The scientists study a certain species of fungus, spores of which end up in lake sediments that date back some 15,000 years.
"The spores from this fungus are preserved in the lake, and the fungus only grows on animal dung," Gill says.
When there were many large animals, there was lots of dung. When the animals went away, so did the dung and the fungus that lived on those droppings. So, by studying the amount of this fungus in various layers of lake sediment, Gill and her group have pieced together a timetable that helps resolve how and when these animals died out.
One of the long-held ideas had been that a climate shift caused a change in vegetation, and the new plant matter was no good for these grazing animals, so they starved.
Gill and company have disproved that, however, by putting a date on the animals' decline: It occurred more than 14,000 years ago.
"This happens before some of the widespread vegetation change that we see in the areas that we studied, which suggest to us that habitat loss is actually not a cause of the decline, but possibly a consequence," Gill says.
That is, the vegetation might have changed after the browsing animals disappeared and stopped munching on it.
The new dates also help eliminate other ideas that have been argued over the years. John Alroy at the University of California, Santa Barbara says it's clear that the extinctions couldn't have been caused by a cold snap called the Younger Dryas.
"These data show that the extinction happened well before that time, and there's also been a recent paper arguing that the extinction might have been caused by the impact of a comet, and that impact appears to have happened much, much later than the decline, at least [at] this location," Alroy says.
So what does that leave? Well, human beings were moving into North America at that time, so Alroy says this is more evidence that hunters played a key role in driving these large animals to extinction.
"Now, really the question is: Exactly what did humans do to cause this large extinction?" Alroy says.
Gill is interested in that question, too, because, she notes, human beings are now forcing another mass extinction as we reshape habitat around the world.
Thursday, November 19, 2009
People just LOVE fishing, don't they?
credits to NPR
Aid organizations concerned about overfishing on tropical reefs often try to encourage fishermen out of their boats by offering them better-paying jobs on shore. But this strategy actually may make matters worse.
Fish Or Coconuts
Take, for example, the story of Kiribati, an island nation in the central Pacific. Kiribati (pronounced KIR-a-bahs) has a simple economy. People either catch fish, or they pick coconuts from their trees and produce coconut oil. Sheila Walsh, a postdoctoral researcher at Brown University, says most people do a bit of each.
The Kiribati government was concerned about overfishing. So it came up with a plan: It would subsidize the coconut oil industry.
"The thought was that by paying people more to do coconut agriculture, they would do less fishing," says Walsh. "And this would fulfill two goals: One, they would reduce overfishing; and two, people would be better off. They would have higher incomes."
It hit us like a bumper sticker saying -- a bad day fishing is better than a good day working. And that's sort of the story here.
- Sheila Walsh
Walsh wanted to know whether this plan was working, and the government invited her to study the issue. So, as part of her graduate work at the Scripps Institution of Oceanography, she flew to Kiribati to interview fishermen.
Coconut Subsidies Cause More Fishing
"And it turned out that, actually, the result of paying people more to do coconut agriculture was to increase fishing," she says. In fact, fishing increased by a startling 33 percent. The reef fish population dropped by an estimated 17 percent, putting the whole ecosystem at risk.
"It was a bit of a surprise, and we were wondering: What's going on here?"
The answer was simplicity itself. Walsh's study concludes that people earned more money making coconut oil, which meant they could work less to support themselves. And they spent their new leisure time fishing.
"It hit us like a bumper sticker saying — a bad day fishing is better than a good day working. And that's sort of the story here," Walsh says.
Fishing For Pleasure
It turns out she had stumbled into a universal truth about fishing. Fishermen aren't just in it for the money. Anthropologist Richard Pollnac of the University of Rhode Island says, just think of those snazzy sport-fishing excursions.
"People pay big money to go sports-fishing," he notes. There aren't very many occupations that people will actually pay money to do in their leisure time, he says.
So fishing as an occupation provides psychic benefits, as well as money. Pollnac argues that not just individuals but whole cultures get hooked on the thrill of being out on the water, and the gamble of coming back with either a boatload or empty-handed.
"This type of an occupation selects for a certain type of personality, and that kind of personality will not be happy in many other occupations other than fishing," Pollnac says. As a result, attempts to get fishermen to do something else — even something that pays better — often end in failure.
"There have been projects where they had vessel buyback programs, and almost 50 percent of the fishermen used that money to buy another boat to do another type of fishing, and in some cases get right back into fishing," Pollnac says.
The track record for international projects is poorly studied, which makes Walsh's research notable. Pollnac says he can't point to any great successes.
"A great deal of the international development money, I would argue, is wasted."
This problem is not lost on Craig Leisher at the Nature Conservancy. His organization does spend money to help fishermen seek other livelihoods. But does it keep them out of their boats?
"Well, no," he says. "It doesn't work to get them off the water. Rarely."
New Jobs Should Be On Water
He says the Nature Conservancy creates non-fishing jobs, but only as a tactic to help during a transition. For example, fishermen may need a temporary source of income when a new no-fishing zone is established. Fishermen lose their fishing income for a while — until fish populations in the no-fishing zone grow large enough to provide a new source of fish in the surrounding waters.
"What we have found with our research is that a lot of alternative income activities are not successful in the long term, so we look for activities that can benefit communities in the near term, just two or three years," Leisher says.
Which brings us back to the island nation of Kiribati. Walsh says she's trying to help the government figure out how to fix the problem of overfishing, which they'd accidentally made worse. Maybe, she says, the government can create new jobs out on the water by hiring the fishermen to patrol newly created nature preserves.
Aid organizations concerned about overfishing on tropical reefs often try to encourage fishermen out of their boats by offering them better-paying jobs on shore. But this strategy actually may make matters worse.
Fish Or Coconuts
Take, for example, the story of Kiribati, an island nation in the central Pacific. Kiribati (pronounced KIR-a-bahs) has a simple economy. People either catch fish, or they pick coconuts from their trees and produce coconut oil. Sheila Walsh, a postdoctoral researcher at Brown University, says most people do a bit of each.
The Kiribati government was concerned about overfishing. So it came up with a plan: It would subsidize the coconut oil industry.
"The thought was that by paying people more to do coconut agriculture, they would do less fishing," says Walsh. "And this would fulfill two goals: One, they would reduce overfishing; and two, people would be better off. They would have higher incomes."
It hit us like a bumper sticker saying -- a bad day fishing is better than a good day working. And that's sort of the story here.
- Sheila Walsh
Walsh wanted to know whether this plan was working, and the government invited her to study the issue. So, as part of her graduate work at the Scripps Institution of Oceanography, she flew to Kiribati to interview fishermen.
Coconut Subsidies Cause More Fishing
"And it turned out that, actually, the result of paying people more to do coconut agriculture was to increase fishing," she says. In fact, fishing increased by a startling 33 percent. The reef fish population dropped by an estimated 17 percent, putting the whole ecosystem at risk.
"It was a bit of a surprise, and we were wondering: What's going on here?"
The answer was simplicity itself. Walsh's study concludes that people earned more money making coconut oil, which meant they could work less to support themselves. And they spent their new leisure time fishing.
"It hit us like a bumper sticker saying — a bad day fishing is better than a good day working. And that's sort of the story here," Walsh says.
Fishing For Pleasure
It turns out she had stumbled into a universal truth about fishing. Fishermen aren't just in it for the money. Anthropologist Richard Pollnac of the University of Rhode Island says, just think of those snazzy sport-fishing excursions.
"People pay big money to go sports-fishing," he notes. There aren't very many occupations that people will actually pay money to do in their leisure time, he says.
So fishing as an occupation provides psychic benefits, as well as money. Pollnac argues that not just individuals but whole cultures get hooked on the thrill of being out on the water, and the gamble of coming back with either a boatload or empty-handed.
"This type of an occupation selects for a certain type of personality, and that kind of personality will not be happy in many other occupations other than fishing," Pollnac says. As a result, attempts to get fishermen to do something else — even something that pays better — often end in failure.
"There have been projects where they had vessel buyback programs, and almost 50 percent of the fishermen used that money to buy another boat to do another type of fishing, and in some cases get right back into fishing," Pollnac says.
The track record for international projects is poorly studied, which makes Walsh's research notable. Pollnac says he can't point to any great successes.
"A great deal of the international development money, I would argue, is wasted."
This problem is not lost on Craig Leisher at the Nature Conservancy. His organization does spend money to help fishermen seek other livelihoods. But does it keep them out of their boats?
"Well, no," he says. "It doesn't work to get them off the water. Rarely."
New Jobs Should Be On Water
He says the Nature Conservancy creates non-fishing jobs, but only as a tactic to help during a transition. For example, fishermen may need a temporary source of income when a new no-fishing zone is established. Fishermen lose their fishing income for a while — until fish populations in the no-fishing zone grow large enough to provide a new source of fish in the surrounding waters.
"What we have found with our research is that a lot of alternative income activities are not successful in the long term, so we look for activities that can benefit communities in the near term, just two or three years," Leisher says.
Which brings us back to the island nation of Kiribati. Walsh says she's trying to help the government figure out how to fix the problem of overfishing, which they'd accidentally made worse. Maybe, she says, the government can create new jobs out on the water by hiring the fishermen to patrol newly created nature preserves.
Wednesday, November 18, 2009
In all my life, I've never heard of the Tsingy
check out the full article at National Geographic
"There's a crazy landform in Madagascar called a tsingy, which, euphemistically translated from Malagasy, means "where one cannot walk barefoot." It's basically a treacherous forest of limestone spires that could impale anything, and cut straight through ropes and harnesses. It's one of the few places on Earth that, because of its remote location and dangerous landscape, has remained relatively unexplored. And it took National Geographic photographer Stephen Alvarez five days to reach it to shoot the story "Stone Forest" in November's magazine."
Friday, November 13, 2009
Fantastic Mr. FOXP2
credit to NYTimes
Of the 20,000 genes in the human genome, few are more fascinating than FOXP2, a gene that underlies the faculty of human speech.
All animals have an FOXP2 gene, but the human version’s product differs at just 2 of its 740 units from that of chimpanzees, suggesting that this tiny evolutionary fix may hold the key to why people can speak and chimps cannot.
FOXP2 came to light in a large London family, half of whose members have severe problems in articulating and understanding speech. All turned out to have a mutation that disrupted this vital gene.
This year, one inquiry bore fruit, although of a somewhat ambiguous nature, when biologists in Leipzig, Germany, genetically engineered a mouse with the human version of FOXP2 substituted for its own. The upgraded mice squeaked somewhat differently from plain mice and were born with subtle alterations in brain structure. But mice and people are rather distant cousins — their last common ancestor lived some 70 million years ago — and the human version of FOXP2 evidently was not able to exert a transformative effect on the mouse.
A scientific team led by Dr. Daniel H. Geschwind of the University of California, Los Angeles, has now completed a parallel experiment, which is to put the chimp version of FOXP2 into human neurons and see what happens. These were neurons living in laboratory glassware, not a human brain, so they gave a snapshot of FOXP2 only at the cellular level. But they confirmed suspicions that FOXP2 was a maestro of the genome.
The gene does not do a single thing but rather controls the activity of at least 116 other genes, Dr. Geschwind’s team says in the Thursday issue of Nature.
Like the conductor of an orchestra, the gene quiets the activity of some and summons a crescendo from others. Surprisingly, the chimp version of the gene had a more forceful effect in the human nerve cells than did the human version.
“The human FOXP2 seems to be acting on a more refined set of genes,” Dr. Geschwind said in an interview from London.
Several of the genes under FOXP2’s thumb show signs of having faced recent evolutionary pressure, meaning they were favored by natural selection. This suggests that the whole network of genes has evolved together in making language and speech a human faculty.
And some of the genes in FOXP2’s network have already been implicated in diseases that include disorders of speech, confirming its importance in these faculties.
But the FOXP2 network is certainly not the only set of genes involved in language. For one thing, FOXP2 is equally active on both sides of the human brain, whereas the language faculty is asymmetric, Dr. Geschwind said.
By studying the other genes in the FOXP2 network, Dr. Geschwind said, he hoped “to use FOXP2 as a lever to get a view of the molecular machinery in a biological language circuit.”
In a commentary on the new finding, Martin Dominguez and Dr. Pasko Rakic of Yale describe it as an important discovery that “provides a starting point for future studies of the molecular basis of language and human evolution.”
Of the 20,000 genes in the human genome, few are more fascinating than FOXP2, a gene that underlies the faculty of human speech.
All animals have an FOXP2 gene, but the human version’s product differs at just 2 of its 740 units from that of chimpanzees, suggesting that this tiny evolutionary fix may hold the key to why people can speak and chimps cannot.
FOXP2 came to light in a large London family, half of whose members have severe problems in articulating and understanding speech. All turned out to have a mutation that disrupted this vital gene.
This year, one inquiry bore fruit, although of a somewhat ambiguous nature, when biologists in Leipzig, Germany, genetically engineered a mouse with the human version of FOXP2 substituted for its own. The upgraded mice squeaked somewhat differently from plain mice and were born with subtle alterations in brain structure. But mice and people are rather distant cousins — their last common ancestor lived some 70 million years ago — and the human version of FOXP2 evidently was not able to exert a transformative effect on the mouse.
A scientific team led by Dr. Daniel H. Geschwind of the University of California, Los Angeles, has now completed a parallel experiment, which is to put the chimp version of FOXP2 into human neurons and see what happens. These were neurons living in laboratory glassware, not a human brain, so they gave a snapshot of FOXP2 only at the cellular level. But they confirmed suspicions that FOXP2 was a maestro of the genome.
The gene does not do a single thing but rather controls the activity of at least 116 other genes, Dr. Geschwind’s team says in the Thursday issue of Nature.
Like the conductor of an orchestra, the gene quiets the activity of some and summons a crescendo from others. Surprisingly, the chimp version of the gene had a more forceful effect in the human nerve cells than did the human version.
“The human FOXP2 seems to be acting on a more refined set of genes,” Dr. Geschwind said in an interview from London.
Several of the genes under FOXP2’s thumb show signs of having faced recent evolutionary pressure, meaning they were favored by natural selection. This suggests that the whole network of genes has evolved together in making language and speech a human faculty.
And some of the genes in FOXP2’s network have already been implicated in diseases that include disorders of speech, confirming its importance in these faculties.
But the FOXP2 network is certainly not the only set of genes involved in language. For one thing, FOXP2 is equally active on both sides of the human brain, whereas the language faculty is asymmetric, Dr. Geschwind said.
By studying the other genes in the FOXP2 network, Dr. Geschwind said, he hoped “to use FOXP2 as a lever to get a view of the molecular machinery in a biological language circuit.”
In a commentary on the new finding, Martin Dominguez and Dr. Pasko Rakic of Yale describe it as an important discovery that “provides a starting point for future studies of the molecular basis of language and human evolution.”
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