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Recalibrated Formula Eases Women’s Workouts
By TARA PARKER-POPE, The New York Times, July 5, 2010
If you are a woman who exercises, get ready to do some math.
Last week, researchers at Northwestern Medicine in Chicago announced a new formula for calculating a woman’s maximum heart rate, a measure commonly used by athletes to pace themselves and monitor their progress. In a study of nearly 5,500 healthy women, scientists discovered that a decades-old formula for calculating heart rate is largely inaccurate for women, resulting in a number that is too high.
The news may be a vindication to many women who have struggled to keep up with lofty target heart rates espoused by personal trainers and programmed into treadmill displays.
The commonly used formula subtracts a person’s age from 220. But based on the data collected in the Chicago study, the right formula for calculating a woman’s maximum heart rate is a little more complicated: 206 minus 88 percent of a woman’s age.
The findings are significant because many runners, cyclists and other exercisers obsessively monitor their heart rates by taking their pulse and rely on the old formula to gauge the intensity of the workout. The typical goal is to stay within 65 to 85 percent of the estimated maximum heart rate, depending on whether the athlete is trying to build aerobic capacity or increase endurance.
But the new study shows that for women, the number typically derived from the standard formula is far off the mark. Using the old formula of 220 minus age, a 40-year-old woman would achieve an average maximum heart rate of 180 beats per minute. That means her pulse should stay around 153 beats per minute during her workout to achieve a target heart rate of 85 percent.
But based on the new calculation, the same woman’s average maximum heart rate is 171 beats per minute, meaning her desired target heart rate is just 145 beats per minute, 8 beats a minute slower than under the old formula. Although the gap seems small on paper, it can be the difference between an exhilarating workout or a frustrating one that ends in exhaustion.
“There’s nothing wrong with achieving a higher heart rate with exercise, and if you can maintain that, it’s fine,” said Dr. Martha Gulati, a cardiologist and assistant professor of medicine and preventive medicine at Northwestern, who led the study. “But it might be that some women are getting tired and need to stop or slow down because they’re not able to maintain their heart rate at the higher level. But they’ve been using the wrong numbers.”
During the study, researchers collected maximum heart rate data from 5,437 healthy women, aged 35 to 93, who took part in treadmill tests during which they exercised as long and hard as they could until they had to stop. After following the women for 16 years, the researchers found a link between abnormal heart rate responses and higher risk for heart attack.
But the data also helped generate the new formula to calculate maximum heart rate. And it is important to remember that even this formula is based on averages, Dr. Gulati notes. Some women may find that the heart rate calculation is too low or still too high.
Michael Lauer, director of the division of cardiovascular sciences at the National Heart Lung and Blood Institute, called the work the “best study of exercise in asymptomatic women that we have.”
“We’ve always told people to use 220 minus age based on data in men,” said Dr. Lauer. “This new equation can give women a better estimate of what their peak heart rate ought to be.”
Of course, the new formula for women also raises new questions about the reliability of the old heart rate calculations for men. The original formula stems from research in the early 1970s that reviewed average maximum heart rates from 10 studies of men. The formula was a general calculation made for discussion purposes among academics, never intended to be used by the public.
However, the simplicity of the calculation appealed to a generation of exercisers who were looking for guidance about how hard to push themselves to improve fitness and improve their heart health. Companies promoting heart rate monitors, fitness clubs and family doctors all embraced the formula as a simple measure of fitness and the 220 minus age calculation became standard fitness advice.
But many researchers say it is ridiculous to base exercise goals on a person’s age rather than individual fitness level.
“The fitness industry, by attaching this to every treadmill ever made, kind of perpetuated this formula,” says Dr. Tim Church, an exercise researcher and director of preventive medicine at the Pennington Biomedical Research center in Baton Rouge, La. “There’s the idea that the formula was somehow not working out for women, but I’d make the argument that it doesn’t work out for anybody.”
In 2001, a University of Colorado team also concluded that the standard heart rate equation was inaccurate for both men and women. They devised a similar formula they said applied to both sexes — maximum heart rate equals 208 minus 0.7 times age — but the equation never caught on with the public.
Dr. Church says that except for elite athletes heart rate monitoring is not very useful and can distract from finding an exercise program you enjoy and will stick to. “Everyone kind of has their own natural pace,” Dr. Church says. “If you like to work a little harder, then work harder. If you like to work less hard but a little longer, then do that. Find what works for you.”
British Panel Clears Scientists
By JUSTIN GILLIS, The New York Times, July 7, 2010
A British panel on Wednesday exonerated the scientists caught up in the controversy known as Climategate of charges that they had manipulated their research to support preconceived ideas about global warming.
But the panel also rebuked the scientists for several aspects of their behavior, especially their reluctance to release computer files supporting their scientific work. And it declared that a chart they produced in 1999 about past climate was “misleading.”
The new report is the last in a series of investigations of leading British and American climate researchers, prompted by the release of a cache of e-mail messages that cast doubt on their conduct and raised fresh public controversy over the science of global warming.
All five investigations have come down largely on the side of the climate researchers, rejecting a number of criticisms raised by global-warming skeptics. Still, mainstream climate science has not emerged from the turmoil unscathed.
Some polls suggest that the recent controversy has eroded public support for action on climate change, complicating the politics of that issue in Washington and other world capitals. And leading climate researchers have come in for criticism of their deportment, of their episodic reluctance to share data with climate skeptics, and for not always responding well to critical analysis of their work.
“The e-mails don’t at all change the fundamental tenets of the science,” said Roger Pielke Jr., a professor of environmental studies at the University of Colorado. “But they changed the notion that people could blindly trust one authoritative group, when it turns out they’re just like everybody else.”
The researcher at the center of the controversy was Phil Jones, a leading climatologist who had headed the Climatic Research Unit of a British university, the University of East Anglia. He had stepped down temporarily pending results of the inquiry, but was reinstated on Wednesday to a job resembling his old one.
The university solicited and paid for the new report, which climate skeptics assailed. “This is another example of the establishment circling the wagons and defending their position,” said Myron Ebell, director of energy and climate change policy at the Competitive Enterprise Institute in Washington.
The Climatic Research Unit, often referred to as C.R.U., has played a leading role in efforts to understand the earth’s past climate. Embarrassing e-mail messages sent by Dr. Jones and other scientists were purloined from a computer at the university in November and posted to the Internet, prompting a round of accusations.
Some of the scientists were forced to admit to poor behavior, such as chortling about the death of one climate skeptic. But were the researchers guilty of any scientific misconduct?
“On the specific allegations made against the behavior of C.R.U. scientists, we find that their rigor and honesty as scientists are not in doubt,” said the new report, led by Muir Russell, a retired British civil servant and educator.
The University of East Anglia welcomed the findings on Wednesday, declaring that an unjust attack on its scientists had been found spurious. Dr. Jones — who had said he considered suicide after the e-mail messages emerged — issued a more muted statement, saying he needed time to reflect. “We have maintained all along that our science is honest and sound, and this has been vindicated now by three different independent external bodies,” Dr. Jones said.
Last week, the second of two reviews at Pennsylvania State University exonerated Michael Mann, a scientist there who was also a focus of the controversy.
The latest report was by no means a complete vindication. Echoing the findings of an earlier report by a parliamentary committee in London, the reviewers criticized the scientists at the Climatic Research Unit for consistently “failing to display the proper degree of openness” in responding to demands for backup data and other information under Britain’s public-record laws.
On one of the most serious issues raised by the e-mail messages, the Russell panel did find some cause for complaint, but it did not issue the robust condemnation sought by climate skeptics.
The issue involved a graphic for a 1999 United Nations report, comparing recent temperatures with those of the past. Dr. Jones wrote an e-mail message saying he had used a “trick” to “hide” a problem in the data. After the e-mail messages came out, Dr. Jones said he had meant “trick” only in the sense of a clever maneuver.
The Russell panel concluded that the data procedure he used was acceptable in principle, but should have been described more fully, and his failure to do so had produced a “misleading” graphic.
The issue involved an effort to reconstruct the climate history of the past several thousand years using indirect indicators like the size of tree rings and the growth rate of corals. The C.R.U. researchers, leaders in that type of work, were trying in 1999 to produce a long-term temperature chart that could be used in a United Nations publication.
But they were dogged by a problem: Since around 1960, for mysterious reasons, trees have stopped responding to temperature increases in the same way they apparently did in previous centuries. If plotted on a chart, tree rings from 1960 forward appear to show declining temperatures, something that scientists know from thermometer readings is not accurate.
Most scientific papers have dealt with this problem by ending their charts in 1960 or by grafting modern thermometer measurements onto the historical reconstructions.
In the 1999 chart, the C.R.U. researchers chose the latter course for one especially significant line on their graph. This technique was what Dr. Jones characterized as a “trick.”
The recent season of controversy included close scrutiny of the Intergovernmental Panel on Climate Change, the United Nations body that produces a major review of climate science every few years.
The Russell panel found little reason to question the advice that the British scientists had given to the climate panel, or the conclusions of that body. The panel declared in 2007 that the earth was warming and that human activity was the major reason.
However, small errors in the 2007 report keep coming to light. A review issued earlier this week by the Netherlands Environmental Assessment Agency found several, including a case in which the panel overstated the potential impact of global warming on fish catches.
The Netherlands agency also found that the climate change panel had tended to emphasize the negative effects of global warming while playing down positive ones, like greater tree growth in northern climates. It recommended better balance and a greater emphasis on fact-checking.
“The idea that these things could be perfect is a fallacy,” said Gavin Schmidt, a climate researcher at Columbia University. Christopher B. Field, an ecologist at the Carnegie Institution for Science and a leader in the United Nations climate body, said he foresaw an opportunity “to really do a better job in characterizing what we know and what we don’t know” in the group’s next report, due in 2014.
Yet another evaluation of the panel’s work is under way, with results due in August.
Dr. Pielke, who is largely persuaded by the mainstream consensus on climate change, has criticized both climate skeptics and the scientific community for the tone of their debate.
“It has been dominated for a number of years by people at the poles — the most activist scientists emphasizing alarm, versus the most ardent skeptics saying we don’t have to do anything,” Dr. Pielke said. “This recent controversy has opened the eyes of a lot of people to a much richer tapestry of views on climate policy that are out there, which I think is a good thing.”
Clues of Britain’s First Humans
By NICHOLAS WADE, The New York Times, 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.
By TARA PARKER-POPE, The New York Times, July 5, 2010
If you are a woman who exercises, get ready to do some math.
Last week, researchers at Northwestern Medicine in Chicago announced a new formula for calculating a woman’s maximum heart rate, a measure commonly used by athletes to pace themselves and monitor their progress. In a study of nearly 5,500 healthy women, scientists discovered that a decades-old formula for calculating heart rate is largely inaccurate for women, resulting in a number that is too high.
The news may be a vindication to many women who have struggled to keep up with lofty target heart rates espoused by personal trainers and programmed into treadmill displays.
The commonly used formula subtracts a person’s age from 220. But based on the data collected in the Chicago study, the right formula for calculating a woman’s maximum heart rate is a little more complicated: 206 minus 88 percent of a woman’s age.
The findings are significant because many runners, cyclists and other exercisers obsessively monitor their heart rates by taking their pulse and rely on the old formula to gauge the intensity of the workout. The typical goal is to stay within 65 to 85 percent of the estimated maximum heart rate, depending on whether the athlete is trying to build aerobic capacity or increase endurance.
But the new study shows that for women, the number typically derived from the standard formula is far off the mark. Using the old formula of 220 minus age, a 40-year-old woman would achieve an average maximum heart rate of 180 beats per minute. That means her pulse should stay around 153 beats per minute during her workout to achieve a target heart rate of 85 percent.
But based on the new calculation, the same woman’s average maximum heart rate is 171 beats per minute, meaning her desired target heart rate is just 145 beats per minute, 8 beats a minute slower than under the old formula. Although the gap seems small on paper, it can be the difference between an exhilarating workout or a frustrating one that ends in exhaustion.
“There’s nothing wrong with achieving a higher heart rate with exercise, and if you can maintain that, it’s fine,” said Dr. Martha Gulati, a cardiologist and assistant professor of medicine and preventive medicine at Northwestern, who led the study. “But it might be that some women are getting tired and need to stop or slow down because they’re not able to maintain their heart rate at the higher level. But they’ve been using the wrong numbers.”
During the study, researchers collected maximum heart rate data from 5,437 healthy women, aged 35 to 93, who took part in treadmill tests during which they exercised as long and hard as they could until they had to stop. After following the women for 16 years, the researchers found a link between abnormal heart rate responses and higher risk for heart attack.
But the data also helped generate the new formula to calculate maximum heart rate. And it is important to remember that even this formula is based on averages, Dr. Gulati notes. Some women may find that the heart rate calculation is too low or still too high.
Michael Lauer, director of the division of cardiovascular sciences at the National Heart Lung and Blood Institute, called the work the “best study of exercise in asymptomatic women that we have.”
“We’ve always told people to use 220 minus age based on data in men,” said Dr. Lauer. “This new equation can give women a better estimate of what their peak heart rate ought to be.”
Of course, the new formula for women also raises new questions about the reliability of the old heart rate calculations for men. The original formula stems from research in the early 1970s that reviewed average maximum heart rates from 10 studies of men. The formula was a general calculation made for discussion purposes among academics, never intended to be used by the public.
However, the simplicity of the calculation appealed to a generation of exercisers who were looking for guidance about how hard to push themselves to improve fitness and improve their heart health. Companies promoting heart rate monitors, fitness clubs and family doctors all embraced the formula as a simple measure of fitness and the 220 minus age calculation became standard fitness advice.
But many researchers say it is ridiculous to base exercise goals on a person’s age rather than individual fitness level.
“The fitness industry, by attaching this to every treadmill ever made, kind of perpetuated this formula,” says Dr. Tim Church, an exercise researcher and director of preventive medicine at the Pennington Biomedical Research center in Baton Rouge, La. “There’s the idea that the formula was somehow not working out for women, but I’d make the argument that it doesn’t work out for anybody.”
In 2001, a University of Colorado team also concluded that the standard heart rate equation was inaccurate for both men and women. They devised a similar formula they said applied to both sexes — maximum heart rate equals 208 minus 0.7 times age — but the equation never caught on with the public.
Dr. Church says that except for elite athletes heart rate monitoring is not very useful and can distract from finding an exercise program you enjoy and will stick to. “Everyone kind of has their own natural pace,” Dr. Church says. “If you like to work a little harder, then work harder. If you like to work less hard but a little longer, then do that. Find what works for you.”
British Panel Clears Scientists
By JUSTIN GILLIS, The New York Times, July 7, 2010
A British panel on Wednesday exonerated the scientists caught up in the controversy known as Climategate of charges that they had manipulated their research to support preconceived ideas about global warming.
But the panel also rebuked the scientists for several aspects of their behavior, especially their reluctance to release computer files supporting their scientific work. And it declared that a chart they produced in 1999 about past climate was “misleading.”
The new report is the last in a series of investigations of leading British and American climate researchers, prompted by the release of a cache of e-mail messages that cast doubt on their conduct and raised fresh public controversy over the science of global warming.
All five investigations have come down largely on the side of the climate researchers, rejecting a number of criticisms raised by global-warming skeptics. Still, mainstream climate science has not emerged from the turmoil unscathed.
Some polls suggest that the recent controversy has eroded public support for action on climate change, complicating the politics of that issue in Washington and other world capitals. And leading climate researchers have come in for criticism of their deportment, of their episodic reluctance to share data with climate skeptics, and for not always responding well to critical analysis of their work.
“The e-mails don’t at all change the fundamental tenets of the science,” said Roger Pielke Jr., a professor of environmental studies at the University of Colorado. “But they changed the notion that people could blindly trust one authoritative group, when it turns out they’re just like everybody else.”
The researcher at the center of the controversy was Phil Jones, a leading climatologist who had headed the Climatic Research Unit of a British university, the University of East Anglia. He had stepped down temporarily pending results of the inquiry, but was reinstated on Wednesday to a job resembling his old one.
The university solicited and paid for the new report, which climate skeptics assailed. “This is another example of the establishment circling the wagons and defending their position,” said Myron Ebell, director of energy and climate change policy at the Competitive Enterprise Institute in Washington.
The Climatic Research Unit, often referred to as C.R.U., has played a leading role in efforts to understand the earth’s past climate. Embarrassing e-mail messages sent by Dr. Jones and other scientists were purloined from a computer at the university in November and posted to the Internet, prompting a round of accusations.
Some of the scientists were forced to admit to poor behavior, such as chortling about the death of one climate skeptic. But were the researchers guilty of any scientific misconduct?
“On the specific allegations made against the behavior of C.R.U. scientists, we find that their rigor and honesty as scientists are not in doubt,” said the new report, led by Muir Russell, a retired British civil servant and educator.
The University of East Anglia welcomed the findings on Wednesday, declaring that an unjust attack on its scientists had been found spurious. Dr. Jones — who had said he considered suicide after the e-mail messages emerged — issued a more muted statement, saying he needed time to reflect. “We have maintained all along that our science is honest and sound, and this has been vindicated now by three different independent external bodies,” Dr. Jones said.
Last week, the second of two reviews at Pennsylvania State University exonerated Michael Mann, a scientist there who was also a focus of the controversy.
The latest report was by no means a complete vindication. Echoing the findings of an earlier report by a parliamentary committee in London, the reviewers criticized the scientists at the Climatic Research Unit for consistently “failing to display the proper degree of openness” in responding to demands for backup data and other information under Britain’s public-record laws.
On one of the most serious issues raised by the e-mail messages, the Russell panel did find some cause for complaint, but it did not issue the robust condemnation sought by climate skeptics.
The issue involved a graphic for a 1999 United Nations report, comparing recent temperatures with those of the past. Dr. Jones wrote an e-mail message saying he had used a “trick” to “hide” a problem in the data. After the e-mail messages came out, Dr. Jones said he had meant “trick” only in the sense of a clever maneuver.
The Russell panel concluded that the data procedure he used was acceptable in principle, but should have been described more fully, and his failure to do so had produced a “misleading” graphic.
The issue involved an effort to reconstruct the climate history of the past several thousand years using indirect indicators like the size of tree rings and the growth rate of corals. The C.R.U. researchers, leaders in that type of work, were trying in 1999 to produce a long-term temperature chart that could be used in a United Nations publication.
But they were dogged by a problem: Since around 1960, for mysterious reasons, trees have stopped responding to temperature increases in the same way they apparently did in previous centuries. If plotted on a chart, tree rings from 1960 forward appear to show declining temperatures, something that scientists know from thermometer readings is not accurate.
Most scientific papers have dealt with this problem by ending their charts in 1960 or by grafting modern thermometer measurements onto the historical reconstructions.
In the 1999 chart, the C.R.U. researchers chose the latter course for one especially significant line on their graph. This technique was what Dr. Jones characterized as a “trick.”
The recent season of controversy included close scrutiny of the Intergovernmental Panel on Climate Change, the United Nations body that produces a major review of climate science every few years.
The Russell panel found little reason to question the advice that the British scientists had given to the climate panel, or the conclusions of that body. The panel declared in 2007 that the earth was warming and that human activity was the major reason.
However, small errors in the 2007 report keep coming to light. A review issued earlier this week by the Netherlands Environmental Assessment Agency found several, including a case in which the panel overstated the potential impact of global warming on fish catches.
The Netherlands agency also found that the climate change panel had tended to emphasize the negative effects of global warming while playing down positive ones, like greater tree growth in northern climates. It recommended better balance and a greater emphasis on fact-checking.
“The idea that these things could be perfect is a fallacy,” said Gavin Schmidt, a climate researcher at Columbia University. Christopher B. Field, an ecologist at the Carnegie Institution for Science and a leader in the United Nations climate body, said he foresaw an opportunity “to really do a better job in characterizing what we know and what we don’t know” in the group’s next report, due in 2014.
Yet another evaluation of the panel’s work is under way, with results due in August.
Dr. Pielke, who is largely persuaded by the mainstream consensus on climate change, has criticized both climate skeptics and the scientific community for the tone of their debate.
“It has been dominated for a number of years by people at the poles — the most activist scientists emphasizing alarm, versus the most ardent skeptics saying we don’t have to do anything,” Dr. Pielke said. “This recent controversy has opened the eyes of a lot of people to a much richer tapestry of views on climate policy that are out there, which I think is a good thing.”
Clues of Britain’s First Humans
By NICHOLAS WADE, The New York Times, 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.
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no subject
Date: 2010-07-08 03:10 pm (UTC)no subject
Date: 2010-07-08 05:35 pm (UTC)bodies. they are so weird.