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Lost in a Million-Year Gap, Solid Clues to Human Origins
By JOHN NOBLE WILFORD, The New York Times, September 18, 2007
Sometimes the maturity of a field of science can be measured by the heft of its ambition in the face of the next daunting unknown, the mystery yet to be cracked.
Neurobiology probes the circuitry of the brain for the secrets of behaviors and thoughts that make humans human. High-energy physics seeks and may be on the verge of finding the so-called God particle, the Higgs boson thought to endow elementary particles with their mass. Cosmology is confounded by dark matter and dark energy, the pervasive but unidentified stuff that shapes the universe and accelerates its expansion.
In the study of human origins, paleoanthropology stares in frustration back to a dark age from three million to less than two million years ago. The missing mass in this case is the unfound fossils to document just when and under what circumstances our own genus Homo emerged.
The origin of Homo is one of the most intriguing and intractable mysteries in human evolution. New findings only remind scientists that answers to so many of their questions about early Homo probably lie buried in the million-year dark age.
It is known that primitive hominids — human ancestors and their close kin — walked upright across the plains of Africa at this time. They were presumably larger members of the genus Australopithecus, the best known of which was the Lucy species, Australopithecus afarensis, that had thrived up to three million years ago.
At about 2.6 million years ago, some clever hominids were knapping stone tools. Then, or some time later, scientists suspect, the first Homo appeared, but there is no confirmed evidence of this step.
Subsequent finds, from a time beginning after 1.9 million years ago, revealed an early Homo identified as Homo habilis, the “handy man,” a species with a somewhat larger brain and a more humanlike face, teeth and stature than the apelike australopithecines.
Habilis was generally accorded an important place as the first of the genus, preceding the more advanced Homo erectus and, ultimately, modern humans — Homo sapiens. But certainty has been elusive. A report last month in the journal Nature renewed debate over the habilis’s place in human evolution.
William H. Kimbel, a paleoanthropologist at the Institute of Human Origins at Arizona State University, said that the million-year period “has long been the source of frustrating gaps” in the hominid fossil record. “It’s not that sites containing rocks this age are particularly rare, or that the time period in eastern Africa has not been searched by several groups,” Dr. Kimbel said. “The problem is that the fossil yield has thus far been low or poorly preserved, compared to the time periods on either side of this interval.”
A succession of recent discoveries has extended evidence of hominids reaching back from three million to beyond six million years ago, close to the estimated time of the divergence of the human and chimpanzee lineages. The hominid trail from two million years forward has been fairly well worked, by fossil hunters as well as geneticists and archaeologists tracking migrations out of Africa and across Eurasia. Researchers have determined that anatomically modern Homo sapiens emerged in Africa less than 200,000 years ago.
G. Philip Rightmire, a specialist in habilis and erectus research at Harvard, said searches into the mystery period had yielded mostly the remains of various species of Australopithecus, the genus that came to a dead end around one million years ago.
Bones were found in 2.5-million-year-old sediments associated with some of the earliest known stone tools, used to butcher animals. A coincidence, or evidence of the first toolmaking species? Hard to tell.
A skull and other fossils, uncovered by a team led by the Ethiopian anthropologist Berhane Asfaw, were named the new species Australopithecus garhi. The researchers said the specimen had the projecting apelike face, small braincase and limb bones suggesting descent from the much earlier Lucy species. But if this was a candidate ancestor of early Homo, “a lot of evolution had to take place rather quickly” to complete the transition, a scientist said at the time.
With one possible exception, no fossils that are conclusively Homo have appeared in that period, Dr. Rightmire said. “That suggests there was not much Homo around then,” he said.
Nevertheless, Tim D. White of the University of California, Berkeley, one of the most experienced hunters of hominid fossils, said that his teams and several others were “pushing hard” to explore sites in Ethiopia and Kenya that may produce evidence of earlier Homo origins. Prospects are uncertain. Some prominent sites of previous hominid discoveries are underlain with lava flows and other geological barriers to digging into the deeper past.
At present, most paleoanthropologists think a solitary upper jaw represents the likeliest candidate for a Homo from that period. The find, reported in 1996 by a team led by Dr. Kimbel, was made in the Hadar badlands of Ethiopia, near the site of the much earlier Lucy skeleton and on a surface with a scattering of stone tools. The 2.3-million-year-old jaw was tentatively assigned to the genus Homo.
Dr. Kimbel remains cautious. “The Hadar jaw could represent a population of early Homo that was specifically in the ancestry of habilis,” he said. “Or it could represent a stem population from which ultimately descended all of the Homo species currently known from after two million years ago.”
Alan Walker, a professor of biological anthropology at Pennsylvania State University who studies hominid anatomy, agreed that the jaw was apparently “the earliest direct evidence” of Homo. It shows that the individual had the short face and squared-off palate of Homo, but with teeth that were larger and more primitive. The only other traces of possible Homo presence before two million years ago are some loose teeth from the Omo basin in Ethiopia and some fossil fragments from Kenya and Malawi. The recent Nature report on two new fossils, a 1.44-million-year-old habilis and a 1.55-million-year-old erectus, underscored the uncertainties about early Homo, even after the dark age.
The lead authors, Fred Spoor of University College London and Meave G. Leakey of the National Museums of Kenya, emphasized in the article and in a news release that their findings challenged the view that habilis and erectus evolved one after the other in a linear succession. Their research showed that the two overlapped for almost half a million years and, as they speculated to the media, both species could have had their origins well before two million years ago, possibly from a common ancestor.
Eric Delson, a paleoanthropologist at the American Museum of Natural History and the City University of New York, said that was possible. “It’s always difficult to know what is the earliest specimen of any lineage,” Dr. Delson added. “One always finds something older and older.”
A significant insight from the report, he said, may be the recognition that “there’s more diversity of species in this time period than we expected.”
Several scientists, notably Dr. White of Berkeley, took issue with the interpretation seeming to imply that evidence for the two species overlapping in time and exhibiting variable sizes was new. That, he said, had been recognized for a couple of decades.
Dr. Kimbel, who was not involved in the new research, defended the authors, saying that they had not “meant to imply that habilis could not have been ancestral to erectus, presumably on the basis of their being contemporaneous at Turkana,” the site in Kenya where the fossils were found.
Susan C. Anton, an anthropologist at New York University who was a member of the Spoor-Leakey team, said, “My money is still on habilis as the potential ancestor, but there is a lot of room for additional knowledge, given the dearth of fossils.”
Other scientists tended to agree but noted that habilis had been clouded with doubt. The first habilis fossils were collected in the early 1960s in the Olduvai Gorge of Tanzania by Louis Leakey, patriarch of the fossil-hunting family and Meave Leakey’s father-in-law.
Is habilis really one, two, possibly three species? Some scientists are not sure. Did erectus descend from habilis in a single, unbroken lineage, a process called anagenesis? “This is the only option that is no longer on the table,” Dr. Anton said.
Other experts agree that anagenesis has been refuted by recent evidence that erectus and habilis co-existed for a long time in East Africa, although perhaps in separate ecological niches. So could erectus and habilis have sprung from a much earlier common ancestor? No one can say there were no intermediate Homo species before habilis, back in the dark age. Or perhaps some habilis members left Africa earlier and, after an isolation that favors rapid evolutionary change, returned to Africa as erectus, living side by side with the habilis population that had remained behind.
A hominid site far from Africa has thus taken on new significance. In the 1990s, scientists turned up Homo fossils at the village of Dmanisi, in the republic of Georgia. The craniums, resembling fossils from Kenya, confirmed the presence of erectus on the fringes of Europe at least 1.7 million years ago.
The puzzle is, the Dmanisi fossils look like erectus, but are very small, like habilis. A few researchers raise the possibility that a population of habilis evolved into erectus outside Africa, perhaps in or near Georgia.
“There’s nothing to rule out the idea that habilis-like creatures moved into Eurasia prior to 1.8 million years,” said Dr. Rightmire of Harvard. “They may have given rise to erectus, as we see at Dmanisi, and then erectus moved back, joining the surviving habilis there.”
A new report, to be published Thursday in Nature, will review more skeletal evidence of the transitional aspects of the Dmanisi specimens.
But Dr. Anton said the Dmanisi remains were important as examples of size variability within the erectus species and its adaptations to local environments, not for “any special tie to earliest Homo, such as habilis.”
Writing in the Annual Review of Anthropology in 2004, Dr. Anton and Carl C. Swisher III, a geologist at Rutgers University, concluded that the relationships among erectus and various possible nonerectus Homo groups in Africa “currently are quite muddled and require substantial revisitations.”
Even if the mystery of the origins of the genus Homo is a sign of paleoanthropology’s maturing reach into the deep past, it still leaves the redrawing of the human family tree very much a work in progress. Daniel E. Lieberman, a paleoanthropologist at Harvard, said that filling in the tree matters to scientists, and not only out of innate curiosity about human ancestry.
“At a basic level, one wants to know when and where transformations occurred so one can put them into their appropriate evolutionary context,” Dr. Lieberman said.
He said that that could reveal the dietary and environmental causes of species change, leading eventually to modern humans with the ambition to find their origins.
Dr. Lieberman said that he and colleagues “are relentlessly optimistic that we have all the information we need to answer our big questions, but just haven’t figured out the order in which to connect the dots.”
But the real problem, he added, with resignation tempering optimism, “is that the fossil record doesn’t have enough dots.”
Scientist at Work | Phung Tuu Boi: Through the Forest, a Clearer View of the Needs of a People
By CHRISTIE ASCHWANDEN, The New York Times, September 18, 2007
A LUOI VALLEY, Vietnam — Phung Tuu Boi reaches down to inspect one of the spiny shrubs lined up in a row before him. A few feet away, a cow grazes serenely in this emerald valley in the hills of central Vietnam.
Mr. Boi, a forester and director of the Center for Assistance in Nature Conservation and Community Development in Hanoi, points to the cow. “See this?” he says. “Very, very bad.”
An invisible poison clings to the soil beneath the cow’s muddy hoofs. During a short stretch of the Vietnam War this patch of ground served as an American Special Forces air base, and while the soldiers departed long ago, a potent dioxin from the Agent Orange that they stored and sprayed here lingers still.
Mr. Boi, a lively, passionate man whose enormous smile rarely leaves his face, has dedicated his career to repairing the ecological damage left by what people here call the American War. And while he has had much success in the last 30 years, his task is far from over.
When Mr. Boi began working here in 1975, he found an ecosystem decimated by war. Aerial spraying of defoliants like Agent Orange had destroyed large swaths of forest. Without live roots to anchor the soil, monsoon rains washed away the topsoil and its nutrients, allowing invasive grasses to take over and prevent forest regeneration.
A botanist by training, Mr. Boi’s initial goal was to reforest the denuded land. But he soon realized the forest ecosystem was not the only thing struggling to recover from Agent Orange.
The Pako, Ta Oi, Catu and Kinh people of A Luoi valley (called A Shau during the war) eke out a meager existence in a region with one of Vietnam’s shortest growing seasons. (This reporter visited the valley on a grant from the Pulitzer Center on Crisis Reporting.) These tribal groups, who live in one-room huts with dirt floors and no indoor plumbing, depend on forest products to survive, and Mr. Boi came to recognize that his work was as vital to them as to the tigers and elephants whose habitat he was working to restore.
Mr. Boi enlisted the help of the Australian acacia tree. The acacia grows up to six and a half feet per year and, after five years, can be harvested to make paper and furniture. The tree also improves the soil and quickly provides the canopy that trees need to take root.
“It’s a good model for forest restoration,” said Chris Dickinson, a conservation biologist and technical adviser with the World Wildlife Fund for Nature in Hue, Vietnam, adding that the acacia “grows on poor nutrients and can shade out the grasses.”
The trees also provide residents with a cash crop. “The demand for acacia is seemingly insatiable,” Dr. Dickinson said. “Ikea uses it for garden furniture.”
Mr. Boi has used this humble acacia tree to reforest thousands of hectares in central Vietnam. Emboldened by these successes, he has applied his botanical model of remediation to tackle a far more difficult problem.
Though dioxin has dropped to relatively low levels in areas that were aerially sprayed during the war, studies by Canadian scientists have shown that numerous highly contaminated spots remain at certain places where American forces stored Agent Orange.
The cow that caught Mr. Boi’s attention grazes on one such “hot spot,” the former A So air base in Dong Son, where scientists from Hatfield Consultants in Vancouver, British Columbia, have measured soil levels of TCDD, the dioxin in Agent Orange, more than 200 times greater than the residential standard set forth by the United States Environmental Protection Agency.
Dioxin takes decades to break down. Remediating this site would require millions of dollars, and when it comes to financing, the more heavily populated hot spots in Danang and Bien Hoa take precedence.
If the Dong Son hot spot were in New Jersey or Florida, a barbed wire fence and a warning might be enough to deter people from entering the area, but such solutions break down in the face of extreme poverty. “You put up a fence, and the people are so poor that anything they can get their hands on, they’ll take down and use,” said Wayne Dwernychuk, an environmental scientist who did studies for Hatfield Consultants.
“Their economy is geared to agriculture,” Dr. Dwernychuk said. “If you take that land out of the production cycle, it’s very hard to rationalize to them when they don’t see the problem.”
He added that the chemical that taints this soil could not be seen, smelled or tasted.
Pointing to the former air base’s most contaminated site, Mr. Boi said: “The local people are poor and uneducated, and they don’t understand. Children come here to play and they collect insects and other things to eat.”
Dioxin accumulates in animal fats, and the molecules also glom onto soil particles that can be ingested through inadequately washed root crops like manioc. Poor sanitation and a diet that relies on fowl that peck on tainted soil keep dioxin exposure a constant threat. Dr. Dwernychuk and his colleagues have found elevated TCDD levels in the blood and breast milk of local residents, evidence that the chemical continues to make its way into the food chain.
Nguyen Van Phom, the mayor of Dong Son, blames dioxin for the health problems he says plague 60 of the 240 families in the village. Whether these conditions, which include limb deformities and deafness, are the result of dioxin remains unproved, though the Institute of Medicine at the National Academy of Sciences has linked Agent Orange exposure in American veterans to an increased risk of some health problems, including cancer and diabetes.
The Canadian studies prompted the Vietnamese government to move more than two dozen families off the most contaminated ground, but efforts to educate residents about the risks have proved difficult. Most cannot read and many speak only faltering Vietnamese, relying instead on tribal dialects.
Mr. Boi has developed a low-tech solution to overcome these problems: a fence made of trees covered with cactus-sharp needles to deter humans and animals alike. Mr. Boi hopes this so-called green fence will not only discourage trespassers, but also provide them with an economic incentive to leave the barrier intact. Once mature, the trees he has chosen to make up the fence, Gleditschia australis, produce a fruit that residents can sell to make soaps and medicinals. Gleditschia, a type of honey locust, is disease and insect resistant, and its thorns and soft wood should deter residents from cutting it down for firewood.
The green fence promises a workable solution to a costly problem, said William H. Farland, a former scientist with the Environmental Protection Agency who is vice president for research at Colorado State University. “It’s very expensive to clean dioxin up to background levels,” Dr. Farland said. “The main issue is to prevent human exposure, not just to clean up the soils.”
While a full remediation project would cost millions of dollars, Mr. Boi estimated that his project could be done for just $30,000. Last December, with the help of a $10,000 grant from the World Bank and the aid of about a dozen farmers, Mr. Boi planted the first 10,000 seeding trees. But despite its auspicious start, the project has hit a few snags.
Though hardy, the locust trees failed to thrive in soil stripped of its nutrients by rains that followed defoliation decades ago, and a spate of intense storms flooded the site shortly after planting, drowning many of the seedlings. With their thorns still small, the trees that survived made attractive food for wandering livestock. Today, only a single row of small trees remain.
In the face of these challenges, no one would fault Mr. Boi for returning to his comfortable office in Hanoi and moving on to something else. But he views this setback as nothing more than a necessary learning experience. With the lessons gleaned from his initial failure, he has developed a new plan.
Before his next round of planting, Mr. Boi will bolster the soil with fertilizers. Then he will plant larger seedlings, and in addition to the original locust fence, he will add rows of acacia on either side to create a three-layer fence. The acacia will help protect the locust trees, improve the soil and provide another cash crop for residents, Mr. Boi says, pointing to a photo schemata of the fence that he carries with him everywhere, sharing with anyone who will listen.
Mr. Boi needs $20,000 more to finish the fence. He has received no government financing and has resorted to spending his own money to keep the project alive. But Mr. Boi refuses to give up, even if it means digging deeper into his own pockets. Success is his only option. If he gives up on this project, the cows will continue to graze on tainted soil, and another generation of children will grow up eating insects caked with dioxin-rich dirt.
From Ozone Success, a Potential Climate Model
By ANDREW C. REVKIN, The New York Times, September 18, 2007
In 1985, scientists studying the air over Antarctica stumbled on a gaping breach in the billion-year-old atmospheric radiation shield that makes Earth’s surface habitable.
The discovery of a seasonal “hole” in this veil of ozone molecules was so unexpected — “the surprise of the century,” one chemist later called it — that it was presumed to be a data glitch.
It wasn’t. Soon other experts found a connection between the ozone hole and the use of chlorofluorocarbons, or CFCs, and similar synthetic chemicals in solvents, refrigeration, sprays and the like.
The chemical threat to the ozone layer had been identified in 1974, and industries and governments were planning to shift to safer substitutes. But it took the ozone hole, glaring from satellite images like a purple bruise, to make eliminating such chemicals a global imperative. On Sept. 16, 1987, an initial batch of countries signed the Montreal Protocol, a treaty that has since grown and led to bans on 95 percent of the ozone-eating compounds.
On Sunday, diplomats, scientists and environmentalists gathered in Montreal to celebrate the 20th anniversary of the treaty and to spend a week discussing possible new steps to speed an end to remaining ozone threats.
Many are using the anniversary to bolster the idea that a similar success can be achieved with carbon dioxide and other heat-trapping greenhouse gases linked to global warming (including some of the ozone-destroying chemicals and some of the replacements for them). Fresh international climate talks begin at the United Nations on Monday and at a meeting in Washington organized by the White House late next week. Some veterans of both the ozone and climate fights insist that the Montreal success is a model for climate action.
“The lesson from Montreal is that curbing global warming will not be as hard as it looks,” said David D. Doniger, an early campaigner against ozone-damaging chemicals for the Natural Resources Defense Council who now directs the group’s climate work.
But many experts on the circumstances — scientific, diplomatic and economic — surrounding the 1987 treaty signing say that while some things are similar now, like the looming environmental risks revealed by evolving science, almost everything else is very different.
Ozone molecules, tenuous trios of oxygen atoms, serve as a planetary sun block of sorts, limiting the bombardment of the Earth’s surface by ultraviolet radiation that can cause skin cancers and cataracts, and harm some plants and animals.
When F. Sherwood Rowland and Mario J. Molina first posited in 1974 that CFCs and similar chemicals could waft to the stratosphere and break up ozone, the threat quickly captured public attention.
In 1977, long before the climate disaster movie “The Day After Tomorrow,” Hollywood released “Day of the Animals,” in which ozone destruction caused wildlife to run amok.
But it was cancer that really brought the issue home, said Susan Solomon, a senior scientist with the National Oceanic and Atmospheric Administration who in 1986 led work linking CFCs and related chemicals to polar ozone losses. “Skin cancer is deeply personal, and virtually every person on the planet has either known someone who has had cancer or had it themselves,” Dr. Solomon said.
The risks from global warming are far different, said Dr. Solomon, who was the co-leader of the latest scientific report by the Intergovernmental Panel on Climate Change. “It is much less personal for most people, except perhaps if you’re in places like Vanuatu,” she said, referring to one of several low-lying island nations threatened by rising seas. “It’s mostly beyond our generation.”
In the 1980s, despite persistent scientific uncertainties over the threat to the ozone layer, action to move away from ozone-damaging chemicals was swift, largely because there was little cost involved and alternatives were developed as the need arose, experts said.
To preserve the ozone shield, the United States, joined soon by Canada and Scandinavian countries, banned “nonessential” uses of CFCs — hair sprays, for example — in 1978, just three years after the theory was first described in the journal Nature.
The Natural Resources Defense Council, seizing on an opening left by a proposed rule to limit CFCs that was written in the last days of the Carter administration, filed a lawsuit in 1984 that prompted the Environmental Protection Agency to seek broader bans. The domestic action helped set the stage for treaty talks.
“That N.R.D.C. suit was critical because it turned the burden of proof around from having to show there was a problem to proving there was not,” said Roger A. Pielke Jr., a political scientist at the University of Colorado, Boulder.
Still, $135 billion worth of air conditioners and other equipment in the United States, and billions more around the world, relied on the old chemicals, and the science remained murky. So DuPont and other companies waited to seek alternatives, according to company scientists.
In 1985, the murk cleared somewhat. An international scientific assessment of CFCs and ozone created a near-worldwide consensus that the risks of allowing the long-lived chemicals to keep building in the atmosphere were unacceptable.
DuPont, while gaining less than 2 percent of its revenues from such compounds, saw a need to find substitutes and the prospect of new markets, and began a $500 million research effort that spawned a suite of alternatives.
With global warming, in contrast, economists and climate experts say it will take billions of dollars a year in basic research, sustained over many years, to even have a chance of finding energy sources that can compete with fossil fuels but produce no greenhouse gases.
In addition, the ozone treaty gave developing countries a decade-long grace period on CFC phaseouts and compensated them for the cost of shifting to safer chemicals. Talks over strengthening climate agreements have stumbled repeatedly over efforts to get concrete commitments on emissions cuts from the United States, and the involvement of developing countries, particularly giants like China.
The final momentum for the Montreal treaty was provided by the discovery of the ozone hole, which served as kind of wake-up call, for the first time bringing home the realization that humans could have a direct effect on the planet’s future.
Environmental campaigners have for years been seeking a comparable icon for climate change, be it drowning polar bears, Hurricane Katrina or the deadly European heat wave of 2003. But the incremental nature of the threat posed by building greenhouse gases is for many still trumped by concerns like Iraq and health care.
Mack McFarland, the chief atmospheric scientist for DuPont, said the surprise appearance of the ozone hole should serve as a warning to anyone waiting for stronger evidence of danger before acting to cut emissions of greenhouse gases.
“The science of ozone is so simple compared to the global climate system,” Dr. McFarland said. Referring to the discovery of the polar hole, he added: “If we missed something so fundamental with ozone, what are we missing with the climate system? Admittedly, it can go either way. But do we want to take that chance?”
By JOHN NOBLE WILFORD, The New York Times, September 18, 2007
Sometimes the maturity of a field of science can be measured by the heft of its ambition in the face of the next daunting unknown, the mystery yet to be cracked.
Neurobiology probes the circuitry of the brain for the secrets of behaviors and thoughts that make humans human. High-energy physics seeks and may be on the verge of finding the so-called God particle, the Higgs boson thought to endow elementary particles with their mass. Cosmology is confounded by dark matter and dark energy, the pervasive but unidentified stuff that shapes the universe and accelerates its expansion.
In the study of human origins, paleoanthropology stares in frustration back to a dark age from three million to less than two million years ago. The missing mass in this case is the unfound fossils to document just when and under what circumstances our own genus Homo emerged.
The origin of Homo is one of the most intriguing and intractable mysteries in human evolution. New findings only remind scientists that answers to so many of their questions about early Homo probably lie buried in the million-year dark age.
It is known that primitive hominids — human ancestors and their close kin — walked upright across the plains of Africa at this time. They were presumably larger members of the genus Australopithecus, the best known of which was the Lucy species, Australopithecus afarensis, that had thrived up to three million years ago.
At about 2.6 million years ago, some clever hominids were knapping stone tools. Then, or some time later, scientists suspect, the first Homo appeared, but there is no confirmed evidence of this step.
Subsequent finds, from a time beginning after 1.9 million years ago, revealed an early Homo identified as Homo habilis, the “handy man,” a species with a somewhat larger brain and a more humanlike face, teeth and stature than the apelike australopithecines.
Habilis was generally accorded an important place as the first of the genus, preceding the more advanced Homo erectus and, ultimately, modern humans — Homo sapiens. But certainty has been elusive. A report last month in the journal Nature renewed debate over the habilis’s place in human evolution.
William H. Kimbel, a paleoanthropologist at the Institute of Human Origins at Arizona State University, said that the million-year period “has long been the source of frustrating gaps” in the hominid fossil record. “It’s not that sites containing rocks this age are particularly rare, or that the time period in eastern Africa has not been searched by several groups,” Dr. Kimbel said. “The problem is that the fossil yield has thus far been low or poorly preserved, compared to the time periods on either side of this interval.”
A succession of recent discoveries has extended evidence of hominids reaching back from three million to beyond six million years ago, close to the estimated time of the divergence of the human and chimpanzee lineages. The hominid trail from two million years forward has been fairly well worked, by fossil hunters as well as geneticists and archaeologists tracking migrations out of Africa and across Eurasia. Researchers have determined that anatomically modern Homo sapiens emerged in Africa less than 200,000 years ago.
G. Philip Rightmire, a specialist in habilis and erectus research at Harvard, said searches into the mystery period had yielded mostly the remains of various species of Australopithecus, the genus that came to a dead end around one million years ago.
Bones were found in 2.5-million-year-old sediments associated with some of the earliest known stone tools, used to butcher animals. A coincidence, or evidence of the first toolmaking species? Hard to tell.
A skull and other fossils, uncovered by a team led by the Ethiopian anthropologist Berhane Asfaw, were named the new species Australopithecus garhi. The researchers said the specimen had the projecting apelike face, small braincase and limb bones suggesting descent from the much earlier Lucy species. But if this was a candidate ancestor of early Homo, “a lot of evolution had to take place rather quickly” to complete the transition, a scientist said at the time.
With one possible exception, no fossils that are conclusively Homo have appeared in that period, Dr. Rightmire said. “That suggests there was not much Homo around then,” he said.
Nevertheless, Tim D. White of the University of California, Berkeley, one of the most experienced hunters of hominid fossils, said that his teams and several others were “pushing hard” to explore sites in Ethiopia and Kenya that may produce evidence of earlier Homo origins. Prospects are uncertain. Some prominent sites of previous hominid discoveries are underlain with lava flows and other geological barriers to digging into the deeper past.
At present, most paleoanthropologists think a solitary upper jaw represents the likeliest candidate for a Homo from that period. The find, reported in 1996 by a team led by Dr. Kimbel, was made in the Hadar badlands of Ethiopia, near the site of the much earlier Lucy skeleton and on a surface with a scattering of stone tools. The 2.3-million-year-old jaw was tentatively assigned to the genus Homo.
Dr. Kimbel remains cautious. “The Hadar jaw could represent a population of early Homo that was specifically in the ancestry of habilis,” he said. “Or it could represent a stem population from which ultimately descended all of the Homo species currently known from after two million years ago.”
Alan Walker, a professor of biological anthropology at Pennsylvania State University who studies hominid anatomy, agreed that the jaw was apparently “the earliest direct evidence” of Homo. It shows that the individual had the short face and squared-off palate of Homo, but with teeth that were larger and more primitive. The only other traces of possible Homo presence before two million years ago are some loose teeth from the Omo basin in Ethiopia and some fossil fragments from Kenya and Malawi. The recent Nature report on two new fossils, a 1.44-million-year-old habilis and a 1.55-million-year-old erectus, underscored the uncertainties about early Homo, even after the dark age.
The lead authors, Fred Spoor of University College London and Meave G. Leakey of the National Museums of Kenya, emphasized in the article and in a news release that their findings challenged the view that habilis and erectus evolved one after the other in a linear succession. Their research showed that the two overlapped for almost half a million years and, as they speculated to the media, both species could have had their origins well before two million years ago, possibly from a common ancestor.
Eric Delson, a paleoanthropologist at the American Museum of Natural History and the City University of New York, said that was possible. “It’s always difficult to know what is the earliest specimen of any lineage,” Dr. Delson added. “One always finds something older and older.”
A significant insight from the report, he said, may be the recognition that “there’s more diversity of species in this time period than we expected.”
Several scientists, notably Dr. White of Berkeley, took issue with the interpretation seeming to imply that evidence for the two species overlapping in time and exhibiting variable sizes was new. That, he said, had been recognized for a couple of decades.
Dr. Kimbel, who was not involved in the new research, defended the authors, saying that they had not “meant to imply that habilis could not have been ancestral to erectus, presumably on the basis of their being contemporaneous at Turkana,” the site in Kenya where the fossils were found.
Susan C. Anton, an anthropologist at New York University who was a member of the Spoor-Leakey team, said, “My money is still on habilis as the potential ancestor, but there is a lot of room for additional knowledge, given the dearth of fossils.”
Other scientists tended to agree but noted that habilis had been clouded with doubt. The first habilis fossils were collected in the early 1960s in the Olduvai Gorge of Tanzania by Louis Leakey, patriarch of the fossil-hunting family and Meave Leakey’s father-in-law.
Is habilis really one, two, possibly three species? Some scientists are not sure. Did erectus descend from habilis in a single, unbroken lineage, a process called anagenesis? “This is the only option that is no longer on the table,” Dr. Anton said.
Other experts agree that anagenesis has been refuted by recent evidence that erectus and habilis co-existed for a long time in East Africa, although perhaps in separate ecological niches. So could erectus and habilis have sprung from a much earlier common ancestor? No one can say there were no intermediate Homo species before habilis, back in the dark age. Or perhaps some habilis members left Africa earlier and, after an isolation that favors rapid evolutionary change, returned to Africa as erectus, living side by side with the habilis population that had remained behind.
A hominid site far from Africa has thus taken on new significance. In the 1990s, scientists turned up Homo fossils at the village of Dmanisi, in the republic of Georgia. The craniums, resembling fossils from Kenya, confirmed the presence of erectus on the fringes of Europe at least 1.7 million years ago.
The puzzle is, the Dmanisi fossils look like erectus, but are very small, like habilis. A few researchers raise the possibility that a population of habilis evolved into erectus outside Africa, perhaps in or near Georgia.
“There’s nothing to rule out the idea that habilis-like creatures moved into Eurasia prior to 1.8 million years,” said Dr. Rightmire of Harvard. “They may have given rise to erectus, as we see at Dmanisi, and then erectus moved back, joining the surviving habilis there.”
A new report, to be published Thursday in Nature, will review more skeletal evidence of the transitional aspects of the Dmanisi specimens.
But Dr. Anton said the Dmanisi remains were important as examples of size variability within the erectus species and its adaptations to local environments, not for “any special tie to earliest Homo, such as habilis.”
Writing in the Annual Review of Anthropology in 2004, Dr. Anton and Carl C. Swisher III, a geologist at Rutgers University, concluded that the relationships among erectus and various possible nonerectus Homo groups in Africa “currently are quite muddled and require substantial revisitations.”
Even if the mystery of the origins of the genus Homo is a sign of paleoanthropology’s maturing reach into the deep past, it still leaves the redrawing of the human family tree very much a work in progress. Daniel E. Lieberman, a paleoanthropologist at Harvard, said that filling in the tree matters to scientists, and not only out of innate curiosity about human ancestry.
“At a basic level, one wants to know when and where transformations occurred so one can put them into their appropriate evolutionary context,” Dr. Lieberman said.
He said that that could reveal the dietary and environmental causes of species change, leading eventually to modern humans with the ambition to find their origins.
Dr. Lieberman said that he and colleagues “are relentlessly optimistic that we have all the information we need to answer our big questions, but just haven’t figured out the order in which to connect the dots.”
But the real problem, he added, with resignation tempering optimism, “is that the fossil record doesn’t have enough dots.”
Scientist at Work | Phung Tuu Boi: Through the Forest, a Clearer View of the Needs of a People
By CHRISTIE ASCHWANDEN, The New York Times, September 18, 2007
A LUOI VALLEY, Vietnam — Phung Tuu Boi reaches down to inspect one of the spiny shrubs lined up in a row before him. A few feet away, a cow grazes serenely in this emerald valley in the hills of central Vietnam.
Mr. Boi, a forester and director of the Center for Assistance in Nature Conservation and Community Development in Hanoi, points to the cow. “See this?” he says. “Very, very bad.”
An invisible poison clings to the soil beneath the cow’s muddy hoofs. During a short stretch of the Vietnam War this patch of ground served as an American Special Forces air base, and while the soldiers departed long ago, a potent dioxin from the Agent Orange that they stored and sprayed here lingers still.
Mr. Boi, a lively, passionate man whose enormous smile rarely leaves his face, has dedicated his career to repairing the ecological damage left by what people here call the American War. And while he has had much success in the last 30 years, his task is far from over.
When Mr. Boi began working here in 1975, he found an ecosystem decimated by war. Aerial spraying of defoliants like Agent Orange had destroyed large swaths of forest. Without live roots to anchor the soil, monsoon rains washed away the topsoil and its nutrients, allowing invasive grasses to take over and prevent forest regeneration.
A botanist by training, Mr. Boi’s initial goal was to reforest the denuded land. But he soon realized the forest ecosystem was not the only thing struggling to recover from Agent Orange.
The Pako, Ta Oi, Catu and Kinh people of A Luoi valley (called A Shau during the war) eke out a meager existence in a region with one of Vietnam’s shortest growing seasons. (This reporter visited the valley on a grant from the Pulitzer Center on Crisis Reporting.) These tribal groups, who live in one-room huts with dirt floors and no indoor plumbing, depend on forest products to survive, and Mr. Boi came to recognize that his work was as vital to them as to the tigers and elephants whose habitat he was working to restore.
Mr. Boi enlisted the help of the Australian acacia tree. The acacia grows up to six and a half feet per year and, after five years, can be harvested to make paper and furniture. The tree also improves the soil and quickly provides the canopy that trees need to take root.
“It’s a good model for forest restoration,” said Chris Dickinson, a conservation biologist and technical adviser with the World Wildlife Fund for Nature in Hue, Vietnam, adding that the acacia “grows on poor nutrients and can shade out the grasses.”
The trees also provide residents with a cash crop. “The demand for acacia is seemingly insatiable,” Dr. Dickinson said. “Ikea uses it for garden furniture.”
Mr. Boi has used this humble acacia tree to reforest thousands of hectares in central Vietnam. Emboldened by these successes, he has applied his botanical model of remediation to tackle a far more difficult problem.
Though dioxin has dropped to relatively low levels in areas that were aerially sprayed during the war, studies by Canadian scientists have shown that numerous highly contaminated spots remain at certain places where American forces stored Agent Orange.
The cow that caught Mr. Boi’s attention grazes on one such “hot spot,” the former A So air base in Dong Son, where scientists from Hatfield Consultants in Vancouver, British Columbia, have measured soil levels of TCDD, the dioxin in Agent Orange, more than 200 times greater than the residential standard set forth by the United States Environmental Protection Agency.
Dioxin takes decades to break down. Remediating this site would require millions of dollars, and when it comes to financing, the more heavily populated hot spots in Danang and Bien Hoa take precedence.
If the Dong Son hot spot were in New Jersey or Florida, a barbed wire fence and a warning might be enough to deter people from entering the area, but such solutions break down in the face of extreme poverty. “You put up a fence, and the people are so poor that anything they can get their hands on, they’ll take down and use,” said Wayne Dwernychuk, an environmental scientist who did studies for Hatfield Consultants.
“Their economy is geared to agriculture,” Dr. Dwernychuk said. “If you take that land out of the production cycle, it’s very hard to rationalize to them when they don’t see the problem.”
He added that the chemical that taints this soil could not be seen, smelled or tasted.
Pointing to the former air base’s most contaminated site, Mr. Boi said: “The local people are poor and uneducated, and they don’t understand. Children come here to play and they collect insects and other things to eat.”
Dioxin accumulates in animal fats, and the molecules also glom onto soil particles that can be ingested through inadequately washed root crops like manioc. Poor sanitation and a diet that relies on fowl that peck on tainted soil keep dioxin exposure a constant threat. Dr. Dwernychuk and his colleagues have found elevated TCDD levels in the blood and breast milk of local residents, evidence that the chemical continues to make its way into the food chain.
Nguyen Van Phom, the mayor of Dong Son, blames dioxin for the health problems he says plague 60 of the 240 families in the village. Whether these conditions, which include limb deformities and deafness, are the result of dioxin remains unproved, though the Institute of Medicine at the National Academy of Sciences has linked Agent Orange exposure in American veterans to an increased risk of some health problems, including cancer and diabetes.
The Canadian studies prompted the Vietnamese government to move more than two dozen families off the most contaminated ground, but efforts to educate residents about the risks have proved difficult. Most cannot read and many speak only faltering Vietnamese, relying instead on tribal dialects.
Mr. Boi has developed a low-tech solution to overcome these problems: a fence made of trees covered with cactus-sharp needles to deter humans and animals alike. Mr. Boi hopes this so-called green fence will not only discourage trespassers, but also provide them with an economic incentive to leave the barrier intact. Once mature, the trees he has chosen to make up the fence, Gleditschia australis, produce a fruit that residents can sell to make soaps and medicinals. Gleditschia, a type of honey locust, is disease and insect resistant, and its thorns and soft wood should deter residents from cutting it down for firewood.
The green fence promises a workable solution to a costly problem, said William H. Farland, a former scientist with the Environmental Protection Agency who is vice president for research at Colorado State University. “It’s very expensive to clean dioxin up to background levels,” Dr. Farland said. “The main issue is to prevent human exposure, not just to clean up the soils.”
While a full remediation project would cost millions of dollars, Mr. Boi estimated that his project could be done for just $30,000. Last December, with the help of a $10,000 grant from the World Bank and the aid of about a dozen farmers, Mr. Boi planted the first 10,000 seeding trees. But despite its auspicious start, the project has hit a few snags.
Though hardy, the locust trees failed to thrive in soil stripped of its nutrients by rains that followed defoliation decades ago, and a spate of intense storms flooded the site shortly after planting, drowning many of the seedlings. With their thorns still small, the trees that survived made attractive food for wandering livestock. Today, only a single row of small trees remain.
In the face of these challenges, no one would fault Mr. Boi for returning to his comfortable office in Hanoi and moving on to something else. But he views this setback as nothing more than a necessary learning experience. With the lessons gleaned from his initial failure, he has developed a new plan.
Before his next round of planting, Mr. Boi will bolster the soil with fertilizers. Then he will plant larger seedlings, and in addition to the original locust fence, he will add rows of acacia on either side to create a three-layer fence. The acacia will help protect the locust trees, improve the soil and provide another cash crop for residents, Mr. Boi says, pointing to a photo schemata of the fence that he carries with him everywhere, sharing with anyone who will listen.
Mr. Boi needs $20,000 more to finish the fence. He has received no government financing and has resorted to spending his own money to keep the project alive. But Mr. Boi refuses to give up, even if it means digging deeper into his own pockets. Success is his only option. If he gives up on this project, the cows will continue to graze on tainted soil, and another generation of children will grow up eating insects caked with dioxin-rich dirt.
From Ozone Success, a Potential Climate Model
By ANDREW C. REVKIN, The New York Times, September 18, 2007
In 1985, scientists studying the air over Antarctica stumbled on a gaping breach in the billion-year-old atmospheric radiation shield that makes Earth’s surface habitable.
The discovery of a seasonal “hole” in this veil of ozone molecules was so unexpected — “the surprise of the century,” one chemist later called it — that it was presumed to be a data glitch.
It wasn’t. Soon other experts found a connection between the ozone hole and the use of chlorofluorocarbons, or CFCs, and similar synthetic chemicals in solvents, refrigeration, sprays and the like.
The chemical threat to the ozone layer had been identified in 1974, and industries and governments were planning to shift to safer substitutes. But it took the ozone hole, glaring from satellite images like a purple bruise, to make eliminating such chemicals a global imperative. On Sept. 16, 1987, an initial batch of countries signed the Montreal Protocol, a treaty that has since grown and led to bans on 95 percent of the ozone-eating compounds.
On Sunday, diplomats, scientists and environmentalists gathered in Montreal to celebrate the 20th anniversary of the treaty and to spend a week discussing possible new steps to speed an end to remaining ozone threats.
Many are using the anniversary to bolster the idea that a similar success can be achieved with carbon dioxide and other heat-trapping greenhouse gases linked to global warming (including some of the ozone-destroying chemicals and some of the replacements for them). Fresh international climate talks begin at the United Nations on Monday and at a meeting in Washington organized by the White House late next week. Some veterans of both the ozone and climate fights insist that the Montreal success is a model for climate action.
“The lesson from Montreal is that curbing global warming will not be as hard as it looks,” said David D. Doniger, an early campaigner against ozone-damaging chemicals for the Natural Resources Defense Council who now directs the group’s climate work.
But many experts on the circumstances — scientific, diplomatic and economic — surrounding the 1987 treaty signing say that while some things are similar now, like the looming environmental risks revealed by evolving science, almost everything else is very different.
Ozone molecules, tenuous trios of oxygen atoms, serve as a planetary sun block of sorts, limiting the bombardment of the Earth’s surface by ultraviolet radiation that can cause skin cancers and cataracts, and harm some plants and animals.
When F. Sherwood Rowland and Mario J. Molina first posited in 1974 that CFCs and similar chemicals could waft to the stratosphere and break up ozone, the threat quickly captured public attention.
In 1977, long before the climate disaster movie “The Day After Tomorrow,” Hollywood released “Day of the Animals,” in which ozone destruction caused wildlife to run amok.
But it was cancer that really brought the issue home, said Susan Solomon, a senior scientist with the National Oceanic and Atmospheric Administration who in 1986 led work linking CFCs and related chemicals to polar ozone losses. “Skin cancer is deeply personal, and virtually every person on the planet has either known someone who has had cancer or had it themselves,” Dr. Solomon said.
The risks from global warming are far different, said Dr. Solomon, who was the co-leader of the latest scientific report by the Intergovernmental Panel on Climate Change. “It is much less personal for most people, except perhaps if you’re in places like Vanuatu,” she said, referring to one of several low-lying island nations threatened by rising seas. “It’s mostly beyond our generation.”
In the 1980s, despite persistent scientific uncertainties over the threat to the ozone layer, action to move away from ozone-damaging chemicals was swift, largely because there was little cost involved and alternatives were developed as the need arose, experts said.
To preserve the ozone shield, the United States, joined soon by Canada and Scandinavian countries, banned “nonessential” uses of CFCs — hair sprays, for example — in 1978, just three years after the theory was first described in the journal Nature.
The Natural Resources Defense Council, seizing on an opening left by a proposed rule to limit CFCs that was written in the last days of the Carter administration, filed a lawsuit in 1984 that prompted the Environmental Protection Agency to seek broader bans. The domestic action helped set the stage for treaty talks.
“That N.R.D.C. suit was critical because it turned the burden of proof around from having to show there was a problem to proving there was not,” said Roger A. Pielke Jr., a political scientist at the University of Colorado, Boulder.
Still, $135 billion worth of air conditioners and other equipment in the United States, and billions more around the world, relied on the old chemicals, and the science remained murky. So DuPont and other companies waited to seek alternatives, according to company scientists.
In 1985, the murk cleared somewhat. An international scientific assessment of CFCs and ozone created a near-worldwide consensus that the risks of allowing the long-lived chemicals to keep building in the atmosphere were unacceptable.
DuPont, while gaining less than 2 percent of its revenues from such compounds, saw a need to find substitutes and the prospect of new markets, and began a $500 million research effort that spawned a suite of alternatives.
With global warming, in contrast, economists and climate experts say it will take billions of dollars a year in basic research, sustained over many years, to even have a chance of finding energy sources that can compete with fossil fuels but produce no greenhouse gases.
In addition, the ozone treaty gave developing countries a decade-long grace period on CFC phaseouts and compensated them for the cost of shifting to safer chemicals. Talks over strengthening climate agreements have stumbled repeatedly over efforts to get concrete commitments on emissions cuts from the United States, and the involvement of developing countries, particularly giants like China.
The final momentum for the Montreal treaty was provided by the discovery of the ozone hole, which served as kind of wake-up call, for the first time bringing home the realization that humans could have a direct effect on the planet’s future.
Environmental campaigners have for years been seeking a comparable icon for climate change, be it drowning polar bears, Hurricane Katrina or the deadly European heat wave of 2003. But the incremental nature of the threat posed by building greenhouse gases is for many still trumped by concerns like Iraq and health care.
Mack McFarland, the chief atmospheric scientist for DuPont, said the surprise appearance of the ozone hole should serve as a warning to anyone waiting for stronger evidence of danger before acting to cut emissions of greenhouse gases.
“The science of ozone is so simple compared to the global climate system,” Dr. McFarland said. Referring to the discovery of the polar hole, he added: “If we missed something so fundamental with ozone, what are we missing with the climate system? Admittedly, it can go either way. But do we want to take that chance?”
