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Genome Study Provides a Census of Early Humans
By NICHOLAS WADE, The New York Times, January 19, 2010
From the composition of just two human genomes, geneticists have computed the size of the human population 1.2 million years ago from which everyone in the world is descended.
They put the number at 18,500 people, but this refers only to breeding individuals, the “effective” population. The actual population would have been about three times as large, or 55,500.
Comparable estimates for other primates then are 21,000 for chimpanzees and 25,000 for gorillas. In biological terms, it seems, humans were not a very successful species, and the strategy of investing in larger brains than those of their fellow apes had not yet produced any big payoff. Human population numbers did not reach high levels until after the advent of agriculture.
Geneticists have long known that the ancestors of modern humans numbered as few as 10,000 at some time in the last 100,000 years. The critically low number suggested that some catastrophe, like disease or climate change induced by a volcano, had brought humans close to the brink of extinction.
If the new estimate is correct, however, human population size has been small and fairly constant throughout most of the last million years, ruling out the need to look for a catastrophe.
The estimate, reported in the issue on Tuesday of The Proceedings of the National Academy of Sciences, was made by a team of population geneticists at the University of Utah led by Chad D. Huff and Lynn B. Jorde.
The human population a million years ago was represented by archaic species like Homo ergaster in Africa and Homo erectus in East Asia. The Utah team says its estimate of 18,500 implies “an unusually small population for a species spread across the entire Old World.”
But that estimate would apply to the worldwide population only if there were inbreeding between the humans on the different continents. If not, and if modern humans are descended from just one of these populations, like Homo ergaster in Africa, then the estimate would apply only to that.
Richard G. Klein, a paleoanthropologist at Stanford, said it was hard to believe the population from which modern humans are descended was as small as 18,500 “unless they were geographically restricted to Africa or a small part of it.”
There is no independent way of assessing a genetics-based estimate of population size at this period, Dr. Klein said, although archaeologists have developed ways of assessing ancient populations of more recent times.
The Utah team based its estimate on the genetic variation present in two complete human genomes, one prepared by the government’s human genome project and the other by J. Craig Venter, the genome sequencing pioneer. The government decoded a single copy of a mosaic genome derived from a medley of people, apparently of European and Asian origin. Dr. Venter decoded both copies of his own genome, the one inherited from his father and the one from his mother.
The Utah team thus had three genomes to work with and looked at ancient elements known as Alu insertions, the youngest class of which appeared in the human genome around a million years ago. The amount of variation seen in the DNA immediately surrounding the Alu insertions gave a measure of the size of human population at that time.
Their estimate agrees almost exactly with an earlier one, also based on Alu insertions but with sparser data. The insertions tag ancient regions of the genome that are unaffected by the recent growth in population, Dr. Huff said.
OBSERVATORY: The Platypus Is Cute but Far From Harmless
By HENRY FOUNTAIN, The New York Times, January 19, 2010
In “The Nutmeg of Consolation” by Patrick O’Brian, the 14th in his series of maritime novels, the good Dr. Stephen Maturin’s unabashed joy at finally seeing a platypus in Australia is almost immediately tempered by the incapacitating pain he experiences when he is stung by poisonous spurs on the animal’s rear legs.
Dr. Maturin could be forgiven if he didn’t know that the platypus is among the few mammals that produce venom (and with platypuses, only the male does). Even those who know about platypus venom do not really know much about it.
They know a little more now. Researchers in Japan have identified some of the constituents of the venom that may help make it so painful.
Using high-performance liquid chromatography and other techniques, Masaki Kita of the University of Tsukuba, Daisuke Uemura of the Nagoya University and colleagues analyzed venom samples and identified about a dozen peptides, small chains of amino acids that are the building blocks of proteins. Their findings are reported in The Journal of the American Chemical Society.
In earlier laboratory studies, the researchers found that crude venom caused cultured nerve cells to take up calcium ions slowly and continuously. This gave a hint as to how the venom acts, since calcium flux into nerve cells is linked to the sensation of pain. One of the peptides identified, called heptapeptide-1, was shown to increase calcium ion flux by itself. That suggests it may be the main component responsible for the venom’s effect.
Ancient Egypt’s Toxic Makeup Fought Infection, Researchers Say
By SINDYA N. BHANOO, The New York Times, January 19, 2010
The elaborate eye makeup worn by Queen Nefertiti and other ancient Egyptians was believed to have healing powers, conjuring up the protection of the Gods Horus and Ra and warding off illnesses.
Science does not allow for magic, but it does allow for healing cosmetics. The lead-based makeup used by the Egyptians had antibacterial properties that helped prevent infections common at the time, according to a report published Friday in Analytical Chemistry, a semimonthly journal of the American Chemical Society.
“It was puzzling; they were able to build a strong, rich society, so they were not completely crazy,” said Christian Amatore, a chemist at the École Normale Supérieure in Paris and one of the paper’s authors. “But they believed this makeup was healing — they said incantations as they mixed it, things that today we call garbage.”
Dr. Amatore and his fellow researchers used electron microscopy and X-ray diffraction to analyze 52 samples from containers of Egyptian makeup preserved at the Louvre.
They found that the makeup was primarily made by mixing four lead-based chemicals: galena, which produced dark tones and gloss, and the white materials cerussite, laurionite and phosgenite.
Because the samples had disintegrated over the centuries, the researchers were not able to determine what percentage of the makeup was lead.
Although many written texts, paintings and statues from the period indicate that the makeup was extensively used, Egyptians saw it as magical, not medicine, Dr. Amatore said.
In ancient Egypt, during periods when the Nile flooded, Egyptians had infections caused by particles that entered the eye and caused diseases and inflammations. The scientists argue that the lead-based makeup acted as a toxin, killing bacteria before it spread.
But while their research provides a fascinating insight into an ancient culture, the scientists say the makeup is not something that should be used today.
Dr. Amatore said that the toxicity of lead compounds overshadowed the benefits and that there had been many documented cases of poisoning as a result of lead in paints and plumbing in the 20th century.
Neal Langerman, a physical chemist and the president of Advanced Chemical Safety, a health safety and environmental protection consulting firm, said, “You probably won’t want to do this at home, especially if you have a small child or a dog that likes to lick you.”
Nonetheless, Dr. Langerman said, it makes sense that the Egyptians were attracted to the compounds.
“Lead and arsenic, among other metals, make beautiful color pigments,” he said. “Because they make an attractive color and because you can create a powder with them, it makes sense to use it as a skin colorant.”
The issue of lead in makeup continues to be debated in the cosmetics industry, particularly with regard to the small amounts of lead found in some lipsticks.
While some advocacy groups and doctors argue that, over time, lipstick wearers might absorb levels of lead that could result in behavioral issues, the Food and Drug Administration has said that the trace amounts of lead in makeup are too small to cause harm.
“It’s the dose that makes the poison,” Dr. Langerman said, in paraphrasing the Renaissance physician Paracelsus. “A low dose kills the bacteria. In a high dose, you’re taking in too much.”
By NICHOLAS WADE, The New York Times, January 19, 2010
From the composition of just two human genomes, geneticists have computed the size of the human population 1.2 million years ago from which everyone in the world is descended.
They put the number at 18,500 people, but this refers only to breeding individuals, the “effective” population. The actual population would have been about three times as large, or 55,500.
Comparable estimates for other primates then are 21,000 for chimpanzees and 25,000 for gorillas. In biological terms, it seems, humans were not a very successful species, and the strategy of investing in larger brains than those of their fellow apes had not yet produced any big payoff. Human population numbers did not reach high levels until after the advent of agriculture.
Geneticists have long known that the ancestors of modern humans numbered as few as 10,000 at some time in the last 100,000 years. The critically low number suggested that some catastrophe, like disease or climate change induced by a volcano, had brought humans close to the brink of extinction.
If the new estimate is correct, however, human population size has been small and fairly constant throughout most of the last million years, ruling out the need to look for a catastrophe.
The estimate, reported in the issue on Tuesday of The Proceedings of the National Academy of Sciences, was made by a team of population geneticists at the University of Utah led by Chad D. Huff and Lynn B. Jorde.
The human population a million years ago was represented by archaic species like Homo ergaster in Africa and Homo erectus in East Asia. The Utah team says its estimate of 18,500 implies “an unusually small population for a species spread across the entire Old World.”
But that estimate would apply to the worldwide population only if there were inbreeding between the humans on the different continents. If not, and if modern humans are descended from just one of these populations, like Homo ergaster in Africa, then the estimate would apply only to that.
Richard G. Klein, a paleoanthropologist at Stanford, said it was hard to believe the population from which modern humans are descended was as small as 18,500 “unless they were geographically restricted to Africa or a small part of it.”
There is no independent way of assessing a genetics-based estimate of population size at this period, Dr. Klein said, although archaeologists have developed ways of assessing ancient populations of more recent times.
The Utah team based its estimate on the genetic variation present in two complete human genomes, one prepared by the government’s human genome project and the other by J. Craig Venter, the genome sequencing pioneer. The government decoded a single copy of a mosaic genome derived from a medley of people, apparently of European and Asian origin. Dr. Venter decoded both copies of his own genome, the one inherited from his father and the one from his mother.
The Utah team thus had three genomes to work with and looked at ancient elements known as Alu insertions, the youngest class of which appeared in the human genome around a million years ago. The amount of variation seen in the DNA immediately surrounding the Alu insertions gave a measure of the size of human population at that time.
Their estimate agrees almost exactly with an earlier one, also based on Alu insertions but with sparser data. The insertions tag ancient regions of the genome that are unaffected by the recent growth in population, Dr. Huff said.
OBSERVATORY: The Platypus Is Cute but Far From Harmless
By HENRY FOUNTAIN, The New York Times, January 19, 2010
In “The Nutmeg of Consolation” by Patrick O’Brian, the 14th in his series of maritime novels, the good Dr. Stephen Maturin’s unabashed joy at finally seeing a platypus in Australia is almost immediately tempered by the incapacitating pain he experiences when he is stung by poisonous spurs on the animal’s rear legs.
Dr. Maturin could be forgiven if he didn’t know that the platypus is among the few mammals that produce venom (and with platypuses, only the male does). Even those who know about platypus venom do not really know much about it.
They know a little more now. Researchers in Japan have identified some of the constituents of the venom that may help make it so painful.
Using high-performance liquid chromatography and other techniques, Masaki Kita of the University of Tsukuba, Daisuke Uemura of the Nagoya University and colleagues analyzed venom samples and identified about a dozen peptides, small chains of amino acids that are the building blocks of proteins. Their findings are reported in The Journal of the American Chemical Society.
In earlier laboratory studies, the researchers found that crude venom caused cultured nerve cells to take up calcium ions slowly and continuously. This gave a hint as to how the venom acts, since calcium flux into nerve cells is linked to the sensation of pain. One of the peptides identified, called heptapeptide-1, was shown to increase calcium ion flux by itself. That suggests it may be the main component responsible for the venom’s effect.
Ancient Egypt’s Toxic Makeup Fought Infection, Researchers Say
By SINDYA N. BHANOO, The New York Times, January 19, 2010
The elaborate eye makeup worn by Queen Nefertiti and other ancient Egyptians was believed to have healing powers, conjuring up the protection of the Gods Horus and Ra and warding off illnesses.
Science does not allow for magic, but it does allow for healing cosmetics. The lead-based makeup used by the Egyptians had antibacterial properties that helped prevent infections common at the time, according to a report published Friday in Analytical Chemistry, a semimonthly journal of the American Chemical Society.
“It was puzzling; they were able to build a strong, rich society, so they were not completely crazy,” said Christian Amatore, a chemist at the École Normale Supérieure in Paris and one of the paper’s authors. “But they believed this makeup was healing — they said incantations as they mixed it, things that today we call garbage.”
Dr. Amatore and his fellow researchers used electron microscopy and X-ray diffraction to analyze 52 samples from containers of Egyptian makeup preserved at the Louvre.
They found that the makeup was primarily made by mixing four lead-based chemicals: galena, which produced dark tones and gloss, and the white materials cerussite, laurionite and phosgenite.
Because the samples had disintegrated over the centuries, the researchers were not able to determine what percentage of the makeup was lead.
Although many written texts, paintings and statues from the period indicate that the makeup was extensively used, Egyptians saw it as magical, not medicine, Dr. Amatore said.
In ancient Egypt, during periods when the Nile flooded, Egyptians had infections caused by particles that entered the eye and caused diseases and inflammations. The scientists argue that the lead-based makeup acted as a toxin, killing bacteria before it spread.
But while their research provides a fascinating insight into an ancient culture, the scientists say the makeup is not something that should be used today.
Dr. Amatore said that the toxicity of lead compounds overshadowed the benefits and that there had been many documented cases of poisoning as a result of lead in paints and plumbing in the 20th century.
Neal Langerman, a physical chemist and the president of Advanced Chemical Safety, a health safety and environmental protection consulting firm, said, “You probably won’t want to do this at home, especially if you have a small child or a dog that likes to lick you.”
Nonetheless, Dr. Langerman said, it makes sense that the Egyptians were attracted to the compounds.
“Lead and arsenic, among other metals, make beautiful color pigments,” he said. “Because they make an attractive color and because you can create a powder with them, it makes sense to use it as a skin colorant.”
The issue of lead in makeup continues to be debated in the cosmetics industry, particularly with regard to the small amounts of lead found in some lipsticks.
While some advocacy groups and doctors argue that, over time, lipstick wearers might absorb levels of lead that could result in behavioral issues, the Food and Drug Administration has said that the trace amounts of lead in makeup are too small to cause harm.
“It’s the dose that makes the poison,” Dr. Langerman said, in paraphrasing the Renaissance physician Paracelsus. “A low dose kills the bacteria. In a high dose, you’re taking in too much.”
