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Early life could have been based on arsenic
This week–
SOUNDBITES
It’s arsenic, but not as we know it A DEADLY poison, arsenic is best known for snuffing out life. But could it have played a key role in the origins of life on Earth? Felisa Wolfe-Simon of Harvard University thinks so because the toxin behaves so similarly to phosphorus, an essential ingredient in nearly all living things. Much more arsenic would have been available in Earth’s primordial oceans than phosphorus. And while microbial activity was necessary later to unlock phosphorus from rocks, arsenic could have dissolved in water from hydrothermal vents. Phosphorus binds to four oxygen atoms to form a negatively charged phosphate ion that is used to build the backbone of DNA’s double helix. Phosphate is also key in adenosine
triphosphate (ATP), the “universal energy currency” that supplies energy to most life on Earth. Wolfe-Simon and Paul Davies of Arizona State University in Tempe think arsenic could do the same jobs. Just as phosphorus forms phosphate ions, so arsenic readily forms arsenate ions.
“Microbes living in Antarctica or on Saturn’s moon Titan might have evolved to take advantage of faster-reacting arsenate” Arsenate isn’t suitable for life today, because it tends to latch onto adenosine diphosphate molecules, blocking the production of ATP. However, without much phosphorus available, the first life might have evolved to make use of the next best thing, Wolfe-Simon says.
Mesopotamians turned symbols into logos PRODUCT branding first emerged in ancient Mesopotamia, the birthplace of cities and writing. So claims David Wengrow, an archaeologist at University College London, who says that bottle stops stamped with symbols some 5000 years ago are evidence of the first branded goods. Around 8000 years ago, villagedwelling Mesopotamians began making personalised stone seals, which they pressed into the caps and stoppers used to seal food and drink. Originally these goods would have been traded directly with neighbours and travellers. But when urbanisation began – a little over 5000 years ago – city residents increasingly had to deal with products of uncertain origin. 10 | NewScientist | 26 April 2008
George W. Bush explains why he is opposing a Senate measure that would place mandatory limits on greenhouse gases beginning in five years, followed by annual reductions (Associated Press, 18 April)
‹ Primitive life is very common and intelligent life is fairly rare. Some would say it has yet to occur on Earth.› Stephen Hawking outlines his views on the possibility of intelligent life elsewhere in the universe during a lecture in Washington DC to mark NASA’s 50th anniversary (Associated Press, 21 April)
‹ How important is life and how important are cars? I say life first and cars second.› At a conference in London, Bolivian president Evo Morales criticises the growing of biofuels in place of food crops in South America (The Guardian, London, 22 April) G. DAGLIORTI/ARCHAEALOGICAL MUS. BAGHDAD/ART ARCHIVE
MICHAEL REILLY
‹ There is a wrong way and a right way to approach reducing greenhouse gas emissions.›
“If you put arsenic in a test tube with adenosine, you immediately get lots of adenosine monoarsenate,” which is structurally similar to adenine, the “A” letter in DNA’s code of A, C, G and T, says Wolfe-Simon. If early life did use arsenate, single-celled organisms with arsenate-based DNA may still be around today wherever phosphorus is scarce. The only stumbling block to the idea is that arsenic-based DNA tends to break down quickly. “You don’t want to build your DNA out of a compound with a half-life in the order of a couple of minutes,” points out Steve Benner of the Foundation For Applied Molecular Evolution in Gainesville, Florida. However, he points out that it could be a good thing in extreme cold, where chemical reactions move very slowly. Microbes living in Antarctica or on Saturn’s moon Titan might find phosphate-based DNA too sluggish to work with and have evolved to take advantage of faster-reacting arsenate instead. G
‹ I remember saying I would be much more comfortable promoting eating roadkill.›
Lisa Lange, vice-president of People for the Ethical Treatment of Animals, on the controversy within the organisation generated by its $1 million prize for devising a commercially viable way of –A seal of approval?– producing artificial meat (The New York Times, 21 April) Wengrow says the symbols in caps and stoppers came to play an important role in telling people about the quality and origins of products such as oils and wine. He has described how the seals might have been used to ensure quality control, to give provenance for goods or to show that they conformed to a standardised system. By looking at the symbol on a wine stopper, says Wengrow, consumers came to know whether or not to trust that bottle (Current Archaeology, vol 49, p 7). Many stoppers have been found in the ancient city of Uruk, now in
Iraq, where some 20,000 people lived 5000 years ago. The symbol impressions are the first images produced mechanically in human history, says Wengrow. The images have long been regarded as works of art, but he believes that what we now consider art may actually have been promotional branding. “I think Wengrow is onto something,” says Mitchell Rothman, an anthropologist at Widener University in Chester, Pennsylvania, although he is not convinced that the ancients were using branding “in the commercial sense”. Jeff Hecht G
‹ We can confidently say it has influenced and shaped world events, and the Nighthawk can rest knowing its mission is complete.› US air force colonel Jeff Harrigian, commenting on the official retirement of the four remaining F-117 stealth fighter planes, which made their final operational flight on Monday (Alamogordo Daily News, New Mexico, 22 April)
www.newscientist.com
SOUNDBITES
It’s arsenic, but not as we know it A DEADLY poison, arsenic is best known for snuffing out life. But could it have played a key role in the origins of life on Earth? Felisa Wolfe-Simon of Harvard University thinks so because the toxin behaves so similarly to phosphorus, an essential ingredient in nearly all living things. Much more arsenic would have been available in Earth’s primordial oceans than phosphorus. And while microbial activity was necessary later to unlock phosphorus from rocks, arsenic could have dissolved in water from hydrothermal vents. Phosphorus binds to four oxygen atoms to form a negatively charged phosphate ion that is used to build the backbone of DNA’s double helix. Phosphate is also key in adenosine
triphosphate (ATP), the “universal energy currency” that supplies energy to most life on Earth. Wolfe-Simon and Paul Davies of Arizona State University in Tempe think arsenic could do the same jobs. Just as phosphorus forms phosphate ions, so arsenic readily forms arsenate ions.
“Microbes living in Antarctica or on Saturn’s moon Titan might have evolved to take advantage of faster-reacting arsenate” Arsenate isn’t suitable for life today, because it tends to latch onto adenosine diphosphate molecules, blocking the production of ATP. However, without much phosphorus available, the first life might have evolved to make use of the next best thing, Wolfe-Simon says.
Mesopotamians turned symbols into logos PRODUCT branding first emerged in ancient Mesopotamia, the birthplace of cities and writing. So claims David Wengrow, an archaeologist at University College London, who says that bottle stops stamped with symbols some 5000 years ago are evidence of the first branded goods. Around 8000 years ago, villagedwelling Mesopotamians began making personalised stone seals, which they pressed into the caps and stoppers used to seal food and drink. Originally these goods would have been traded directly with neighbours and travellers. But when urbanisation began – a little over 5000 years ago – city residents increasingly had to deal with products of uncertain origin. 10 | NewScientist | 26 April 2008
George W. Bush explains why he is opposing a Senate measure that would place mandatory limits on greenhouse gases beginning in five years, followed by annual reductions (Associated Press, 18 April)
‹ Primitive life is very common and intelligent life is fairly rare. Some would say it has yet to occur on Earth.› Stephen Hawking outlines his views on the possibility of intelligent life elsewhere in the universe during a lecture in Washington DC to mark NASA’s 50th anniversary (Associated Press, 21 April)
‹ How important is life and how important are cars? I say life first and cars second.› At a conference in London, Bolivian president Evo Morales criticises the growing of biofuels in place of food crops in South America (The Guardian, London, 22 April) G. DAGLIORTI/ARCHAEALOGICAL MUS. BAGHDAD/ART ARCHIVE
MICHAEL REILLY
‹ There is a wrong way and a right way to approach reducing greenhouse gas emissions.›
“If you put arsenic in a test tube with adenosine, you immediately get lots of adenosine monoarsenate,” which is structurally similar to adenine, the “A” letter in DNA’s code of A, C, G and T, says Wolfe-Simon. If early life did use arsenate, single-celled organisms with arsenate-based DNA may still be around today wherever phosphorus is scarce. The only stumbling block to the idea is that arsenic-based DNA tends to break down quickly. “You don’t want to build your DNA out of a compound with a half-life in the order of a couple of minutes,” points out Steve Benner of the Foundation For Applied Molecular Evolution in Gainesville, Florida. However, he points out that it could be a good thing in extreme cold, where chemical reactions move very slowly. Microbes living in Antarctica or on Saturn’s moon Titan might find phosphate-based DNA too sluggish to work with and have evolved to take advantage of faster-reacting arsenate instead. G
‹ I remember saying I would be much more comfortable promoting eating roadkill.›
Lisa Lange, vice-president of People for the Ethical Treatment of Animals, on the controversy within the organisation generated by its $1 million prize for devising a commercially viable way of –A seal of approval?– producing artificial meat (The New York Times, 21 April) Wengrow says the symbols in caps and stoppers came to play an important role in telling people about the quality and origins of products such as oils and wine. He has described how the seals might have been used to ensure quality control, to give provenance for goods or to show that they conformed to a standardised system. By looking at the symbol on a wine stopper, says Wengrow, consumers came to know whether or not to trust that bottle (Current Archaeology, vol 49, p 7). Many stoppers have been found in the ancient city of Uruk, now in
Iraq, where some 20,000 people lived 5000 years ago. The symbol impressions are the first images produced mechanically in human history, says Wengrow. The images have long been regarded as works of art, but he believes that what we now consider art may actually have been promotional branding. “I think Wengrow is onto something,” says Mitchell Rothman, an anthropologist at Widener University in Chester, Pennsylvania, although he is not convinced that the ancients were using branding “in the commercial sense”. Jeff Hecht G
‹ We can confidently say it has influenced and shaped world events, and the Nighthawk can rest knowing its mission is complete.› US air force colonel Jeff Harrigian, commenting on the official retirement of the four remaining F-117 stealth fighter planes, which made their final operational flight on Monday (Alamogordo Daily News, New Mexico, 22 April)
www.newscientist.com