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Life may have begun in icy seas
This week
Colin Barras
Michael Schwab/Getty
Life may have begun in icy seas this could sometimes have dropped to today’s polar temperatures. For ice to be present at these relatively low latitudes, the planet must have been locked in a severe ice age at least once during the Archaean. Oxygen isotopes in ancient rocks had previously been used to calculate sea temperature at this
DID life begin in the freezer? Early Earth may not have been as hot and hellish as we thought, and our planet may have been in a deep ice age when life first emerged. This is according to an analysis of rocks from South Africa that formed about 3.5 billion years ago, during the Archaean period. “Key organic molecules Previous research suggested for the origin of life that the ocean in which these could have become more rocks formed was hot – perhaps concentrated in ice” around 85 °C. But Maarten de Wit at the Nelson Mandela Metropolitan University in Port time, but de Wit believes that Elizabeth, South Africa, now says these indicated a misleadingly ocean temperatures at that time warm temperature, due to local were similar to today’s. hydrothermal activity. South Africa’s Barberton Working with Harald Furnes at Greenstone Belt, where these the University of Bergen, Norway, rocks are now found, formed at a de Wit looked instead at rocks latitude of 20° to 40° – equivalent that formed in the deep sea, away to the border between the tropics from ancient hydrothermal vents. and mid-latitudes today. De Wit These rocks contained gypsum, says ocean temperatures here a mineral that only grows if water would have been around 26 °C, temperatures are below 40 °C. while evidence of glacial activity What’s more, in a sequence of in some of these rocks suggests nearby Archaean rocks that
–A chilly start to life on Earth?–
formed in shallow water about 30 million years later, de Wit and Furnes found evidence of dropstones, which are associated with icebergs, suggesting that ocean temperatures must have plummeted and the planet was in the grip of an ice age (Science Advances, doi.org/bcw2). Don Lowe at Stanford University in California says his team’s extensive studies in the area have found no evidence of glaciation, but he doesn’t
Jie Yang (Yunnan University; China)
Oldest Fossilised nervous system
Preserved inside 520 million-year-old fossils, this is the most ancient nervous system we have ever seen. The fossils are of Chengjiangocaris kunmingensis, a creature around 10 centimetres long, with multiple pairs of legs and a heart-shaped head. Found in southern China, the five
10 | NewScientist | 5 March 2016
Cambrian fossils belonged to a group of organisms that gave rise to insects, crustaceans and other arthropods. Most interesting of all is its nerve cord and associated neurons. “The detail of this fossil is exquisite,” says Rob DeSalle of the American Museum of Natural History in New York, who
was not involved in the discovery. The animal had a nerve cord that ran the length of its body, with bulbous nodes of neurons located between appendages. “It’s almost like a mini-brain for each pair of legs,” says Javier Ortega-Hernández of the University of Cambridge, whose team analysed and described the fossil. Surprisingly, they found dozens of fine, subsidiary nerves fanning out across the entire length of the nerve cord, making this nervous system more complex than those seen in today’s descendants, and proving that evolution isn’t a one way street to complexity (PNAS, DOI: 10.1073/ pnas.1522434113). Andy Coghlan
entirely dismiss the idea that ice may have been present. De Wit and Furnes’s ideas are supported by the research of Ruth Blake at Yale University. She says her isotope work also suggests relatively cool water temperatures in the Archaean, similar to those of today’s tropical oceans. Life first appears in the fossil record around 3.4 billion years ago, although some think it may have evolved millions of years earlier. If there was ice present when life emerged, this would bolster theories that suggest important stages in the origin of life occurred inside frozen water. “Key organic compounds thought to be important in the origin of life are more stable at lower temperatures,” says Jeffrey Bada at the University of California at San Diego. He adds that important organic molecules, which might have been present in tiny quantities in the early ocean water, could have become more concentrated in ice. But if life did emerge on a cool Earth, it wouldn’t necessarily have done so at freezing temperatures. Instead, it could have formed around hydrothermal vents, and there is no clear way to determine which theory is correct. n
Colin Barras
Michael Schwab/Getty
Life may have begun in icy seas this could sometimes have dropped to today’s polar temperatures. For ice to be present at these relatively low latitudes, the planet must have been locked in a severe ice age at least once during the Archaean. Oxygen isotopes in ancient rocks had previously been used to calculate sea temperature at this
DID life begin in the freezer? Early Earth may not have been as hot and hellish as we thought, and our planet may have been in a deep ice age when life first emerged. This is according to an analysis of rocks from South Africa that formed about 3.5 billion years ago, during the Archaean period. “Key organic molecules Previous research suggested for the origin of life that the ocean in which these could have become more rocks formed was hot – perhaps concentrated in ice” around 85 °C. But Maarten de Wit at the Nelson Mandela Metropolitan University in Port time, but de Wit believes that Elizabeth, South Africa, now says these indicated a misleadingly ocean temperatures at that time warm temperature, due to local were similar to today’s. hydrothermal activity. South Africa’s Barberton Working with Harald Furnes at Greenstone Belt, where these the University of Bergen, Norway, rocks are now found, formed at a de Wit looked instead at rocks latitude of 20° to 40° – equivalent that formed in the deep sea, away to the border between the tropics from ancient hydrothermal vents. and mid-latitudes today. De Wit These rocks contained gypsum, says ocean temperatures here a mineral that only grows if water would have been around 26 °C, temperatures are below 40 °C. while evidence of glacial activity What’s more, in a sequence of in some of these rocks suggests nearby Archaean rocks that
–A chilly start to life on Earth?–
formed in shallow water about 30 million years later, de Wit and Furnes found evidence of dropstones, which are associated with icebergs, suggesting that ocean temperatures must have plummeted and the planet was in the grip of an ice age (Science Advances, doi.org/bcw2). Don Lowe at Stanford University in California says his team’s extensive studies in the area have found no evidence of glaciation, but he doesn’t
Jie Yang (Yunnan University; China)
Oldest Fossilised nervous system
Preserved inside 520 million-year-old fossils, this is the most ancient nervous system we have ever seen. The fossils are of Chengjiangocaris kunmingensis, a creature around 10 centimetres long, with multiple pairs of legs and a heart-shaped head. Found in southern China, the five
10 | NewScientist | 5 March 2016
Cambrian fossils belonged to a group of organisms that gave rise to insects, crustaceans and other arthropods. Most interesting of all is its nerve cord and associated neurons. “The detail of this fossil is exquisite,” says Rob DeSalle of the American Museum of Natural History in New York, who
was not involved in the discovery. The animal had a nerve cord that ran the length of its body, with bulbous nodes of neurons located between appendages. “It’s almost like a mini-brain for each pair of legs,” says Javier Ortega-Hernández of the University of Cambridge, whose team analysed and described the fossil. Surprisingly, they found dozens of fine, subsidiary nerves fanning out across the entire length of the nerve cord, making this nervous system more complex than those seen in today’s descendants, and proving that evolution isn’t a one way street to complexity (PNAS, DOI: 10.1073/ pnas.1522434113). Andy Coghlan
entirely dismiss the idea that ice may have been present. De Wit and Furnes’s ideas are supported by the research of Ruth Blake at Yale University. She says her isotope work also suggests relatively cool water temperatures in the Archaean, similar to those of today’s tropical oceans. Life first appears in the fossil record around 3.4 billion years ago, although some think it may have evolved millions of years earlier. If there was ice present when life emerged, this would bolster theories that suggest important stages in the origin of life occurred inside frozen water. “Key organic compounds thought to be important in the origin of life are more stable at lower temperatures,” says Jeffrey Bada at the University of California at San Diego. He adds that important organic molecules, which might have been present in tiny quantities in the early ocean water, could have become more concentrated in ice. But if life did emerge on a cool Earth, it wouldn’t necessarily have done so at freezing temperatures. Instead, it could have formed around hydrothermal vents, and there is no clear way to determine which theory is correct. n