Evolution Runs Faster on Short Timescales Examine evolution over the course of years or centuries, and you’ll find that it progresses much more quickly than it does over geologic time. Now the oldest viruses on the planet are enabling scientists to calibrate this evolutionary clock.
Remains of microorganisms at least 3,770 million years old have been discovered by an international team led by UCL scientists, providing direct evidence of one of the oldest life forms on Earth.
Tiny filaments and tubes formed by bacteria that lived on iron were found encased in quartz layers in the Nuvvuagittuq Supracrustal Belt (NSB), Quebec, Canada.
The NSB contains some of the oldest sedimentary rocks known on Earth which likely formed part of an iron-rich deep-sea hydrothermal vent system that provided a habitat for Earth's first life forms between 3,770 and 4,300 million years ago. "Our discovery supports the idea that life emerged from hot, seafloor vents shortly after planet Earth formed. This speedy appearance of life on Earth fits with other evidence of recently discovered 3,700 million year old sedimentary mounds that were shaped by microorganisms," explained first author, PhD student Matthew Dodd (UCL Earth Sciences and the London Centre for Nanotechnology). (...)
Prior to this discovery, the oldest microfossils reported were found in Western Australia and dated at 3,460 million years old but some scientists think they might be non-biological artefacts in the rocks. It was therefore a priority for the UCL-led team to determine whether the remains from Canada had biological origins.
The researchers systematically looked at the ways the tubes and filaments, made of haematite - a form of iron oxide or 'rust' - could have been made through non-biological methods such as temperature and pressure changes in the rock during burial of the sediments, but found all of the possibilities unlikely.
The haematite structures have the same characteristic branching of iron-oxidising bacteria found near other hydrothermal vents today and were found alongside graphite and minerals like apatite and carbonate which are found in biological matter including bones and teeth and are frequently associated with fossils.
They also found that the mineralised fossils are associated with spheroidal structures that usually contain fossils in younger rocks, suggesting that the haematite most likely formed when bacteria that oxidised iron for energy were fossilised in the rock. (...)
Researchers said Tuesday they had uncovered fossils showing that complex life on Earth began more than 1.5 billion years ago, nearly a billion years earlier than previously thought.
But the evidence, published in Nature Communications, immediately provoked debate, with some scientists hailing it as rock solid, and others saying they were wholly unconvinced.
After first emerging from the primordial soup, life remained primitive and unicellular for billions of years, but some of those cells eventually congregated like clones in a colony.
Scientists even took to calling the later part of this period the "boring billion", because evolution seemed to have stalled.
But at some point there was another huge leap—arguably second in importance only to the appearance of life itself—towards complex organisms.
This transition progressively gave rise to all the plants and animals that have ever existed.
Exactly when multi-cell eukaryotes—organisms in which differentiated cells each contain a membrane-bound nucleus with genetic material—showed up has inflamed scientific passions for many decades.
The new study is sure to enrich that tradition.
"Our discovery pushes back nearly one billion years the appearance of macroscopic, multicellular eukaryotes compared to previous research," Maoyan Zhu, a professor at the Nanjing Institute of Geology and Palaeontology, told AFP.
The fossils were uncovered in Hebei Province's Yanshan region, where Mao Zedong and his communist army hunkered down during World War II before coming to power.
Zhu and colleagues found 167 measurable fossils, a third of them in one of four regular shapes—an indication of complexity. (...)
What Sparked the Cambrian Explosion? An evolutionary burst 540 million years ago filled the seas with an astonishing diversity of animals. The trigger behind that revolution is finally coming into focus