Is life on Earth 700m years older than we thought?
LIFE on Earth may have started hundreds of millions of years earlier than previously thought, research suggests.
The planet formed around 4.5billion years ago and fossil remains – the current best way of dating life – have shown it could have emerged up to 3.8billion years ago.
But now researchers from the University of Bristol have calculated that it may be possible to trace a ‘universal common ancestor’ of all life back to around the same time a huge cosmic collision led to the creation of Earth.
They used a new method taking genetic material from organisms living today and calculating backwards to their possible origins.
Around 4.5billion years ago an early form of our planet collided with another slightly smaller one that scientists have called Theia.
The enormous explosion that resulted led to the formation of both the moon and the heavy iron core at the centre of the Earth.
The blast would have entirely ‘sterilised’ the planet but out of the impact life soon took shape, scientists believe.
Earth at that stage would have been a fiery, inhospitable place. The form that the earliest life took is not known but it would have been extremely basic and able to withstand high temperatures.
Whatever form it took survived numerous meteor and asteroid impacts, including a period called the ‘extreme heavy bombardment’ 3.9billion years ago.
The basic form of life carried on and eventually gave rise to all others on Earth, including humanity.
The earliest fossils containing evidence of life forms are claimed to be 3.8billion years old and were found in the isua greenstone Belt in greenland, although these are highly contested. some researchers say ‘micro-fossils’ from the strelley Pool Formation in Australia are in fact the oldest ‘conclusive’ fossils of early life, dating back 3.4billion years.
Holly Betts, lead author of the study from the University of Bristol’s school of Earth sciences, said: ‘The last stage of Earth’s formation was the moon-forming impact, around 4.5billion years ago.
‘Life on Earth is almost as old as the Earth as we know it. There’s quite a strong school of thought that whatever life there was would be something that could deal with pretty high temperatures.’
Co-author Dr Tom Williams said the researchers analysed both fossil and genetic information to make the calculation. He added: ‘We can use an approach called the “molecular clock”, loosely based on the idea that the number of differences in the genomes of two living species, say a human and a bacterium, are proportional to the time since they shared a common ancestor.’
With this method, the team at Bristol, along with mark Puttick from the University of Bath, were able to derive a timescale for the history of life on Earth that did not rely on the debatable age of the oldest accepted fossil evidence.
Co-author Professor Davide Pisani said: ‘Using this approach we were able to show that the last universal common ancestor of all cellular life forms existed very early in Earth’s history, almost 4.5billion years ago – not long after Earth was impacted by the planet Theia, the event which sterilised Earth and led to the formation of the moon.
‘This is significantly earlier than the currently accepted oldest fossil evidence would suggest.’
it was only in the past 570million years that the kind of life forms we are familiar with began to evolve, starting with arthropods. These were followed by fish 530million years ago, land plants 475million years ago and mammals 200million years ago.
our species, Homo sapiens, only emerged 200,000 years ago.
‘It could deal with high temperatures’
‘Impact sterilised the planet’