Life Appears To Have Evolved
And Gone Extinct Several Times

Australian scientists have developed a new theory that life may have evolved on earth and become extinct several times, only to evolve again.
A team of researchers have developed the theory that the earth was sufficiently benign in its early development to have supported life, rather than being an inhospitable molten environment void of water, as previously thought.
The theory, developed by Curtin University professor Simon Wilde, is based upon researchers' analysis of a single tiny grain of zircon found in a remote area of Western Australia.
Professor Wilde says the new research show it may have been possible that life evolved and was completely extinguished several times in catastrophic, meteorite-triggered extinction events well before life is currently thought to have begun.
He says the researchers have dated the zircon crystal at 4.404 billion years old, which is 130 million years older than any previously dated crystal and just 100 million years younger than the earth itself is believed to be.
"It is not only the oldest material found so far, but provides constraints on the cooling history of earth, the development of oceans and the formation of the moon," Professor Wilde said.
Professor Wilde says the rock formation in which the zircon was formed had to have had contact with water, making the emergence of life theoretically possible.
He says the prevailing view is that the earth was formed about 4.55 billion years ago, requiring 700 million years for magma and lava to cool sufficiently before the evolution of life could begin.
However, Professor Wilde says the discovery shows the earth may have been cool enough to have water, continents and conditions that could even have supported life much earlier.
"It's radical and we do not have the evidence for it, but if you have water, you could have life," he said.
The earliest known biochemical evidence for the existence of life and a hydrosphere is currently estimated to be 3.85 billion years old, while the oldest microfossils are dated at 3.5 billion years

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