What we previously thought about how life spurred on earth from the first multi-cellular life 4.5 billion years ago may not be the first. A new study suggests that life may have come and gone long before the ones that preceded the life that we know today.
Complex life forms may have existed on Earth and that means nothing close or related to anything that thrived on Earth's recorded past or thrives in the present that we know today.
Earth is thought to be 4.5 billion years old. But 1 billion years after earth was made, two of the three kingdoms of life arose, which are bacteria -mitochondria that we see in our cell today- and archaea. The third one, eukaryote, the proponent of complex life, arose only around 1.75 billion years ago.
As to why the eukaryote only came later, the scientists proposed that Earth may have been oxygen deprived around the time when only the bacteria and eukaryote were thriving.
But a new study
in the University of Washington challenged what was previously believed, complex life may have been present before eukaryotes. The researchers found evidence that the Earth's atmosphere spiked between 2.4 and 2 billion years ago before it dropped off again drastically.
"There is fossil evidence of complex cells that go back maybe 1.75 billion years," said Roger Buick, member of Astrobiology Program of the University of Washington. "But the oldest fossil is not necessarily the oldest one that ever lived - because the chances of getting preserved as a fossil are pretty low."
"This research shows that there was enough oxygen in the environment to have allowed complex cells to have evolved, and to have become ecologically important, before there was fossil evidence," he added. "That doesn’t mean that they did - but they could have."
I wonder if this finding may be linked to the recent study suggesting that the unknown 5 percent in the Earth's core is silicon
. Scientists say that a silicon core may have affected the oxygen level of Earth 4.5 billion years ago.
See: 1 Million-Year Old Bacteria, Antibiotic-Resistant Found in Cave Disputes Old Belief