* Astronomy

Planet's oldest fossils found in Pilbara, experts say

Scientists analysing Australian rocks have discovered traces of bacteria that lived a record-breaking 3.49 billion years ago, a mere billion years after Earth formed. If the find withstands the scrutiny that inevitably faces claims of fossils this old, it could move scientists one step closer to understanding the first chapters of life on Earth. The discovery could also spur the search for ancient life on other planets.
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Large bacterial population colonised land 2.75 billion years ago

There is evidence that some microbial life had migrated from the Earth's oceans to land by 2.75 billion years ago, though many scientists believe such land-based life was limited because the ozone layer that shields against ultraviolet radiation did not form until hundreds of millions years later.
But new research from the University of Washington suggests that early microbes might have been widespread on land, producing oxygen and weathering pyrite, an iron sulphide mineral, which released sulphur and molybdenum into the oceans.
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UAlberta researchers track down earliest known animal

University of Alberta researchers have uncovered physical proof that animals existed 585 million years ago - 30 million years earlier than previous records show.
The discovery was made by U of A geologists Ernesto Pecoits and Natalie Aubet in Uruguay. They found fossilised tracks a centimetre-long, slug-like animal left behind 585 million years ago in silty, shallow-water sediment.
A team of U of A researchers determined that the tracks were made by a primitive animal called a bilaterian, which is distinguished from other non-animal, simple life forms by its symmetry - its top side is distinguishable from its bottom side - and a unique set of "footprints."
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Precambrian fossils, once thought to be embryos, reinterpreted as... something else

Spectacular fossils from Doushantuo in China appeared to resolve this issue. The tiny remains date from the Ediacaran, but appeared to share features with animal (more properly, metazoan) embryos, suggesting that metazoans were around for many millions of years, even though we've been unable to identify any fossils of their adult forms. Since their initial announcement, however, this interpretation has been challenged, with some even suggesting that the fossils were little more than clusters of bacteria.
Now, a group has performed X-ray imaging of the internal structure of the fossils and concluded that they most certainly aren't bacteria... but it's not actually clear what they are. The most likely identity, according to the researchers, is a relative of the first metazoans.
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