Scientists Found Evidence Of The Biggest Event In Earth’s History
—
Was the Cambrian Explosion 530 million years ago which, for unclear reasons, began life as we know it on Earth. This was first noted in the 1840s. After that, everything else is minor.
It was closer to 540 million, and it wasn't the beginning of "life as we know it on Earth". The oldest undisputed bacterial fossils (stromatolites) are well over 3 billion years old, with some tentative fossil traces and chemical signatures indicating life as old as 3.6 and 3.8 billion years.
The early Cambrian was the first appearance of most of the major lineages of animals - arthropods, vertebrates, mollusks, etc, though there are fossils of simple animals like corals and sponges that predate the Cambrian explosion by tens of millions of years (and algae etc predating it by hundreds of millions of years).