When did animal life begin to appear in the oceans?
480 million and 472 million years ago, during the early part of a period known as the Ordovician, according to recent research.
Discoveries continue, and theories continue to develop or even get over-turned! We can make reasonable guesses from what we observe, but if we are not observing some critical evidence, or interpret an observation incorrectly, we could still be wrong!
More research is always interesting. A REAL scientist knows that the "Science" is NEVER "settled"!