It’s hard to really say. They believe that life started to appear around 3.5 to 3.7 billion years ago, which means that earth was without life for around a billion years. Fossil records in Australia show single celled and simple multicellular life around 3.5 billion years ago. There might well have been life before this time, but with out fossil records, it is impossible at this time to know. At that time Australia would have been part of a giant land mass that formed a super continent, a lot larger than anything present today.
I read up on this earlier in the week! I’m learning more from working with Wonders that I do normally!
Yes, there were little green-blue bacteria called cyanobacteria, and other similar little single celled life which were the first creatures. They produced oxygen and other gases, which were all pretty much in balance, until something happened in the Earth’s crust that meant that an element called nickel was running out. The other bacteria needed this to make their gases like methane, but they started to die out as the nickel ran out. The cyanobacteria started increasing in numbers because they basically no competition. This was before 2.7 billion years ago. At this point in time, oxygen wasn’t in the air, but instead was used to make things like rocks with iron in them become rusty. Suddenly all the stores for oxygen ran out, and there was a huge explosion of extra oxygen. It couldn’t be stored anywhere, so it went into the atmosphere. This was called the Great Oxidative Event. After this point, life had to adapt to an atmosphere that contained oxygen, and it was this point in time where life started to become more complex, with multi-cell creatures that eventually built up to become even bigger animals, with legs, and lungs, and a different method of reproduction. Eventually after a whole load of evolution, we appeared!
Does that make any sense? If you have any questions about it, let me know. I didn’t know about the Great Oxidative Event until Monday, but I think it’s fascinating!