The early Earth and the Earth today differ a lot in what the conditions on the planet were and are in the present.
1. The days and nights were much shorter;
Because the Moon was much closer to the Earth than what is now, the days and the nights lasted much less. The reason for that is that the Moon was orbiting faster around the Earth than in the present.
2. The atmosphere had much different composition;
The atmosphere of the early Earth was nothing like today's atmosphere, as for starters, that atmosphere would not be enabling breathing, especially not for the bigger species. The thing is that the oxygen levels were very low, and they only started to increase after the marine organisms started to use the process of photosynthesis when they released very large amounts of oxygen in the atmosphere.
