Name one reason life was impossible on early earth

It was clear that back before the first man and also the first women was on the earth, there were certain things that had to be settled first before us humans were able to live on the earth it's self. One reason that it may be very impossible to live on the earth would be the fact that the earth was not ready. The oxygen was not the same as what it used to be back in that time. There was water, but not that much water as what we have today. And not only this, but also the fact that the majority of the land was made from hot lava, which was originally for the reptiles of the land and for them to take there purpose for a straight part. This would be a major point of why we were not eligible to live on the earth at this time.

The atmosphere was toxic and the temperature was scorching 

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.