What was the first living thing on earth?

Question: What was the first living thing on earth?
- Keywords:
  earth,
  first,
  living,
  thing
Asked by gigi123 to Helen, Ian, rhysphillips on 23 Jun 2011.
- Ian van der Linde answered on 23 Jun 2011:
  
  There is a popular theory that before any life developed that we would recognise today, there was a form of life based on rock that could respond to its surrounding and replicate! You’ve probably heard of the primordial soup – some people say that before this there was a “rock soup”!
- Rhys Phillips answered on 23 Jun 2011:
  
  Something that resembles what we’d now recognise as bacteria I think.
- Helen Fletcher answered on 23 Jun 2011:
  
  In terms of the first living thing with cells, the first organism on earth was probably a simple single-celled prokaryote, similar to bacteria that we still have around now. The oldest actual evidence we have is from structures found in Australia that are 3.5 billion years old! They show evidence of things similar to living mats of microorganisms that we can still see today.

Question: What was the first living thing on earth?