The start of life on Earth

The Urey Miller experiment showed that the chemicals of life on Earth could be produced on Earth under the conditions that were thought to be occurring between 3.5 and 4 billion years ago.  Geological evidence tells us that liquid water was around and that no oxygen was present at this time.  

Some of the mudstones that make up the Barbeton mountain range in South Africa are up to 3.5 billion years old.  Microscopic analysis of these suggests that there are fossilised bacteria in these rocks.  Not only do they look similar to modern bacteria, but some appear to be dividing, an indication of life.

Similar finds of bacteria have recently been announce in Western Australia.

The step from the chemicals of life to life itself is not well understood.  While scientists have been able to make cell components, they have been unable to asseble them into anything resembling a cell.  It is an area of some molecular biologists whose aim is to make a "synthetic cell".


How did the first bacteria obtain energy and nutrients?

It is possible that the earliest bacteria consumed the complex molecules that were formed before life arose. That would make them heterotrophic ("eats others").  As these molecules were exhausted, some bacteria were utilising the energy provided from minerals in volcanic springs.  These types of bacteria are autotropic (make their own food), more specifically chemoautotrophic (make their own food using simple chemicals).  However, some bacteria began using a far more available source of energy to make their own food, the sun.  

This was the start of photosynthesis for life on Earth, and would allow some organisms to produce their own food by sunlight.  This was the beginning of photoautotrophic life on Earth.  One of the by-products of this was oxygen.  It was this oxygen that would change everything for Earth and shape it's future.