Origin of life

The origin of life on earth is unknown. However evidence is accumulating. The broad outline of evolution is known. The earth was formed from an accretion of dust and gas orbiting the sun. Essentially it is thought that  gravity pulled particles together and they in turn attracted more until the earth was formed.

This formation occurred about 4.5 billion years ago. It is believed that early earth was intensely volcanic and was being bombarded by meteors. It was thought, when I was a lad ,that life started in some shallow pools irradiated by the sun and struck by lightning. From the mix of chemicals produced some organisation took place allowing the very simple single cell organism to reproduce and evolve.

All life is essentially closely similar using the same biochemistry. Although we see a huge variety of plants and animals now it is all, at an elementary chemical level ,the same. The ability to reproduce at a chemical level depends on the double helix of DNA. This can split, join a messenger chain and then form a new helix which is faithful copy of the original. A faithful copy which can change very slightly under the influence of various accidents. Most of these accidents prevent good reproduction and produce an inferior organism. Just occasionally the accident produces an organism better suited to its environment. This will then out breed the exiting less well fitted ones and gradually replace them. This is evolution.

Clearly this is a very, very slow process. However evolution has a great amount of time to work. Deep time is so vast that it is difficult to comprehend. The analogy I like is a length of wire stretched from London to Birmingham to represent the whole of time on earth. Then imagine an inch clipped off the end- this would represented the whole of recorded history.

It used to be thought that life was very fragile demanding a narrow range of temperature, pressure etc to live not to mention sunlight to provide energy and water to provide the medium in which the chemicals could interact. However as investigation has deepened so it is now appreciated life can exist under far more extreme conditions. This life is very simple but the so called extremophiles have been found is the most extraordinary of places.

The most extraordinary is around volcanic vents under the ocean. These vents are teeming with life but they are so deep as to be in total darkness. The organisms derive their energy from the hydrogen sulphide gas released at the vent. This is a departure from the energy of photosynthesis.  Increasingly scientists think the only condition for life is the presence of water. Although Mars is too cold for liquid water to exist now there is plenty of evidence that at one time liquid water was present so hence the huge interest in life on Mars. This will be very simple single cell remains but it may be there to find.

Above I mentioned the muddy irradiated pool as a possible origin of life. Certainly it was found years ago that simple chemicals under influence of heat and lightning produced a mix containing complex chemicals needed for life. Other possibilities exist for example meteors and comets contain complex chemicals which could be the source.

Recently some very intriguing evidence has emerged of possible elementary life which may have started around undersea vents. Certainly these are dated only a few hundred million years after earth formed and are the oldest candidates for the remains of early life. Much yet is still to be discovered.

Get ready to laugh at Denis Norden’s favourite military joke.

A Cockney soldier gets a short leave pass and rushes home. He returns soaking wet. “Blimey” says his mate is “it still raining in London?” The soldier replies” no, when I got home the wife was in the bath”.