In the beginning

In the latest in a series of Friday features, we unlock another of the secrets in the scientific world with the help of lecturers at UCO’s degree partners at Huddersfield University. Today: the origins of life on Earth by Dr Roger Jewsbury, School of Applied Sciences, University of Huddersfield

Though Charles Darwin was able to explain what life has done in the meantime, he could never answer the question of how it all started.

However, latest research may now explain how a few chemicals on the surface of Earth transformed into life itself . . .

We know from the age of fossils that life started during the first quarter of the lifetime of the earth, but we are still not sure how it happened, and we have no idea how likely it was as, so far, we have no evidence for life elsewhere in the universe.

We are able to explain the composition of Earth and the known universe starting with simple nuclear particles formed after the big-bang, followed by well-understood nuclear reactions which create the known elements in stars.

Some of this matter then cooled to form Earth and other planets.

Once a simple form of replicating life was formed on Earth, we have the model of evolution by natural selection that Charles Darwin proposed and supported by evidence from his observations 150 years ago.

But it is that change from inanimate chemicals to the earliest form of life that is not yet understood.

There are many ideas, and there has been some success with experiments over the last 50 years, but nothing yet has been totally convincing.

Suggestions include reactions at deep-sea thermal vents where unusual forms of life are found today.

Other theories involve reactions with clay which is thought to have been common on the surface of Earth then — and reactions on the seashore heated by radioactivity and the seeding of life from outer space which just transfers the question elsewhere.

Darwin himself suggested that life may have started in a warm little pond from salts, light and electricity from lightning.

We do know that the atmosphere would have been different at the time — for example, the oxygen we breathe was formed only once there were the earliest forms of life such as blue-green algae.

Oxygen can be used as an indicator of life, at least life similar to ours, and observing significant amounts on another planet would contribute to evidence of life there.

We can observe molecules in space, more than 130 have been found to date, by their characteristic absorption of light.

So far, the observations have mostly been of inter-stellar space, but NASA has plans to try to detect oxygen in planetary atmospheres using the absorption of infra-red light reflected from the surface by ozone, a form of oxygen.

All known life forms on Earth involve the large molecules DNA and RNA.

DNA stores the genetic instructions. It relates parent to child, is used in paternity cases and in tracing ancestors.

DNA consists of two long strands made of alternating sugar and phosphate units with one of four different bases attached to each sugar.

It is the sequence of these four bases along the backbone that provides the code for all known living matter.

DNA is very stable, hence its forensic use but the very closely related single-stranded molecule RNA which is also self-replicating is thought to be more likely to have been formed first. Many people have thought that it would be impossible for such a complex molecule as RNA to form spontaneously from its constituents and many years of experiments have failed to provide the supporting evidence until now.

Starting with organic compounds identified in inter-stellar gas and phosphate which would have been present on Earth’s surface, researchers have been able to make the building blocks for RNA demonstrating that its formation on Earth could have been possible.

This has involved trying many different combinations of chemicals over 10 years of work.

It is too early yet to be sure that this is the breakthrough that will enable us to understand how life could have arisen, but it is a hopeful sign that this question might soon be answered.