The second in a series of science blogs looking at evolution.
From the beginning of civilisation it seems that humans must have wondered how their existence had come about. We can say this because very early paintings and artifacts indicate that the humans who made them observed life around them . Often the answer to these primitive questions was to invent an omnipotent, supernatural being who had created the world and all its life. After the Middle Ages human understanding had progressed to a point where not only a body of basic science was being built up but standardised investigative techniques (i.e. scientific investigation) were also beginning to be used. For many scientists it became clear that the ‘supernatural being’ was not a valid explanation for the existence and diversity of life.
In the early 19th Century, scientists received plant and animal samples from newly discovered areas of the world and the huge scope of life was realised. Life was nearly everywhere on the planet – so how did life on Earth begin?
Scientists at the time could observe the appearance and behaviour of living animals and plants and could use observation and basic microscopes to look at organs, structures and tissues of plants and animals. The more they investigated the greater the realisation that life was very diverse, yet had many similarities – e.g. all mammals have a similar skeleton structure, yet there are thousands of separate species (currently about 4260) ranging in size and behaviour from a blue whale to a giraffe to a human being to a bat to a shrew. How could groups of living beings be so similar yet so different?
At this time fossil evidence was beginning to be found that indicated that in the past different animals and plants inhabited the Earth. In some cases the fossil evidence indicated that different forms of familiar animals had lived in the past (e.g. the horse). So not only was life diverse but it was changing over time. Other questions could now be asked – ‘Why have some species of plants and animals died out?’ and, ‘How do new species of plants and animals develop?’ Before theories could be developed to answer these questions much meticulous scientific investigation had to be undertaken and the results placed in time context (see the next blog Explaining evolution 3 – Time scales).