The Outer Limits

David Toomey explores how our perception of life on earth has changed through the ages

The Biologist Vol 60(4) p20-23

Many natural philosophers in the 17th century assumed that all living organisms were visible to the naked eye and were surprised when contemporaries, such as Antony van Leeuwenhoek in Holland and Robert Hooke in England, discovered life so small it could be seen only through a magnifying lens. There were whole microcosms in a drop of water.

In subsequent years, some naturalists assumed upper limits on an organism's size. Then, in the 19th century, natural philosophers discovered the remains of creatures that had roamed the Earth for millions of years, many larger than any land animal known.

By the 20th century, natural philosophers had come to be called scientists and the subcategory of scientists termed biologists were...

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