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Cell Biology
The World of Cells
The First Cells
The First Cells

It was once believed that the formation of the first cell was the most difficult and time consuming part of creation, but once that first cell had formed, it had not taken long for multicellular organisms to evolve.

Fossil evidence shows that multicellular life came into existence about 600 million years ago, however, the age of the earth was over 4.6 billion years old. Putting these two facts together, it seemed that the earth was lifeless for its first 3 billion years, and during that time the constituents of the first cells were slowly synthesized, drawn together and assembled into the first proto-cell.

However, once the first cell had been formed, well understood evolutionary forces took over and very quickly multicellular creatures appeared, adapted to a wide variety of environmental condition and rapidly spread out over the surface of the planet.

But this conventional view appears to be wrong. In 1965 E.S. Barghoorn and J.W. Schopf looked inside a type of rock known as Fig-Tree cert which was thought to be at least 3.1 billion years old. There they found the fossilized remains of tiny micro-organisms which were only visible using the electron microscope. These newly discovered creatures had very simple structures and closely resembled modern bacteria, so Barghoorn and Schopf called their discovery Eobacterium isolatum which means "solitary dawn bacterium."

Such evidence has pushed back the dawn of life from 600 million years to 3.1 billion year ago!.

These 'dawn bacteria' evolved very slowly, and their descendants are probably today's prokaryotic cells. Prokaryotes are very simple, single-celled organisms, without internal compartments and are usually surrounded by a cell wall. What is most important about them is that they do not have a nucleus, hence the name prokaryote (pro = before; kary = nucleus).

For more than 1.5 billion years, it seems, the 'dawn bacteria' had the world to themselves, but then, about 1.2 to 1.4 billion years ago a more complex cell evolved. This was probably the ancestor of today's eukaryotic cells (eu = true: kary = nucleus). Eukaryotic cells are larger than prokaryotic cells, they have internal compartments called organelles, they have a nucleus and have the ability to form multicellular structures. It was from the first eukaryotic cells that all multicellular life has evolved.


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© 2001, Professor John Blamire