We know what the dinosaurs were like because they left their bulky bones to become fossils, But the first animals were tiny, soft bodied creatures. What's more, the first animals lived and died more than a billion years before the dinosaurs. Traces of the first small, boneless creatures are very hard to find.

One way to solve a problem is to attack it on two fronts. In this case, we can examine the distant past when the first animals lived. At the same time, we can examine certain animals that live in the present. Maybe we can find comparisons between the very ancient and the modern types. Scientists, who cannot bear to leave a problem unsolved, have already found a few clues for us in the past and the present.

Let's examine the earth’s crust where specimens of ancient animals have been preserved in fossilized forms. Limestones were made from the shells of small sea dwellers. We think that petroleum was formed from small plants and animals of the ancient seas. Some of the earth's minerals were charged by the life processesof small plants and animals, somewhat as yeast cells change stodgy/into spongy bread.

Some of the earths rocks bearing traces of early life date back 2,000 million years. Limestones are still being formed and other minerals changed by small, modern creatures   so with one giant stride we carry our investigation into the present,

It seems reasonable to suppose that some of the first animals which left hints of their existence in the ancient rocks were somewhat like our own mineral makers.

These modern fellows are sea dwelling protozoa, tiny animals that carry on the entire business of living with but a single cell. A good example of a modern protozoan is the small, soft, water dwelling amoeba,

Science is still probing into the secrets of the dim past and there are still many mysteries to be solved. Some say that the protozoa developed much later from even simpler animals. The first humble animals may have been like the chemicals around them   with just one difference. They could use energy to feed, multiply and hand on the gift of life.

Experts disagree as to whether plants or animals came first. Some say that, since animals feed on plants, then plants must have come first. Others say that, since plants need the carbon dioxide produced by animals, then animals must have come first. This problem is still a mystery.