Evolution

When looking at the variety of animal species, one wonders where they all came from! Fossil evidence shows that animals have been living on our planet for at least 700 millions years. Due to different survival needs, they slowly diversified with some forms becoming more and more complex through the ages, colonizing all environments. This long, slow process, still going on today, is called evolution.

Life most probably started in water, and some of the first animal life forms still in existance today are fishes. They seem to have appeared around 500 millions years ago. From them stemmed the amphibians which, with insects, were among the first animals to live out of water, approximately 350 millions years ago. From these ancient species came reptiles, mammals and birds. Many kinds of animals have ceased to exist long ago. Dinosaurs, for example, were a category of reptiles which disappeared mainly around 65 millions years ago.

Animal evolution through the ages can be traced through a variety of evidence. Fossil evidence consists of animal remains (generally bones) which have been fossilized in rocks. These fossils display how the animals gradually changed over the ages. The science that study fossils is called paleontology. Like archaeologists, paleontologists dig up the data they work with, but unlike archaeologists who are primarily anthropologists studying past human societies, paleontologists are primarily biologists, studying the evolution of all life forms.

Other evidence of evolution is the familiarity between some living animal species. Sometime it is very easy to notice. Take for example dogs, wolfs, coyotes, and foxes, or again grasshoppers, crickets and locusts. Their resemblance suggests they are in some way related and share common ancestors.

Try to classify animals you know in families, and observe in which ways they can be related. Think, for example, of what animals are closely related to bees? To cats? To deers? To humans? Then, if you want to create a bigger evolutionary tree, see if you can group together some of these families into bigger families, and so on. This is called classification, and it gives an idea of how animals evolved through time by making a sort of family tree.