What is “evolution”? The dictionary says that evolution is the process by which plants and animals change genetically over time. So what does that mean? Basically, “evolution” means “change”. Each animal is special and different from every other animal. Even two of the same kind of animal are different in some way. These differences happen because each animal has a special kind of code within its cells called “genes”. This code tells cells how to grow, and it makes every animal a little different from her brothers and sisters. When a dinosaur lays one hundred eggs, each baby dinosaur will have a special set of genes that makes her different from all the others. Some will have larger eyes or longer teeth. Some will have different colors. The babies get their genes from their parents, but none of them are exactly the same as their parents.
Imagine that one hundred baby dinosaurs were born one year. Let’s say that that same year there were fewer leaves on the trees than in other years. That means that there wasn’t enough food to feed all the baby dinosaurs. But some babies were born with longer necks. The dinosaurs with the longest necks would be able to reach leaves higher up on the tree. These babies would survive. The ones with the shorter necks would die. The long-necked dinosaurs would then grow up to have babies of their own. A long-necked mother would pass her long-neck genes on to her babies. Over time – after many thousands of years and lots and lots of dinosaur babies – the species would slowly change. This process is called “natural selection".
According to the theory of evolution, life on earth began as tiny one-celled creatures living in the ocean. These creatures changed bit by bit into all the different creatures that are living here today: fish, insects, lions, whales, monkeys, and human beings. A group of animals can change into a new species that, after thousands of years, is very different from its great-great-grandparents. The theory of evolution was invented by Charles Darwin in 1836. Darwin studied animals his entire life and traveled all over the world to look at different species. He noticed how a species might change in different environments. He wrote a book called The Origin of Species. Darwin’s ideas made many people angry, because most people at the time believed that God created the universe and the earth and all of the animals in seven days. This is called “Creationism”. Today, many people still believe that God created the earth, but most scientists will agree with Darwin’s theory of evolution.