Introduction to taxonomy

Look! Donkeys. And another one. But that one doesn't look exactly like a donkey. Nor a horse.

No, that's right. That one's half donkey, half horse. What d'ya mean 'half'? Its father is a horse, and its mother is a donkey. That animal is a mule.

It's a cross between two species. Let's start at the beginning.. There is a kind of animal called horse. We all know that. Horses can mate with other horses.

They have foals, which grow up and in turn can mate and have new foals. When two animals can mate and have an offspring that is fertile - that can have kids - we say that they are of the same species. Horse is an animal species. Donkey is another animal species. Donkeys can mate with other donkeys and have fertile offspring.

But if a horse and a donkey have an offspring together, the result is a mule, which is sterile, and can't have any offspring. Donkeys and horses are different species. But, how can donkeys and horses still have offspring, if they're not the same species? Well, because they are closely related. Not cousins, or second cousins - but closely enough.

All plant and animal species have a scientific name in latin, in two words. Wild horses are Equus ferus. Here is the donkey. Equus africanus. You see?

The name equus is the same for both species. It's the genus name. Equus. Are there more species in the genus 'Equus'? Yes, for example zebra.

This is the plains zebra, Equus quagga. The same genus name, but a different species name. But what does it mean that they are relatives? We can see clearly that horses, donkeys and zebras look somewhat similar and behave in similar ways. They walk on four hooves, and they have pointed ears.

They eat grass, and live in herds. But the most important thing is that they have a common origin. Once, many millions of years - and many generations - back in time, these horse-like animals had a common ancestor. Some animals left the herd, and took off. Their offspring slowly adapted to new habitats, and eventually, they became so different from the original group, that they had become a new species.

So the common ancestor gave rise to new individuals that look similar in some ways, but also are clearly different. Different species, but related. We can follow the development of a species further back than that. We have seen how the species wild horse belongs to the genus horse. And it also belongs to the horse family - 'equidae', and the class mammals - 'mammalia'.

You might know about mammals. These are all animals that give birth to living young and suckle them. Like dogs, elephants, and -- human beings. Yes. We are mammals and belong to the same class as horses.

We can trace the development of our species, from the class mammals, via the order primates and the family hominids all the way to the species Homo sapiens. This is the scientific name for the human being. And of course there are other branches to follow. In the family hominids we also find the great apes - orangutan, gorilla, and chimpanzee, on the branch tips. These are humans' closest living relatives on Earth.

It's easy to see that they share several characteristics with us. We also see that when we group all plant and animal species, a giant 'tree' of all life on earth results. And at the bottom of the tree, one single common ancestor. -- The division of species into different genera and families is called taxonomy. The tree of taxonomy is large and complex. You don't need to know it in detail, but it is important to understand how it works; and it's very useful to biologists.

The scientific names give biologists around the world a common language to discuss their research. The clear rules for the classification make it easier to identify and classify newly discovered species. And it's very useful to those working to conserve endangered species, to know which species are related to each other. You see? We are all related, although distant.

Ahhh... I hope they won't all start turning up at our family reunions!