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Hello.

As a rule of thumb, one species cannot mate with another species and that very fact is

a way of telling species apart.

But there are hybrids which will once thought the exception to this rule, the offspring

of different species.

Yet the more we look, the more common these hybrids appear to be and the more vital to evolution

from the beginning of life to now and from now onwards.

And they challenge your idea of what a species is and what separates one species from another.

With me to discuss hybrids are Sandra Napp, Tropical Botanist at the Natural History

Museum, Nick Lennardov, Lecturer in Evolutionary Biology at the University of Sheffield and Steve

Jones, Senior Research Fellow in Genetics at University College London.

Steve Jones, can you tell us what a hybrid is?

Well, you've given us already the simple definition which is an individual whose parents

come from two different species across.

Classic example, of course, which people tend to know about, is things like mules which

are the offspring of horses and donkeys and in fact sterile.

But they were always thought to be little quirks, as you said.

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