A researcher at St John's College, University of Cambridge, found that mammal subspecies play a more important role in evolution than previously thought.

A species is a group of animals that can interbreed freely amongst themselves.

Some species contain subspecies – populations within a species that differ from each other with different physical traits and their own breeding ranges.

Northern giraffes have three subspecies that usually live in different locations to each other, while red foxes have the most subspecies – 45 known varieties – spread all over the world.

Humans have no subspecies.

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My research investigating the relationship between species and the variety of subspecies proves that sub-species play a critical role in long-term evolutionary dynamics and in future evolution of species

Laura van Holstein

Lead author, Laura van Holstein, a PhD student in biological anthropology, said: "We are standing on the shoulders of giants.