How is a mouse like a giraffe?

There are thought to be over 5,400 species of mammals living on Earth. They come in all shapes and sizes - from tiny mice to towering giraffes, and scale-covered pangolins to 100-tonne whales.

But despite their differences now, all mammals stemmed from one common ancestor, with the earliest mammal fossils currently thought to date to between 220 and 165 million years ago.

Watch as senior curator of mammals Louise Tomsett explains the surprising similarity between mice and giraffes.

It's all in the neck

Mice and giraffes live drastically different lives – not to mention that giraffes tower over mice by over five meters.

A giraffe's neck is extraordinary long, making up a large part of its height. This allows the animal to reach the leaves of tall trees. But an elongated neck is also integral to the courtship behaviour of 'necking'.

Necking involves males duelling by swinging their heads like battering rams into each other's ribs and legs. Those with longer necks usually stand to an advantage in these battles.

Despite its elongated form, the neck of a giraffe is made up of just seven large bones known as cervical vertebrae.

By comparison, the body of the common house mouse (Mus musculus) is only around 10 centimetres long, its tail contributing more to the overall length.

However, despite outward appearances, the small rodent bears one striking similarity to Earth's tallest living terrestrial creature on a skeletal level.

Mice also have seven cervical vertebrae in their necks, though extremely small compared to those of a giraffe.

Mice and giraffes experienced two very different evolutionary journeys from their common ancestor to end up as the vastly different animals they are today.

With few exceptions, such as manatees and sloths, almost all mammals - including humans - possess seven neck bones.