Kristie Malone, of Waihopa School, asks :-

Why are gorilla's arms longer than their legs and why are our arms shorter?

Jo Knight, Curator of Community Programmes at the Auckland Zoo, responded.

What the gorilla looks like today is the product of millions of years of evolution driven by a need to take advantage of their environment.

The fossils that have been found of apes that lived 10 million years ago show that they were much lighter in build than the ones that exist today. They were probably much more active and could swing and leap around in the trees. Long arms are a big advantage when reaching from branch to branch.

Today's tree-swinging experts are the gibbons who have enormously long thin arms. Their young first learn to swing and then to walk. Their arms are so long that they hold them up in the air, hung up like washing, to stop them dragging on the ground.

Orangutans spend most of their time in the trees but have shorter arms because they are heavier than the gibbons. Our large Orangutan, Horst, measures 3 metres from wrist to wrist and has arms which Arnold Schwartzeneger would be proud of.

The chimpanzee and the gorilla have become mainly ground dwelling, but have kept some arm-swinging anatomy. Their arms are slightly longer than their legs but not by much. Humans walk upright and use their arms for jobs other than transport, so theirs have become much lighter and more delicate.