Inside Nature's Giants

The Australian Outback is home to millions of kangaroos but, sadly, every year thousands are fatally injured in traffic accidents. Veterinary scientist Mark Evans and comparative anatomist Joy Reidenberg take the opportunity to delve inside these bizarre animals.

They uncover the kangaroo's lower jaw, which splits in two, and a massive Achilles tendon that enables it to hop like a frog.

But it's the reproductive anatomy they find most surprising: the male genitalia is back to front, while females have three vaginas as well as the pouch in which they grow their young from jelly-bean-sized embryos.

Meanwhile, Simon Watt heads into the Blue Mountains, just outside Sydney, to follow in the footsteps of Charles Darwin. Back in 1836, when the young naturalist visited Australia, he wondered why the animals there were so different to those back home.

Joined by Darwin's great, great grandson Christopher, Simon goes in search of some of these other creatures. Including a bird that decorates its nest with an assortment of blue ornaments - from clothes pegs to bottle tops - and a primitive mammal that lays eggs like a reptile.

Christopher explains how these animals and the island they live on played a crucial role in developing his ancestor's then-heretical ideas on evolution.

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