Radio Times: Review by:; Mark Braxton

The snail and the narwhal aren’t obvious stable-mates, but they are linked
– at least in this programme. Both have developed a twist: the narwhal with its ferocious prong and the snail with its chic mobile home.

There are many theories as to why the Arctic-dwelling narwhal has a tusk at all – weapon, food-catching utensil, icebreaker – but scientists are still trying to work it out, after four centuries as a source of myth. When a 16th-century seaman found such a narwhal tusk (actually a tooth) and thought it was a unicorn’s horn, Elizabeth I is said to have paid £10,000 for it.

It’s another half-hour packed to the gunwales with dazzling and delightful facts.

About this programme

4/5. David Attenborough questions why spirals are so widespread in nature. He gleans some answers by examining the narwhal's tusk and the spiral shells found on snails and ammonites, as he continues to discover nature's evolutionary anomalies.