Water horses: a mother and baby hippo swim at a zoo in Mexico City. Photo: Getty
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Michael Brooks: Hippo fossils offer clues about swimming

Fossilised guides to what the earth was like millions of years ago are rare, and understanding water tracks can make a difference.

Swimming is unlikely to be something you think about in scientific terms. If you’re doing it at the beach, it’s meant to be fun. And if you’re at a pool, it’s relaxing, or part of an exercise routine. To many scientists, though, swimming is an aide to understanding our place in the world.

Three British scientists have just published their observations of hippopotamus swimming. And not by any old hippo – they were interested in the swimming style of a now-extinct species called Hippopotamus gorgops.

Their interest was piqued by some peculiar tracks in what was once a small lake in northern Kenya. The tracks suggest that 1.4 million years ago a hippo had pushed itself off from the edge, before half walking and half swimming across the lake. It would have been the first observation of fossilised swim tracks made by mammals, so the scientists went to watch modern hippos swimming in a shallow pool to see whether the tracks made sense. They did: the observed hippos paddled through a pool, leaving similar hoof marks on the bottom.

Fossilised guides to what the earth was like millions of years ago are rare. We have to take advantage of every available clue, and understanding water tracks can make a difference. Last year, fossilised tracks that had been associated with a dinosaur stampede were reinterpreted as a river crossing.

We are unlikely ever to find out exactly how land-based dinosaurs swam, but it’s a good bet they looked nothing like we do in the pool. Most four-limbed land creatures swim doggy-paddle. When researchers took chimps and orang-utans for a swim, however, they found breaststroke was the natural instinct for staying afloat. It is probably easier for creatures built with shoulders and hips which have evolved to reach for branches to move limbs parallel to the surface of the water.

Not that our fastest swimmers use breaststroke any more. The front crawl has been in human use for thousands of years, but our observations of the natural world have made it even more efficient. Watching the swimming events at the Commonwealth Games, you’ll see several tricks copied from more natural swimmers.

At the turn, for instance, the competitors will empty their lungs, making them less buoyant. Doing this enables them to use their energy to move forward rather than maintain depth, which is why marine mammals and birds exhale deeply before diving into water.

It is important to remain streamlined when under water, so the leg kick has to be kept to no more than one-third of the body’s length – which is how much the dolphin’s tail moves naturally. Competitors are allowed to swim no more than 15 metres of each length under water and they will make the most of this, as the water there offers one-fifth the resistance of the drag just beneath the surface, research shows.

Swimmers can gain an advantage by mimicking penguins’ and dolphins’ streamlined shape and smooth surface. Hence, swimsuits are engineered to hold the human body in an optimum shape and to allow water to move past with minimal resistance.

That said, you can’t mimic everything in nature. Studies of the clawed frog showed the importance of a long push-off from the end of the pool: its pelvis actually slides along its backbone to give extra length to its legs. But not even the Olympic champion Michael Phelps could manage that. 

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 23 July 2014 issue of the New Statesman, Summer Double 2014

Photo: Getty
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Elusive sharks, magic carpets, and other summer radio highlights

American singer Beth Ditto on BBC 6 Music is hands down the guest presenter of the season.

A trio of things to divert us as we drift into the dog days: the Norwegian non-fiction hit Shark Drunk makes a perfectly dreamlike Book of the Week (BBC Radio 4, weekdays, 9.45am). Its author, Morten Strøksnes, navigates the waters around the Lofoten Islands looking for a Greenland shark, a highly elusive and languorous creature that can reach 200 years in age and has fluorescent-green parasites covering its milky, sad eyes.

Strøksnes is frequently distracted by the strange summer beauty of the islands. Like a naive hero in a dark-edged John Bauer illustration, he is helplessly drawn to their tiny shores, wandering through forests of rowan dripping with chlorophyll or sitting among a species of pretty yellow flower with a fragrance that has earned it the label “arse-wiper gut grass”. Oh, happy picnics!

Then, to a discussion about the “saucy bits” in One Thousand and One Nights on the BBC World Service’s The Forum (1 August, 9am). Dipping into the massive, ancient Indian/Persian collection of stories about flying carpets and genies reminds me a little of surfing the web – it’s a book that contains so many voices. Such a mixture of moralising and immoral behaviour and tall tales. On and on it goes. (The title in Arabic, Alfu Laylatin wa-Laylah, means “endless”.)

How about this? “The porter saw a girl with eyes like a wild heifer, a neck like a cake for eating and a mouth like the sea of Solomon.” A neck like a cake for eating. Phenomenal lines rush past in a gleefully gurgling whoosh, like water let out of the bath.

Finally, hands down the guest presenter of the summer is the American singer Beth Ditto, with her two-hour stint on BBC 6 Music (28 July, 7pm). Clicking her fingers, speaking with a wink, never short of a compassionate anecdote, Ditto has a unique knack of introing a song as good as Planningtorock’s “Living It Out” by increasingly raising her voice as the music starts thrumming beneath, and then louder still, like someone with her hand on the door of a holiday-island nightclub, excitedly shouting instructions at you before everybody bursts in, minus several flip-flops, and heads straight for the bar.

Antonia Quirke is an author and journalist. She is a presenter on The Film Programme and Pick of the Week (Radio 4) and Film 2015 and The One Show (BBC 1). She writes a column on radio for the New Statesman.

This article first appeared in the 27 July 2017 issue of the New Statesman, Summer double issue