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

Iain Cameron
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Meet Scotland's 300-year-old snow patch, the Sphinx

Snow patch watchers expect it to melt away by the weekend. 

This weekend, Scotland's most resilient snow patch, dubbed Sphinx, is expected to melt away. The news has been met with a surprising outpouring of emotion and nationwide coverage. Even The Financial Times covered the story with the headline "The end is nigh for Britain's last snow". The story has also gone international, featuring in radio reports as far away as New Zealand.

So what is it about Sphinx that has captured the public’s imagination?  Some have suggested it could be symbolic. The Sphinx represents how we all feel, helpless and doomed to a fate determined by leaders like Donald Trump and Kim Jong Un. 

Regular contributors to the Facebook page “Snow Patches in Scotland”  have their own, more prosaic theories. One tells me that the British are “generally a bit obsessed with weather and climate”, while another says snow-patches are "more interesting than anything Trump/May/Boris or Vladimir have to say”.

Those more interested in patches of snow than the existential consequences of international relations could be dismissed as having seriously skewed priorities, but there's more to the story of Sphinx than lies on the surface. 

For a start it's thought to be 300 years old, covering a small square of the Cairngorms for centuries with just six brief interruptions. Last time the Sphinx disappeared was 11 years ago. Though it may melt away this weekend, it is expected to be back by winter. 

Iain Cameron, the man who set up the Facebook page "Snow Patches in Scotland" and someone who has recorded and measured snow patches since he was a young boy, says that Sphinx has shrunk to the size of a large dinner table and he expects it will have melted entirely by this Saturday.

It came close to disappearing in 2011 as well, he adds. In October of that year, Sphinx at around its current size and only a heavy snowstorm revived it.

"They tend to keep the same shape and form every year," Cameron tells me. "It might sound weird to say, but it’s like seeing an elderly relative or an old friend. You’re slightly disappointed if it’s not in as good a condition."

But why has Sphinx survived for so long? The patch of land that Sphinx lies above faces towards the North East, meaning it is sheltered from the elements by large natural formations called Corries and avoids the bulk of what sunlight northern Scotland has to offer. 

It also sits on a bid of soil rather than boulder-fields, unlike the snow patches on Britain's highest mountain Ben Nevis. Boulder-fields allow air through them, but the soil does not, meaning the Sphinx melts only from the top.

Cameron is hesistant to attribute the increased rate of Sphinx's melting to climate change. He says meterologists can decide the causes based on the data which he and his fellow anoraks (as he calls them) collect. 

That data shows that over the past 11 years since Sphinx last melted it has changed size each year, not following any discernable pattern. “There is no rhyme or reason because of the vagaries of the Scottish climate," says Cameron.

One thing that has changed is Sphinx's title is no longer quite so secure. There is another snow patch in near Ben Nevis vying for the position of the last in Scotland. Cameron says that it is 50:50 as to which one will go first.