As summer continues in Australia, and with it, the long, warm evenings and baking hot weekends, many of us are thinking about the same thing: Going for a swim.
Be it bodysurfing or laps, in beaches, rivers or pools, we've been making up for lost time as La Niña's grip slowly weakens.
But swimming is far more than just an Aussie pastime. It's been part of humanity since before humanity as we know it existed, and has a rich – but also dark – cultural and political history.
Neanderthal ear bones
So just how long have we been going for a dip?
Karen Eva Carr, an associate professor emerita at Portland State University and the author of the new book Shifting Currents: A World History of Swimming, says the earliest evidence recently emerged from excavations in Italy.
Roughly 100,000-year-old remains of a group of Neanderthals, who had been living on Italy's Mediterranean coast, had ear bones that were infected with swimmer's ear.
They "appeared to have been diving to the bottom of a cove where they lived, and bringing up seashells from the bottom, clams and other things", Eva Carr tells ABC RN's Late Night Live.
As for us Homo sapiens, Eva Carr's book describes how "most modern humans knew how to swim when they left Africa [where modern humans emerged], and even if these people didn't, they had time to learn how to swim from Neanderthals when they arrived in the north, at least 42,000 years ago".
And here in Australia, early Indigenous people were "probably also swimmers", with Eva Carr pointing to oral histories, as "traditional stories assume that most people can swim".
A cold snap that changed everything
Starting about 33,000 years ago, a massive cold snap changed how many people around the world approached swimming.
During the last Ice Age, Earth entered another cold period, reaching its coldest point about 23,000 years ago, when glaciers reached as far south as places like England.
Conditions in the north weren't great for learning to swim.
"During this Ice Age, all across northern Asia, from Japan, Korea, northern China, and Europe, everybody in that area seems to have forgotten how to swim. It just didn't get warm enough, even in the summer, for people to want to swim," Eva Carr says.
As a result, communities in this "northern zone" lost the cultural habit of swimming. Swimming came to mean drowning, so bodies of water became places of danger, full of mythical creatures like dragons and sea monsters.
People in more temperate areas continued to swim – setting up a planetary divide of who could swim and who couldn't.
But as the climate picked up and people moved around the planet, things changed.
Swimming lessons in ancient Egypt
From around 2,900 BCE, there's pictorial and written evidence that the ancient Egyptians – in an area away from the once-cold northern zone – were keen swimmers.
"They've got a good form. They're using a nice overarm stroke. They seemed to really know what they're doing," Eva Carr says.
For example, in carvings from one tomb, a powerful governor named Kheti boasts that as a child, he had swimming lessons with the pharaoh's children.
It wasn't just wealthy Egyptians who swam – there's evidence that people from different walks of life, all up and down the Nile River, learnt how to swim.
Swimming was also popular across the African continent.
Eva Carr points to numerous stories that show this, including one ancient Ethiopian story, where a husband-to-be has to show his courage by swimming to an island, spending the night there and then swimming back. If he does so, he gets the right to marry his lover.
Learning from other people
Around 700 BCE, the Europeans, Assyrians and other groups started to trade more with Egypt.
"They're all impressed with how sophisticated the Egyptians are … All these northern people start to use Egyptian papyrus for writing, eat Egyptian dates, wear Egyptian glass beads and Egyptian linen dresses," Eva Carr says.
"They also begin to learn how to swim – to show how sophisticated they are."
As swimming spreads, there's evidence of what was perhaps the world's first floaty: Assyrians using an inflated goat skin.
One carving shows Assyrian soldiers blowing into these devices to stay afloat as they swim across a river.
A similar thing was happening on the other side of the planet – people in the northern parts of Asia had forgotten how to swim during the last Ice Age, but this changed as they connected with people further south.
"Just as people swam in ancient Egypt but not further north in Europe and West Asia, they also swam in South East Asia and Indonesia, but not further north in northern China or Japan."
So, northern Chinese and Japanese non-swimmers learned from the southern Chinese swimmers in the same way that Europeans learned from Egyptians.
A pastime of the wealthy
In Europe, as more people learned to swim, a class divide hardened – it became only the domain of the rich.
"In Europe, people associated swimming with being rich. So it was something only rich people were supposed to do, like having fancy clothes or eating fancy food," Eva Carr says.
"Ordinary people didn't know how."
It's apparent in a quote from Greek philosopher Plato, who said "an uneducated person can't read or swim", like people today may say "read or write".
And as the years went on, it was a very specific type of swimming that the wealthy indulged in.
"If they do swim, they swim only the breaststroke to show that they are civilised, non-splashing people."
Dehumanising and exploiting
During the Age of Exploration, European powers crisscrossed the world. But many on these ships could not swim.
For example, neither Captain Cook nor his crew "knew how to swim and they were all nervous around water". Because of this, they were astounded by the swimming abilities of those they encountered across the Pacific.
But these swimming abilities were twisted by the European powers to dehumanise and exploit Indigenous people.
Indigenous peoples' swimming abilities were wrongly labelled as "natural" in contrast to so-called "scientific" swimming techniques that well-off Europeans learnt.
"Europeans started to feel that it's OK to enslave people because they can swim – because it shows that they're not really human," Eva Carr says.
The Europeans "drew a big distinction between people who splash when they swim, who are 'savages' and should be enslaved, and people who swim calmly and scientifically".
It was just one of many racist assertions used to justify cruelty inflicted on millions of people.
Racist laws
As swimming became a popular pastime in many countries, racial divides around it became law.
"[There was] a worldwide pattern of excluding black and brown people from swimming places," Eva Carr says.
"That started in South Africa, where the first beaches were segregated in about 1888 and it spread from there, all over the world."
The idea was "the water is only for 'civilised' white swimmers".
But people fought back.
Eva Carr points to one example in 1964, when African Americans tried to desegregate a Florida motel pool by jumping in, only to have the motel manager respond by pouring in a form of hydrochloric acid.
Here in Australia, local laws barring Indigenous people from swimming pools was one of the factors that prompted the Freedom Rides in 1965.
Swimming today
Into the 21st century and the uptake of swimming hasn't become universal. Far from it. As Eva Carr says: "Most people used to know how to swim and today most people don't."
It's impossible to know exactly how many people can't swim. But according to one poll, based on more than 150,000 interviews in 142 countries and areas, 55 per cent of people aged 15 and older cannot swim unassisted.
Eva Carr says the past still echoes, through two main ways: "These European non-swimmers who forgot how to swim in the last Ice Age have spread their fear of the water around the world. And also the idea that only rich people should be able to swim."
Eva Carr says there are also modern barriers that stop people from learning to swim.
"It takes a while and you have to have access to a pool and teachers and encouragement."
But she says many people are prevented from this process, with reasons ranging from "the water near them is too polluted to swim in" or "it's fenced off only for tourists".
"I think it's a terrible shame."
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