Everywhere That
Turtles Go

Most claims about connection are wishes. This one is a range map.

In Sand Talk, Tyson Yunkaporta — Apalech clan, Wik — sets out to tell part of a big story, and marks plainly whose it is and that it was given to be given away:

Read quickly, that last sentence sounds like a lovely figure of speech. It isn't one. It is a testable statement about where an animal lives, and the reach of the story is pinned to the reach of the turtle.

So we did the obvious thing and checked. The sentence holds. What follows is what we found on the way — including two places where the turtle's own biology turns out to say the opposite of what everybody assumes.

A path that meanders is not a path that failed. It is just how a path is.

Roughly 357 living species of turtle, and they are almost everywhere you are.

Sea turtles in every warm ocean. Freshwater turtles in rivers, lakes, billabongs, ditches, drainage canals and city ponds on six continents. Tortoises on land from the Mojave to Madagascar to the Aldabra atoll. Softshells buried in river mud. The only continent without them is Antarctica — and the only reason is the cold.

They are also old. The turtle body plan has been recognisably itself for more than 200 million years. It has crossed oceans, watched continents split, and outlasted the animals that were supposed to be the story.

Yunkaporta's sentence works because of a fact about the world, not a fact about language. If you want one animal that nearly every human community on Earth has had to live alongside, look at your options. There are not many. The turtle is one of them.

Which means every people had to think about it — and, as we'll see, they did not all think the same thing.

"Even in desert country" is the part of the sentence that sounds like a stretch. It is the part that is most literally true.

In the Pilbara and Gascoyne of Western Australia, Chelodina steindachneri lives in pools that can dry up and stay dry for a year or more. It does not leave and it does not die. It digs into the riverbed or bank and waits, and comes back to the surface after heavy rain.

Across the world in the Mojave, the desert tortoise Gopherus agassizii spends up to 95% of its life underground, in burrows, out of a heat that would kill it in the open.

And here is the part that makes it more than trivia: those burrows are not only the tortoise's. Other animals shelter in them. The desert tortoise is a keystone species — the one who dug itself a survivable place made a survivable place for everybody else.

Which is, more or less, the whole argument for building rooms that fit the people who need them most.

Everyone knows what a turtle shell is for. Everyone is wrong about how it started.

It did not begin as armour. In Eunotosaurus africanus, an early relative on the turtle stem line from the South African Karoo, the ribs broaden long before there is anything shell-like to hide inside. Lyson and colleagues (Current Biology, 2016) put the case plainly: broadened ribs on their own provide little protection, and they cost you — a stiffened trunk shortens your stride and slows you down, and it gets in the way of breathing.

What broad ribs are good for is digging. A rigid trunk is a stable base to swing a powerful forelimb against. The shell starts as the anchor for a shovel. Protection is an exaptation — a use the structure was not built for, discovered later, and now the only use anyone remembers.

Read it back onto spread 4 and the sentence closes: the animal that got everywhere, including desert country, got there by first learning to go down.

The thing you are told is a hiding place is the thing that let somebody survive.

Every adaptation is a bargain, and in turtles you can read the receipt.

Almost every land vertebrate breathes with its ribs. The ribcage expands, the lungs fill. Mammals, birds, crocodilians, lizards — all of us, all the time, without thinking about it.

Lock your ribs into a shell and that door closes. It is not a small inconvenience; it is the removal of the standard mechanism for staying alive. And Lyson and colleagues (Nature Communications, 2014) found the stem-line evidence for exactly this trade already in place: a rigid ribcage, the inferred loss of the muscles between the ribs, and the bony signatures of a different system taking over.

What took over is a sling of abdominal muscle wrapped around the lungs and organs — a division of labour in which the ribs gave up ventilation and the belly muscles picked it up. No other animal breathes this way.

So: they lost the ordinary way, and they are not diminished. They are a turtle. They went everywhere.

Once you have a shell, you have a head problem. There are two solutions alive today, and neither is the right one.

The hidden-necked turtles — Cryptodira — fold the neck vertically, in an S, and pull the head straight back under the front of the shell. Sea turtles, tortoises, snappers, sliders, softshells. They are the ones most people picture.

The side-necked turtles — Pleurodira — do not pull back at all. They lay the neck sideways along the shell's edge, tucking the head in under the rim. Every living one lives in fresh water in the southern hemisphere: South America, Africa and Madagascar, and Australia. Their map is a map of Gondwana, the supercontinent that broke apart beneath them.

These are not a good version and a poor version. They are two lineages that met the same constraint and answered it differently, and both are still here, hundreds of millions of years on.

The turtle a reader in Sydney pictures and the turtle a reader in Ohio pictures fold their heads away by different means. Neither of them is doing it wrong.

In most turtles, nothing in the egg says what sex the hatchling will be. The nest says.

It is called temperature-dependent sex determination. Cooler sand, one outcome; warmer sand, the other; and a narrow pivotal temperature between them where a fraction of a degree decides. The machinery is now partly known: the enzyme KDM6B strips a silencing mark from the male-determining gene Dmrt1 and switches the male path on, and at warmer, female-producing temperatures a signalling protein binds the Kdm6b locus and shuts it down.

And it is not even tidy across the group. In the Asian yellow pond turtle, researchers found XY chromosomes and temperature sensitivity in the same animal, working together. The neat binary of "genetic or environmental" was ours, not the turtles'.

Which brings us to the philosophers of the Discworld. In Terry Pratchett's novels, the great turtle Great A'Tuin carries the world, and the learned spend enormous effort trying to determine A'Tuin's sex. They never manage it.

The joke is better than they knew. They were looking in the wrong place. In a real turtle the answer is not written in the animal at all. It is in the temperature of the sand where somebody laid it.

A sea turtle hatchling crosses the beach once, in the dark, weighing less than a bar of soap. Decades later it comes back to lay its own eggs on the same stretch of coast.

How? Earth's magnetic field varies from place to place, and every stretch of coastline carries a slightly different signature. The evidence is that a hatchling learns the field of its natal beach and holds onto it — geomagnetic imprinting — then uses it to navigate home across an ocean.

Brothers and Lohmann (Current Biology, 2015) tested this against nineteen years of nesting records along 600 km of Florida coast. As the field drifted, the nesting drifted with it. Where two stretches of coast came to share a signature, turtles crowded in; where the signatures pulled apart, nesting thinned.

They are carrying a route in the body, learned once, held for a lifetime, and read against a planet that keeps quietly moving underneath it.

A route held as knowledge, carried across a life, tying a people to a country. That is a rhyme with what a songline does — and a rhyme is all it is. The Larrakia story is not turtle magnetoreception, and turtle magnetoreception is not a songline. Two true things, next to each other.

Yunkaporta records Oldman Juma Fejo giving the sequence in the shell, and then records their own reaction to it:

Here is what is on an actual carapace. The keratin plates — scutes — are laid out to a plan: a small one at the neck, then five down the midline, flanked by four pairs at the sides and about twelve pairs around the rim. Five in a row along the centre of the shell is not a poetic flourish. It is what you count when you look.

And we will say plainly where the passage stops being biology. Yunkaporta goes on to call this the golden ratio "that all nature is built upon, from flowers and trees to your body and even DNA." That last step is not supported. The golden ratio is not a general law of living form, and it is not in the structure of DNA.

Both things are true at once, and we are not going to collapse them. A knowledge system that counts a real pattern in a real animal is not made better by a modern number, and not made worse by that number turning out to be over-claimed. The count in the shell is right. The cosmology is Larrakia. The maths claim is a maths claim, and it doesn't stand.

Because turtles are almost everywhere, almost everybody had to think with one. What they thought is not the same thought.

In Haudenosaunee and Anishinaabe accounts, Sky Woman falls, animals dive for earth, the muskrat surfaces with mud in its claws, and the land is spread on a great turtle's back. This is why Turtle Island is a name for the continent — not a metaphor for it, a name.

In the Chinese Huainanzi, the four poles of the world collapse, and Nüwa cuts the legs from the great sea turtle ao to prop the sky back up. The turtle is not a foundation; it is a repair.

In the Hindu texts, Kurma is Vishnu's tortoise form, a pivot on the seabed so a mountain can be used to churn the ocean. Kurma is not carrying the world. The world-on-a-turtle's-back story is not this story, and the conflation is a Western habit.

And in Terry Pratchett's Discworld, Great A'Tuin — Chelys galactica — swims through space with the world on its back, and nobody knows where or why.

Here is the connection, and it is not that these are one story. They are five peoples who met the same animal and each made something different of it. The turtle didn't unify anybody. It gave everybody something to think with, and then let them think.

A note we owe you: "turtles all the way down" is not William James and not Bertrand Russell. James wrote it with rocks, in 1882. The turtle version was hung on him in a 1967 thesis and has been repeated ever since. Its earliest printed appearance is from 1854.

One last fact, and then the thing we actually came to say.

A turtle shell is not a house it climbed into. The carapace is the animal's ribs and vertebrae, grown wide and fused. It is bone. And bone, as Iwao Yasuda found in the 1950s, is piezoelectric: press it and it answers with a small electrical charge. That is where this whole collection started, on page one of Bone Song.

So the shell is not inert cover. It is a living structure that turns pressure into signal — the part of the animal that responds when the world leans on it.

Which is why the phrase grates. "Come out of your shell" is said to quiet kids, to Autistic kids, to anyone whose way of being in a room is read as absence. It assumes the shell is a hiding place, and that the real person is elsewhere. In the animal that gave us the phrase, the shell is the skeleton. There is no coming out. There is no one in there behind it.

And the ones who did all that are in trouble. Around 75% of the testudine species studied show slow or negligible senescence — most of them age more slowly than we do, and some barely age at all. A lineage that largely does not die of being old is being killed anyway: roughly half of all turtle species are threatened. Deep time is no protection from a net, a road, or a bought beach.

Asked whether that is really true, Didactylos shrugs and says the Turtle exists, that this will go on happening whether or not you believe it, and — the three words the whole zine has been walking toward — "It is real."