Stephen Baxter - Stone spring

The comet swam out of the dark. Its light bathed the planet that lay ahead, reflecting from a hemisphere that gleamed a lifeless bone-white.

Vast ice caps covered much of North America and central Asia. In Europe a single monstrous dome stretched from Scotland to Scandinavia, in places piled kilometres thick. To the south was a polar desert, scoured by winds, giving way to tundra. At the glaciation’s greatest extent Britain and northern Europe had been abandoned entirely; no human had lived north of the Alps.

At last, prompted by subtle, cyclic changes in Earth’s orbit, the climate had shifted – and with dramatic suddenness. Over a few decades millennia-old ice receded north. The revealed landscape, scoured to the bedrock, was tentatively colonised by the grey-green of life. Migrant herds and the humans who depended on them slowly followed, taking back landscapes on which there was rarely a trace of forgotten ancestors.

With so much water still locked up in the ice, the seas were low, and all around the world swathes of continental shelf were exposed. In northern Europe Britain was united with the continent by a bridge of land that, as it happened, had been spared the scouring of the ice. As the thaw proceeded, this north land, a country the size of Britain itself, became rich terrain for humans, who explored the water courses and probed the thickening forests for game.

But now, in the chill nights, eyes animal and human were drawn to the shifting light in the sky. The comet punched into the atmosphere. It disintegrated over North America and exploded in multiple airbursts and impacts, random acts of cosmic violence. Whole animal herds were exterminated, and human survivors, fleeing south, thought the Sky Wolf was murdering the land they had named for him. One comet fragment skimmed across the atmosphere to detonate over Scandinavia.

In time the skies cleared – but the remnant American ice caps had been destabilised. One tremendous sheet had been draining south down the Mississippi river system. Now huge volumes of cold water flowed through the inland sea that covered the Gulf of St Lawrence, chilling the north Atlantic. Around the world the ice spread from the north once more, and life retreated to its southern refuges. This new winter lasted a thousand years.

But even as the ice receded again, even as life took back the land once more, the world was not at rest. Meltwater fuelled rising seas, and the very bedrock rebounded, relieved of the weight of ice – or it sank, in areas that had been at the edge of the masses of ice and uplifted by its huge weight. In a process governed by geological chance, coastlines advanced and receded. The basic shape of the world changed around the people, constantly.

And to north and south of the rich hunting grounds of Europe’s north land, generation on generation, the chill oceans bit at the coasts, seeking a way to sever the land bridge.

The Year of the Great Sea: Winter Solstice. The day of Ana’s blood tide, with her father missing and her mother dead, was always going to be difficult. And it got a lot worse, early that very morning, when the two Pretani boys walked into her house.

Sunta, Ana’s grandmother, sat with Ana opposite the door. Ana was holding open her tunic, the skin of her exposed belly prickling in the cold air that leaked in around the door flap. Sunta dipped her fingertips in a thick paste of water, menstrual blood and ochre, carefully painting circles around Ana’s navel. The sign, when finished, would be three big concentric circles, the largest spanning Ana’s ribs to her pubis, with a vertical tail cutting from the centre down to her groin. This was the most ancient mark of Etxelur, the sign of the Door to the Mothers’ House – the land of ancestors. Later this painting would be the basis of a tattoo Ana would carry through her life.

Thus they sat, alone in the house, when the two Pretani boys pushed through the door flap.

They looked around. They just ignored the women. There was snow on their shoulders and their boots. Under fur cloaks they wore tunics of heavy, stiff hide, not cloth as the Etxelur women wore. The boys dumped their packs on the floor’s stone flags, kicked at pallets stuffed with dry bracken, walked around the peat fire in the big hearth, tested the strength of the house’s sloping wooden supports by pushing at them with their shoulders, and jabbered at each other in their own guttural language. To Ana it was as if two bear cubs had wandered into the house.

For her part Sunta didn’t even look up. ‘Pretani,’ she murmured.

Fourteen years old, Ana had only a blurred memory of the last time Pretani had come to Etxelur, a memory of big men who smelled of leather and tree sap and blood. ‘What are they doing in our house? I thought the snailheads were coming for the midwinter gathering.’

Sunta, sitting cross-legged, was stick-thin inside a bundle of furs. She was forty-seven years old, one of the oldest inhabitants of Etxelur, and she was dying. But her eyes were sharp as flint. ‘Arses they are, like the last time they were here, like all Pretani, like all men. But it is custom for the chief Pretani to lodge in my house, the house of the Giver’s mother, and here they are. Oh, just ignore them.’ She continued working on the design on Ana’s belly, her clawlike finger never wavering in the smooth arcs it drew.

But Ana couldn’t take her eyes off the Pretani. She tried to remember what her mother had told her about them before she died. They were younger than they had looked at first. Boy-men, from the forests of Albia.

Under tied-back mops of black hair, both of them wore beards. The older one had a thick charcoal-black line tattooed on his forehead. But the younger one, who was probably not much older than Ana, had a finer face, a strong jaw, thin nose, high brow, prominent cheekbones. No forehead scars. He peered into the stone-lined hole in the ground where they kept limpets for use as bait in fishing, and he studied the way the house had been set up over a pit dug into the sand, knee deep, to give more room. These were features you wouldn’t find in houses in the woods of Albia, she supposed, where nobody fished, and drainage would always be a problem. The younger boy was similar enough to the other that they must be brothers, but he seemed to have a spark of curiosity the other lacked.

He glanced at Ana, a flash of dark eyes as he caught her watching him. She looked away.

His brother, meanwhile, raised his fur-boot-swathed foot and swung a kick at the wall, not quite opposite where the women sat. Brush snapped, and layers of dried kelp fell to the floor. Even a little snow fell in.

At last Sunta rose to her feet. She wore her big old winter cloak, sealskin lined with gull down, and as she rose stray wisps of feathers fluttered into the air around her. She wasn’t much more than two-thirds the size of the Pretani, but she looked oddly grand. ‘Stop that.’ She switched to the traders’ tongue. ‘I said, stop kicking my wall, you big arse.’

The man looked down at her, directly for the first time. ‘What did you call me?’

‘Oh, so you can see me after all. Arse. Arse.’ She bent stiffly and slapped her bony behind, through the thickness of her cloak.

Ana sought for the words in the unfamiliar tongue. ‘But then,’ she said, ‘grandmother calls all men arses.’

The Pretani’s gaze flickered over her body, like a carrion bird eyeing up a piece of meat. She realised she was still holding open her tunic, exposing her throat and breasts and belly. She fumbled to close it.

Her grandmother snapped, ‘Leave that. You’ll smudge the paint.’ In the traders’ tongue she said, ‘You. Big fellow. Tell me your name.’