Walks With Thunder, as he often did, tried to explain life to Longtusk.

"…The Fireheads are strange, but there is a logic to everything they do. Almost everything, anyhow. They are predators, like the wolves and foxes. So they must hunt."

"I know that. Deer and aurochs—"

"Yes. But such animals pass by this way only infrequently, as they follow their own migrations in search of their fodder for summer or winter. And so the Fireheads must store the meat they will eat during the winter. That is the purpose of the pits — even if all those dead carcasses are repellent to us. And it explains the way they salt their meat and hang it up to dry in strips, or soak it in sour milk, and—"

"But," Longtusk complained, "why do they not follow the herds they prey on, as the wolves do? All their problems come from this peculiar determination to stay in one place."

Walks With Thunder growled, "But not every animal is like the mastodont — or the mammoth. We don’t mind where we roam; we go where the food is. But many animals prefer a single place to live. Like the rhinos."

"But these Fireheads have nothing — no fat layers, hardly any hair, no way of keeping warm in the winter or digging out their food."

"But they have their fire. They have their tools. And," Walks With Thunder said with a trace of sadness, "they have us."

"Not me," rumbled Longtusk. "They have me trapped. But they don’t have me."

To that, Walks With Thunder would say nothing.

Longtusk disturbed a carpet of big yellow butterflies that burst into the air, startling him. One of the butterflies landed on the pink tip of his trunk, tickling him. He swished his trunk to and fro, but couldn’t shake the butterfly free; finally, the mocking brays of the mastodonts sounding in his ears, he blew it away with a large sneeze.

They came to a river which meandered slowly between gently sloping hummocks. Vegetation grew thickly, down to the water’s edge: grass, herbs and a stand of spruce forest almost tall enough to reach Longtusk’s shoulders. Farther downstream there were thickets of birch and even azalea, with lingering pink leaves from their spring bloom. In the longer grass wild flowers added splashes of color: vetch, iris, primroses, mauve and blue and purple and yellow.

The mastodonts were allowed to rest. They spread out, moving through the sparse trees with a rustle of branches, tearing off foliage and shoving it into their mouths greedily. Some of them walked into the water, sucking up trunkfuls of the clear, cold liquid and spraying it over their heads and backs.

Longtusk was still hobbled. He moved a little away from the rest, seeking the grass and steppe vegetation he preferred.

He had never been here before. It seemed a congenial place — for mastodonts anyhow. But Longtusk, clad in his thick fur, was already too hot, and mosquitoes buzzed, large and voracious. He looped his trunk into his mouth, extracted a mixture of spit and water, and blew it in a fine spray over his face and head and belly.

He wondered what the Fireheads wanted from this place. Stone, perhaps. The Fireheads liked big flat slabs of stones to put inside their huts and storage pits — but he could see no rock of that kind here. Perhaps they would bring back wood; the mastodonts were strong enough to knock over and splinter as many trees as required.

The keepers came to round up the mastodonts, calling softly and tapping their scalps and flanks with their bone-tipped goads. The mastodonts cooperated with only routine rumbles of complaint.

All the mastodonts had worked here many times before, and they appeared to know what to do. The most skillful and trusted, led by Walks With Thunder, walked down toward the river. They came to a place where the grass had been worn away by deep round mastodont footprints. They began to scrape at the muddy river bank with their tusks and feet, and clouds of mosquitoes rose up around them as they toiled.

Longtusk could see that they were uncovering something: objects that gleamed white in the low sun. He wondered what they were.

…There was a sudden, sharp stench, a stink of death and decay, making Longtusk flinch. Some of the mastodonts trumpeted and rumbled in protest, but, under the calm, watchful eye of Walks With Thunder, they continued to work. Perhaps something had died here: a bison or rhino, its carcass washed along the river.

Soon, with the supervision of the keepers, they were dragging the large white objects from the mud. Walks With Thunder dug his tusks under one of the objects and wrapped his trunk over the top; he rammed his feet against the ground and hauled, until the clinging, cold mud gave way with a loud sucking noise, and he stumbled back.

The thing’s shape was complex, full of holes. It was mostly white, but something dark brown clung to it here and there, around which mosquitoes and flies buzzed angrily.

It might have been a rock.

Jaw Like Rock stood alongside Longtusk, swishing his tail vigorously. "I can stand the work," the squat Bull muttered. "It’s these wretched mosquitoes that drive me to distraction."

Longtusk asked, "Are those rocks heavy?"

Jaw turned to look at him quizzically. "What rocks?"

"The rocks they are pulling out of the river bank."

Jaw hesitated. He said carefully, "Nobody has told you what we’re doing here? Thunder hasn’t explained?"

"No. Aren’t they rocks?"

Jaw fell silent, seeming troubled.

Longtusk found, at his feet, a patch of what looked like mammoth dung. He poked at it and it crumbled. It was dried out, stale, half frozen, obviously old. Regretfully he lifted a few crumbs to his mouth; their flavor was thin.

Since the day he had been separated from his Family by the fire storm — despite the way the Fireheads had him undertake these jaunts across the countryside — he had never seen a single one of his own kind.

But the expeditions always headed south.

He asked Jaw about this.

"Sometimes there are expeditions to the north, Longtusk," Jaw rumbled. "But—"

"But what?"

Jaw Like Rock hesitated, uncomfortable. "Ask Walks With Thunder."

Longtusk growled, "I’m asking you."

"It is difficult to work there. It is poor land. The ice is retreating northward and uncovering the land; but the new land is a rocky desert. To the south, plants and animals have lived for many generations, and the soil is rich…"

He’s keeping something from me, Longtusk thought. Something about the northern lands, and what the Fireheads do there.

"If the south is so comfortable, why do the Fireheads live where they do? Why not stay where life is easy?"

Jaw sneezed as pollen itched at his trunk. He slid his trunk over one tusk and began to scratch, scooping out lumps of snot. "Because to the south there are already too many Fireheads. They have burned the trees and eaten the animals, and now they fight each other for what remains. Fireheads are not like us, Longtusk. A Firehead Clan will not share its range with another.

"Bedrock tried to take the land belonging to another Clan. There was a battle. Bedrock lost. So he has come north, as far as he can, so that his Clan can carve out a new place to live."

Longtusk tried to understand what all this meant.

He imagined a line that stretched, to east and west, right across the continent, dividing it into two utterly different zones. To the south there was little but Fireheads, mobs of them, fighting and breeding and dying. To the north the land was as it had been before, empty of Fireheads.

And that line of demarcation was sweeping north, as Firehead leaders like Bedrock sought new, empty places to live, burning across the land like the billowing line of fire which had separated him from his Family.

It was to the north that Longtusk knew he must return one day, when the chance arose. For it was to the north — where there were no Fireheads, in the corridor of silent steppe which still encircled the planet below the ice — that was where the mammoth herds roamed.