THE MEMORIES CAME back like a sudden volley of stones whacking me on the forehead. The trouble had begun when I’d leaned out of a dank hunting cave by the river that morning and peeked around at a herd of macrauchenia. The beasts had stood hoof-deep in the oozing mud of the riverbank, sucking up the brown water with their flexible little trunks and dumping it into their big toothy mouths. I had felt the cool wind gusting through the trees and shivered.

For months now, it had seemed to me that our normally steamy jungle air had been slowly getting colder. The usually shiny green leaves on the gourd trees were a strange yellowish brown and now carpeted the forest floor. The beautiful red and violet orchids that normally grew in the sunny spots of the jungle had paled and shriveled. Even the gourd fruit—whose fuzzy pink shells my clan folk used to cover their private bits—were smaller this year, resulting in many uncomfortable glances and awkward silences. I had asked around and no one could remember seeing so many bare trees, not to mention bare bottoms. In my head a small warning voice had been growing louder and louder. “Lug,” the voice kept saying, “this is big.”

Yes, the events of the morning were all coming back to me. There had been seven other boys in the hunting cave with me. We were all about the same age, but I was the shortest and skinniest by far.

“You guys chilly at all?” I whispered to Chip and Rock, a tubby pair of twins.

“Shut …” Chip grunted, squinting his eyes like he was trying to remember something.

“… up?” Rock volunteered.

The first twin gave a satisfied nod, confirming that up was indeed the word he was looking for. I looked around the cave at the other boys. None of these chunkers were shivering like me.

Rock pointed at the largest macrauchenia. “Good beast!” he grunted.

“Yah!” said Chip, ogling the animal. “Good for headstone!”

No one else in my clan seemed to care that it was getting colder. All they ever cared about was playing in the next big headstone game against the Boar Riders.

Headstone is a game where you bash the opposing players’ heads with stones. In order to increase the risk of major injury, all players are also required to ride large animals while doing their bashing. My clan rode macrauchenia—fierce, striped jungle llamas with impressively long necks and short trunks—and so were known as the Macrauchenia Riders. Our neighboring rival clan—the Boar Riders—mounted huge razorback boars and got a big kick out of calling us Llama’s Boys. Not to be outdone, my clan had dubbed the Boar Riders Piggybacks. Beyond shouting at each other every few years at the Big Game, the two clans never spoke. I had been taught that the Boar Riders were probably secret cannibals with no laws and fewer table manners, and that thrashing them in the Big Game was the most important thing a Macrauchenia Rider could do.

In our clan, a caveboy could only become a caveman by catching a wild macrauchenia, breaking it in, and riding it in the Big Game. If you failed at any step, you were considered unworthy, cast out into the jungle, and expected to politely die. In all the stories I’d heard, only one banished caveboy was said to have survived into cavemanhood. They called him Crazy Crag, and some people whispered that he was still out there roaming the forest. I’d never seen Crag myself but, if he was alive, I kind of envied him. I was pretty sure he didn’t have to play headstone and could do whatever he wanted. Not that I wanted to be all alone in the jungle. I guess I just never felt like I belonged in my clan.

All the fathers had sat in the back of the hunting cave that morning and grunted excitedly. Tradition held that the boy who caught the biggest beast before the Big Game would someday become the clan’s next Big Man.

Go, BONEHEAD!” cheered Boulder the Bountiful, our current Big Man. Even in the dim dawn light, I could make out Boulder’s hulking form in the rear of the cave. He had a blackbird’s nest of a beard that hid his face in secret shadow—nearly everything but his eyes, which were a cold milky blue.

“Bonehead … head … ed,” the cave walls echoed.

Bonehead glanced back at his father with a predatory grin. He was built like a slightly smaller version of Boulder except he was bristle-skulled, with small watery blue eyes and a thin-lipped mouth that had more gaps than teeth. But the most distinctive thing about Bonehead was the foot-long white bone that pierced his nose. He had once killed a baby jungle llama for it.

Unfortunately, Boulder’s bellow did more than just encourage his son. It also startled several of the macrauchenia into glancing up.

“You first, Little Slug!” hissed Bonehead when he saw this.

I tried to ignore him, but his best friend, Bugeyes, chimed in. He was another specimen you wouldn’t want to meet in a dark cave. Bugeyes was not as big (or dumb) as Bonehead, but he was twice as ugly, and with a surprisingly high-pitched voice for a kid his size.

“Lug’s too small to be a slug,” squeaked Bugeyes. “He’s more like the flea I squashed in my armpit this morning!”

Bonehead laughed like a snorting pig.

The rest of the jungle llamas lifted their heads, craned their long necks, and peered at the cave suspiciously.

“Biggest beast mine,” Bonehead growled at me, suddenly serious again. “Got it, flea?”

I couldn’t help staring at the repulsive little black whiskers sprouting above his lips and made a mental note to add those to my next painting of him.

“Fine with me,” I whispered. I was much more focused on surviving the next hour than in becoming the tribe’s next Big Man someday.

“Fine with me. Said flea!” jeered Bonehead, looking around to make sure everyone had heard this piece of poetic brilliance.

All of the other boys laughed nervously, not wanting to get on Bonehead’s bad side. All except for a silent burly kid called Stony, who was gently cradling a bright orange tree frog with his thick banana-like fingers. Stony had wide-set hazel eyes and a wild tangle of dusty brown hair crowning his sloping forehead. Although Stony never spoke, he did have a very expressive unibrow. It wiggled on his low forehead like a giant fuzzy caterpillar as he flashed me a friendly, if slightly moronic, bucktoothed smile.

I turned away and forced myself to focus on the herd of macrauchenia. I hated being called small by Bonehead and Bugeyes but, as my mother liked to say, right now I had bigger stones to split. Despite their cute little flexible trunks, jungle llamas possess strong biting teeth and explosively powerful legs that can smash in your head like an overripe gourd fruit. I had spent many quiet mornings observing them and painting pictures of them on the walls of my secret art cave. I knew their strengths, but what were their weaknesses?

“Give me bigger stone.” Bonehead’s voice interrupted my thoughts.

I turned back and saw him trade with Bugeyes, then tuck his new stone into his banana-leaf sash.

*You’ll notice that “Stone good for art” is not listed. Our Clan Council considers making art to be uncaveman-like behavior—a waste of time when you could be bashing perfectly good heads with perfectly good stones. That is why I kept my art cave a secret.

I tried to picture which way the jungle llamas would take off when all eight of us gave chase. Looking downriver I could make out the gray limestone cliffs that housed our village caves. Upriver I glimpsed the clearing that served as our clan’s headstone practice field. Across the water, rising out of the jungle, loomed the great misty peak of Mount Bigbigbig. The base of its southern slope was not far from the opposite bank, but I had been taught that the mountain was sacred and should never be climbed. And I knew that beyond it was the territory of the Boar Riders. Of course, the other possibility was that the macrauchenia herd wouldn’t run away at all, but simply charge the first boy to emerge from the cave.

“You first, Little Slug!” Bonehead commanded, elbowing me in the ribs.

I picked up a rock, fixed my gaze on a young doe—the smallest macrauchenia in the herd—and took a deep breath to calm my racing mind. Then Bonehead shoved me out of the cave.

“LUUUUUUUUG!” cheered a familiar voice from the back of the cave. I glanced back and was amazed to see my father smiling proudly at me. Then it dawned on me that he thought I’d charged out of the cave first. Of course, I hadn’t charged out at all—I’d been thrown out. Still, my father was proud of me, and for a moment I was as happy as a dodo in springtime.

“YAAAAAAARGH!” roared Bonehead, shooting out of the cave just after me. He was followed by all the other boys—including Bugeyes, Chip and Rock, and the silent Stony bringing up the rear.

“YAAAAAAAAAAAARGH!” roared our proud fathers in unison behind us. The macrauchenia chase was on.

I slowed down. My chosen doe was standing her ground, obviously unimpressed with me. When I was a short stone’s throw from her, I stopped to see what all the other guys were up to. On my left, I saw Bugeyes brandishing a stone as he stared down a jungle llama that was desperately trying to look away. I could relate to that animal.

Behind Bugeyes, Chip and Rock had trapped two macrauchenia between themselves and the river. Then a sickening thud to my right revealed Bonehead grabbing hold of the largest beast and bashing it into submission with his rock. Only Stony and I did not have a llama, but Stony wasn’t even trying. He was happily sitting on a rock, licking his frog.

“Think!” I said to myself, looking back at the doe. “Think!”

The doe charged.

Bad, I thought. Very bad. No chance of outrunning her, I desperately looked around once more. The llama followed my gaze and stopped a mere step away from me.

I knew I was supposed to bash it in the head with my rock, but I couldn’t help admiring the animal up close. I observed the long graceful curve of her neck up to her strong jaw and found myself memorizing her subtly dappled fur pattern for my next painting. I peered into her big liquid-brown eyes, framed by lovely black eyelashes. After that, everything went black.