Something in the nest was already finished growing, and it was smaller than everything else there.
The nest was one of many, laid in soft ground somewhere in what is now Argentina, about ninety five million years ago. Round white eggs, packed close together, none of them bigger than a grapefruit.
Inside one of them, a small heart was already beating.
Her mother had left days before, the way titanosaur mothers do. No guard stood over the nest. No shadow watched from the tree line. The eggs simply waited in the warm ground, alone, the way thousands of eggs like them waited across that same stretch of country.
When she finally broke free of the shell, she was small enough to fit inside two cupped hands.
Around her, other shells were cracking too, and small animals no bigger than she was scattered out across the nesting ground, learning to walk on their own before anyone had shown them how.
Nobody carried her.
Nobody needed to.
She found the nearest low plants and started eating, the way her kind always had, and the forest did not so much as glance down at her.
Seasons turned.
She grew the way her kind grow, which is to say slowly, decades stretching out one after another while she kept eating and kept walking on four legs that thickened beneath her like the trunks of the very trees she browsed.
Her neck lengthened first, reaching for leaves that smaller animals in that forest could never touch.
One year, a low branch that had always been just out of reach bent easily under her open mouth.
Nobody had cleared it for her.
She had simply grown enough to take it.
Later still, whole stands of forest that had never bothered to notice a hatchling began to lean and creak when she passed beneath them, the ground answering each footstep with a sound felt more than heard.
She did not chase anything.
She did not need to. Plants do not run, and a plant eating giant only needs time, and there was a great deal of time left in her.
By the time she was fully grown, she stood among the largest animals ever to walk the Earth, one of the biggest known, scientists think somewhere close to seventy tonnes of her, carried on four legs built like columns to hold the weight above them.
She still remembered, in whatever way a creature like her could remember, that she had once fit inside two hands.
She laid her own eggs eventually, many of them, round and white and no bigger than a grapefruit, tucked into soft ground and left the way she herself had been left.
She did not stay to guard them either.
That was never how it worked, out here.
Millions of years later, someone would find a single bone from her back, taller than a child standing beside it, and a shin bone about a metre and a half long, and from those few enormous pieces they would try to imagine the whole of her.
They would get the size roughly right.
What they could never quite picture was the grapefruit sized beginning that made it all possible, waiting quietly in warm ground, one heartbeat at a time, before it grew into a mountain that walked.