What made Polynesians' ancestors sail out into the Pacific long, long ago? As with many questions worth asking, the answer is elusive.

Those early seafarers, whose homelands were as far north as modern southeastern China, struck out across the great waters millennia ago; their descendants would eventually colonize even the most far-flung Pacific islands of Rapa Nui (Easter Island) and Hawai'i. Links between Austronesian languages — more than 1,000, scattered across half the globe — sketch a monumental diaspora.

Modern-day traditional navigators, such as the Hokule'a crew, have traced the pioneers' paths backward through time and space to learn how they traversed the ocean. Geneticists, archaeologists and linguists have followed geographic and cultural clues to determine who they were, where they came from, and when.

But the why of it all has taken a little longer to unfold.

That's what is exciting about "Lost Maritime Cultures," a groundbreaking exhibition opening tomorrow at Bishop Museum. The show brings together material objects from the daily lives of Polynesians' earliest known ancestors, proto- and pre-Austronesians, who lived long ago on the Asian continent.

The goods are the product of more than three decades of research, primarily by Chinese archaeologists, to unearth what these cultures were like, how they developed and how they're related. Many exhibition artifacts are on loan from Chinese sources; assembled together, the objects — from symbolic jade accessories to canoe paddles to funerary urns — voice a story deeper than genetics or geography alone can tell.

"This is new. ... It's the first time we've put everything together to showcase these cultures," says Bishop Museum archaeologist and exhibition organizer Tianlong Jiao, whose research has helped to flesh out contemporary understanding of the "lost" maritime civilizations.

And it's a start to answering why Hawaiians' ancestors originally left Asia for the sea and its uncharted islands.

Decorative elements on ceramic artifacts, and even their physical composition (such as Neolithic pottery tempered with shells or rice husks), tell us that the ancient civilizations were sustained by land and sea. Their peoples cultivated rice, hunted and looked to the ocean for provision.

EARLY NAVIGATORS

The earliest of these cultures, the Hemudu, thrived about 5,000 to 7,000 years ago in what is now China's Zhejiang province. Bone and wood plows show that they tilled the soil; other artifacts, such as graceful funerary urns for children, reveal a spiritual connection to the land.

Yet these were seafaring peoples as well, skillful navigators of the bays and small islands that dot the area's rugged shoreline. Multiple wooden paddles have cropped up at Hemudu excavation sites, suggesting that canoes provided transportation and fishing sojourns on rivers and lakes — and possibly inshore as well. Other objects imply that Hemudu people worshipped the sun and birds, both significant in navigational practice.

So did their descendants leave because they could — because they knew how to sail, and their specialized maritime adaptations became a way of life? Perhaps.

THE PUSH

But the ocean may have supplied more than lunch: It may have given them reason to move onward. Geology shows that rising sea levels — together with agriculturally driven population increases — eventually put pressure on these cultures' environments, sending inhabitants into the vast waters to find new, fertile lands.

Still, any motivational speaker would attest that fighting inertia requires not just motivation but also energy and will.

"Something drove them," writes Peter Bellwood. A researcher widely recognized for his proposed maps of Austronesian migration, Bellwood contributes an essay — and an interesting theory — to the "Lost Maritime Cultures" exhibition catalog.

These peoples of the past, Bellwood argues, suffered a timeless malady: teenage angst. He speculates that founding new island communities became a prime, culturally approved outlet for young people seeking to prove themselves.

In fact, southeastern China's later maritime cultures, including the Liangzhu "Civilization of Jade" and the early Bronze Age Fubin civilization, were strongly hierarchical. Prestigious burial objects such as crown-shaped jade ornaments and bronze artifacts chronicle a tale of social stratification — tantalizing incentive, perhaps, for youths who longed to "go forth and prosper."

CONNECT THE DOTS

"Over the hills and through the woods, to Grandmother's house we go," reads the fairy tale. If only tracing ancestral paths were so simple.
For a long time, it was: Island to island, through channel and ocean, that's how Grandmother came — or so the theory went. Polynesians' ancestors, it was said, migrated from relatively near jumping-off points in Southeast Asian archipelagos, such as Indonesia and New Guinea, and fanned out through the Pacific.
Only decades ago, that idea seemed pretty solid. But since then, those who study bloodlines, lands and languages have traced Polynesian ancestral origins deeper into the past, and farther north, to the Philippines, Taiwan and even across the strait to the coastline of what is now southeastern China.
Scientists now believe that this area's "lost" maritime civilizations are the ultimate ancestral cultures of the seafaring Austronesians, whose descendants would go on to inhabit Polynesia.