40,000 years ago, humans were already fishing for tuna and sharks in deep waters

People living on islands in Southeast Asia were not just getting by 40,000 years ago. They were heading into deep water and coming back with big, fast fish.

Organic boats and ropes usually rot away, so direct proof is rare. What survives are tools, fish bones, and clues in microscopic wear on stone edges.

What the tools really show

Riczar Fuentes of Ateneo de Manila University and his colleagues focus on what stone tools reveal about plant processing and boat work.

Their approach links tool wear and plant fibers to practical needs like rope, nets, and bindings for watercraft and in a recent publication, they argued that a web of indirect signs can confirm real maritime skill. 

“The identification of boat building materials through direct or indirect evidence is vital in understanding movements across and within island environments,” wrote Fuentes.

The same stone tools carry tiny traces that point to fiber extraction. Those fibers become cordage, lines, and netting strong enough for boat seams and fishing gear.

This kind of tracing work has a name. Researchers call it traceology, a method that reads microscopic wear to reconstruct how a tool was used.

Why seafaring this early matters

Crossing channels between islands takes planning, timing, and control. Drifting on rafts would not explain repeated arrivals in specific places over long spans of time.

The region in question is Island Southeast Asia, a sprawl of land and sea that demanded reliable water travel. Within it sits Wallacea, the chain of islands between Asia and Australia that always required open-water crossings.

Archaeologists now think people here were more than lucky passengers on currents. The tool evidence suggests deliberate building, organized labor, and coordination.

That kind of know-how changes how we picture daily life. It also explains how communities kept moving, trading, and adapting across thousands of years.

Hooks, sharks, and tuna at Jerimalai

“Here we report remains of a variety of pelagic and other fish species dating to 42,000 years before the present,” wrote Sue O’Connor from Australian National University, in a report describing the fish record and early gear.

The same study documents the earliest known shell fishhooks at Jerimalai, a rock shelter on Timor-Leste’s coast dated between about 23,000 and 16,000 years ago. These are small, precise tools that speak to careful crafting and targeted fishing.

The bone counts are not trivial. The team identified 38,687 fish bones from 2,843 individual fish. Crucially, the assemblage includes remains of pelagic species that live in deeper water beyond reefs. 

From Timor to the Philippines

Timor-Leste is only part of the picture. A broad record from the Philippines now shows long-term fishing that spans at least 30,000 years.

Work in Mindoro’s caves adds detail on how coastal people managed reefs and deeper zones. That study tracked which fish families show up, and when, across changing shorelines and habitats.

These finds tie into plant fibers and tool wear in the same region. The combined record points to people who planned, built, and fished with skill, not luck.

Patterns like these do not appear once and vanish. They persist, which suggests teaching, apprenticeship, and shared practice.

How boats came together

Wood planks, sewn edges, and lashings would have relied on sturdy plant fibers. The tool traces match steps needed to strip, twist, and finish those fibers into ropes and lines.

Other research shows that making string is not a recent trick, citing evidence that short fibres fragment from Abri du Maras in France records twisted plant strands more than 40,000 years ago.

This does not mean people in Europe and Southeast Asia did the same thing in the same way. It shows that fiber technology was within the reach of human hands and minds wherever materials allowed.

If people could twist string, they could weave nets, lash boat parts, and make lines. That opens the door to deep-water travel and targeted fishing.

Rethinking migration across islands

Obsidian moving between islands in southeastern Indonesia and Timor-Leste points to sustained contact. The pattern fits a late Pleistocene to early Holocene interaction zone rather than one-off drifts.

Stone does not sail itself, and it does not walk across channels. Its movement reflects planned trips, return journeys, and social ties.

Those ties likely included sharing routes and seasons. You do not reach a tuna run by guessing, you reach it by knowledge passed along.

As knowledge spreads, technology improves. Better ropes, better lines, and better boats raise the odds of a safe return.

Why this changes the story we tell

For a long time, scholars looked for the earliest big changes in a few famous regions. These finds push us to broaden the map and timeline.

Here, technical skill is not just tool design, it is teamwork. People needed group effort to build, carry, launch, and maintain boats.

But not teamwork alone, it is also about logistics. Fibers must be harvested, processed, and stored, and repairs must be made fast when seawater and sun wear things down.

Taken together, the fish bones, the hooks, and the traces on stone tools point to a culture that understood the sea. The work looks careful, repeatable, and tied to seasons and migrations.

What remains to figure out

Boats do not preserve well, so many details will stay hidden. Even so, the indirect signs add up and form a consistent picture.

Future experiments can test which plants, tools, and fiber twists hold up under load. Those trials can feed back into the archaeological read on use wear.

More underwater and coastal work could reveal net weights, sinkers, or preserved cord in unusual conditions. Every new fragment can lock one more piece into place.

Across all of this, one message stands firm. People in Island Southeast Asia were organized and capable on the water far earlier than many assumed.

The study is published in Journal of Archaeological Science: Reports.

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