"The area was naturally a wetland, with natural swamps, but they modified these with weirs, channels and dams to make the whole landscape eel-friendly," says Builth. Some of the modifications were impressive. In parts, the channels were dug through rock to allow water to flow from swamp to swamp. Some of the chains of channels and ponds stretched more than 30 kilometres. But Builth's research revealed something more remarkable. She estimated the output from these eel farms could have fed up to 10,000 people. On the basis of this research, she believed this was more an ancient fishing industry than a subsistence farm, and she set out to prove it.



She had noticed the landscape was scattered with burnt, hollowed out trees that were often next to the eel traps. Could the structures have been ancient smokehouses? Smouldering fires could have been lit in the bases of the trees and the freshly caught eels hung up above, to be preserved by the smoke. To confirm the theory, Builth took soil samples from the bases of four trees. Laboratory analysis revealed that the samples did contain traces of eel fat.

"Suddenly the whole picture changed. The Gunditjmara weren't just catching eels, their whole society was based around eels. And that to me was the proof," she says. The villages associated with the Lake Condah fish farm, she says, were actually more like company towns, with dwellings built to house the people who worked the farms. "It's like you have your council houses for the factory. That's what was going on here," says Builth. Archaeologists know a society undergoes a quantum leap in sophistication when it can produce a surplus of food, because the community has more time to devote to pursuits other than basic survival. "This puts the people here in a different category than we've generally put Aboriginal groups."

Aborigines are usually thought of as living in small communal bands, where power and wealth are shared relatively equally. But Builth believes the Lake Condah farmers lived in a much more complex society. "I think what we had here was a hierarchical, structured society. We had chiefs, for example, with lots and lots of power."

Perhaps the biggest surprise about the Gunditjmara prehistoric fishing society came when Heather asked Monash University geologist Peter Kershaw to try to put a date on it. He drilled into some of the ponds that still have water today (much of the area was drained in the 1800s) to take cores of soil from the muddy bottom. Kershaw was able to drill 13 metres before hitting the bedrock, which produced a core that stretched all the way from the present day down to soil made 18,000 years ago. Like a forensic scientist, Kershaw hoped to date the eel farm from indirect evidence. Eventually he found the region of the core where the plant species abruptly changed. The vegetation had gone from being dominated by plants that preferred a drier environment, to water-loving aquatic species. "This doesn't occur naturally," says Kershaw. "It had to have some help. People have been here - that is the most likely explanation. And those people could well have been human eel farmers flooding the area with an artificial ponding system."

But the most dramatic finding was when Kershaw radiocarbon-dated the part of the core showing the abrupt change. It was 8000 years old, making the fish farming industry at Lake Condah one of the most ancient. The only comparable group at this early time were the indigenous people on America's north-west coast, who caught salmon as they naturally migrated up the rivers. But the Gunditjmara's farming practices were far more developed. They actually brought the young eels in from the ocean and trapped them in their artificial waterways for up to 20 years.

Builth also suspects the Gunditjmara traded the smoked eels across Victoria and South Australia. The famous escaped convict William Buckley, who lived with Aborigines for many years, mentioned eels from western Victoria in his diaries, and so did Victoria's first protector of Aborigines, George Augustus Robinson. Builth was originally attracted to Lake Condah because of the boulders scattered all over the ground. Many of them seemed clumped into circular patterns. Since the 1970s, people had argued these were the remains of the village huts' stony foundations. But the claims had always been controversial. In 1990, the Lake Condah stone circles were officially surveyed, and the conclusion - after just a 40-day study - was that most of the circles were not hut foundations at all.

This was too much for Builth and she began her Lake Condah research. The research eventually ended with a highly praised PhD thesis that demolished the Victorian Archaeological Survey's negative conclusions. To prove that the circles of stones were not natural formations, Builth painstakingly measured and weighed each of the rocks in them. She then performed a statistical analysis and showed that the chance of their coming together in this way naturally was almost zero. The only likely remaining explanation was that the circles were the stone foundations of huts. So how could previous archaeologists have missed all this, given the scale of the operation and that the fish farms would still have been operating when Europeans arrived?

Builth suspects it is because the Gunditjmara disappeared quickly after white settlers came. "History tells us, many (of the settlers) had a military background and they knew tactics - they knew how to survive - they knew how to win, and they knew how to get rid of Aboriginal people pretty quickly." By the time archaeologists had arrived in Australia the only Aboriginal people still leading traditional lifestyles in significant numbers were the ones living on the less desirable land.

"Most studies - certainly anthropological studies - focused on people dwelling in desert in semi-arid conditions, because they were the last people to live in their traditional land. These people (the Gunditjmara) were the first to lose their land, that's the difference." Heather Builth's research is the subject of tonight's Catalyst program on ABC TV at 8pm.