When the man passed away, he had not yet reached 50.

He belonged to a tribe that had settled near the Sangker River in Battambang province, likely cultivating the fields and raising animals. On the side, they hunted for boars, and even turtles, one of which would be laid in his grave to accompany him to his next life. Alongside pottery, jewellery and bangles, he would survive in fossilised form until thousands of years later when he would be discovered by a team of archaeologists in Cambodia.

One of these archaeologists is Heng Sophady, deputy director general for Cultural Heritage at the Ministry of Culture and Fine Arts, who has devoted his life to uncovering Cambodia’s ancient past. For almost 10 years, he and his French-Cambodian team have been digging in Laang Spean cave in Battambang’s Ratanak Mondol district, making discoveries like the man’s grave, which provide evidence of the earliest known civilisations in Cambodia.

With its wide, open mouth and high ceilings, Laang Spean covers about 1,200 square metres and is the biggest of 13 caves on Phnom Teak Treng.

All of them have stories to tell, but with the mountain still riddled with landmines only Laang Spean has been explored at length. That exploration has revealed layer upon layer of ancient history dating back to as early as approximately 69,000 BC.

The team has discovered six graves – and as many bodies – so far, with five of them men and one a woman. Experts believe they were buried between 1,360 BC and 1,400 BC, during the Neolithic Period.

“They used the cave as a cemetery,” Sophady said. “The Neolithic people lived in the lowlands near the river. They had agriculture, and they domesticated animals.”

Dates in this video are referenced in BP, or “before present” – years before 1950

All six bodies were buried with what are believed to be gifts – such as wild boars, pottery and jewellery – meant as offerings for the next life, Sophady said. It is thought that animals with them represented the “spirit animals” of the person, or possibly they were meant as food for the afterlife.

The team has discovered other intriguing things about the ancient people, some of which elicit more questions than answers. All of the bodies were buried with their feet facing north and their heads south – except for the woman, who was laid in the inverse direction. And some of them had their teeth cut – a tradition also found in prehistoric Vietnam and Laos, and still practised today among the Jarai ethnic minority in Cambodia for decorative purposes. This could potentially indicate how far back the traditions of the Jarai date, he said.

The dig has also unearthed more practical discoveries about the extent of human advancement and interaction at that time.

“We learned that they’re skilled in the hunting of animals, they are skilled in the making of stone tools, and maybe they also had some trade; they connected to another group of people,” Sophady said, explaining that bangles found were made from sea shells, meaning they were carried from far away.

They resemble those found in Samrong Sen – another significant excavation site – in Kampong Chhnang province, as well as some discovered in Thailand and Vietnam.

Laang Spean was initially discovered as a historic site in the 1960s by a French couple, Roland and Cécile Mourer, who found human remains, but no burial site. Owing to increasing tensions in the Kingdom, they stopped their excavations in 1971 at 1.5-metres deep. It would only be in 2009 that the digging would be taken up again with the support of the French National Museum of Natural History. It is now the deepest excavation site on the Southeast Asian peninsula, at 10 metres.

“It’s a beautiful place,” said Hubert Forestier, a French researcher. “You have protection, you have good, fresh air, and when it’s sunny in the plain, it’s good here.” That’s one explanation Forestier gives as to why the cave has seen human activity dating back tens of thousands of years.

The Neolithic people may not have realised that in digging graves they were disturbing evidence of life, not death rituals, in the cave.

Before the Neolithic used it as a cemetery, Hoabinhians lived there, he said, with evidence dating from 9,500 BC to 3,500 BC. They would hunt for snakes and boars, and even the remains of a rhinoceros were found.

Climbing down a metal scaffold, Forestier points to layers in the soil with different colours: orange, black, grey and brown, which are evidence of climate change.

Three stone pebbles likely to have come from a river about 5 kilometres away – indicating humans may have passed by – were found five metres under the ground, a depth corresponding roughly to 69,000 BC.

Even further down, at about 8 metres, Forestier runs his fingers over an ash-coloured segment.

“That could be interesting; if it’s volcanic . . . it could be from the Toba [eruption],” he said, referring to a volcanic eruption in Indonesia believed to have caused a climatic catastrophe some 74,000 years ago.

At the bottom of the 10-metre hole, air is sparse and hot, so excavators only stay about one hour at a time before switching out.

“If you gained some weight in winter in France, it’s not too bad – you lose weight again. It’s very difficult to work,” Forestier says.

Once re-emerged on the surface, Forestier checks on the team: no major discoveries today. This is likely the last time this year the team will visit the cave. Every year, the researchers excavate for two months beginning in early February. In November, experts then analyse the remains stored at the Ministry of Culture in Phnom Penh and archive their findings.

“Archaeology is destruction and reconstruction,” Forestier said, noting that it’s impossible to dig deeper without destroying what came later. “With each sediment you open a new page. When you turn the page, you forget, you destroy the previous page.”

To prevent the information from being lost, the excavation team has, since 2009, meticulously noted down every finding. Forestier hopes to publish a book after the end of the last scheduled excavation in 2020, when he hopes they will have reached the bedrock.

“Our job is to write [down] all the history before Angkor. We know a lot about pre-Angkorian, but . . . what happened in prehistory?” asked Forestier.

But while archaeologists are trying to preserve Cambodia’s historical record, in other parts of the country unknown traces of past civilisation are likely being destroyed.

While this cave is protected by a sub-decree of the Ministry of Culture, cement companies have torn down others.

Sophady said archaeologists were only able to do preliminary visits in caves now lost.

“Unfortunately we did not have time to conduct our research before the cement factory started,” he said. “They exploded the limestone to make cement.”

About 18 kilometres away from the cave, a massive cement factory, the Chinese-Cambodian Battambang Conch Cement Company Ltd, has recently opened with an annual production capacity of 1.7 million tonnes. While it is unclear who is responsible for demolishing nearby caves, the existence of the factory is likely to ramp up quarrying activity in the area.

A manager of the factory, who requested anonymity, said although the Ministry of Culture had once come to speak with them, he was unconcerned about potential destruction of historical artefacts.

“We received permission from the Ministry of Mines and Energy,” he said, insisting his company only sourced limestone from the mountain adjacent to the factory. “Even for the suppliers, we make sure they have a licence . . . We have nothing to do with the Ministry of Culture.”

The painstaking work conducted by Sophady and other archaeologists is unlikely to keep pace with the country’s rapid rate of change as it modernises. All he asks is to be able to excavate a site before it is destroyed.

“Of course, we are a developing country, so the government needs to develop our country by different projects, but archaeology is also important,” he said. “If we could conduct research before the developing project starts, it’d be much better.”