This story originally appeared on Undark and is part of the Climate Desk collaboration.

Every evening after archaeologist Shanti Pappu and her colleagues head home for the night, two watchmen patrol the team’s excavation site—a plot of dry scrubland near Sendrayanpalayam village, a two-hour drive from Chennai in southern India.

Without such vigilance, the site could easily be disturbed.

To the left of the carefully dug trenches, for instance, lies a bulldozed pit, dredged to remove sand and gravel for a public works project before the researchers started their excavation in 2019, says Pappu, the founder of Sharma Center for Heritage Education in Chennai. A similar instance of land-gouging, or a passerby randomly collecting exposed artifacts—mostly stone tools, crafted by human ancestors tens or hundreds of thousands of years ago to dig for tubers and slice through meat—would disrupt the careful process of excavation that’s integral to the team’s research.

“We dig very, very slowly, just 5 centimeters at a time, ensuring nothing is disturbed around each stone tool,” says Annamalai, a member of the excavation crew who goes by a single name, speaking through an interpreter. But a bulldozer, he adds, destroys everything at one go.

Undisturbed plots are vital for meaningful prehistoric research. A stone tool or fossil is only as good as the context in which it is found, whether on the soil surface or deep underground. Disturbed artifacts are like pages ripped at random from a book—perhaps good for a brilliant quote that’s worth revisiting, but useless to understand the whole story. And anything that interferes with the location of the artifact can dramatically change how researchers interpret how human ancestors lived in the region.

Much of the land holding the country’s buried past is, however, being disturbed and rapidly transformed for modern development—agriculture, roads, infrastructure, and expanding cities. Under Prime Minister Narendra Modi, in particular, the government has pushed for more roads, industrial corridors, and large hydroelectric dams, even proposing changes to existing environmental and archaeological heritage protection legislations to ease the way for businesses.

Protecting prehistoric sites can involve years of litigation over land acquisition, as well as battling encroachments. And vandalism and theft is rampant across sites and monuments. The ephemeral nature of the sites is a major roadblock to the slow, deliberate pace of fieldwork for prehistoric research, which often spans decades.

Such research isn’t just an academic exercise, says Katragadda Paddayya, an emeritus professor at Deccan College, Pune. “We have lot of diversity in languages, cultures, and ethnic groups,” Paddayya says.

“Archaeology, history, and anthropology,” he adds, “have a big role to enlighten the society about what India is: an area with tremendous diversity, and that there are various archaeological and anthropological processes behind this diversity.”

Sites like Sendrayanpalayam could hold answers to the region’s role in human evolution, Pappu says, just like its more famous counterpart, Attirampakkam, about 2.5 miles away. Attirampakkam has been a hotbed for archaeologists since 1863, when British geologist Robert Bruce Foote first discovered stone tools in the region. More recently, studies led by Pappu and Kumar Akhilesh, director of Sharma Center, catapulted the site into the international spotlight when they reported that early humans in Attirampakkam were making and innovating stone tools even earlier than similar tools were thought to have spread by humans migrating out of Africa.

But such sites for sustained, long-term research are hard to come by. Many of the sites that Paddayya discovered in Karnataka when he began his field studies in the 1960s are now rice fields, for example, thanks to extensive networks of irrigation canals. In 2018, an independent researcher highlighted that construction of a government medical college and a hospital had begun on an important prehistoric site in Maharashtra before the area could be studied in detail. And in central India, a site called Hathnora, which has yielded the oldest known human ancestor fossil in the country, lies unprotected on the banks of the Narmada River, threatened by erosion and relentless human bustle.