This article originally appeared on Motherboard.
Humans have always had a tendency to view bodies of water as giant dumpsters. You put the gook and trash in and then it magically disappears—or floats someplace else at least. The problem is, dirty water makes people and animals sick, and as examples such as the syringe tide—where medical waste and trash washed up on New York City beaches in the late 1980's—have taught us, all the nastiness comes back to us eventually.
Polluted waterways are a phenomenon that've become almost synonymous with the modern, industrialized era, but it appears fouling up our waters is something people have been doing for a long time. A group of international anthropologists have found evidence for what may be the oldest known polluted river in human history. Humans were contaminating it with copper some 7,000 years ago in Southern Jordan. Not only does this finding tell us that we've been dirtying up our surroundings for some time, but it also provides a glimpse at a revolutionary turning point in human history: when people stopped making tools out of stone and began forging them from metal. The findings are published in Science of the Total Environment.
The details of how exactly early humans started molding tools and weapons out of metal is extremely hazy, so anthropologists have looked for clues from before the Bronze Age that hint at experimentation with fire and ores. For this particular study, an international group of researchers scoured the Wadi Faynan region in Southern Jordan, a place of early human habitation, for just such clues.
In the banks of what's now a dried up riverbed the researchers found sediments contaminated with copper dated to around 7,000 years ago, indicating that people were smelting copper around this waterway at some point. These early metallurgists probably made copper by mixing charcoal with bluish-green copper ore (found naturally in the region) and then heating the mixture in a potted crucible over a fire. The process was so labor intensive that people likely made beads or ceremonial items rather than any kind of tools.
"These populations were experimenting with fire, experimenting with pottery, and experimenting with copper ore, and all three of these components are part of the early production of copper metals from ores," said anthropologist Russell Adams, of Waterloo University in Canada. "This region is home to the world's first industrial revolution," he said. And it came at a price.
The waste created from copper smelting, known as slag, contaminated the water of this ancient river and leached into the soil. Over time, people in Faynan eventually built large copper mines and furnaces during the Bronze Age and dumped heavy amounts of slag into the waterways. The slag, which contains such byproducts as arsenic, mercury and thallium, was likely absorbed by plants and then subsequently eaten by humans and livestock.
According to Adams, the negative effects of metal poisoning in ancient populations here were probably widespread. Infertility, malformations, and premature death all likely plagued these ancient peoples because of it.
7,000 years later in the United States, even with regulations in place to protect us from pollution, metal contamination is still a major problem for human health. Heavy amounts of lead in residents' drinking water in Flint, Michigan is just one example. For all our progress, at least in this respect, not much has changed in 7,000 years.