Ancient hominins Faced Lead Poisoning from Natural Sources
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New research reveals that our ancestors experienced lead exposure long before industrial pollution,highlighting the dangers of natural lead deposits and their impact on early hominin health and development.
A prehistoric Hazard
Lead poisoning is often associated with modern industrial activities, but a growing body of evidence shows that our hominin ancestors faced exposure to this toxic element long before the advent of smelting, plumbing, or automobiles. Recent studies reveal that natural sources of lead – present in bedrock, soil, and released by geological events – posed a meaningful threat to early human health.
Early Evidence of Lead Exposure
this isn’t the first indication of lead exposure in ancient hominins. A 2018 study documented lead exposure in two Neanderthals who lived in France approximately 250,000 years ago, during their childhoods. This discovery represented the oldest known examples of lead exposure at the time and is included in a more recent inquiry led by Joannes-Boyau and colleagues.
Further supporting this, a 2015 study published in Scientific Reports found that Spanish caves inhabited by Neanderthals contained heavy metal concentrations, including lead, exceeding current standards for “contaminated soil.”
Natural Sources of Lead
The presence of lead in the environment isn’t solely a result of human activity. Lead occurs naturally in bedrock and soil. This natural occurrence is so prevalent that archaeologists can even use lead isotope ratios to determine the origin of certain artifacts. Diffrent regions and rock types exhibit varying lead concentrations, with minerals like galena (lead sulfide) being notably rich in the element.
The type of lead exposure documented in the recent study would have been particularly impactful during a period when young hominins frequently put rocks, dirt, and other objects in their mouths, increasing their risk of ingestion.
Gigantopithecus blacki and High Lead Levels
Fossils unearthed from the Queque cave system in China, including those of Gigantopithecus blacki – an extinct gorilla-like ape dating back 1.8 million years – revealed lead levels exceeding 50 parts per million. Joannes-Boyau and his team describe this as “a substantial level of lead that could have triggered some developmental, health, and perhaps social impairments.”
Environmental Pathways to Exposure
Even for hominins not residing in lead-rich caves, exposure was possible through various environmental pathways. Wildfires and volcanic eruptions release lead particles into the atmosphere. Erosion and flooding can carry lead-rich rock and sediment into water sources. Imagine an Australopithecus species living downstream from a lead-rich mica outcrop – erosion could contaminate their drinking water, as well as the water consumed by the gazelles they preyed upon or the berries they gathered.
Understanding Lead Concentrations
The following table provides a general overview of lead concentrations in different environments:
| Environment | Typical Lead Concentration (ppm) |
|---|---|
| Average Soil | 50-200 |
| Lead-Rich soil | >300 |
| Queque Cave Fossils (Gigantopithecus blacki) | >50 |
| Contaminated Industrial Sites | >1000 |
