🧠 Our human ancestors were exposed to lead, and it influenced our evolution

The discovery of chemical signatures of lead in hominid fossils challenges our understanding of ancient environmental pressures. The presence of this toxic metal, long before human industrial activities, raises questions about its role in our ancestors' brain development.

Dental analyses reveal recurrent exposure over much longer periods than imagined, showing a lasting interaction between geochemistry and biological evolution.


Interdisciplinary research combining archaeology, genetics, and neuroscience demonstrates how this natural element may have influenced hominid evolutionary trajectories. The study of fossil samples from multiple sites worldwide documents for the first time the antiquity and persistence of this lead exposure.

Fossil evidence of ancient exposure

The examination of 51 fossil teeth using high-precision geochemical techniques revealed characteristic signatures of lead exposure. These analyses conducted by the geoarchaeology research group at Southern Cross University detected bands of lead concentration corresponding to different periods of dental growth. The presence of these chemical markers in specimens dating back up to two million years indicates repeated exposure episodes throughout early childhood.

The geographical and chronological distribution of the analyzed samples covers multiple continents and species. Researchers were able to make comparisons between different hominid groups, including representatives of the genus Homo and australopithecines. Exposure patterns vary between species, likely related to their dietary habits and respective environments. Some groups show more intense signals than others, possibly reflecting behavioral differences.

Probable sources of this ancient contamination include natural processes such as volcanic activity or groundwater circulation in metal-rich geological formations. Unlike contemporary industrial pollution, this prehistoric exposure was intermittent and linked to specific environmental factors.

Differential impacts on brain development

The team at the University of California, San Diego developed in vitro brain models to test the neurodevelopmental effects of this ancient exposure. These miniature brain structures, grown from stem cells, were specifically programmed to produce two distinct forms of the NOVA1 gene. This gene, which acts as a conductor during brain formation, exists in a modern version in current humans and in an archaic form carried by Neanderthals. Researchers were thus able to compare, in a controlled environment, how these two genetic variants responded to identical toxic aggression.

Lead exposure caused significant disruptions in the organization of neurons expressing the FOXP2 gene, particularly in organoids carrying the archaic variant of NOVA1. These alterations mainly affected brain regions associated with language and communication development. Models containing the modern version of the gene showed increased resistance to these neurotoxic effects.

Comprehensive proteomic study highlighted differences in signaling pathways affected by lead depending on the genetic variant. The modern variant appears to confer relative protection by modulating the response to oxidative stress and preserving the integrity of specialized neural circuits. This work provides new insights into the molecular mechanisms that may have influenced the evolution of cognitive abilities in hominids.

To go further: What is a brain organoid?

Brain organoids are three-dimensional structures grown in the laboratory from stem cells. They partially reproduce the organization and some functions of human brain tissues. These models allow the study of neural development under controlled conditions.

Their fabrication involves guiding stem cell differentiation toward specific neuronal types. Over weeks, these cells self-organize into complex structures. Researchers can thus observe developmental processes inaccessible in the living human brain.

These models have certain limitations, such as the absence of vascularization and connections with other brain regions. Nevertheless, they offer an ethical alternative to animal experimentation. Their use is spreading in the study of neurodegenerative diseases.

What role does the FOXP2 gene play in language?

The FOXP2 gene codes for a transcription factor essential to the development of neural circuits for language. Mutations in this gene cause severe articulation and grammar disorders in humans. Its involvement in coordinating orofacial movements is well established.

In vertebrates, FOXP2 influences vocal learning and plasticity of specialized brain nuclei. Songbirds show dynamic expression patterns of this gene during song acquisition.

Recent research indicates that FOXP2 regulates the expression of hundreds of other genes in neurons. It interacts with various signaling pathways involved in synaptogenesis and neuronal migration. Its alteration affects multiple aspects of brain development.