Did life on Earth originate from earth (as in clay)? Origin stories across many cultures point to clay as the vessel of life, the primordial material upon which life on Earth was built. The most famous origin story is the biblical Book of Genesis (2:7), which tells of Adam being created out of dust. Other similar accounts are found throughout the Near East – in the Epic of Gilgamesh from Mesopotamia, as well as in Egyptian mythology and various Greek texts. But what does science have to say about the truth of these stories? Below is a summary of several strands of scientific discoveries that could shed some light on the “clay hypothesis.”

1. Clay as Biological Templates

Clay was suggested by the Irish crystallographer John Bernal (1901-1971) as a means of concentrating primitive biomolecules onto their surface, making it available for other chemical reactions. More recently, American chemist James Ferris (1932-2016) showed that long chains of RNA, a possible precursor to DNA, can be created from simple organics in the presence of clay minerals and water.

2. Clay and Chiral Forms

The next piece of evidence comes from studies that investigate the chirality of biological molecules. Living organisms exhibit “homochirality,” meaning biological molecules like amino acids and sugars are predominantly “left-handed” or “right-handed”. Recent studies suggest that clay surfaces might have preferentially selected or catalyzed the formation of one chiral form over another, a critical step toward life as we know it.

3. Micaceous Clays as Niches for Life-giving Biochemical Processes

Perhaps the most compelling hypothesis linking clay to the origin of life posits that life emerged in the spaces between sheets of mica-rich (micaceous) clay minerals. The leading proponent of this Mica Hypothesis is former UC Santa Barbara biophysicist Helen Hansma (b. 1945) who argued that the structure of micaceous clay could provide stable micro-environments for ions like potassium (K+) to concentrate. This high K+ concentration in the mica’s interlayer space aligns with the high K+ concentration found inside all living cells today, suggesting life began in a high-potassium environment rather than a high-sodium ocean. Professor Hansma further argues that the constant ebb and flow of water and changes in temperature could cause the mica sheets to move open and shut, providing mechanical energy that drives chemical reactions similar to how enzymes function in modern cells.

The evidence for the mica hypothesis is largely based on observations of how modern biomolecules interact with mica surfaces in lab settings primarily using atomic force microscopy (AFM). These studies indicate that all major classes of biological macromolecules (proteins, nucleic acids, lipids, and carbohydrates) readily adsorb and interact with mica surfaces under aqueous solutions. Other research have observed DNA molecules “swimming” or moving on the surface of mica under water, demonstrating the dynamic environment possible in the spaces between sheets that facilitate pro-life chemical reactions.

Summary

While life did not originate directly from clay, the scientific evidence suggests clay minerals played an important role as catalyst and scaffold for the formation of the early complex molecules, like RNA, and protocells. Clay’s surface, particularly micaceous ones, can concentrate crucial organic molecules, protect them from damage, and facilitate the polymerization needed to form the building blocks of life, like long strands of RNA which are precursors to DNA and fundamental to the protein formation.

WATCH – Clay, Mica and the Origins of Life (duration: 2.40 minutes)