Perhaps life on Earth really began with mud

Helen Hansma says that life on Earth may have begun among the mica plates.

In myths and origin stories around the world, various cultures and religions refer to clay as the vessel of life, the primary substance that the creator gods saturate with a self-sufficient existence.

Nowadays we have biology to explain what life is like, but can these ancient tales hit the mark more often than we think?

In a paper written to commemorate the work of Ned Seaman, inventor of the field of DNA nanotechnology, University of California, Santa Barbara biophysicist Honorable Hansma outlines her age-old idea that primitive life, in the pre-cellular arrangements that evolved into our fat and protein-built cells , you may have started in flour mud. Her paper appears in Biophysical Journal.

You can listen to an in-depth audio explanation of Hansma’s theory below:

Hansma’s hypothesis was originally proposed nearly 16 years ago, and joins many other speculations about how life on Earth first appeared. Among them are the well-known “RNA world,” where self-replicating RNA molecules evolved into DNA and proteins, and the concept of “metabolism first,” which says life evolved from spontaneous chemical reactions. There is also a “pizza” hypothesis that claims that life could come from terrestrial organic biomolecules. Other hypotheses about clay say that life may have arisen on montmorillonite, or iron-rich clay.

Hansma didn’t set out to figure out how to live evolved Down to earth when she first came up with her idea. Instead, as a biophysicist and program director at the National Science Foundation circa 2007, she was playing with her favorite toys—a dissecting microscope, slicing the mica she was cutting into plates.

“When I looked at the bits of green algae and raw brown on the edges of the mica sheets, I thought this would be a good place for life to originate,” she said in an article she wrote for NSF about her work.

Her idea includes elements from other notions of spontaneous generation (how life arose from nonliving matter), asserting that precursors to biomolecules and metabolic processes can all be sandwiched between layers of mica. It is an environment that provided some protection from the outside world, but allowed the free exchange of water and other substances that would otherwise become essential to cells.

“My picture is that the surfaces of the mica sheets were a great place for molecules to grow and processes to develop, and eventually everything life needed was on the mica,” she says.

Essentially, mica served as scaffolding and “reaction chambers”, where metabolic processes could occur and develop.

Hansma adds that the advantage of mica clay over montmorillonite is that the mica, with potassium ions holding the mica sheets together, does not swell and thus provides a more stable environment. In contrast, monmorillonite sheets are held together by smaller sodium ions, which leads to shrinkage and swelling during wet dry cycles and a less stable environment.

The presence of potassium ions in micro-clay is another factor in favor of the mica clay hypothesis: cells in living organisms contain high intracellular concentrations of potassium, making mica “a more likely home to the origins of life than montmorillonite.”

And where would this prebiotic assembly obtain the energy to react and maintain itself in the absence of the biochemical energy that now powers our bodies? At the time, sunlight was one filter, Hansma suggests, as would mechanical energy, through the opening and closing of the mica sheets as water flowed in and out.

“It appears that these open and closed motions were ways to smash molecules together, before there was chemical energy,” she says. This forced convergence could have enhanced intermolecular interactions, similar to the actions of enzymes today. Different interacting molecules combine to form RNA, DNA, and proteins. The lipids in the mixture will eventually wrap around the clusters of large molecules and become the cell membrane.

These are just a few of the arguments in Hansma’s hypothesis that give way to life after I started in the exact mud. Further support can be found in the aging of mica, in the affinity of the mineral with biomolecules and other factors believed to have promoted the evolution of life from inanimate molecules.

While it is unlikely that we will know for sure what happened? For nearly four billion years, it’s clear, Hansma says, that “life imitates mica in many ways.”

source: University of California, Santa Barbara