Cell biology Earth's habitability Intelligent Design

At Evolution News: The Problem of Phosphorus

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David Coppedge extends extends Michael Denton’s illumination of the prior fitness characteristics of Earth to sustain life as we know it.

Michael Denton’s series of books about our Privileged Species, culminating with The Miracle of Man, brings together an astonishing collection of natural “coincidences” that make human life possible. These finely tuned parameters, from the nature of water to the composition of earth’s atmosphere and crust, to the metals that inhabit key enzymes, and many more, leave readers with little choice but to conclude with Denton that the scientific evidence converges on a prior fitness for life on earth. Unlike astrobiologists who are content to discuss mere habitability, Denton proposes that these details appear designed beforehand for complex beings like us, with bodies and brains equipped to invent and use technology. 

Yet among the chemical elements he considers in detail in his books, there is one he passed over comparatively lightly: the element phosphorus (P). 

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An Essential Element

Phosphorus, element 15 in the periodic table, is essential for energy (ATP, adenosine triphosphate), the genetic code with its sugar-phosphate backbone, cell membranes, hormones, bones and teeth, and much more. After describing the exquisite fitness of phosphates for energy in cells in The Miracle of the Cell, Denton quotes Edward O’Farrell Walsh who summed up this element’s importance: “It is no exaggeration to say ‘without phosphorus: no life.’”

And yet the bioavailability of P sets up a problem. While it is the 11th most abundant element in the crust, it tends to be concentrated in certain isolated places, far from the plants and animals that need it. This is obvious from the fact that we need to buy fertilizers for our gardens and farms. Phosphate is the middle number in the familiar triad of elemental ratios in store-bought fertilizers such as “21-10-3” which stands for amounts of N, P, and K in the product. Nitrogen can be obtained from the atmosphere, and potassium (K), while also not ubiquitous, is more abundant than phosphorus. 

Worse, most inorganic phosphorus (Pi) is locked up in insoluble rocks like apatite and phosphorite. (Elemental P is highly reactive; Pi is almost always found in phosphates, PO4, which are what life uses.) Although small concentrations can be found globally, 70 percent of the commercially available phosphate deposits are in Morocco and China. Readers may recall hearing at the outset of Russia’s invasion of the Ukraine that 28 percent of the world’s fertilizer is exported by those two countries, threatening global food shortages.

Humans have known for millennia that fertilizing plants increases their yield. Once phosphorus was identified as an essential element in fertilizer, people went looking for it. Bat guano served the purpose in the 19th and 20th centuries, but demand for phosphorus has risen sharply since the mid 1950s, and guano is not sufficiently abundant for the global demand. The world has 8 billion hungry people to feed, not counting all the other species in the biosphere needing phosphate.

An Instructive Primer

Last month, Current Biology published an instructive primer by Yves Poirier, Aime Jaskolowski, and Joaquín Clúa on “Phosphate acquisition and metabolism in plants.”

Current economically exploitable P-rich deposits could be exhausted within 50–100 years, with the mining of sub-optimal phosphate rock potentially extending production for an additional 200–300 years. Regardless of the various estimates, P-rich deposits are finite resources, and their limited availability will eventually become a key issue for long-term food security. [Emphasis added.]

With these disturbing facts in mind, how can we fit the phosphorus problem into Denton’s hypothesis of prior fitness for complex life?

Design to the Rescue

PAE (Pi Acquisition Efficiency) refers to the suite of strategies plants use for acquiring inorganic phosphate. Once they have it, they also optimize its use in cells.

The authors describe sets of design principles (they call them adaptations) for optimizing phosphate.

These strategies are all mediated by molecular machines arranged in cooperative systems that monitor and regulate P levels.

Animals possess numerous strategies to maintain optimal phosphorus levels as well. They, too, have organs and systems highly dependent on P for their genetic code, energy, membranes, signaling — the whole toolkit plants have, and more. Vertebrates need P for bones and teeth (hydroxyapatite). Animals return the favor to plants through their urine and manure — recycling phosphorus naturally long before humans invented agriculture. Leaf litter and decay of plant material also recycles P to the soil. It doesn’t all have to come from Morocco and China.

For humans, the richest sources of bioavailable Po are dairy, red meat, poultry, seafood, legumes, and nuts (Harvard Nutrition Source). In modern times, additives of inorganic phosphorus, used for preservatives, contribute a non-trivial amount of Pi to the human diet, which is readily absorbed. P toxicity is rare because the body is very effective at removing excess P through the kidneys. 85 percent of our phosphorus is stored in bones and teeth. These stores serve as a backup reservoir for P in times of phosphorus deficiency.

Scientific materialists who deny any prior fitness of the planet for life must surely wonder how earth got its original supply of phosphorus and the other requisite elements. They must believe that the solar nebula had the right concentration of each element, and that they all ended up in the shallow crust to be available for land organisms. The evolutionary timeline, with its rapid colonization of the oceans and rich biomes like tropical rainforests, coral reefs, and montane forests, does not picture a biosphere starved for phosphorus.

The success of the biosphere through time provides ample circumstantial evidence of adequate availability of phosphorus from the beginning, despite P’s uniqueness as a limiting factor for life in solid form. Studying the phosphorus cycle in detail — from astronomy through geology through biology — would be a good research project for design-favoring scientists. It would eliminate a potential exception to Denton’s “prior fitness” argument. Most likely, with the circumstantial evidence at hand, it could become one of its strongest examples.

The analysis of the essential role of phosphorus in living systems highlights a feature of design that can be simply stated, namely, having something go right, when there are so many more ways for it to go wrong.

See the complete article at Evolution News.

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