May 2, 2019 | Jerry Bergman

Photosynthesis: Darwin’s Great Mystery Is Still a Mystery

Darwin’s Great Mystery, Photosynthesis, Is Still a Mystery

by Jerry Bergman, PhD

The origin of photosynthesis has always been a profound problem for evolution. A 2019 study by one of the leading researchers in this area, Tanai Cardona, from the Department of Life Sciences at Imperial College London, has confirmed the fact that after decades of research we are no closer today to answering the origin of photosynthesis than we were before. This is true after

an incessant stream of speculative ideas and debates on the evolution of photosynthesis that started in the first half of the twentieth century and shows no signs of abating. Some of these speculative ideas have become commonplace, are taken as fact, but find little support.[1]

This is the same conclusion made over 70 years ago by a 1957 study of the evolution of photosynthesis. It concluded that we had, at that time, nothing more than some theories, all of which were very problematic and little more than speculative just-so-stories.[2] The origin of photosynthesis is so critical that Leslie called it “the last of the great inventions of microbial metabolism” that changed “the planetary environment forever.”[3]

This “invention” by bacteria was so stunningly complex that the best and brightest scientists are still trying to understand its biochemical details. The problem for evolution is that life either uses the enormously complex photosynthesis system, or a very different system, to manufacture food and produce usable forms of energy. No viable transitional forms have been found, so imagination must take over, producing the just-so-stories discussed in the next sections.

What Photosynthesis Does

Photosynthesis is the process by which plants use sunlight to manufacture carbohydrates from carbon dioxide and water. The term photosynthesis means to synthesize using light energy. Light consists of energetic photons. With enzymes in the plant cells, the energy in sunlight splits water molecules (photolysis), breaking water apart to produce oxygen, hydrogen, and electrons. The oxygen diffuses out of the plant as a waste product which animals in turn breathe in order to sustain animal life. The hydrogen, along with the electrons energized by light, converts a compound called NADP into NADPH by adding a hydrogen. That energized molecule is later used, through a series of molecular machines, to provide the energy to add inorganic phosphate to Adenosine Diphosphate (ADP) to produce Adenosine Triphosphate (ATP). This is the light-dependent reaction.

The ATP, NADPH and other chemicals are used in a chain of reactions called the Calvin Cycle to build a form of sugar called glucose. Glucose consists of carbon, hydrogen and oxygen in the following common ratio: C6H12O6. All of this takes place in a stack of systems called grana inside of the thylakoids located in specially designed organelles called chloroplasts. Located in plant leaf cells, chloroplasts contain chlorophyll, the molecule that gives plants their green color. Besides chlorophyll pigment, photosynthesis  requires close to 100 other proteins.[4] Professor Cardona adds that, after 200 years researching the origin of photosynthesis problem, it is still

too soon to claim that we understand how photosynthesis originated, let alone to claim that we understand the photochemistry of the earliest reaction centers to ascertain that the origin of anoxygenic photosynthesis pre-dates the origin of oxygenic photosynthesis.[5]

Chlorophyll: A Very Special Molecule

Chlorophyll organelles are themselves very complex, well-designed systems, containing a lipid-soluble 59 atom hydrocarbon tail (C20H39) and a flat hydrophilic head with a magnesium ion at its center, plus a side group which depends on the type of chlorophyll. All plants that use chlorophyll are some shade of green, thus called green plants. They use energy in sunlight to turn carbon dioxide into sugars that the cell can use for building blocks and energy. In addition to plants, many kinds of algae, protists and bacteria use photosynthesis to manufacture food and produce usable forms of energy. Photosynthesis is for these reasons very critical for life on Earth. All green plants either directly or indirectly depend on it.

The only exception are certain organisms, called chemoautotrophs, that obtain their energy directly from chemical reactions using sulfur, iron or other minerals. In the life pyramid—as in the pyramids built by the Egyptians—the largest area is the base. Similarly, the base of the life pyramid (the largest part) consists of green plants. All life forms in the upper levels of the life pyramid depend on the base. This includes the primary consumers of plants (mice and other small animals and herbivores) and small carnivores such as raccoons, and the highest level, the large carnivores, the wolves and tigers.[6]

Irreducible Complexity vs. Rife Speculation

The problem has always been, how did photosynthesis evolve? Since many kinds of algae and protists and bacteria rely on plants to produce food directly or indirectly, and plants themselves use it to build their own food, all life depends on photosynthesis. There are only few exceptions, like extremophiles at the ocean floor. All herbivores and most omnivores depend on photosynthesis. Even all carnivores ultimately depend on the herbivores that they consume, which eat plants. How photosynthesis could have evolved is acknowledged as a complete mystery. What is not a mystery, as Gaidos writes under the heading “Intelligent Design,” is that

Photosynthetic organisms are designed for efficiency. The light absorbing chlorophyll molecules found in leaves, for example, aren’t just arbitrarily scattered throughout the cell, but are tightly packed into tiny organelles, crammed into spaces where they touch each other frequently. So when excited by a photon, the chlorophylls no longer act as individuals, but band together to create a system that works in concert.[7]

Intelligent design is not just intuitive, it is testable.

Ignoring the problem of “Intelligent Design” that Gaidos observed, evolutionists attempt to explain its origin with sheer guesswork. In the following paper, written by an evolutionist, bold italics have been added to the terms that illustrate the speculative nature of all theories of photosynthesis evolution:

The earliest reductant for photosynthesis may have been H2. The carbon isotope composition measured in graphite from the 3.8-Ga Isua Supercrustal Belt in Greenland is attributed to H2-driven photosynthesis, rather than to oxygenic photosynthesis as there would have been no evolutionary pressure for oxygenic photosynthesis in the presence of H2. Anoxygenic photosynthesis may also be responsible for the filamentous mats found in the 3.4-Ga Buck Reef Chert in South Africa. Another early reductant was probably H2S. Eventually the supply of H2 in the atmosphere was likely to have been attenuated by the production of CH4 by methanogens, and the supply of H2S was likely to have been restricted to special environments near volcanos.[8]

Cardona responded to the rife speculation of the photosynthesis origins problem by warning that

For the field to move forward unhindered, more critical, cautious, yet open thought is required. The temptation to speculate will always be too sweet to resist; nonetheless, we should strive to keep the lines between assumptions, hypotheses, predictions.”[9]

In 2019 Cardona added,

Sam Granick opened his seminal 1957 paper titled ‘Speculations on the origins and evolution of photosynthesis’ with the assertion that there is a constant urge in human beings to seek beginnings (I concur). … Here, I review and scrutinize three widely accepted ideas that underpin the current study of the evolution of photosynthesis.[10]

He then proceeded to

demonstrate that these three ideas are often grounded in incorrect assumptions built on more assumptions with no experimental or observational support. I hope that this brief review will not only serve as a cautionary tale but also that it will open new avenues of research aimed at disentangling the complex evolution of photosynthesis and its impact on the early history of life and the planet.[11]

The Great Oxidation Event: Another Just-so-Story

Photosynthesis requires oxygen to function. Thus, oxygen must exist on the earth before photosynthesis can function.

[When] oxygenic photosynthesis originated also remains controversial. Wide uncertainties exist for the earliest detection of biogenic oxygen in the geochemical record, or the origin of water oxidation in ancestral lineages of the phylum Cyanobacteria.”[12]

The early Earth is believed by scientists to have had very little oxygen or even none at all. They know that oxygen would have been very detrimental to life’s building blocks at the origin of life. If we go back far enough to the evolutionists’ scenario of the Earth’s formation, when it was still cooling from the hot mass evolutionists imagine, how long did it take for microbes to “invent” this highly complex yet vital process?

Professor Cardona adds that “When and how oxygenic photosynthesis originated remains a highly debated subject with dates ranging from 3.8 billion years (Ga) to shortly before 2.4 Ga, the onset of the Great Oxidation Event (GOE)” (sometimes termed the “Great Oxygenation Event”). The degree of error in the estimate—3.8 to 2.4 billion years (a span of 1.4 billion years)— is a very, very long time! It illustrates the level of speculation involved in their guesstimates. Cardona bases his speculation that the Great Oxidation Event occurred 3.4 billion years ago by

using sequence comparisons and Bayesian relaxed molecular clocks that this … event may have occurred in the early Archean more than 3.4 billion years ago, long before the most recent common ancestor of crown group Cyanobacteria and the Great Oxidation Event.[13]

He then speculates,

If the origin of water oxidation predated this gene duplication event, then that would place primordial forms of oxygenic photosynthesis at a very early stage in the evolutionary history of life.”[14]

That’s a lot of irreducible complexity for Darwinians to “invent” quickly in their scenario! Eleven years ago, R. Buick noted, “The atmosphere has apparently been oxygenated since the ‘Great Oxidation Event’ ca 2.4 Ga ago, but when the photosynthetic oxygen production began is debatable,” nonetheless speculation abounds.[15]

When all is said and done,

The origin of photosynthesis using tetrapyrrole compounds (such as chlorophylls) has long been one of the most complex and challenging issues in biology. Many schools of thought have emerged, each with its own assumptions and [each] with evidence supporting a particular origin of photosynthesis.”[16]

And, one could add, each is based on a hefty dose of guesswork and just-so-storytelling.

Is the “Great Oxidation Event” a myth? See:

References

[1] Cardona, Tania. 2019. Thinking twice about the evolution of photosynthesis. Open Biology.  https://royalsocietypublishing.org/doi/10.1098/rsob.180246.

[2] Granick S. 1957. Speculations on the origins and evolution of photosynthesis. Annals of the New York Academy of Science. 69, 292 – 308

[3] Laslie, Mitch. 2009. On the Origin of Photosynthesis. Science. 323:1286-1287. March 6, p. 1296.

[4] Leslie, 2009.

[5] Cardona, 2019

[6] Weber, Lewis. 2010. Animals London: Publications International .p. 62-63.

[7] Gaidos, Susan, 2009,  Living. From Green Leaves to Bird Brains. Science News.  May 9 p. 28.

[8] Olson, John. 2006. “Photosynthesis in the Archean era”. Photosyn. Research. 88 (2): 109–17. p. 109.

[9] Cardona, 2019, p. 10.

[10] Cardona, 2019, p. 1.

[11] Cardona, 2019, p. 1.

[12] Cardona, Tania. 2018. Early Archean origin of heterodimeric Photosystem I.  Heliyon 4 e00548

[13] Cardona, 2018, p. 1.

[14] Cardona, 2018.

[15] Buick, R 2008. When did oxygenic photosynthesis evolve. Phil. Trans. Royal Soc. B, Biol. Sci. 363 (1504): 2731–43.

[16] Xiong, Jin. 2007. Photosynthesis: What Color was its Origin? Genome Biology. 7(12):245;1-5.


Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology at several colleges and universities including for over 40 years at Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored, are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.

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