Uploaded February 2026 | Updated September 2026, 2 weeks ago
On the Evolution of Life — Why Sunlight Capture Creating the Biosphere Evolved Twice and Only Twice
When life evolved, there were two pathways for life to extract chemical energy from photons of sunlight. I chat about a newly published evolutionary biology paper on why only these two pathways exist, after billions of years of evolution.
References
Bluesky link introducing the new peer-reviewed scientific paper in Nature:
https://bsky.app/profile/wcratcliff.bsky.social/post/3mdycyp34wk2c
Link to peer-reviewed paper in Nature published Feb 2, 2026
Title: Priority effects inhibit the repeated evolution of phototrophy
Link: nature.com/articles/s44260-026-00069-z
Abstract
The emergence of phototrophy is one of the most significant innovations in the history of life, vastly increasing available metabolic energy. Phototrophy is, however, known to have arisen only twice. This raises a curious question: if phototrophy was accessible enough to evolve twice, why has it never arisen again despite billions of years of subsequent evolution? Through physiological modeling, we demonstrate that chlorophototrophy and retinalophototrophy together saturate the bioenergetic landscape available to light-harvesting systems. They represent opposite solutions to key biophysical trade-offs: maximizing efficiency per photon versus maximizing metabolic flux, specialization versus versatility, and sophistication versus simplicity. Together they create an evolutionary priority effect, blocking any newly-arising phototrophic system from succeeding. By revealing the basis of this competitive exclusion, our work sheds light on a general principle - that early innovations can saturate ecological space such that they constrain future evolutionary possibilities, making apparently ‘easy’ innovations appear as rare events.
Perplexity.ai query: Explain in simple terms what chlorophototrophy and retinalphototropy are?
perplexity.ai/search/explain-in-simple-terms-what-c-rZ7QJ0pSQou1YEC4J.xKqA
Chlorophototrophy and retinalphototrophy are two different ways microbes use light to get energy, based on two different pigments.
Chlorophototrophy (chlorophyll-based):
- Uses chlorophyll or bacteriochlorophyll to capture light.
- Light energy drives electron transfer reactions in reaction centers, creating both ATP and strong chemical reductants (like NADPH).
- Those reductants can be used for CO₂ fixation, so many chlorophototrophs can build organic matter from inorganic carbon (classical photosynthesis).
- This is the mode used by plants, algae, cyanobacteria, and many anoxygenic photosynthetic bacteria.
- A simple picture: it is the “plant-style” system, with chlorophyll, electron transport chains, and often full photosynthesis and carbon fixation.
Retinalphototrophy (rhodopsin-based):
- Uses retinal-binding rhodopsin proteins (e.g., bacteriorhodopsin, proteorhodopsin) instead of chlorophyll.
- When retinal absorbs a photon, the rhodopsin changes shape and pumps ions (usually protons) across the membrane, directly building an ion gradient.
- ATP synthase then uses that ion gradient to make ATP, but there is no chlorophyll reaction center and typically no full photosynthetic electron transport chain or CO₂ fixation.
- It is usually considered simpler and less efficient for biomass production than chlorophototrophy, but it works in very nutrient-poor or extreme environments and occurs in all three domains of life.
- A simple picture: it is a “light-driven proton pump” system—more like using light to run a tiny battery charger than a full photosynthetic factory.
Phototrophy: google.com/search?q=phototrophy&sourceid=chrome&ie=UTF-8
Chlorophototrophy: google.com/search?q=chlorophototrophy&sourceid=chrome&ie=UTF-8
Retinalphototrophy: google.com/search?q=retinalophototrophy&sourceid=chrome&ie=UTF-8
Eukaryogenesis: google.com/search?q=eukaryogenesis&sourceid=chrome&ie=UTF-8
Chloroplasts: google.com/search?q=chloroplasts&sourceid=chrome&ie=UTF-8
Heme: google.com/search?q=heme&sourceid=chrome&ie=UTF-8
kDa: google.com/search?q=150+kDa&sourceid=chrome&ie=UTF-8
Wikipedia: Pareto Front: en.wikipedia.org/wiki/Pareto_front
Wikipedia: Photosynthetically Active Radiation (PAR): en.wikipedia.org/wiki/Photosynthetically_active_radiation
Wikipedia: Sunlight en.wikipedia.org/wiki/Sunlight
Please donate to PaulBeckwith.net to support my research and videos connecting the dots on abrupt climate system mayhem.
Year end - Year start GoFundMe:
gofundme.com/f/help-paul-continue-his-climate-emergency-research
Please subscribe to my YouTube channel. As well as my website, and YouTube, you can find me on Patreon, Facebook, Twitter/X, LinkedIn, Instagram, Reddit (multiple climate channels within), Quora, TikTok, Discord, Mastodon, Twitch, Vimeo, Bluesky, TruthSocial, Threads, Substack, Tumblr, Pinterest, etc...
On the Evolution of Life — Why Sunlight Capture Creating the Biosphere Evolved Twice and Only Twice
When life evolved, there were two pathways for life to extract chemical energy from photons of sunlight. I chat about a newly published evolutionary biology paper on why only these two pathways exist, after billions of years of evolution.
References
Bluesky link introducing the new peer-reviewed scientific paper in Nature:
https://bsky.app/profile/wcratcliff.bsky.social/post/3mdycyp34wk2c
Link to peer-reviewed paper in Nature published Feb 2, 2026
Title: Priority effects inhibit the repeated evolution of phototrophy
Link: nature.com/articles/s44260-026-00069-z
Abstract
The emergence of phototrophy is one of the most significant innovations in the history of life, vastly increasing available metabolic energy. Phototrophy is, however, known to have arisen only twice. This raises a curious question: if phototrophy was accessible enough to evolve twice, why has it never arisen again despite billions of years of subsequent evolution? Through physiological modeling, we demonstrate that chlorophototrophy and retinalophototrophy together saturate the bioenergetic landscape available to light-harvesting systems. They represent opposite solutions to key biophysical trade-offs: maximizing efficiency per photon versus maximizing metabolic flux, specialization versus versatility, and sophistication versus simplicity. Together they create an evolutionary priority effect, blocking any newly-arising phototrophic system from succeeding. By revealing the basis of this competitive exclusion, our work sheds light on a general principle - that early innovations can saturate ecological space such that they constrain future evolutionary possibilities, making apparently ‘easy’ innovations appear as rare events.
Perplexity.ai query: Explain in simple terms what chlorophototrophy and retinalphototropy are?
perplexity.ai/search/explain-in-simple-terms-what-c-rZ7QJ0pSQou1YEC4J.xKqA
Chlorophototrophy and retinalphototrophy are two different ways microbes use light to get energy, based on two different pigments.
Chlorophototrophy (chlorophyll-based):
- Uses chlorophyll or bacteriochlorophyll to capture light.
- Light energy drives electron transfer reactions in reaction centers, creating both ATP and strong chemical reductants (like NADPH).
- Those reductants can be used for CO₂ fixation, so many chlorophototrophs can build organic matter from inorganic carbon (classical photosynthesis).
- This is the mode used by plants, algae, cyanobacteria, and many anoxygenic photosynthetic bacteria.
- A simple picture: it is the “plant-style” system, with chlorophyll, electron transport chains, and often full photosynthesis and carbon fixation.
Retinalphototrophy (rhodopsin-based):
- Uses retinal-binding rhodopsin proteins (e.g., bacteriorhodopsin, proteorhodopsin) instead of chlorophyll.
- When retinal absorbs a photon, the rhodopsin changes shape and pumps ions (usually protons) across the membrane, directly building an ion gradient.
- ATP synthase then uses that ion gradient to make ATP, but there is no chlorophyll reaction center and typically no full photosynthetic electron transport chain or CO₂ fixation.
- It is usually considered simpler and less efficient for biomass production than chlorophototrophy, but it works in very nutrient-poor or extreme environments and occurs in all three domains of life.
- A simple picture: it is a “light-driven proton pump” system—more like using light to run a tiny battery charger than a full photosynthetic factory.
Phototrophy: google.com/search?q=phototrophy&sourceid=chrome&ie=UTF-8
Chlorophototrophy: google.com/search?q=chlorophototrophy&sourceid=chrome&ie=UTF-8
Retinalphototrophy: google.com/search?q=retinalophototrophy&sourceid=chrome&ie=UTF-8
Eukaryogenesis: google.com/search?q=eukaryogenesis&sourceid=chrome&ie=UTF-8
Chloroplasts: google.com/search?q=chloroplasts&sourceid=chrome&ie=UTF-8
Heme: google.com/search?q=heme&sourceid=chrome&ie=UTF-8
kDa: google.com/search?q=150+kDa&sourceid=chrome&ie=UTF-8
Wikipedia: Pareto Front: en.wikipedia.org/wiki/Pareto_front
Wikipedia: Photosynthetically Active Radiation (PAR): en.wikipedia.org/wiki/Photosynthetically_active_radiation
Wikipedia: Sunlight en.wikipedia.org/wiki/Sunlight
Please donate to PaulBeckwith.net to support my research and videos connecting the dots on abrupt climate system mayhem.
Year end - Year start GoFundMe:
gofundme.com/f/help-paul-continue-his-climate-emergency-research
Please subscribe to my YouTube channel. As well as my website, and YouTube, you can find me on Patreon, Facebook, Twitter/X, LinkedIn, Instagram, Reddit (multiple climate channels within), Quora, TikTok, Discord, Mastodon, Twitch, Vimeo, Bluesky, TruthSocial, Threads, Substack, Tumblr, Pinterest, etc...
