Evolution textbooks are suffocating: very low levels of Oxygen!

Producing Oxygen from CO₂ on Mars
requires a temperature of 1500° Fahrenheit = 815° Celsius (source)

Notorious Elon Musk wants to ensure the "long-term survival of consciousness" by ferrying a million settlers to permanent residency on Mars by 2050. A tiny problem: there is no Oxygen in the Martian atmosphere!

Next problem: transporting sufficient Oxygen from Earth to Mars is out of the question. Solution: produce it locally from CO₂ in the Martian atmosphere by technological methods. This is technically feasible in principle. That is to say, there is enough CO₂ in the atmosphere. The only problem: the required device needs a temperature of 1500° Fahrenheit or 815° Celsius. That is a huge amount of energy. Where do you get that energy from? Solar power is rather weak on Mars. It is only 43% of that on Earth. In this way you won't produce Oxygen fast, cheap and in sufficient amounts. 

By the way: how has this been done on the Earth? How did the earth produce enough atmospheric Oxygen? In order to produce 21% Oxygen in the atmosphere of a reasonably large planet, one needs massive large-scale machinery at huge costs. Who's going to pay for this? All billionaires on Earth would not be enough I guess. Or, alternatively, construct machinery producing Oxygen during a very very long time. But who's going to wait for that? 

The slow method was the 'solution' adopted on planet Earth. Nobody has ever paid for it. An atmosphere consisting of 21% Oxygen is priceless and we got it for free. It has been engineered by cyanobacteria (blue-green algae). Some 2,5 billion years ago. They produced Oxygen as a byproduct of photosynthesis. We should be grateful to them.

Humans are addicted to Oxygen

Australopithecus afarensis are runners! (Nature)

All animals on Earth require Oxygen to live. Especially predators which need to outrun their prey. If the oxygen supply to the brain is cut off for more than a couple of minutes, we lose consciousness [5]. 15% Oxygen is the minimum level for a healthy human brain function. If Oxygen levels on Earth were to fall below 15%, animals would suffocate. Once I found myself in a very crowded train and experienced difficulty in breathing and was afraid to faint. 

We are animals addicted to Oxygen. Just have a look at the anatomy and physiology of animal bodies. Their bodies are dominated by harnessing Oxygen from the air: large lungs, tracheae, nose, heart, blood, a large and complicated network of big and small blood vessels, red blood cells, hemoglobin with iron [10], and so on. An unborn baby receives oxygen from their mother through an umbilical cord.  Physical exertion causes faster breathing, faster heartbeat, and higher Oxygen consumption. Even while we are sleeping, we breath. Exposure to Carbon monoxide (CO) is deadly because it replaces the Oxygen in the bloodstream and very soon you will die from suffocation. Humans can't stay alive without oxygen for longer than 4 minutes.  Mammals living in the sea such as whales and dolphins need to go to the surface to get Oxygen. And so on.

All this is common knowledge. Most people know there is 21% Oxygen in the atmosphere, but don't know that there was no Oxygen at all in the atmosphere of the young Earth. How did the Earth arrive at 21%? How long did it take? Why specifically 21%? What mechanism keeps atmospheric Oxygen levels at 21% for millions of years? Despite a growing world population and burning increasing amounts of fossil fuel ( = more Oxygen consumption) and simultaneously a worldwide deforestation (= less Oxygen production).

The habitable zone of a planet is defined as having the right distance to its star in order to have liquid water. That is evidently a physical property. However, to be habitable for warmblooded intelligent mammals, a planet must have sufficient Oxygen in its atmosphere. I don't know whether planets with Oxygen created by pure physical means can exist. On Earth the large percentage of Oxygen is in fact a biological property: photosynthesis. On Earth there is a wonderful cooperation between animals and plants. Plants produce Oxygen, which is consumed by animals. Animals produce CO2 which is consumed by plants. The waste product of plants is food for animals and the waste product of animals is food for plants. There is a wonderful balance between Oxygen consumers and Oxygen producers that apparently keeps the Oxygen percentage within strict limits. Paradoxically, first there must be life before a planet can become habitable for intelligent life.

 

What Do the Textbooks Say?

Any theory aiming to explain life on Earth has to explain these facts. The theory of evolution is supposed to explain the diversity of life on Earth [3]. But does it explain 21% Oxygen?  What do the evolution textbooks say about Oxygen?

+ Strickberger's Evolution and later editions together with Brian K. Hall and Benedikt Hallgrímsson do a very good job at explaining the importance of Oxygen.

+ Brian K. Hall (2010) "Evolution: Principles and Processes. Does a good job. (however, this is not a 'standard' evolution textbook).

- Douglas J. Futuyma, Mark Kirkpatrick (2023) Evolution. :

"When photosynthesis evolved in cyanobacteria and other bacteria, it introduced oxygen in the atmosphere: perhaps the most important effect of life on Earth's environment" (p.458) (2023) (emphasis mine)

That's about it! Nothing about the evolution of photosynthesis. Ozon is not in the index. If the authors really think atmospheric Oxygen is "the most important effect of life on Earth's environment" one would expect that the authors devoted much more space to the topic! The book has 615 pages!

- Freeman and Herron Evolutionary Analysis (4th edition) 

The evolution of atmospheric oxygen is briefly mentioned in a short paragraph (p.701). Photosynthesis: next to nothing. No ozone layer, no UV. Note: the book has 800 pages!

- Bergstrom and Dugatkin (2023) Evolution 3rd edition:  

The planetary and geological context of evolution of life on earth is almost completely absent! The importance of oxygen, ozon and photosynthesis for life on Earth is nowhere to be found. The book has 778 pages!

- Zimmer and Emlen: Evolution. Making Sense of Life 2020. This is a beautifully designed book, but the rise of Oxygen in the Earth's atmosphere is mentioned only in passing (p.78). Photosynthesis, C3-, C4- photosynthesis are mentioned briefly in the section 3.5 'Traces of Vanished Biology' (p.72). But no ozon, 'aerobic', 'anaerobic' or 'metabolism' in the index. Apparently evolution takes place in a vacuum! In his Evolution The Triumph of an idea (2001) Zimmer has a paragraph about Oxygen as a possible causal factor of the Cambrian explosion (p.126). Not a minor issue! A capture of a picture of an underwater plant reads: "An underwater plant releases bubbles of oxygen as it carries out photosynthesis. ... plants provide us with the oxygen we need to breathe" (page 101). Excellent, but that's all! An isolated remark in the capture of an illustration.

- Eli C. Minkoff (1983) 'Evolutionary Biology' is the oldest evolution textbook I possess. In a short paragraph about Cyanobacteria he writes: "The free oxygen in the Earth atmosphere is believed to have originated as a byproduct first of blue-green algal photosynthesis and later of the photosynthesis of eukaryotic plants" (page 421). Excellent statement, but considering the 627 pages of the book, it is nothing.

Conclusion 

Oxygen's presence in the atmosphere is one of the few major revolutions in the history of life on Earth. But all Evolution textbooks except Strickberger fail to point out this fact. Why is that? How should we understand this weird omission? [1,2]. Is an Oxygen-rich atmosphere 'just' the environment that simply can be assumed to exist in the theory of evolution? [3]. Is 21% Oxygen outside the domain of the theory of evolution because it is a non-biological property? But free Oxygen is produced by photosynthesis! It is a biological phenomenon! It clearly falls within the domain of evolution theory. Maybe, the textbook authors think that evolution of atmospheric Oxygen on planet Earth is in the domain geology and climatology? I think that a good scientific theory should not be hindered by disciplinary borders! [6],[7].

In my opinion, for example, Earth System Science [4] is needed to explain why the Earth is (still) a habitable planet. Genes alone cannot do that! Think about this: the modern theory of evolution cannot explain why the Earth is home to life, be it extinct or extant species, simple or complex. Certainly, we cannot explain the evolution of life on Earth without DNA. DNA is extremely important for life and evolution, but DNA on its own cannot explain why there are animals on Earth! Take a deep breath –preferably at sea level– and think about that!

Notes

1. The idea is now more than fifty years old: Arthur N. Strahler (1987) 'Science and Earth History. The Evolution/Creation Controversy', Prometheus Books, hardback 552 pages. Graphic on page 315 illustrates two hypotheses about the evolution of the evolution of Oxygen in the Earth's atmosphere. (based on publication dating back to 1964 and 1984.!)
2. A. H. Knoll, S B Carroll (1999) Early animal evolution: emerging views from comparative biology and geology : "If assembly of the developmental toolkit was not by itself the trigger for the Cambrian explosion, can we identify environmental events that could have released the morphogenetic potential of these genes? The most likely candidate for such an environmental gate keeper is molecular oxygen."
3. Evolution explains the diversity of life given the origin of life, given the geological and atmospheric conditions on earth? But what if the 'given' is partly produced by the products of evolution?
4. Tim Lenton, Andrew Watson (2011) Revolutions that made the Earth. Important book. Earth System Science. See for a short introduction: Tim Lenton (2016) 'Earth System Science: A Very Short Introduction' Recommended.
   
5. Nick Lane Oxygen (2002) page 272. This book first opened my eyes! Recommended.
   
6. "Some of the most fascinating questions whose answers still remain obscure to science lie at the interface between traditional fields. Of course, disciplines are not real entities. They are artificial constructs made by people. "  Charles S. Cockell (2018) Preface The Equations of Life.
7. Relevant biological subdisciplines:

8. 

   Earth & environmental science, Plant science & Ecology, Genetics & Evolution, Microbiology, Virology, Human & Animal Biology, Molecular & Cellular Biology. In this context 'Astronomy' should be replaced with 'Astrobiology'.
   

9. The CDC estimates that about one in every 700 births has some oxygen deprivation-related complication. Other studies have indicated that as many as one in 200 babies experiences these problems. (added: 22 Jan 25)
10. There's no point in breathing without iron. Without iron in my blood, it doesn't matter how much I breathe... Anja Røyne (2020) The Elements We Live By. How Iron Helps Us Breathe, Potassium Lets Us See, and Other Surprising Superpowers of the Periodic Table. (added: 26 Jan 25)

 

Postscript

I found a blogpost about de 2014 TV serie Cosmos (Neil deGrasse Tyson) episode 9 where the rise of Oxygen in the atmosphere of the early Earth is discussed (Dutch). See: wikipedia.

Postscript 22 Jan 2025: Oxygen again

A recent Nature Research Highlight article Three pulses of breaths toward three evolutionary shifts (2024) is a good example of proposing correlations between geological data and the evolution of animals during Ediacaran and the early Cambrian period. Note: although the 13 authors of the original research publication are all Earth scientists and published in Global and Planetary Change (not an Evolution journal), they included a lot of data about fossil animals. Hopefully these results will one day appear in the evolution textbooks! 

I gratefully acknowledge Gerdien de Jong for making me aware of these publications. 

Postscript 24 Jan 2025: Iodine

I watched a video from a  science blogger Earth's Dramatic Transformation 500 Million Years Ago May Be Due to Iodine based on a remarkable publication:
Evolution of the iodine cycle and the late stabilization of the Earth’s ozone layer
As an evolutionary biologist I feel more and more embarrassed how little I know about evolution on Earth!!! How could evolution ever have been teached without non-biological factors!!!