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Research has revealed, for example, that a strategically designed and strategically timed encounter with a smaller planet dispersed proto-Earth’s thick atmosphere and thousands-of-kilometers-deep ocean, increased the mass and density of proto-Earth, and resulted in the formation of Earth’s large moon.² The collision between (and consequent merger of) the two planets resulted in Earth’s possessing a large, hot, and dynamic core. This unique core gave rise to Earth’s Goldilocks crust. Earth’s crust is not too thick, nor is it too thin. It is just the right thickness to make possible a long history of life on its uppermost surface and, eventually, global human civilization.³ Now a team of geophysicists has discovered that Earth’s crust is just right for life in several other marvelous ways. 

A Clever Analytical Approach
While several mysteries concerning Earth’s crust remain, just days before Christmas 2023, a team of geophysicists led by Zhen-Jie Zhang published a breakthrough paper unveiling what researchers had previously considered undecipherable details about Earth’s outer shell of rock.⁴ Their work brought to light fresh insights that are already yielding dramatic new evidence for design.

Igneous rocks are the product of the cooling and solidification of magma, or lava. Igneous rocks comprise about 15% of Earth’s continents and nearly all of Earth’s oceanic crust. Basalts are the most widespread and abundant of Earth’s igneous rocks. Basalts come from Earth’s asthenosphere.

The asthenosphere is the layer that lies between Earth’s crust and mantle. It is thicker than Earth’s crust but much thinner than Earth’s mantle. Earth’s asthenosphere has an exceptionally low viscosity. Viscosity refers to resistance to stirring. For example, peanut butter is more viscous than syrup and syrup is more viscous than water. The low viscosity of Earth’s asthenosphere lowers the melting point of minerals, explaining why basalts in the asthenosphere are in liquid form and why basaltic rocks are so abundant in Earth’s crust.

Zhang’s team noted that data from various petrologists’ experiments revealed that oxides in basalt primary melts (basalts that have suffered little or no chemical alteration since cooling and solidifying from their molten form) are sensitive to the pressure of melting but show little or no sensitivity to the chemical compositions in either the asthenosphere or the upper mantle. They then explained how this property of basalt primary melts combined with measurements of oxides in the basalt primary melts could be used to determine the thickness of Earth’s lithosphere at the location and age of the basalt sample. (The lithosphere constitutes Earth’s crust plus that part of Earth’s upper mantle that does not move, relative to the crust.) 

So, Zhang and his colleagues then supervised a machine-learning algorithm to analyze global geo-databases (e.g., EarthChem and GEOROC) of basalts. By this means they were able to determine ongoing, cyclical variations in the thickness of Earth’s crust throughout the past 3.8 billion years. 

Three Discoveries Come to Light
First, Zhang’s team’s analysis revealed that a supercontinent forms as Earth’s crust thickens, and it breaks apart when Earth’s crust thins. At its thickest, Earth’s crust averages a depth of 140 kilometers, while at its thinnest, a depth of about 70 kilometers, on average. Zhang’s team also observed a slight trend: the minimum thickness becomes thinner with each succeeding supercontinent cycle. During the most recent cycle, the average crust thickness declined to 60 kilometers. At present, the average thickness is 72 kilometers. 

Second, the team’s study revealed that five supercontinent cycles have occurred during the past 3 billion years, with a periodicity that averages about 0.6 billion years, and that the duration of each supercontinent decreases with each progressive cycle, shortening from 0.50 billion years to 0.12 billion years (see figure). 

Figure: Supercontinents in Earth’s Past History
The bars indicate the varying durations of Earth’s supercontinents.
Data credit: Zhang et al.; Figure credit: Hugh Ross

Third, and most importantly, Zhang’s team established that there has never been a “stagnant lid” regime in Earth’s history—a time when the crust was a single stationary plate. Zhang and his colleagues determined that Earth’s crust has always consisted of multiple plates constantly moving relative to one another. In other words, during the entire time in which stable solid rock features have existed on Earth’s surface, plate tectonic activity has been ongoing. Plate tectonics has endured throughout the past 3.8 billion years. This research result thereby confirms the conclusions of a study, published in 2020, based on the buildup of argon isotopes in Earth’s atmosphere.⁵   

How Plate Tectonics Impact Life, and Vice Versa
What particularly caught my attention as I read the paper published by Zhang’s team is that the duration of plate tectonics on Earth appears identical to the duration of life on Earth. Both began at the same time and have continually persisted throughout the past 3.8 billion years.

This simultaneity is unsurprising when we recognize that life’s persistence on Earth requires sustained plate tectonic activity to recycle the nutrients life requires. At the same time, however, the persistence of plate tectonics at the level this recycling demands depends upon the existence of an abundance of iron- and sulfur-based anoxygenic photosynthetic life. These microbes play a crucial role in producing the black shales that facilitate the tectonic motion. 

Black shales are more buoyant than seafloor basalts. Black shales also contain high concentrations of heavy radioisotopes, especially uranium-235 and uranium-238. Radioisotope decay in the black shales generates heat. This heat combined with the shales’ greater buoyancy destabilizes the adjacent crust. This weakening facilitates the sliding of one tectonic plate past an adjacent plate or the sliding of one tectonic plate underneath an adjacent plate.

For advanced life to be possible, a long history of microbial life must precede it. For Earth’s surface environment to become chemically ready to support the flourishing of plants and animals requires at least 3 billion years of preparation by a huge abundance and diversity of microbial life. Even more time is required to permit the existence of human beings.⁶   

Thus, for humans to exist on Earth, life’s origin must have occurred no later than 3.8 billion years ago. Likewise, plate tectonics must have begun no later than 3.8 billion years ago, which means Earth must have cooled sufficiently from its merger with the rocky planet Theia⁷ no more recently than 3.8 billion years ago. This simultaneity and precise timing and design testifies of exquisite orchestration.

One More “Aha!”
Zhang and his colleagues add in the concluding paragraphs of their paper that “Earth was eventually primed for the arrival of a colorful Phanerozoic with the Cambrian explosion of metazoans.”⁸ In other words, the team noted that the sudden explosion of multiple animal phyla with intestinal tracts, circulatory systems, and complex internal and external organs—an event known as the Cambrian explosion—depended on a dramatic acceleration of the crustal thinning that initiated a supercontinent breakup. How so? 

The breakup of Gondwana generated massive landslides into the seas (the Great Unconformity), producing vast continental shelves that brought about the chemical transformation and oxygenation of Earth’s atmosphere and seas. This relatively rapid sequence of events created for the first time in Earth’s history an environment fit for advanced life. Thus, it made possible the Avalon and Cambrian bursts of life just early enough to make way for the future existence of human beings. A more thorough explanation of these events and their meticulous orchestration can be found in Improbable Planet,⁹ Designed to the Core,¹⁰ and Rescuing Inerrancy.¹¹ Each new discovery points to the work of a supernatural, super-intelligent Creator who intended for us to be here and to recognize his handiwork.

Endnotes

1. Hugh Ross, Designed to the Core (Covina, CA: RTB Press, 2022), 207–220.
2. Hugh Ross, Improbable Planet: How Earth Became Humanity’s Home (Grand Rapids, MI: Baker Books, 2016), 43–61.
3. Ross, Designed to the Core, 207–220.
4. Zhen-Jie Zhang et al., “Lithospheric Thickness Records Tectonic Evolution by Controlling Metamorphic Conditions,” Science Advances 9, no. 50 (December 15, 2023): id. eadi2134, doi:10.1126/sciadv.adi2134.
5. Meng Guo and Jun Korenaga, “Argon Constraints on the Early Growth of Felsic Continental Crust,” Science Advances 6, no. 21 (May 20, 2020): id. eaaqz6234, doi:10.1126/sciadv.aaz6234.
6. Ross, Improbable Planet, 119–142.
7. For details and documentation on the collision between proto-Earth and Theia, see Ross, Improbable Planet, chapter 5, pages 43–61.
8. Zhang et al., “Lithospheric Thickness Records,” page 8 of 13.
9. Ross, Improbable Planet, 143–197.
10. Ross, Designed to the Core, 183–223.
11. Hugh Ross, Rescuing Inerrancy: A Scientific Defense (Covina, CA: RTB Press, 2023), 161–172.

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Darwin’s Claim
Naturalism is the hypothesis that strictly natural processes explain the origin and history of all species of life that have ever existed on Earth. With the publication of Charles Darwin’s book On the Origin of Species¹ (1859) naturalism eventually became mainstream science. Darwin claimed that all life arose by common descent through a gradual branching pattern of evolution driven by natural selection from an original microbial species. He predicted that future fossil discoveries would affirm his hypothesis. 

Darwin’s book (see figure 1) shook the world from its theistic complacency. Within a few decades, naturalism replaced theism as the dominant worldview among research biologists studying the history of Earth’s life. This tsunami continues to this day. In 2015, evolutionary biologist and University of Chicago professor Jerry Coyne declared in his book, Faith Versus Fact, “The greatest scripture-killer ever penned [On the Origin of Species] demolished an entire series of biblical claims by demonstrating that purely naturalistic processes—evolution and natural selection—could explain patterns in nature.”²

Naturalistic Drivers of Biological Evolution
Darwin proposed that natural selection was the sole driver of the evolution of life. Dutch botanist and geneticist Hugo de Vries demonstrated in 1901 that mutations are another significant factor. In the last few decades, evolutionary biologists have discovered two additional natural mechanisms that drive changes in life-forms: gene exchange and epigenetics.

Of the four mechanisms, natural selection and mutations play the dominant role. Gene exchange and epigenetics play minor roles, with gene exchange playing a bigger role for microbial species than it does for large-bodied organisms.  

Evolutionary biologists and geneticists have searched in vain for a fifth naturalistic mechanism. If one exists, it must play a very minor role.

Fossil Record Challenges
The four known naturalistic mechanisms for generating changes in life-forms all make relatively small step changes. Mutations are capable of generating the biggest changes but the vast majority of mutations are neutral. That is, the changes they generate are neither harmful nor beneficial. Of those that are nonneutral, harmful mutations outnumber beneficial mutations by at least 10,000 to 1 and sometimes by 10,000,000 to 1. The high ratio of harmful (or deleterious) to beneficial mutations explains why ecologists observe far more extinction events than speciation events in their field studies.³

Naturalistic processes—natural selection, mutations, gene exchange, and epigenetics—all require long time periods to produce significant changes. Such changes, however, require a stable or gradually changing environment. Catastrophic environmental events will either negate the changes or result in extinction. Plus, all of these natural processes predict a bottom-up development of taxonomic hierarchy (see figure 2). That is, natural processes predict that over time they will first produce a proliferation of species, which, in much more time, will produce a proliferation of genera—and so on until one or more phyla finally appear. 

Figure 2: Hierarchical Classification of the Body Structures of Organisms
Credit: Wikimedia Commons

The problem with these predictions is that the fossil record reveals the opposite: a top-down hierarchy. As paleontologists Douglas Erwin, James Valentine, and John Sepkoski have observed with respect to the Avalon and Cambrian explosions, “The major pulse of diversification of phyla occurs before that of classes, classes before that of orders, and orders before that of families.”⁴

The Cambrian explosion refers to the sudden appearance, 538.79 ± 0.21 million years ago,⁵ of animals with digestive tracts, circulatory systems, skeletons, and internal and external organs. These animals require a minimum atmospheric oxygen level of 10%, and they appear in the fossil record at the very moment that level is reached.⁶

The Cambrian phyla do not appear in a time-separated sequence. The most advanced phylum, chordata, the phylum to which all humans and all vertebrates belong, appears at the same time as the most primitive Cambrian phyla. It’s at the beginning, not the middle or the end of the Cambrian period. Furthermore, it is not just the nonvertebrate chordates that appear at the beginning of the Cambrian. Vertebrate fish also appear at that time. 

For many decades, paleontologists were convinced that among present-day animal phyla the bryozoa phylum (animals with body sizes ranging from 0.1 to 0.9 millimeters) was exceptional in that it did not appear during the Cambrian period. Rather, the earliest bryozoa fossils appeared 60 million years later during the Tremadocian stage of the Ordovician period. However, this claim was overturned by recent discoveries of bryozoa fossils on Kangaroo Island, Australia, and in Southeast China.⁷ These discoveries establish that bryozoa animals appeared much earlier, at the beginning of the Cambrian period. 

At that time 50 or more animal phyla appeared.⁸ Thirty animal phyla exist on Earth today. Of these 30, at least 28 were present during the Cambrian period with most, if not all, present at the beginning of the Cambrian.   

Creation Implications
As paleontologists Kevin Peterson, Michael Dietrich, and Mark McPeek state in a review paper, “Elucidating the materialistic basis for the Cambrian explosion has become more elusive, not less, the more we know about the event itself.”⁹ They are not alone in drawing such conclusions. Nearly all paleontologists who have written reviews on the Cambrian explosion in the peer-reviewed scientific literature have made this concession.¹⁰  

While naturalistic models cannot explain the proliferation of phyla before classes, of classes before orders, and of families before orders, a biblical creation model can. Psalm 104 implies that the God of the Bible is “on a mission” to pack Earth with as much life as possible, as diverse as possible, and for as long as possible. Such a mission ensures that when God finally creates Adam and Eve they and all their offspring will possess all the biodeposits they need to launch and sustain civilization at a level that makes the redemption of untold humans possible.¹¹

God’s mission also requires that he ensures that just-right life is present on Earth at just-right abundances and at just-right times to perfectly compensate for the Sun’s ongoing increase in brightness and changes in its flaring activity. Today, the Sun burns 19–24% more brightly than it did at the time of life’s origin 3.8 billion years ago (see figure 3).

Figure 3: Sun’s Luminosity History
At its birth the Sun brightened quickly as it accumulated mass. During its youth, however, the Sun lost 15% or more of its mass, enough to cause more than an 80% loss of its luminosity (light emission). As it aged, its nuclear furnace converted more and more hydrogen into helium, increasing the Sun’s core density. This increasing core density results in more efficient nuclear burning. The increasingly efficient nuclear burning causes the Sun’s brightness once again to increase, gradually. The Sun’s brightening continues to this day and will one day generate so much heat energy as to make Earth uninhabitable. The dotted line indicates the current era. Credit: Hugh Ross

Normally, even a 1% alteration in solar luminosity would cause advanced plants and animals to go extinct. Avoiding such extinction requires sequentially replacing life on Earth with life-forms that more efficiently remove greenhouse gases from Earth’s atmosphere through accelerating the silicate-carbonate cycle at just-right rates.¹² However, only a Mind who knows the future physics of the Sun and who possesses the power to create whatever life-forms he pleases, in whatever amounts and diversity he chooses, would be capable of ensuring that just-right life is present on Earth at just-right times. 

Therefore, for multiple scientific reasons, naturalistic mechanisms are not adequate to explain the history of life on Earth. Far from “Scripture-killing,” the fossil record supports a model positing that miraculous interventions by the God of the Bible must play the predominant role.   

Endnotes

1. Charles Darwin, On the Origin of Species (London: John Murray, 1859).
2. Jerry Coyne, Faith vs. Fact: Why Science and Religion Are Incompatible (New York: Viking, 2015), 2. 
3. Field studies are conducted by humans during the era of human existence. According to Genesis 1 and Psalm 104:29–30, previous to the first appearance of humans God actively created new life-forms to replace those that went extinct. However, after God created humans he ceased from creating new forms of life. This cessation explains why the appearances of new life-forms exceeded those going extinct during the prehuman era while the extinction rate greatly exceeds the speciation rate during the human epoch. The mechanisms of natural selection, mutations, gene exchange, and epigenetics can explain the few speciation events observed to occur during the human epoch.     
4. Douglas H. Erwin, James W. Valentine, and J. John Sepkoski Jr., “A Comparative Study of Diversification Events: The Early Paleozoic versus the Mesozoic,” Evolution 41, no. 6 (November 1, 1987): 1183, doi:10.2307/2409086.
5. Ulf Linnemann et al., “New High-Resolution Age Data from the Ediacaran-Cambrian Boundary Indicate Rapid, Ecologically Driven Onset of the Cambrian Explosion,” Terra Nova 31, no. 1 (February 2019): 49–58, doi:10.1111/ter.12368.
6. Michael Tatzel et al., “Late Neoproterozoic Seawater Oxygenation by Siliceous Sponges,” Nature Communications 8 (September 20, 2017): id. 621, doi:10.1038/s41467-017-00586-5; Yuntao Ye et al., “Tracking the Evolution of Seawater Mo Isotopes through the Ediacaran-Cambrian Transition,” Precambrian Research 350 (November 2020): id. 105929, doi:10.1016/j.precamres.2020.105929; Hugh Ross, “Where Did the Cambrian Oxygen Come From?” Today’s New Reason to Believe (blog), Reasons to Believe, January 24, 2022. 
7. Zhiliang Zhang et al., “Fossil Evidence Unveils an Early Cambrian Origin for Bryozoa,” Nature 599 (November 11, 2021): 251–55, doi:10.1038/s41586-021-04033-w. 
8. Roger Lewin, “A Lopsided Look at Evolution,” Science 241, no. 4863 (July 15, 1988): 291–93, doi:10.1126/science.241.4863.291.
9. Kevin J. Peterson, Michael R. Dietrich, and Mark A. McPeek, “MicroRNAs and Metazoan Macroevolution: Insights into Canalization, Complexity, and the Cambrian Explosion,” BioEssays 31, no. 7 (July 2009): 737, doi:10.1002/bies.200900033.
10. Jeffrey S. Levinton, “The Cambrian Explosion: How Do We Use the Evidence?” BioScience 58, no. 9 (October 2008): 855, doi:10.1641/B580912; Gregory A. Wray, “Rates of Evolution in Developmental Processes,” American Zoologist32, no. 1 (January–February, 1992): 131, doi:10.1093/icb/32.1.123.
11. Hugh Ross, Improbable Planet: How Earth Became Humanity’s Home (Grand Rapids, MI: Baker Books, 2016), 168–69, 192, 196, 223–24; Hugh Ross, A Matter of Days: Resolving a Creation Controversy, 2nd ed. (Covina, CA: RTB Press, 2015), 95–97, 232–33.
12. Hugh Ross, “Weathered Bedrock: Key to Advanced Life on Earth,” Today’s New Reason to Believe (blog), Reasons to Believe, May 7, 2019; Ross, Improbable Planet, 159–64.

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Previous Attempts to Determine Atmospheric Oxygen History
Geochemists have determined the past history of Earth’s atmospheric oxygen level through measurements of isotope ratios and the abundances of certain isotopes. These isotope ratios and isotope abundances serve as proxies (substitutes) for the level of oxygen in the atmosphere. Figure 1 shows Earth’s atmospheric oxygen level throughout Earth’s history determined from these proxies.

Cerium as a Proxy for Oxygen
The dotted line in figure 1 indicates that part of Earth’s history where geochemists lacked good, undisputed proxies. The best proxies they had were measurements of cerium abundance levels and chromium isotopes. Cerium is preferentially scavenged from seawater under high atmospheric oxygen levels.¹ However, cerium oxidation kinetics are poorly constrained and the oxidative pathway has been hotly debated.² Consequently, based on cerium abundances, atmospheric oxygen level estimates from 2.5–4.0 billion years after Earth’s formation range from 0.02–0.2%.³

Chromium as a Proxy for Oxygen
Oxidative weathering of continental landmasses delivers fractionated chromium to seawater. Therefore, the chromium isotope ratios in marine sediments yield a measure of the oxygen level in the atmosphere. Based on chromium isotopes in two studies, atmospheric oxygen levels from 2.5–4.0 billion years after Earth’s formation yielded values of 0.02–0.2%.⁴ Two other studies produced values of 0.2–2.0%.⁵

These disparate values explain why scientists have engaged in such wide-ranging speculations about life during this period. Some have speculated that there may have been brief episodes in the 2.5–4.0-billion-year range of Earth’s age where the atmospheric oxygen level may have been much higher than 2%. In such cases, perhaps plants and animals with body sizes larger than a centimeter may have appeared. Such speculations have caused some evolutionary biologists to conclude that the Avalon (about 575 million years ago) and Cambrian (about 541 million years ago) explosions of life may not have been so explosive. If that is the case, then perhaps God is not as involved in the history of life on Earth as many theists think and claim.

New Measurement of Earth’s Oxygenation History
An international team of a dozen geophysicists and geochemists led by Changle Wang developed a new proxy for determining the atmospheric oxygen level.⁶ That proxy is the iron isotope ratios in iron-rich sedimentary rocks deposited on continental shelves. The team discovered that regardless of the source of iron-II, partial iron-II oxidation in such rocks requires low oxygen levels in shallow marine waters. In turn, low oxygen levels in shallow marine waters are linked to low atmospheric oxygen levels.

Iron isotope ratios proved to be a powerful, reliable proxy for atmospheric oxygen levels mainly because iron is ubiquitous and abundant in marine sedimentary rocks. Therefore, for the first time scientists possess an accurate and complete record of Earth’s atmospheric oxygen levels from 2.5–4.0 billion years after Earth’s birth (2.1–0.6 billion years ago). No longer is it a dotted line in the graph (see figure 2).

Wang’s team established that from 2.1–0.9 billion years ago, Earth’s atmospheric oxygen level remained below 0.2%. Somewhere between 900 and 750 million years ago the atmospheric oxygen level slowly began to rise above 0.2%.

The most recent measurement made by Wang’s team revealed levels from 750 million years ago. The atmospheric oxygen level at that time was about 1%. This level is consistent with the first appearance of eukaryotic predation—tiny primitive animals that feed on other even tinier animals that require a minimum atmospheric oxygen level of 1%. Not until the Avalon explosion at 575 million years ago do scientists see animals in the fossil record that require significantly more atmospheric oxygen.

Earth’s Carbon Dioxide History
Animals also require low atmospheric carbon dioxide levels. High atmospheric carbon dioxide concentrations produce acidosis (low pH) in oceans, lakes, and rivers and in aquatic animal tissues and body fluids. Acidosis is damaging to the long-term health of all aquatic animals and the short-term health of aquatic animals with high metabolic rates.⁷ For air-breathing animals, elevated carbon dioxide levels disrupt respiration and autoregulation of blood supply, which brings on cognitive and respiratory failure and circulatory arrest.⁸

It took three slushball events (ice ages where more than half of Earth’s surface is covered with thick ice) to bring the atmospheric carbon dioxide level down to where large-bodied animals could survive.⁹ These three events were the Sturtian (715–680 million years ago), Marinoan (650–635 million years ago), and Gaskiers (579.9–579.6 million years ago) glaciations. Shortly after the Gaskiers glaciation, Earth’s atmospheric carbon dioxide level finally decreased to a level where large-bodied animals could possibly exist. The first Avalon explosion 575 million years ago marks the first appearance of large-bodied animals.

Philosophical/Theological Implications
The research achievements by Wang’s team close the door on speculations about Earth’s past atmospheric oxygen levels. The last words in their paper are “Surface O₂ levels were changing in step with eukaryotic evolution in the Proterozoic.”¹⁰ In other words, the moment that the atmospheric oxygen level rose to a level permitting the existence of animals requiring at least that level of atmospheric oxygen, at that same moment those animals appeared. There was no drawn-out evolutionary process. The animals appeared as soon as oxygen conditions permitted their existence.

All naturalistic processes (natural selection, mutations, gene exchange, epigenetics) for driving the evolution of life require long time periods to produce any significant changes. However, the fossil record—in combination with the history of Earth’s atmospheric oxygen levels established by Wang’s team—demonstrates that the time periods are extremely brief, indistinguishable from instantaneous. The immediacy with which oxygen-demanding animals appear when atmospheric oxygen levels attain the minimum levels necessary for their survival supports the argument that a supernatural, superintelligent Creator authored such life, as described in Psalm 104.

Endnotes

1. Michael Bau and Andrea Koschinsky, “Oxidative Scavenging of Cerium on Hydrous Fe Oxide: Evidence from the Distribution of Rare Earth Elements and Yttrium between Fe Oxides and Mn Oxides in Hydrogenetic Ferromanganese Crusts,” Geochemical Journal 43, no. 1 (2009): 37–47, doi:10.2343/geochemj.1.0005.
2. Bau and Koschinsky, “Oxidative Scavenging of Cerium”; James W. Moflett, “The Relationship between Cerium and Manganese Oxidation in the Marine Environment,” Limnology and Oceanography 39, no. 6 (September 1994): 1309–18, doi:10.4319/lo.1994.39.6.1309.
3. Eric J. Bellefroid et al., “Constraints on Paleoproterozoic Atmospheric Oxygen Levels,” Proceedings of the National Academy of Sciences USA 115, no. 32 (July 23, 2018): 8104–9, doi:10.1073/pnas.1806216115; Xiao-Ming Liu et al., “A Persistently Low Level of Atmospheric Oxygen in Earth’s Middle Age,” Nature Communications 12 (January 13, 2021): id. 351, doi:10.1038/s41467-020-20484-7.
4. Noah J. Planavsky et al., “Low Mid-Proterozoic Atmospheric Oxygen Levels and the Delayed Rise of Animals,” Science 346, no. 6209 (October 31, 2014): 635–8, doi:10.1126/science.1258410; Devon B. Cole et al., “A Shale-Hosted Cr Isotope Record of Low Atmospheric Oxygen during the Proterozoic,” Geology 44, no. 7 (July 1, 2016): 555–8, doi:10.1130/G37787.1.
5. Donald E. Canfield et al., “Highly Fractionated Chromium Isotopes in Mesoproterozoic-Aged Shales and Atmospheric Oxygen,” Nature Communications 9 (July 20, 2018): id. 2871, doi:10.1038/s41467-018-05263-9; G. J. Gilleaudeau et al., “Oxygenation of the Mid-Proterozoic Atmosphere: Clues from Chromium Isotopes in Carbonates,” Geochemistry Perspectives Letters 2, no. 2 (May 24, 2016): 178–87, doi:10.7185/geochemlet.1618.
6. Changle Wang et al., “Strong Evidence for a Weakly Oxygenated Ocean-Atmosphere System during the Proterozoic,” Proceedings of the National Academy of Sciences USA 119, no. 6 (January 31, 2022): id. e2116101119, doi:10.1073/pnas.2116101119.
7. Hans O. Pörtner, Martina Langenbuch, and Anke Reipschläger, “Biological Impact of Elevated Ocean CO₂ Concentrations: Lessons from Animal Physiology and Earth History,” Journal of Oceanography 60, no. 4 (August 1, 2004): 705–18, doi:10.1007/s10872-004-5763-0.
8. Zaher S. Azzam et al., “The Physiological and Molecular Effects of Elevated CO₂ Levels,” Cell Cycle 9, no. 8 (April 20, 2010): 1528–32, doi:10.4161/cc.9.8.11196; Kris Permentier et al., “Carbon Dioxide Poisoning: A Literature Review of an Often Forgotten Cause of Intoxication in the Emergency Department,” International Journal of Emergency Medicine 10 (April 4, 2017): id. 14, p. 1, doi:10.1186/s12245-017-0142-y.
9. Stephan V. Sobolev and Michael Brown, “Surface Erosion Events Controlled the Evolution of Plate Tectonics on Earth,” Nature 570 (June 5, 2019): 52–57, doi:10.1038/s41586-019-1258-4; Hugh Ross, “Why Do We Need Snowball Events?” Today’s New Reason to Believe (blog), Reasons to Believe, August 5, 2019.
10. Wang et al., “Strong Evidence,” p. 6.

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These animals were predominantly living in Earth’s oceans, especially on the bottom sediment surfaces of continental shelves. For them to have the dissolved oxygen they required, they would need a pulse of bottom seawater oxygen levels on the continental shelves. New research shows how exquisitely fine-tuned geological events provided that oxygen.

Ediacaran Oxygenation
The first large animals to appear on Earth were the Ediacaran fauna. They appeared before the Cambrian explosion during a period known as the Avalon explosion, which occurred 575 million years ago. This period was marked by a sudden transition from microscopic animals to animals with body sizes as large as two meters and body shapes that included fronds, discs, and segments. This transition was possible, in part, because of an equally sudden transition of ocean waters from anoxic (oxygen-deprived) to oxic conditions.

Geological Contributors
A combination of two geological events and two biological events explains the sudden rise of oxygen in Earth’s atmosphere and dissolved oxygen in Earth’s oceans. One of the geological events was the Gaskiers glaciation. The other was the Great Unconformity (GU).

The Gaskiers glaciation lasted from 582 to 580 million years ago. The melting away of vast continental ice sheets that followed the Gaskiers glaciation delivered huge quantities of phosphorus and other nutrients into the oceans. This infusion ignited a multiplication of photosynthetic marine organisms. These organisms gave rise to the Neoproterozoic Oxygenation Event (NOE), resulting in sufficient dissolved oxygen in the oceans to support the Avalon explosion animals.

The melting of the Gaskiers ice sheets was accompanied by the GU. The GU was a worldwide geological upheaval that caused massive landslides to deposit enormous quantities of continental material into the oceans. This deposition created vast continental shelves off the shores of nearly all the continents that generated relatively shallow ocean environments. It also contributed to the influx of nutrients into these continental shelf environments and, thereby, contributed to the multiplication of photosynthetic marine organisms. Since oxygen is a byproduct of photosynthesis, this influx of organisms resulted in the NOE.

Biological Contributors
The first biological event making a contribution to the NOE was the development of fungi-lichen ecosystems on the continental landmasses. These ecosystems formed organic-rich upper soil layers. These layers restricted the consumption of atmospheric oxygen required to weather the subsoil regolith.¹

The second biological event that made a major contribution to the NOE was the origin of sponges. Sponges range in size from microscopic to a half meter in length. These creatures greatly enhance the living space over which photosynthetic bacteria and algae can thrive. Therefore, they played an important role in the multiplication of photosynthetic (oxygen-producing) marine organisms.

Some sponges, especially the smallest ones, are able to tolerate low levels of marine dissolved oxygen. For at least a major part of their life cycle, these sponges can survive at atmospheric oxygen levels as low as 0.1–0.8%,² compared with 21% today. Hence, tiny sponges likely were already contributing to a rise in marine dissolved oxygen even before the melting of the Gaskiers ice sheets and the GU. From 575 million years ago until the extinction of nearly all the Avalon fauna that occurred just a million years before the Cambrian explosion, the proliferation of sponges of increasing body sizes contributed to the rise of marine dissolved oxygen. Would it be enough to support the Cambrian animals?

Cambrian Oxygenation
The Cambrian fauna required much higher marine dissolved oxygen levels than the Avalon fauna. Unlike the Avalon fauna, most of the Cambrian fauna inhabited the seafloor bottoms of continental shelves. These seafloor bottoms typically have a much lower level of dissolved oxygen than the ocean surfaces. Only recently have marine scientists solved the problem of accounting for the origin of the greater oxygen quantity and the transfer of dissolved oxygen from sea surfaces to seafloor bottoms.

The mass extinction event that wiped out the Avalon fauna greatly increased continental weathering. This enhanced weathering increased both organic carbon burial and nutrient delivery in the oceans. The outcome was more dissolved oxygen in the oceans. However, increased continental weathering cannot explain the transfer of dissolved oxygen from sea surfaces to seafloor bottoms.

Sponges came into play in a completely unexpected way. Sponges are filter feeders, meaning that they strain nutrients from water. Researchers have learned that they removed large amounts of dissolved and fine particulate organic carbon from seawater at depths relatively close to the surface. In doing so, sponges shifted respiratory oxygen demand to greater depths.³ The resultant increase in bottom seawater dissolved oxygen led to greater phosphorus burial and greater sequestration of phosphorus by sponge microbial symbionts.⁴ This phosphorus burial and sequestration lowered oxygen demands in bottom seawater and, hence, led to higher dissolved oxygen levels on seafloor bottoms.

Affirmation of Sponges’ Crucial Role
The impact of sponges on seafloor bottom oxygenation depends on their abundance. Sponge spicules (structural elements) do not preserve well. Therefore, sponge abundance cannot be directly obtained from the fossil record. However, geochemists have shown that siliceous sponges manifest distinct silicon isotope ratios.⁵ Isotopes help provide a chemical signature where fossilization is absent.

A team led by Michael Tatzel employed stable silicon isotope data to establish that there was a large expansion of siliceous sponge abundance over the Ediacaran-Cambrian transition.⁶ Tatzel’s team affirmed the crucial role played by sponges in seafloor bottom oxygenation through using germanium/silicon and yttrium/holmium isotope ratios to determine the amounts of dissolved organic carbon in various seawater environments. Molybdenum isotope measurements made by a team of seven geochemists led by Yuntao Ye provided additional confirmation.⁷

Design Implications
Thanks to the work of several independent research teams, it is now established that a two-step sudden rise in atmospheric and dissolved marine oxygen coincided with and made possible the Avalon and Cambrian explosions of animal life. Multiple simultaneous events operated together to produce each of these jumps in oxygen abundance. These events included extraordinary and highly fine-tuned geological episodes as well as extraordinary and highly fine-tuned creations of new life-forms.

As I demonstrated in last week’s article⁸ and in my book Improbable Planet,⁹ the Avalon and Cambrian explosions of animal life show just how intractable naturalistic explanations for life’s history really are. These remarkable events in Earth’s history also show how crucial their fine-tuned features and timing are to make the later appearance of human beings possible.

Endnotes

1. Lee R. Kump, “Hypothesized Link between Neoproterozoic Greening of the Land Surface and the Establishment of an Oxygen-Rich Atmosphere,” Proceedings of the National Academy of Sciences USA 111, no. 39 (September 15, 2014): 14062–14065, doi:10.1073/pnas.1321496111.
2. Daniel B. Mills et al., “Oxygen Requirements of the Earliest Animals,” Proceedings of the National Academy of Sciences USA 111, no. 11 (March 18, 2014): 4168–4172, doi:10.1073/pnas.1400547111.
3. Timothy M. Lenton et al., “Co-evolution of Eukaryotes and Ocean Oxygenation in the Neoproterozoic Era,” Nature Geoscience 7 (April 2014): 257–265, doi:10.1038/ngeo2108; Douglas H. Erwin and Sarah Tweedt, “Ecological Drivers of the Ediacaran-Cambrian Diversification of Metazoa,” Evolutionary Ecology 24, no. 5 (July 13, 2011): 417–433, doi:10.1007/s10682-011-9505-7.
4. Fan Zhang et al., “Phosphorus Sequestration in the Form of Polyphosphate by Microbial Symbionts in Marine Sponges,” Proceedings of the National Academy of Sciences USA 112, no. 14 (April 7, 2015): 4381–4386, doi:10.1073/pnas.1423768112.
5. Katherine R. Hendry et al., “Deep Ocean Nutrients during the Last Glacial Maximum Deduced from Sponge Silicon Isotopic Compositions,” Earth and Planetary Science Letters 292, nos. 3–4 (April 1, 2010): 290–300, doi:10.1016/j.epsl.2010.02.005; Martin Wille et al., “Silicon Isotopic Fractionation in Marine Sponges: A New Model for Understanding Silicon Isotopic Variations in Sponges,” Earth and Planetary Science Letters 292, nos. 3–4 (April 1, 2010): 281–289, doi:10.1016/j.epsl.2010.01.036.
6. Michael Tatzel et al., “Late Neoproterozoic Seawater Oxygenation by Siliceous Sponges,” Nature Communications 8 (September 20, 2017): id. 621, doi:10.1038/s41467-017-00586-5.
7. Yuntao Ye et al., “Tracking the Evolution of Seawater Mo Isotopes through the Ediacaran-Cambrian Transition,” Precambrian Research 350 (November 2020): id. 105929, doi:10.1016/j.precamres.2020.105929.
8. Hugh Ross, “Cambrian Explosion Becomes More Explosive,” Today’s New Reason to Believe (blog), Reasons to Believe, January 17, 2022.
9. Hugh Ross, Improbable Planet (Grand Rapids: Baker, 2016), 172–178.

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Oxygen Content in Earth’s History
The atmospheric oxygen content at Earth’s surface is 20.946% by volume and 23.14% by mass. It has not always been that high. When life originated 3.8 billion years ago (bya), the atmospheric oxygen level was less than 0.001%. Not until 800 million years ago (mya) did oxygen in the atmosphere rise above 0.2%.¹ (The only exception is the epoch 2.45–2.2 bya, when the atmospheric oxygen level rose to 1.0–2.5%.)

Geochemists studying atmospheric oxygen levels from 800–50 mya have found that direct chemical isotope proxies (substitutes) are scarce and reconciling indirect proxy records has also proven challenging.² Nevertheless, geochemists have determined, with some certainty, when atmospheric oxygen levels surged and by how much. According to a 2018 study, levels rose:

• To about 8%, 575 mya (just before the Avalon explosion);
• To 10%, 540 mya (just before the Cambrian explosion);
• To greater than 14%, 423–419 mya (during the Late Silurian period); and
• To greater than 16%, 383–359 mya (during the Late Devonian period).³

The geochemists also determined that there were likely more than a few rapid brief leaps, up and down, in atmospheric oxygen levels from 800–50 mya.

Marine Animal Extinction
The fossil record reveals a decline in extinction rates for marine animals throughout the past 540 million years. The reason for this decline has mystified both paleontologists and evolutionary biologists.

Now, a team of five geologists and biogeologists at universities in California and France have suggested a cause for extinction decline.⁴ The group, led by Richard Stockey, hypothesizes that the decline in marine animal extinction rate is driven largely by the increase in the oxygenation of the atmosphere and oceans that occurred during the early part of the Phanerozoic eon (541 million years ago until the present). In support of their hypothesis, they pointed out that the onset of generally lower marine animal extinction rates coincides with both Earth’s atmosphere and oceans becoming oxygenated to near-modern levels about 380 mya. They reasoned that limited surface oxygenation would increase the volume of anoxic ocean water and make marine animals more vulnerable to extinction. They then launched a project to test their hypothesis against competing explanations for the decline in extinction rates.

The team’s test was made possible thanks to recent advances in Earth system modeling. They used the cGENIE model⁵ “to generate a suite of three-dimensional realizations of potential marine environmental conditions.”⁶ They included in these models a range of atmospheric oxygen and carbon dioxide concentrations.

Stockey and his colleagues discovered in their models that as one moves from the equator to the poles, temperature gradients decrease and the oxygen concentration increases relative to the ocean depth. When the team combined the cGENIE models of ocean biogeochemistry with the known physiology of marine animals, they were able to establish unequivocally that the atmospheric oxygen level is the primary factor determining the vulnerability of marine animals to extinction.

The researchers also identified several secondary factors affecting marine animal extinction:

• The sizes, configuration, and distribution of the continents
• The efficiency of the biological carbon pump in the oceans (sequestration of carbon from the atmosphere by plankton, which die and sink to the ocean bottom where their organic matter becomes trapped in sediments), which plays a role in the distribution of oxygen in the upper water column⁷
• The initial climate state
• Sizes of continental shelves
• Ocean circulation

Stockey’s group showed that even when these five factors are combined they still play a lesser role in governing marine animal extinction than the atmospheric oxygen level.

Design Implications
As I explain in my book Improbable Planet, it took several billion years of Earth being packed with as much photosynthetic life as is physically and chemically possible for the atmospheric oxygen level to rise to where it is today. For much of Earth’s history, minerals in the crust and mantle soaked up oxygen as fast as photosynthetic life produced it. It took over 3 billion years for these oxygen “sinks” to fill up.

The repeated introductions of just-right life-forms at just-right times and in just-right amounts and diversity explain how Earth’s atmosphere and oceans attained the precise oxygen levels required for global human civilization. These introductions occurred at the exact time when the Sun entered into its narrow time window when its flaring activity and its luminosity stability were both at ideal levels. Anything less than a 21% atmospheric oxygen level would deliver a lower agricultural output and lower work output from humans and their domesticated animals. Any higher than a 21% atmospheric oxygen level would result in more grass and forest fires and shorter human lifespans.

Stockey’s team established another design feature in Earth’s oxygenation history that benefits humanity. Presently, the atmospheric oxygen level is optimal to maximize marine animal biomass and biodiversity. It is also optimal for minimizing marine animal extinctions. The bottom line is that only a Mind that knows and understands the future physics of the Sun and Earth and the future needs of humans that he intends to create would also know which geological events to bring about and which life-forms to introduce at the required times and places for humans to exist and thrive.

Endnotes

1. Rosalie Tostevin and Benjamin J. W. Mills, “Reconciling Proxy Records and Models of Earth’s Oxygenation during the Neoproterozoic and Paleozoic,” Interface Focus 10, no. 4 (August 6, 2020): id. 20190137, doi:10.1098/rsfs.2019.0137.
2. Tostevin and Mills, “Reconciling Proxy Records,” id. 20190137; Alexander J. Krause et al., “Stepwise Oxygenation of the Paleozoic Atmosphere,” Nature Communications 9 (October 4, 2018): id. 4081, doi:10.1038/s41467-018-06383-y.
3. Tostevin and Mills, “Reconciling Proxy Records,” id. 20190137.
4. Richard G. Stockey et al., “Decreasing Phanerozoic Extinction Intensity as a Consequence of Earth Surface Oxygenation and Metazoan Ecophysiology,” Proceedings of the National Academy of Sciences USA 118, no. 41 (October 12, 2021): id. e2101900118, doi:10.1073/pnas.2101900118.
5. A. Ridgwell et al., “Marine Geochemical Data Assimilation in and Efficient Earth System Model of Global Biogeochemical Cycling,” Biogeosciences 4, no. 1 (January 25, 2007): 87–104, doi:10.5194/bg-4-87-2007.
6. Stockey et al., “Decreasing Phanerozoic Extinction,” id. e2101900118.
7. K. M. Meyer, A. Ridgwell, and J. L. Payne, “The Influence of the Biological Pump on Ocean Chemistry: Implications for Long-Term Trends in Marine Redox Chemistry, the Global Carbon Cycle, and Marine Animal Ecosystems,” Geobiology 14, no. 3 (May 2016): 207–209, doi:10.1111/gbi.12176.

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