My greatest thrill as a scientist was not when I published my first paper, passed my dissertation defense, or was awarded my first grant (although those were all pretty great). Rather, it happened because of a scientific paper that someone else published. It showed that the chemical results from my grad school research worked in a real living system. I had never talked with those other scientists, but they had applied my results to real life–and it worked!
In another case, I heard that a company had taken some public results of mine and used them on a patent. My basic reaction was the same thrill. Those results aren’t mine any more–they belong to the world and now they have the chance of healing someone’s disease. The true thrill and strength of science comes from the community, through citation and external replication.
This works with scientific theories as well, such as the theory of evolution. When different scientists start noticing the same thing, a story is told and a theory is born. A recent article in Nature Ecology & Evolution, “The Energy Expansions of Evolution,” gives that theoretical thrill, because it brings coherence to so much data at once.
In this article (also featured at The Atlantic), evolutionary biologist and writer Olivia Judson brings together threads of evidence tracing the history of life over billions of years. Judson’s story is a good one, which she divides into “five ‘energetic’ epochs”: geochemical energy, sunlight, oxygen, flesh, and fire. In each epoch, life learned to use a different source of energy, and the new energy caused life to expand and evolve, resulting in the complex ecosystems we are part of today. Like a video-game hero unlocking the next level in a computer game, living organisms unlocked new levels of complexity by evolving the ability to eat and excrete new things.
Judson’s article is a vivid and accessible summary of recent scientific debates. I especially like how she navigates the areas of scientific uncertainty while still conveying the strength of the scientific consensus that life has grown increasingly complex over time. Judson tells how organisms from red algae to sperm whales have tapped into more and more energy using more and more complex structures. The biological records of the past tell a story, and Judson is an engaging storyteller.
I’ve studied chemistry for years, so as I read Judson’s story, images of swirling atoms in chains and hexagons flew through my mind. My 2016 book, A World from Dust: How the Periodic Table Shaped Life, tells this story from a chemical perspective. Judson sees a story in the increasing complexity of what organisms eat and excrete, and I see a story in the increasing concentrations of oxygen, which changed what organisms could eat and excrete. Oxygen affected the geology, chemistry, and biology of the entire planet, allowing—perhaps even compelling—complex life forms to develop.
A third scientist from another discipline also tells this story. About a decade ago, an astrophysicist named Eric Chaisson wrote a book titled Epic of Evolution. True to his roots in the physical sciences, Chaisson counts not energy but power when telling the story of life’s growing complexity. Chaisson’s quantitative approach counts not just how much energy is used by an organism, but how much energy is transformed from one form to another over time—a measure he calls “Energy Rate Density.”
The beauty of Chaisson’s measure is that it can be applied to any structure or collection of structures that transforms energy. If we apply Chaisson’s Energy Rate Density to Judson’s epochs, Energy Rate Density increases over time. In the figure below, Judson’s first epoch of geochemical energy matches Chaisson’s calculations for the Energy Rate Density of organisms that transform energy from the earth itself (around 0.01 watts per kilogram or W/kg). Judson’s second epoch of photosynthesis matches Chaisson’s “photosynthesizers” which transform energy from the sun (0.1-1 W/kg), and the epochs of oxygen and flesh match Chaisson’s “animals” which transform energy from oxygen and other organisms (1-10 W/kg). Finally, Judson’s last epoch of fire matches Chaisson’s calculations for human society. The key point is that both Judson and Chaisson note that energy use moves up over time.
Figure 11.1 from A World from Dust, drawn by Mary Anderson Chaffee.
Within an organism, different organs have different Energy Rate Densities. The human brain has an Energy Rate Density around 15 watts per kilogram, which is higher than any other organ or organism at rest. By Chaisson’s calculations, the power of the human brain stands out and forms the basis for all artificial structures that can transform energy, or “human society.” Campfires, light bulbs, and airplanes are complex structures that can transform up to thousands of watts per kilogram.
The work of Judson, Chaisson, and others like myself converge on a common theme: the directionality of natural history. Nature indeed tells a compelling and amazing story, one of complexity overcoming chaos through eons of slow and patient development. The data allow you to interpret this story as you choose. Some say it’s a story of blind chance, in which meaning is self-assembled, self-referential, and ultimately illusory. But in that case, why is there anything at all? Why do we have these complex bodies, with brains that intuitively expect all these arrows to point to something? The story could have been interrupted at any number of points, by meteor strike or vacuum collapse, and yet, despite the odds, here we are. Are we lucky, or blessed?
Since we’re referring to multiple scientific disciplines already, let’s bring in one more discipline: theology. Humans stand out at the end of this 14-billion-year-long arrow of creation as choice-making, word-speaking, energy-transforming creatures. The fact that the incredibly complex structure of the brain is able to generate language and new kinds of relationships fits well alongside the Christian belief that humans have a special place in creation’s story, created “in the image of God.”
Our distinctive human nature opens questions of meaning and purpose. NT Wright said in his talk at the 2017 BioLogos conference, "If you want to know the meaning of creation, look at humans. If you want to know the meaning of being human, look at Jesus." The theological story is that creation has been sidetracked by sin, but it is now being renewed and transformed in Christ as God’s future is brought into the present. The theological and the scientific stories are like overlapping arrows pointing in the same direction, enriching each other even through our puzzlement as we work out what it all means.
For Christians like myself, this long story points outside itself to its ultimate Author. The awe and wonder I feel as I contemplate the story of nature points to the majesty of its Creator. As Herbert McCabe once wrote, “the world itself raises a question.” Christians have the opportunity to point people to the answer: a man on a cross.