How did life on Earth originate? There are many reported breakthroughs in this area of study, but news items are often overstated and designed to attract readership. Real progress is being made, but the questions are big– and answers complex.
Scientific inquiry into the topic of the origin of life (often shortened to OoL or formalized to abiogenesis) is thriving. A quick internet search of the “top 10 problems of science” will usually find OoL within the top 5. Funding from major federal agencies (NSF, NASA, DARPA, DoE) is growing, and private philanthropic funders like JTF have been joined by others like the Simons Foundation.
When I had the recent pleasure of presiding over the 2016 Gordon Research Conference for life’s origins, speakers attended from six continents — all seven, if we acknowledge fieldworkers based in Antarctica! There is also a strong field of emerging young international scientists moving into the field.
One of the reasons for this state of affairs is that we are far from any consensus answer to the question “how did life on Earth originate?” Every month or so, science news stories appear about major scientific breakthroughs in the field. But news items are often overstated, designed to attract readership. Real progress is being made, but the questions are big and answers complex.
I’ll try to lay out some of the recent history and current status of this exciting discipline, and reflect a bit on it as a Christian.
Beginning with chemistry
OoL research was originally dominated by chemistry, as it searched for how the organic molecules required for life might be generated by the chemical compounds that were prevalent on early Earth. In the 1950s considerable excitement surrounded the experiments by Stanley Miller and Harold Urey, which were able to synthesize amino acids (the building blocks of proteins) and nucleobases (components of DNA). At the same time, a slew of Nobel Prizes was being awarded to discoveries about the molecular basis of life that seemed to reduce to these chemical building blocks. How hard could it be to figure out the missing details that could account for the origin of life? Very difficult, as it turns out.
The fundamental problem is the enormous number of ways that matter and energy can combine to produce small organic molecules, while there are only a few of these that are actually used by biology. So the challenge is not so much how to account for the production of organic molecules — that is relatively simple. Rather, how did a very small subset of those molecules — the ones actually used by life — find each other and organize themselves to work together among a chaotic soup of countless combinations?
Problems of permutations and combinations get far worse as we move to consider the next level of complexity necessary for life as we know it. In modern biology, amino acids link up in a specific order with other amino acids to form proteins. So it is not just the problem of generating the right amino acids, and even of getting them it touch with each other; they must also come together in the precise sequence that provides a protein with its functionality. This is similar to how the sequence of characters in sentence is vitally important to its meaning.
So think of it like this: there are 26 letters plus a space that give us 27 characters out of which English sentences are formed. That means there are 27^66 = 2.95 x 10^94 different ways to write a string of 66 characters like this one: “the sequence of letters I am typing gives meaning to this sentence.” 2.94 x 10^94 is orders of magnitude larger than the number of atoms in our universe! Of course there are other strings of symbols that are functionally similar and sometimes shorter (“this sequence of letters carries specific meaning”) as well as near-misses that are functionally acceptable (“the sequence of letterz I am typing giffs meening to thiz sentence”). But we still have an ocean of gibberish sequences within which to find any specific meaning.
The analogous problem for OoL is to understand how amino acids formed “useful” sequences we know as proteins (or, if you prefer, to form “useful” sequences of DNA that encode these proteins) — and most proteins are many more than 66 characters. Natural selection does the job nicely once we have genetically encoded proteins to work with. But how does that Darwinian process begin?
In the late 20th century it was discovered that RNA — chemical cousin to DNA — can fulfill many of the roles played by proteins while also transmitting genetic information. It might be simpler for RNA to jumpstart the production of proteins (and life) than DNA. This RNA world hypothesis gained enough traction to dominate OoL thinking, arguably up to the present. However it does not solve the fundamental challenge that a total mass of RNA molecules far exceeding the mass of our planet would be required to create one sequence capable by chance of catalyzing its own replication.
Some of the best funded and most prestigious researchers in the field are working to find a way through this puzzle, but none claim to have solved the problem to the satisfaction of others. Indeed, I count myself among those still skeptical that we have witnessed a genuinely plausible reaction pathway to produce individual letters of RNA (amino acids are easier, but don’t explain how to get genetic information, required for evolution as we know it).
In 2016, NASA and the NSF collaborated for the first time to host a think tank (IdeasLab) aimed at generating fundamentally new thinking on the topic of OoL. I had the pleasure of being Principle Investigator for the NSF side of this project. It resulted in almost $9 million dollars of high risk but potentially high return thinking about OoL (PDF of report). During the project I worked with four other mentors to guide these new, interdisciplinary projects into being. The experience was fascinating, convincing me more than ever that exciting growth for the field is coming now from those willing to step back from their own area of expertise enough to remember the topic of OoL is a meeting point of different academic disciplines.
The biggest impact that geology and planetary science have had upon OoL in recent years is to show us that life on our planet seems to have arisen very quickly. Meanwhile, nuclear physics tells us that carbon, hydrogen, oxygen, and nitrogen are the four most abundant chemical elements in the universe capable of forming covalent bonds. Molecular biology and biochemistry tell us that these four elements were enough to produce simple cell membranes, along with sugars, 18 of the 20 amino acids (you need to add sulfur for the other two), and most of the chemical structure for building blocks of DNA.
Microbiology over the past twenty years has been telling us that these components and quick start were sufficient for a system than can adapt to a far wider range of conditions than we ever imagined: conditions similar to extraterrestrial environments within our solar system. Some of the most valuable information we may gather in the next decade about life’s origins seems likely to come from Mars exploration, where the absence of plate tectonics leaves a far better geological record of the minerals and conditions likely present on Earth at the time of life’s origins. Other insights will come from explorations of planets and moons, asteroids, and comets to which we have access.
All of this describes the shift of OoL into Astrobiology — the study of the origin, distribution, and future of life in the universe. And this seems very fruitful at present, because the one example we know of life originating seems to have formed easily and quickly on a pretty ordinary planet. How many more such planets are there?
Over the past generation, astronomy has discovered that most if not all stars in the universe are orbited by planets. Although the hunt continues for a perfect match to our planetary home, each month since has brought us closer to finding Earth-like planets orbiting Sun like stars. We might be missing something really big, but if not then it seems reasonable to expect that some (perhaps many) have harbored independent origins for life.
So where does that leave me as a Christian? From science, evolutionary biology tells me that organisms evolve by natural selection to reflect their environments. Astrobiology helps me to see that principle extending far more broadly.
I do believe in God the universe maker. So as a Christian I believe that the God I work to know built information into the universe, and life reflects this act of creation through evolution. As I re-watch Planet Earth with whichever of my daughters I can catch, from age 2 to 10, we share a sense of wonder. But that might leave you thinking I have a vague and deistic interpretation of creation. Not so. For me the most wondrous part of it all is the firm conviction that the God who brought this mighty universe into being loves me and will do pretty much anything to connect with me. The logos of biology and logic (and so much more) became flesh in order to demonstrate this love.
Going one level deeper, science has recently been reminding me that images are partial (not complete) reflections of an original. Theologically, that changes my sense of being made in the image of God. Science has, in effect, taught me to balance the glory of imago dei with a humility to remember how much less than God I am.
All the more remarkable, then to believe that God loves me enough to have sent his only Son to dwell amongst us. Much of this essay was created against that backdrop of celebrating Christ’s birth. Soon we will move to remember the other side of that wondrous idea: that God’s Son died for us that our images be made whole. For now I align with Plato and the apostle Paul to remember that for now I see through a glass darkly.