Where Should We Look for LUCA, Supposed Ancestor of All Life?

• Evolutionists believe the microbe LUCA was the Last Universal Common Ancestor of all living things.
• Some evolutionists believe they know where LUCA evolved and what LUCA was like.
• Evolutionists disagree about where LUCA evolved and what LUCA was like.
• No scientists have found LUCA.

The microbe LUCA is supposed to have been the Last Universal Common Ancestor of all living things. Using the magic of modern genetics, scientists in 2016 came up with a description of LUCA. This profile describing LUCA’s physiology and habitat, published in Nature Microbiology, generated headlines declaring “Scientists Find LUCA,” “Meet LUCA,” and “Behold LUCA.” And while journalists practically queued up to get LUCA’s autograph, other scientists begged to differ. They believe LUCA evolved in a different setting altogether, one they concocted from chemistry rather than genetics.

The Tree of Life

Evolutionists are convinced that all eukaryotes—organisms whose cells have nuclei—whether unicellular (protozoans and fungi) or multicellular (plants, dogs, and people)—evolved from a unicellular organism without a nucleus—a prokaryote. There are two sorts of prokaryotes: bacteria and archaea. They differ dramatically. Therefore, if evolutionists can find the common ancestor shared by bacteria and archaea, they believe they’ll have solved the broader mystery of life’s origins.

Hot on LUCA’s trail, evolutionary scientists seek where LUCA evolved.

After all, the characteristics of LUCA’s home might offer some clue how that magical moment happened, the moment in which chemicals presumably came to life in LUCA.

Microbial Eve, a Hydrogen-Gobbling Heat Lover

Assuming LUCA was the microbial Eve from which bacteria and archaea evolved long ago when earth was very young, evolutionary biologist William Martin, at Germany’s Heinrich Heine University in Düsseldorf, resolved to trace LUCA's tracks in the genes of modern bacteria and archaea. Bacteria can swap genes with each other, so evolutionists fear the false flags held by such hitchhiking genes might lead to an erroneous interpretation of evolution’s apparent trail through deep time. Nevertheless, Martin figured that any genes shared by at least two species of archaea and two species of bacteria would qualify as LUCA’s fingerprints—genetic evidence of common ancestry passed down faithfully over billions of years.

Surveying 6.1 million prokaryote genes, Martin’s team found 355 such shared gene families. These 355 genes do not provide all the essentials needed by a living organism, but they do include codes for proteins needed to derive energy from hydrogen and carbon dioxide. Archaea that do this—whether they live in marshes or your intestines—produce methane gas, but archaea are not the only organisms able to live on hydrogen and carbon dioxide. Some acetate-producing anaerobic bacteria, such as Clostridium,1 use the same biochemical pathway. This is known as the Wood-Ljungdahl pathway. It is the only carbon-dioxide-capturing pathway found in LUCA’s genetic portrait.

Among the proteins coded for by those 355 genes, there were only five amino acids. Where did LUCA get the other amino acids to build proteins?2 Martin’s team speculates the necessary genes have been obscured from modern eyes by billions of years of mutations or microbial gene swapping. Or perhaps LUCA depended on some sort of “primordial geochemistry”3 to fill the gap until evolution could step in.

There were however plenty of genes to build iron-sulfur clusters in LUCA’s genetic profile. Iron-sulfur clusters are vital components of many proteins, including those in the Wood-Ljungdahl pathway. Necessary for energy metabolism and many other biochemical processes, iron-sulfur clusters are essential to all known cell types. Thus LUCA—as profiled by Martin’s team—had the necessary equipment to obtain energy from hydrogen and carbon dioxide and to build iron-sulfur clusters using iron and sulfur from its environment.

What about LUCA’s habitat? LUCA’s energy-associated genes only coded for enzymes that would be destroyed by exposure to oxygen. Such enzymes are unique to anaerobes, so they conclude LUCA’s habitat must have been oxygen-free. LUCA’s profile also indicated a dependence on hydrogen, which today comes from either geological sources or fermentation. However, fermentation is a biochemical process performed by microbes, which, by definition, could not have already been around when life first evolved. That only leaves geological sources to provide LUCA’s necessary life-building hydrogen. Therefore, they conclude LUCA’s habitat must have provided hydrogen from a geological source. Furthermore, one of LUCA’s enzymes is found exclusively in microbes that thrive in super-hot conditions, like those enjoyed by extremophiles near seafloor fissures from which magma-heated mineral-rich water issues. LUCA’s profilers therefore conclude that LUCA was an anaerobic, heat-loving microbe that lived on hydrogen and carbon dioxide, and that it obtained these, along with iron and sulfur, from deep-sea hydrothermal vents.

A Eureka Moment

“I was flabbergasted at the result, I couldn’t believe it,” Martin exclaimed.4 Describing his reaction to LUCA’s profile, he says, “It’s spot on with regard to the hydrothermal vent theory.”5 Indeed, the hydrothermal vent theory is relatively new. In fact, it is a more modern idea than Darwin’s “warm little pond.”6 Evolutionists have been bouncing between these two points of origins for years. The “warm little pond” rose in prominence last year thanks to a study we reported on by University of Cambridge’s John Sutherland. But Martin’s paper has now thrown genetics behind the hydrothermal vent theory.

Abiogenesis—If Not “How,” Perhaps “Where?”

Since everything in observable biological science indicates that only life can produce life, evolutionary scientists wistfully speculate about the imaginative question of “how” life evolved through natural chemical processes. But we are obviously here, and molecules-to-man evolution is the only explanation evolutionists are willing to accept. Because they therefore assume life evolved from nonliving elements through natural processes, they’d like to know just where it happened. If they only knew where and under what conditions life popped into existence, perhaps they could have a better shot at figuring out how it happened.

We didn’t set out with a preferred scenario; we deduced the scenario from the chemistry.

While evolutionists have faith that once upon a time abiogenesis—life from nonlife—happened, the question of where it happened is hotly debated. One camp favors the wistful Charles Darwin’s “warm little pond.” Their recent champion, Sutherland’s proposal mentioned above, was a trickle-down chemistry scenario in which water carrying simple chemicals is seen percolating across the minerals and metals on the early earth’s surface. In each isolated stream, chemical reactions generate life’s raw materials without interference from chemicals in other streams. These raw materials combine in warm little ponds where, obtaining energy from the sun, additional chemical reactions generate the biochemical building blocks for life, brewing up a rich prebiotic soup. Sutherland says, “We didn’t set out with a preferred scenario; we deduced the scenario from the chemistry.”7 His plausible chemistry—reactions that might have happened if the early earth were the inhospitable sort of place evolutionists believe it was instead of the hospitable place God describes in His Word8—just happened to fit into the “warm little pond” story.

Conversely, the marine origin of life, particularly the hydrothermal vent version, is a more modern idea. In Darwin’s day, no one knew about deep-sea hydrothermal vents. Today’s undersea explorers find many of earth’s extremophiles there. Extremophiles endure conditions and obtain fuel from sources that would kill most organisms, thriving despite the superheated water rich in toxic chemicals. The structure and chemical make-up of deep-sea hydrothermal vents also facilitates spontaneous battery-like chemical reactions. Knowledge of extremophiles and these natural batteries fuels the notion that life, sparked by geochemical energy, started in hydrothermal vents. Martin deduced from his genetic analysis and assumptions what he thinks LUCA would have looked like, and his version of LUCA matched this origins option.

Looking for LUCA in All the Wrong Places

Will either idea finally bridge the gap between our chemical roots and us? Will either even show us where that bridge is? Eureka moments about anaerobic bacteria aside, don’t hold your breath.

Sutherland believes life, energized by the sun, emerged in a warm pond where ordinary chemical reactions deposited the molecular building blocks of life. While Sutherland’s model of chemistry on a hillside long ago supposedly overcomes the problems of cooking up life in one pot, it still cannot provide any plausible way in which chemicals could spontaneously arrange themselves into a living organism, much less generate the information required to make this happen again and again.

The notion that life evolved in hydrothermal vents, as Martin believes his data demonstrates, suffers from the same flaw. Martin believes life, energized by geochemistry, emerged in hydrothermal vents because some modern anaerobic microbes, which he believes diverged from a common evolutionary ancestor, share genes for obtaining energy the same way. Yet again, the availability of an energy source and a physical arrangement that drives chemical reactions do not explain how life could emerge from lifeless chemicals through natural processes, nor has demonstrated it—ever.

In addition to sharing the same overarching flaw as Sutherland’s, Martin’s genetically derived conclusions are based on a logical fallacy.9 Martin, like most other evolutionists today, simply assumes bacteria and archaea evolved from LUCA. Martin then takes the genes shared by some of them as proof that his assumption is not only true but is also evidence of where this mysteriously insupportable and unobservable event took place.

Martin’s elaborate statistical analysis found that some of the same genes are important to microbes that happen to belong in dramatically different categories. He uses these to draw a profile of LUCA because he already believes an evolutionary LUCA existed, not because bacteria and archaea evolved from LUCA. Martin discovered nothing demonstrating those organisms evolved from a LUCA. In fact, far from allowing us to “Behold! Meet LUCA,” nothing he discovered indicates LUCA existed.10

We find common designs in different kinds of living things because they all were originally designed by a wise Common Designer.

But wait! If Martin is wrong, then how did some species of bacteria and archaea end up with the same sorts of genes? The answer is simple when we realize that our Creator made all the various kinds of life in the beginning, about 6,000 years ago. God populated the world with interdependent living organisms that all depend on the same sort of earthly resources and biochemical principles even though they are suited to diverse ecological niches. Why should we be surprised that He used similar biochemical processes more than once, as in the case of enzymes that work in certain sorts of bacteria as well as extremophile archaea? We find common designs in different kinds of living things because they all were originally designed by a wise Common Designer.

How did life start? We have only to look in the opening verses of Genesis. There we learn from a reliable eyewitness, the all-powerful God who never lies (Titus 1:2) and whose Word is true (John 17:17), that within the space of a few days—not billions of years—He made a hospitable world and populated it, each plant, animal, and microbe designed to reproduce and vary only within its created kind. No trickle-down chemistry. No primordial, hydrogen-gobbling biological entity boiling into existence in the depths of the sea. No molecules bumping together until out popped life. Just a world created for the glory of God (Revelation 4:11) to be inhabited (Genesis 1:28, 2:15) by Adam and Eve and their descendants, rebellious people for whom He would later provide redemption through the shed blood of His Son Jesus Christ.