New Research Uncovers All Humans Share a Common Ancestor— And it’s Not Adam

Diversity is often hailed as the essence of beauty—an observation that is readily apparent when we consider the vibrant array of flowers, animals, landscapes, and humans that populate our world.

Contrary to popular beliefs—like those found in biblical texts—the progenitor of all living organisms wasn’t named God or Adam but is known as LUCA.

Modern life evolved from LUCA from various sources. These sources include amino acids used to build proteins in all cellular organisms, the shared energy currency, the presence of cellular machinery, and DNA’s purpose of storing information.

This tiny, rudimentary life form is considered the root of the entire tree of life, encompassing everything from the tiniest bacteria to the most massive creatures that have ever existed.

For a long time, scientists estimated that LUCA emerged approximately 4 billion years ago—around 600 million years after the Earth was formed.

According to Live Science, “[T]he researchers counted the mutations that have occurred over time across the genomes and within 57 genes shared by all 700 organisms, using estimated mutation rates to back-calculate when LUCA lived.”

Scientist Edmund Moody and his colleagues from the University of Bristol compared all the genes in the genomes of living species in a new study, counting the mutations that have occurred in their sequences over time.

While LUCA was previously believed to be 3.9 billion years old, researchers were able to refine this estimate using fossils that contained traces of ancient life. One of these fossils contained 3.48-billion-year-old microbial mats.

“The evolutionary history of genes is complicated by their exchange between lineages,” Dr. Moody said. “We have to use complex evolutionary models to reconcile the evolutionary history of genes with the genealogy of species.”

Researchers have compared LUCA’s origins by analyzing the genes of 700 living species of bacteria and archaea—microbes similar to bacteria that often live in extreme environments.

By remodeling the physiological characteristics of modern living species, the study’s authors were able to work out the biology of LUCA.

To achieve this, they employed a technique that involved analyzing genetic data from modern species and tracking the mutations that have accumulated since these species diverged from their common ancestor—LUCA.

“Our study showed that LUCA was a complex organism, not too different from modern prokaryotes,” said University of Bristol’s Professor Davide Pisani. Prokaryotes are microscopic single-celled organisms that do not have a distinct nucleus with a membrane or specialized organelles.

This new timeframe places LUCA squarely within the Hadean Eon, a tumultuous period named after Hades, the Greek god of the underworld.

The team also determined where LUCA thrived before evolving into modern life. Although the analysis did not pinpoint LUCA’s exact habitat, it suggested that LUCA lived in a shallow, warm ocean environment.

The fact that LUCA managed to survive in such a harsh environment is remarkable.

Their investigation revealed that, despite LUCA’s simplicity as a prokaryote—a single-celled organism lacking a nucleus and membrane-bound organelles—it likely possessed a primitive immune system.

Tim Lenton, a co-author of the study from the University of Exeter, noted, “It’s clear that LUCA was exploiting and changing its environment, but it is unlikely to have lived alone.”

“It’s clear that LUCA was exploiting and changing its environment, but it is unlikely to have lived alone,” said Dr. Tim Lenton, a researcher at the University of Exeter.

Although LUCA remains the oldest known common ancestor, the path from this primordial life form to the complex organisms we see today is still a subject of ongoing research.

Further exploration is needed to fully understand how life evolved from its earliest beginnings.

The research not only pushes back the timeline of LUCA’s existence but also provides fascinating insights into its characteristics and the conditions of early Earth.

“The findings and methods employed in this work will also inform future studies that look in more detail into the subsequent evolution of prokaryotes in light of Earth history, including the lesser studied Archaea with their methanogenic representatives,” said Professor Anja Spang, a researcher at the Royal Netherlands Institute for Sea Research.

Darwin developed a theory, often described as the theory of evolution by natural selection, which recognizes that all living organisms on Earth today trace back to one or a few “original progenitors.”

In On the Origin of Species, Darwin noted: “…adaptive characters, although of the utmost importance to the welfare of the being, are almost valueless to the systematist.”

Understanding natural selection is essential for discovering and interpreting evidence about common ancestry. The process of natural selection is driven by environmental conditions and can occur even if two species do not share a common ancestor.

“Our work draws together data and methods from multiple disciplines, revealing insights into early Earth and life that could not be achieved by any one discipline alone,” said University of Bristol’s Professor Philip Donoghue.

Currently, ten planets could closely resemble Earth, supporting life like LUCA and eventually a future species like humans.

One planet that could potentially support life like LUCA is 22 light-years from Earth and is at least 4.5 times as massive as Earth, according to NASA’s Jet Propulsion Laboratory.

Kepler-22b is located 600 light-years away and is considerably larger than Earth. Dubbed the “super-Earth,” it is unclear if the planet is rocky, liquid, or gaseous.

Located about 2,700 light-years away, Kepler-69c, which is 70 percent larger than Earth, is located in a habitable zone, but researchers are unsure about its composition.

This planet is about 40% larger than Earth and orbits a star that is much cooler than our sun. NASA notes that the planet orbits its star in 267 days. Despite these differences, the planet is in the habitable zone.

Appearing to be about 10% larger than Earth, Kepler0186F rotates around its star just on the edge of the habitable zone. The planet receives just a third of its energy from its star, which is significantly less than what Earth gets from the sun.

Despite being only 33% larger than Earth, this planet orbits its star every 112 days. Time does fly by on this planet, yet it orbits in the habitable zone.

Discovered in 2015, the near-Earth-size planet orbits around a star the size of the sun, according to NASA.

Scientists discovered Kepler-1649C after reanalyzing data from NASA’s Kepler Space Telescope. The planet looked to be in similar size to Earth and orbited its star in the habitable zone.