For over a century, science has held that all life on Earth traces back to a single ancestral cell — one origin, one trunk, one story. A new study now suggests that story may have two beginnings: that bacteria and archaea, the two most ancient domains of life, may have arisen independently from the chemistry of the early Earth, each finding its own path from lifelessness to life. If the evidence holds, it would not merely revise a chapter in biology — it would rewrite the opening line.
Study suggests life on Earth may have originated twice, with bacteria and archaea emerging separately
Life may have started twice, not once, on Earth.
Mark
If bacteria and archaea really did arise separately, how would that even work? Wouldn't they need completely different chemistry?
Mimi
Not necessarily different—just independent. Think of it like two fires starting in different parts of a forest. Both use the same combustion, but they ignite separately. Early Earth had many environments: deep-sea vents, tidal pools, mineral-rich springs. The chemistry that works in one place might not work in another. Two different chemical systems could each cross the threshold into life.
Mark
But we've always been taught that all life shares a common ancestor. Doesn't DNA prove that?
Mimi
DNA is universal now, yes. But if bacteria and archaea started separately, one of them might have eventually absorbed or displaced the other's genetic system. Or they coexisted for millions of years before one lineage dominated. The genetic evidence we see today doesn't necessarily tell us what happened at the very beginning.
Mark
What would change if this is true? Does it matter for us?
Mimi
It matters enormously for how we think about life's rarity or commonness. If life can start twice on one planet, it suggests abiogenesis isn't a one-in-a-trillion fluke. It means we should be looking for life on other worlds in radically different ways—not just Earth-like conditions, but any place where chemistry can organize itself.
Mark
So we've been looking in the wrong places?
Mimi
Not wrong, exactly. But maybe too narrow. We've been searching for life as we know it. If this study is right, life might look completely different elsewhere—built on chemistry we haven't even imagined yet.
El Pulso
- A new study challenges one of biology's most foundational assumptions: that all life on Earth descends from a single common ancestor.
- Researchers found that the core biochemical machinery of bacteria and archaea differs so fundamentally that shared ancestry may not explain it — pointing instead to two separate moments when chemistry became life.
- The conventional 'tree of life' — one trunk splitting into branches — may need to become a forest, with at least two trunks rising from different chemical conditions on the early Earth.
- The hypothesis remains contested, with many scientists defending the single-origin model based on shared genetic sequences and universal cellular features.
- If validated, the dual-origin theory would transform the search for extraterrestrial life, suggesting abiogenesis can occur through multiple chemical pathways — and may not be as rare as once believed.
For over a century, science has held that all life on Earth traces back to a single ancestral cell — one origin, one trunk, one story. A new study now suggests that story may have two beginnings: that bacteria and archaea, the two most ancient domains of life, may have arisen independently from the chemistry of the early Earth, each finding its own path from lifelessness to life. If the evidence holds, it would not merely revise a chapter in biology — it would rewrite the opening line.
For more than a century, biologists have worked from a single assumption: all life on Earth descended from one primordial cell. A new study now proposes that life may have started twice — that bacteria and archaea, two of the three great domains of life, emerged independently from the chemistry of the early Earth.
The researchers traced the metabolic pathways and biochemical machinery within these single-celled organisms, looking for clues about their deepest origins. What they found was striking: the ways bacteria and archaea harvest energy, build proteins, and replicate genetic material follow different chemical logic — differences too fundamental, the authors argue, to be explained by billions of years of divergent evolution. Instead, they propose two separate abiogenetic events: two distinct moments when lifeless chemistry crossed the threshold into life.
The implications reach far beyond a revision to textbooks. The conventional model places bacteria and archaea on branches of a single tree, diverging from one common ancestor before eventually giving rise to eukaryotes — the domain that includes all complex life. A dual-origin hypothesis replaces that single trunk with two, each rooted in different chemical conditions or different corners of the early Earth.
The proposal remains controversial. Many researchers point to shared genetic sequences and universal features of cellular machinery as evidence for a single origin. But the study has forced a genuine reckoning. And if life did emerge twice on one planet, it would suggest that abiogenesis is not a vanishingly rare accident — but something chemistry can accomplish more than once, under more than one set of conditions, perhaps on more worlds than we have dared to imagine.
For more than a century, biologists have operated from a single assumption: that all life on Earth descended from one common ancestor, a primordial cell that gave rise to every bacterium, every plant, every animal that has ever lived. A new study challenges that foundational idea, proposing instead that life may have started twice—that bacteria and archaea, two of the three domains of life, emerged independently from the chemical soup of the early Earth.
The research traces the metabolic pathways and chemical reactions that occur within these single-celled organisms, looking for clues about their deepest origins. What researchers found was striking: the biochemical machinery of bacteria and archaea differs in ways that suggest they did not inherit their core chemistry from a shared ancestor. Instead, the evidence points toward two separate abiogenetic events—two moments when lifeless chemistry became alive.
This is not a small revision to existing theory. The conventional narrative holds that bacteria and archaea diverged from a common ancestor billions of years ago, then later gave rise to eukaryotes, the third domain that includes all complex life. That single trunk, splitting into branches, has shaped how scientists understand evolution itself. But if bacteria and archaea arose independently, the tree of life looks fundamentally different: not one trunk but two, emerging from different chemical conditions or different locations on the early Earth.
The study's authors examined the fundamental biochemical differences between these two domains—the ways they harvest energy, build proteins, replicate their genetic material. In bacteria and archaea, these processes follow different chemical logic. Rather than interpreting these differences as the result of billions of years of divergent evolution, the researchers propose they reflect separate origins. Two different chemical pathways, each one capable of bootstrapping itself into life, each one taking hold in a different environment or at a different time.
If this hypothesis holds up under scrutiny, it would reshape not only how we understand life's history on Earth but how we search for life elsewhere. The discovery of life emerging twice on one planet would suggest that abiogenesis is not a vanishingly rare event but something that can happen under multiple chemical conditions. It would mean that on other worlds—planets with different atmospheres, different mineral compositions, different energy sources—life might arise through entirely different chemical pathways. The search for extraterrestrial life would need to expand beyond looking for life as we know it.
The proposal remains controversial. Many researchers remain convinced by the evidence for a single common ancestor, pointing to shared genetic sequences and universal features of cellular machinery. But the new study has forced a reckoning with an old assumption. Whether life began once or twice, the question itself has reopened a door that seemed long closed.
Citas Notables
The evidence points toward two separate abiogenetic events—two moments when lifeless chemistry became alive.— Study researchers
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