The origin of life on early Earth: a window 4.33 billion years ago

The origin of life on early Earth may have become possible around 4.33 billion years ago. A new computer model suggests that by then, our planet was gradually emerging from an era of devastating asteroid impacts. Environments were appearing in which complex organic molecules could persist long enough to participate in the chemistry that may eventually have led to life.

There is a striking possibility at the heart of the study: the same impacts that had repeatedly destroyed potentially favorable environments may later have helped create them.

Published in Nature Communications on September 22, 2026, the study attempts to narrow down the geological window for the emergence of the hypothetical RNA world.

The RNA-world hypothesis proposes that before modern DNA-based biology evolved, RNA molecules may have served both as carriers of genetic information and as catalysts for chemical reactions. Some RNA molecules can indeed catalyze reactions. Yet a fundamental question remains: when could Earth have provided sufficiently stable conditions for systems built around RNA?

When Earth stopped repeatedly resetting its chemistry

Around 4.5 billion years ago, Earth was far hotter and more geologically violent than it is today. Following the enormous impact associated with the Moon's formation, large objects continued to strike the planet.

Major collisions could vaporize oceans, heat the atmosphere and bury large areas beneath hot debris. Even if complex organic molecules had formed, another catastrophic impact might have destroyed the environment sustaining them.

The researchers developed a three-dimensional numerical model of Earth's early impact history, following the thermal evolution of its crust over a billion-year interval.

They calculated how the crust heated and cooled, where relatively mild temperatures persisted, and how long near-surface environments might remain suitable for complex chemistry. Different impact scenarios were examined and compared with geological evidence, including the ages of ancient zircon crystals.

The simulations suggest that impacts capable of producing global thermal catastrophes became substantially less frequent after approximately 4.4 billion years ago.

Within the upper 300 meters of the crust, regions began to emerge that would no longer undergo extreme reheating after initially cooling.

The team applied several temperature thresholds to assess molecular stability. A conservative limit of 60 °C was used to identify conditions compatible with the long-term preservation of key components of a hypothetical RNA world.

The surprising role of asteroid impacts

The simulations reveal a paradox: impacts may have helped create some of the environments in which prebiotic chemistry could persist.

Collisions deposited enormous quantities of heat into the crust. Groundwater interacting with hot rock could have produced hydrothermal systems, with steep temperature gradients and abundant sources of chemical energy.

Such environments are among the proposed settings for life's origins because they can provide both energy and opportunities for organic molecules to interact.

During the most intense bombardment, these environments were too vulnerable to repeated destruction. As major impacts became less frequent, however, increasingly stable regions could persist.

Combining several measures of thermal suitability, the researchers identified a particularly favorable period for a hypothetical RNA world centered on approximately 4.33 billion years ago.

That date is an estimate of environmental suitability, not a confirmed date for the origin of life. The simulations do not reproduce the synthesis of the first RNA molecules, the appearance of self-replicating chemical systems, or the detailed circulation of water through individual hydrothermal environments.

The precise timing also depends on the assumptions used. In a scenario involving a lower total mass of impacting objects, the favorable window shifted roughly 70 million years earlier.

A possible timeline for life's earliest evolution

The proposed window has an intriguing relationship with another estimate from evolutionary biology.

Previous molecular-clock research places the last universal common ancestor of all organisms alive today, commonly called LUCA, approximately 4.09–4.33 billion years ago.

The midpoint of that interval is about 4.2 billion years ago, roughly 130 million years after the favorable RNA-world window identified in the new study.

LUCA was not the first living organism. A potentially substantial period of biological evolution must have preceded that ancestral population.

The new model offers a possible geological setting for part of that earlier history. Intense bombardment initially prevented complex chemistry from persisting across much of the planet. Eventually, major impacts became rare enough for organic molecules to survive in stable environments, while residual impact heat could still support energy-rich hydrothermal settings.

Early life may not have needed to wait until asteroid bombardment had completely ended. What mattered was the emergence of places where complex chemistry could continue without repeatedly being destroyed.