Scientists Propose a New Way to Search for Signs of Alien Intelligence

The search for extraterrestrial life may be overlooking an important type of evidence: signs of intelligence that do not rely on advanced technology or are limited to biological processes. A recent study suggests expanding the search by considering clues produced by conscious minds, even before the development of radio communication or sophisticated technology.

The proposal comes from American astrobiologist Julia DeMarines, a researcher who has previously worked on biosignatures and technosignatures. In an interview with Space.com, she argues for creating a new category of evidence called “noosignatures,” aimed at identifying traces left by conscious intelligence in matter.

According to DeMarines, the concept fills the gap between biosignatures—indicators of biological activity—and technosignatures, which point to advanced technologies detectable across vast distances. The goal is to explore forms of intelligence that may exist without ever developing radio, satellites, or other sophisticated technologies.

The idea belongs to the field of noosemiotics, inspired by the ancient Greek concept of nous, meaning mind or intellect. Its theoretical roots trace back to the concept of the noosphere, developed in the 1920s by biochemist Vladimir Vernadsky and philosopher and Jesuit priest Pierre Teilhard de Chardin to describe the sphere of human thought surrounding Earth.

More recently, researchers such as Adam Frank, David Grinspoon, and Sara Imari Walker have applied this concept to SETI (Search for Extraterrestrial Intelligence), viewing a planet’s collective intelligence as a kind of planetary-scale cognitive system. In this framework, a noosignature is any observable evidence of the activity of conscious minds.

The Bread Example

To illustrate the concept, DeMarines uses an unusual example: bread. During a project involving Assembly Theory, she was asked to analyze bread as a potential signature of intelligence.

According to the researcher, bread does not occur naturally in the environment. Its production requires accumulated knowledge, agricultural practices, grain processing, and cultural transmission developed over thousands of years. As she told Space.com, “Bread doesn’t simply appear in a molecular cloud—it requires technology, history, and intelligence.”

Assembly Theory, developed by researcher Sara Walker and chemist Lee Cronin, seeks to measure an object’s complexity by calculating the minimum number of steps required to construct it. This measurement is known as the Assembly Index.

Applying this framework, DeMarines argues that the evolution of bread—from early preparations made with wild grains around 14,000 years ago to today’s industrial production methods—reflects the gradual development of human intelligence and culture. Advances in agriculture, wheat domestication, milling technology, and large-scale manufacturing all increase the Assembly Index over time.

Intelligence Beyond Technology

DeMarines argues that intelligence does not necessarily lead to major technological achievements. As an example, she points to dolphins, animals well known for their complex social behavior and high cognitive abilities.

Although dolphins are unlikely to develop technologies comparable to those of humans because of the physical limitations of their flippers, this does not imply a lack of intelligence. The key question, she says, is whether such intelligence leaves detectable traces in its environment.

Another example involves agriculture. According to DeMarines, human farming practices alter Earth’s natural nitrogen cycle through the release of gases into the atmosphere. She notes that roughly three-quarters of human nitrogen emissions occurred before industrialization, driven by agriculture, animal husbandry, and microbial activity in cultivated soils.

In her view, this chemical imbalance could represent a planetary-scale noosignature. If similar atmospheric changes were detected on exoplanets, they might indicate the presence of an intelligent civilization—even in the absence of direct evidence of advanced technology.

A New Approach to the Search for Extraterrestrial Life

For now, DeMarines acknowledges that the greatest challenge is not proving that noosignatures exist, but developing reliable metrics to define them and distinguish them from natural processes.

If this line of research advances, the search for extraterrestrial life could expand beyond traditional biosignatures and technosignatures to include entirely new categories of evidence. The hypothesis also raises the possibility that human intelligence may have become detectable across the universe long before the invention of radio transmissions, through the environmental changes produced by civilization itself.

Julia DeMarines’ work was published as a paper on the open-access scientific repository arXiv, contributing to the growing discussion about how scientists might identify signs of intelligence on other worlds—even when those signs do not fit the technological models traditionally considered in SETI research.