The search for extraterrestrial life has traditionally been divided into two directions: biosignatures (signs of biological processes) and technosignatures (traces of technology). However, a growing number of scientists are proposing to look more broadly — at signs of intelligence that are not necessarily linked to radio telescopes or spacecraft.

What is noosemiotics

Astrobiologist Julia DeMarines is developing a field she calls noosemiotics. The term traces back to the ancient Greek concept of "nous" (mind) and the idea of the noosphere — the sphere of intelligence surrounding a planet. Modern researchers propose looking for noosignatures — traces of conscious activity that remain in matter and the environment.

DeMarines explained that they want to understand whether signs of intelligence can be detected before the invention of radio communication, adding that they are looking for ways in which intelligence leaves an imprint on matter.

Why bread is a good example

As a thought experiment, DeMarines applied Assembly Theory to ordinary bread. This theory assesses the minimum number of steps required to assemble a complex object.

Bread does not emerge spontaneously from a molecular cloud. Its existence requires intelligence, history, grain-processing technology, plant domestication, and culture. The more complex the bread and the more steps that separate it from wild grain, the higher its "assembly index" — and the more clearly the development of intelligence is manifested.

Similarly, one can consider stone tools, writing, agriculture, and other manifestations of intelligence that lie somewhere between a simple biosphere and a high-tech civilization.

Can such traces be detected from a distance?

The main question is how to see noosignatures on other planets. Archaeological artifacts require on-site presence. However, there are also indirect signs. For example, agriculture has disturbed Earth's nitrogen cycle for millennia, releasing excess nitrogen into the atmosphere. Such changes could, in principle, be detected remotely.

If this is the case, signs of intelligent life on Earth could have been visible far earlier than 100 years ago, when humanity began using radio.

Not just technological intelligence

It's important to understand that intelligence does not always equal technology. Dolphins have complex social behavior and high intelligence, but they do not create technology due to their body structure. If similar forms of intelligence are common in the Universe, the traditional search for technosignatures would simply miss them. Noosemiotics attempts to find ways to detect such "non-technological" manifestations of consciousness.

In brief

Scientists are proposing to expand the search for extraterrestrial intelligence beyond biosignatures and technosignatures. Noosignatures are traces of conscious activity that can manifest in complex objects and environmental changes (for example, in agriculture). Even a simple product like bread can be considered a sign of intelligence. This approach could help detect forms of intelligence that do not build radio telescopes but still leave a noticeable trace in the Universe. Julia DeMarines's work is available as a preprint on arXiv.