If Earthís future space travelers
came to this place, they would declare it a Godforsaken wilderness. A trackless
vista of cliffs and escarpments stretches to the horizon. Brown rock scorches under
twin giant suns in a blood-red sky. The air is a thin gruel of sulfur dioxide, methane,
and nitrogen. But thereís more here than meets the eye. In the pore space of the
rocks, something is stirring.
At a boundary layer with the deep
mantle, mildly acidic water bubbles through the rock, driven by heat and pressure
from the interior. Miles underground, microbes thrive in a rich brew of organics
and dissolved minerals. They move by sensing magnetic fields and temperature gradients.
Huge colonies begin to differentiate their function and metabolism to better use
the available resources. Symbiotic behavior emerges.
In the course of ceaseless and random
genetic variation, some organisms develop the ability to vibrate their outer membrane
and sense when it is perturbed. The timing of a return ultrasound wave acts as a
primitive proximity sensor. This brand of microbes maintains the spacing to garner
more resources so it rapidly dominates the colony.
As the strategy becomes more successful,
the organisms with the most powerful emission or most sensitive reception must deal
with a cacophony of ultrasound signals. Some do this by tuning their vibrating membrane
to a fixed frequency channel. Others learn to combine different inputs, moving beyond
stimulus-response to a simple form of signal processing. The sonic champions gradually
migrate to the center of the colony, where they can emit in synchrony and so increase
their power and range.
These profound changes donít happen
overnight. There are tens of millions of years of experimentation and dead ends
before individual organisms begin acting in concert. But once it happens, a positive
feedback loop is set up that spurs even more experimentation.
Something unexpected happens. The
activity of the colony as a whole creates a low frequency sonic signal that travels
easily through rock. Imperceptible to individual microbes, the hum is registered
by the cooperative nexus at the heart of the colony. But there are other low frequency
signals with more remote origins. Gradually, microbial colonies sense each other
throughout the vast subterranean biosphere. The signals form a primitive network.
All this would be invisible to a
casual interstellar tourist. Awareness is too strong a word, too anthropocentric.
At what point does reaction shade into intention, or signal processing shade into
intelligence? We may not have enough distance from the buzz of our own thoughts
to judge. But something interesting is happening here, and the planet, like the
universe itself, is still young.