The Hardest Problem

Bruised theories. Accusations of pseudoscience. Machines that claim to be sentient. The field of consciousness research could be on the verge of a revolution— or once again be relegated to the fringe

- BY ALLISON PARSHALL ILLUSTRATION BY DTAN STUDIO

UNTIL HALF A BILLION YEARS AGO, LIFE ON EARTH WAS SLOW. The seas were home to single-celled microbes and largely stationary soft-bodied creatures. But at the dawn of the Cambrian era, some 540 million years ago, everything exploded. Bodies diversified in all directions, and many organisms developed appendages that let them move quickly around their environment. These ecosystems became competitive places full of predators and prey. And our branch of the tree of life evolved an incredible structure to navigate it all: the brain.

We don't know whether this was the moment when consciousness first arose on Earth. But it might have been when living creatures began to really need something like it to combine a barrage of sensory information into one unified experience that could guide their actions. It's because of this ability to experience that, eventually, we began to feel pain and pleasure. Eventually, we became guided not just by base needs but by curiosity, emotions and introspection. Over time we became aware of ourselves.

This last step is what we have to thank for most of art, science and philosophy—and the millennia-long quest to understand consciousness itself. This state of awareness of ourselves and our environment comes with many mysteries. Why does being awake and alive, being yourself, feel like anything at all, and where does this singular sense of awareness come from in the brain? These questions may have objective answers, but because they are about private, subjective experiences that can't be directly measured, they exist at the very boundaries of what the scientific method can reveal.