Quantum mechanics — the branch of physics that governs atoms and subatomic particles — is famous for its strangeness. It describes a world where particles can exist in two places at once, where outcomes are probabilistic rather than certain, and where observation itself can influence reality. For decades, these effects were thought to apply only in the cold, isolated realm of physics — far from the warm, noisy chaos of living cells. Yet a growing field known as quantum biology is revealing that life itself may depend on quantum phenomena.

The story began with an unexpected discovery in plants. During photosynthesis, light-harvesting proteins transfer energy with almost perfect efficiency — far beyond what classical physics could explain. In the early 2000s, experiments using ultrafast lasers showed that this energy moves through quantum coherence, a process where particles of light (excitons) take multiple paths simultaneously, finding the most efficient route to the reaction center. In other words, plants may use quantum computation to capture sunlight.

Other examples soon followed. Migratory birds, such as robins, appear to navigate using quantum entanglement in their eyes. Specialized proteins called cryptochromes may host pairs of entangled electrons that respond to Earth’s magnetic field, allowing birds to “see” magnetic lines as a visual pattern. Similarly, enzymes — nature’s molecular machines — may use quantum tunneling, where subatomic particles like protons slip through energy barriers instead of going over them, explaining why biochemical reactions happen so quickly.

Even our own bodies show hints of quantum behavior. The human sense of smell might rely on vibrational quantum sensing, distinguishing molecules not just by shape but by how they vibrate at the quantum level. In neuroscience, researchers are exploring whether quantum coherence in microtubules — microscopic structures inside neurons — could play a role in consciousness, though this remains deeply controversial.

What’s emerging is a provocative new picture: biology may not just tolerate quantum effects — it may have evolved to use them.