The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth

The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth by Zoë Schlanger is a study of how plants experience and interact with the world. After developing an interest in plant science, Schlanger realized that plants offer insight into our understanding of consciousness and intelligence, as well as a controversial divide in the research community. In the work, she questions the fundamental assumptions about plants that pervade the scientific community—assumptions about the decisions plants make and why they make them, intelligence, communication, and sensory experience. In pursuing answers to these queries, Schlanger centralizes three themes: The Constant Motion of Biological Creativity, The Complexity of Ecology, and Plant Consciousness.

This guide uses the 2024 hardback edition published by Harper Collins.

Summary

The Light Eaters contains a prologue and 11 chapters. The Prologue and first two chapters explore the basics of plant intelligence and consciousness. Schlanger follows the trajectory of botanical research and the division created by poorly constructed experiments in the 1970s, which resulted in the cessation of funding for research into plant intelligence and behavior. The ramifications of this continue to impact contemporary research, but Schlanger argues that science can change its mind, and new findings suggest that plants may be more intelligent than previously thought. She challenges the notion that talking about plant intelligence anthropomorphizes plants, arguing that limiting intelligence to animals or humans is a form of humancentric bias. Schlanger traces how science has considered plant intelligence and points to Aristotle as the beginning of demoting plants to a lower rung on a hierarchical ladder. Positioning plants in subservience to humans limits how humans think about plants and themselves.

Chapters 3, 4, and 5 look at the communication and sensory experiences of plants. Schlanger cites scientific research and anecdotal evidence of plants altering their chemical compounds in response to predators. These examples suggest that nearby plants, unaffected by the predators, receive communication from the affected plants and behave similarly. Schlanger highlights how plants change in response to their environment and communicate those changes with other plants. Research into the effects of anesthesia on plants and the impact of touch on chemical makeup suggest plants can sense. Electrical waves—which are similar to the way humans and animals think and experience consciousness—offer one theory for how plants experience the world around them.

In Chapters 6, 7, and 8, Schlanger considers a more ecological understanding of plant behavior and plants’ roles in a larger system. Circadian rhythms and the ability to count reveal that plants may have something akin to memory. Furthermore, Schlanger suggests that plants may be able to make decisions based on memory, an act that is often considered the foundation of intelligence. Plants also engage in interspecies communication and biomimicry, which raises the question of whether plants can “see.”

Chapters 9, 10, and 11 present Schlanger’s argument for changing how the scientific community approaches research and advocate for an ecological approach to scientific research. Plants have complex social lives that often conflict with traditional understandings of plant evolution based on the survival of the fittest. Instead, plants engage in eusocial behaviors, emphasizing the whole over the individual. Plants also exhibit care, especially for offspring or close family members, hinting at social lives that mirror human family systems. Schlanger ponders if this means humans could engage in a new way of thinking about the world and whether it is too late to use this information to shape a positive future.