Researchers from a Spanish genomics institute based in Barcelona have traced the roots of neuron evolution to the earliest nerve-like cells found in very small marine organisms known as platozoans, or layered creatures, which rarely exceed a millimeter in size. These findings come from a study conducted by scientists at the Center for Genomic Regulation within the Institute of Science and Technology and are highlighted in a recent scientific publication in Cell.
Lamellar creatures inhabit shallow, warm seas and feed on surface-dwelling algae and microbes living on rock faces. Their bodies are extraordinarily simple, lacking complex organs or specialized limbs. Behavior in these organisms appears to be controlled by peptidergic cells, specialized tissues that secrete peptide signals to regulate movements and feeding in these primitive forms of life.
To understand the roles of different cell types, researchers created a map of all layered cells and cataloged their properties. Each cell type showed a distinct function dictated by a specific set of genes, suggesting an early division of labor that prefigures more complex nervous systems.
Remarkably, peptidergic cells share many features with neurons, which only later became widespread in more complex animals by about 100 million years after these early creatures first appeared. Comparative analyses across species indicated that these similarities are particular to lamellar organisms, underscoring a potential evolutionary bridge between simple signaling cells and true neurons.
The study reveals that peptidergic cells arise from cell vacuoles through signals that resemble the process of neurogenesis, the development pathway of neurons in higher organisms. These cells also harbor multiple gene modules essential for transmitting information, a hallmark of neural communication, suggesting an ancient blueprint for cellular signaling that later evolved into more elaborate nervous networks.
In addition, the researchers employed machine learning methods to demonstrate that layered cell types communicate via an intracellular communication system. In this system, specific proteins known as GPCRs (G protein-coupled receptors) detect external cues and trigger internal signaling cascades within the cells. External cues are carried by neuropeptides, chemical messengers used by neurons across a broad range of physiological processes.
Looking ahead, the authors expect that ongoing genome sequencing of diverse species will continue to illuminate the origins of neurons and the emergence of other cell types. As scientists build a broader catalog of high-quality genomic data, the evolutionary pathways leading to complex nervous systems are likely to become clearer, offering new perspectives on how signaling networks evolved over hundreds of millions of years.
Earlier debates on this topic have touched on major evolutionary events, including how large-scale environmental changes might have influenced the development of advanced tools and behaviors in hominin ancestors. While mammoths and other megafauna faced extinction, such events are thought to have shaped subsequent adaptive strategies in early humans, prompting innovations in technology and survival tactics that resonate with discussions of how complex biological systems arise and diversify.