Juan Pérez-Mercader, a senior research fellow at Harvard’s Department of Earth & Planetary Sciences and the Origins of Life Initiative, has been exploring the possibility of life forms on other planets that are fundamentally different from those on Earth. His research focuses on creating synthetic living systems that do not rely on biochemistry, the chemistry that underlies life on Earth.
In a recent study published in Cell Reports Physical Science, Pérez-Mercader and his colleagues developed two synthetic models or “species” and observed their competition, akin to Charles Darwin’s concept of “the struggle for life.” This experiment aimed to demonstrate the essential properties common to all natural living systems, even in the absence of traditional biochemistry.
These findings suggest that life forms on other planets could potentially arise from different types of chemistry than what we know on Earth. This implies that their physical structures, genetic codes, and metabolic processes might be radically distinct from those of terrestrial life. While the specifics of these hypothetical life forms are unknown, they could exhibit extraordinary variations in morphology, physiology, and overall appearance compared to familiar Earth organisms.
Without the constraints of Earth’s evolutionary history and environmental conditions, alien life could have evolved to utilize alternative chemical reactions, novel building blocks, and fundamentally different mechanisms for energy acquisition and reproduction. They might possess diverse sensory systems, unconventional body plans, and adaptations suited to their unique planetary environments.
The exploration of such possibilities broadens our perspective on the potential diversity of life in the universe and highlights the importance of considering alternative biochemistries when searching for signs of life beyond Earth. Juan Pérez-Mercader’s research is a step forward in understanding the fundamental principles that could govern life elsewhere and paves the way for future discoveries and insights into the nature of extraterrestrial organisms.
Prior to this study, the Pérez-Mercader lab had successfully developed protocells, which are non-biochemical systems based on carbon chemistry. These protocells consist of self-assembling polymer vesicles that arise from a blend of synthetic chemicals unrelated to living organisms. Despite their non-biological nature, these systems exhibit behaviors similar to biochemical cells, including growth, movement, reproduction, and potentially even evolution.
In order to investigate the principle of competitive exclusion in these protocells, the researchers created two distinct species for the study. One species possessed the advantageous trait of light sensitivity, while the other did not. By observing how these systems interacted and competed for resources in an illuminated environment, the researchers found that the light-sensitive species thrived while the other species did not. This observation demonstrated the survival advantage of the best-suited structure in its environment, aligning with the concept of the struggle for existence outlined by Darwin.
These results led Pérez-Mercader to propose that biochemistry is not necessarily essential for the struggle for life. The extinction of the less “fit” protocell species in this study indicated that non-biochemical carbon chemistry could still drive the competitive dynamics of living systems.
These findings prompt the intriguing question of whether there could be chemistries beyond Earth that possess the necessary properties for life. Pérez-Mercader suggests that it is conceivable for certain materials to react chemically and self-organize on a planetary surface under suitable conditions, eventually exhibiting behaviors analogous to those observed in this experiment. Given the potential for the evolution of more complex structures from simple chemistry under favorable circumstances, Pérez-Mercader advocates for an open-minded perspective on the possibility of alternative forms of life in the universe, which may diverge significantly from our current understanding of life on Earth.
Source: Harvard University