Human Photosynthesis

The prospect of harnessing solar energy in the same manner as plants is a compelling one. Such a development would undoubtedly simplify human existence, as the arduous and time-consuming tasks of procuring, cooking, and consuming food could be supplanted by a direct absorption of the sun's energy. The benefits of this paradigm shift would extend beyond mere convenience, however, as overused agricultural lands could be allowed to revert to their natural state, and rates of malnutrition, starvation, and food-borne illness would be significantly reduced.

The concept of green skin has been a recurring theme in science fiction, featuring prominently in various works such as "Star Wars Rebels" and "Guardians of the Galaxy," where characters such as Hera Syndulla and Gamora are depicted with this distinctive trait. However, it is worth considering the possibility of green skin not being limited to fictional extraterrestrial beings. If humans were to possess green skin, it could potentially endow them with the ability to perform photosynthesis, a process utilized by plants to derive sustenance from sunlight.

Plants are a remarkable form of life on Earth due to their unique ability to convert sunlight into food through the process of photosynthesis. The intricate process of photosynthesis enables plants to thrive on sunlight, which is a remarkable feat. In contrast, humans do not possess the ability to undergo photosynthesis, and therefore, must rely on various methods such as farming, slaughtering, cooking, chewing, and digesting to obtain their necessary nutrients. These methods require a significant amount of time and energy expenditure in the form of calories to accomplish.

The burgeoning human population has led to a commensurate increase in the demand for agricultural produce. This demand is not only driven by the energy expended by human bodies but also by the farm machinery utilized in food production, resulting in a significant ecological footprint. The agricultural sector in the United States has been identified as a major contributor to greenhouse gas emissions, accounting for 10% of such emissions, as reported by the United States Department of Agriculture.

The possibility of engineering human photosynthesis by altering our biological makeup to acquire this plant-based ability raises intriguing prospects. The potential benefits of such an innovation are manifold, including significant savings in time and energy for individuals. Additionally, the elimination of the carbon footprint associated with food production and consumption, as well as the eradication of starvation, malnutrition, and food-related allergies and illnesses, would be significant outcomes.

The prognostication of human evolution is deemed unfeasible. However, it is plausible that the utilization of contemporary biotechnological and genetic engineering tools could enable the modification of human cells to perform photosynthesis akin to plants. What prerequisites would be necessary to achieve this feat?

It is noteworthy that certain animals possess the ability to perform photosynthesis. The question arises as to whether humans will eventually acquire this capability. While the notion of human photosynthesis may appear implausible, it is worth noting that photosynthesis is not exclusive to plants. In fact, there exist a few instances of photosynthesis in the animal realm. One such instance is observed in the pea aphid, which employs pigments to capture sunlight and channel it to their cells for energy generation, as reported by the journal Nature.

The Marine Biological Laboratory at Woods Hole recently announced that researchers have successfully uncovered the mystery surrounding Elysia chlorotica, a strikingly green sea slug that bears a resemblance to a leaf, possesses the ability to photosynthesize like a plant, and yet is classified as an animal. The investigation revealed that E. chlorotica sustains its vibrant coloration by ingesting algae and assimilating their photosynthetic genes. This phenomenon represents a unique example of a multicellular organism appropriating genetic material from another.

The Oriental hornet has been observed to utilize a pigment present in its exoskeleton, known as xanthopterin, to convert sunlight into electrons. Recently, a group of students emerged victorious in a science competition by proposing the extraction of this pigment for the purpose of generating renewable electricity to power a car's battery.

The Elysia chlorotica, an emerald green sea slug, has been found to assimilate the cellular components of algae, specifically chloroplasts that produce chlorophyll. This enables the slug to undergo photosynthesis upon exposure to light. According to reports by National Geographic, experiments have demonstrated that these slugs can survive for up to nine months without consuming any food, relying solely on the energy derived from sunlight.

Is it Possible for Humans to Photosynthesize Like Other Members of the Animal Kingdom?

The question of whether humans can photosynthesize like other members of the animal kingdom is a topic of interest. However, the feasibility of this concept is questionable due to the high energy demands of humans. Unlike other organisms such as the pea aphid, hornet, or slug, humans require a significant amount of energy to survive. According to the U.S. government's Office of Disease Prevention and Health Promotion, a full-grown human needs between 1,600 and 2,400 calories per day. The human digestive system breaks down food into glucose, which is stored in cells as adenosine triphosphate (ATP).

The demand for glucose in the human body is much higher than what photosynthesis can provide. Associate Professor Lindsay Turnbull of the University of Oxford has determined that if an adult woman's surface area contained chlorophyll like a leaf, it would only produce 1% of the daily energy requirements for survival. To live solely by photosynthesis, the woman would require a green body with a surface area the size of a tennis court.

In addition to the energy demands, there are other biological requirements that must be met for humans to photosynthesize. For instance, if humans had green skin with cells containing chloroplasts, they would also require porous skin to take in carbon dioxide, a chemical necessary for photosynthesis. However, genetic engineering has not yet reached a level where it can manipulate the human body enough to make these biological requirements possible.

While human evolution predictions do not include photosynthesis, humans have the capacity to solve other problems that threaten their survival, such as starvation, malnutrition, and food borne illnesses.