Imagine a world where humans could harness the power of the sun, just like plants. Instead of eating food, we could simply absorb sunlight to fuel our bodies to photosynthesize.
By exposing yourself to the sunlight throughout the day, you’ll not even be tan, you might be full of green like Shrek & Princess Fiona.
This is one of a science fiction by John Scalzi, let’s have a look on what happens if humans could photosynthesize.
The science of photosynthesis
Photosynthesis is the process plants use to convert sunlight into energy. It happens in the chloroplasts, which are tiny structures in plant cells filled with a pigment called chlorophyll.
Chlorophyll captures sunlight, and plants use this energy, along with water and carbon dioxide, to produce glucose, a type of sugar. This process also releases oxygen into the air, which we need to breathe.
While plants only need about 200 calories a day, a healthy human needs about 2,000 calories daily. This means humans require a lot more energy than plants.
If human could photosynthesize
Our bodies would need to adapt in several ways just like leaves,
- Chloroplasts in Our Skin:
To photosynthesize, humans would need chloroplasts in our skin cells. These chloroplasts would contain chlorophyll, making our skin green.
- Green Skin:
Chlorophyll is the substance that gives plants their green colour. If humans had chloroplasts, we would also appear green. However, people working in offices would not likely be fully green. Similarly, those living in polar regions wouldn’t be completely green either.
- Porous Skin:
Plants absorb carbon dioxide through tiny pores in their leaves. Humans would need similar pores in our skin to take in carbon dioxide. This would make our skin much more porous than it is now.
Photosynthetic humans might reduce their need for food and help the environment by absorbing carbon dioxide and releasing oxygen. However, this isn’t as simple as it sounds.
The challenges and limitations
Photosynthesis is not very efficient. Plants convert only about 5% to 10% of the sunlight they receive into energy. A tree can get about 200 calories from sunlight in a day, but a human needs around 2,000 calories.
This means we would need to absorb a lot of sunlight and spend much of our time lying in the sun. Moreover, our skin would need to change significantly. It would have to be 100 times more porous to absorb enough carbon dioxide.
This would likely make us sweat more, releasing more oxygen into the air, which might make the air smell fresher.
The impact on daily life and society
If humans could photosynthesize, our lifestyles would change dramatically. We would spend more time outdoors, lying in the sun. This could lead to a more relaxed, sedentary lifestyle.
Clothing might become a status symbol, with wealthier people wearing more clothes as a sign that they get enough energy from food and don’t need to photosynthesize.
Our society might also become more environmentally friendly, as photosynthesizing humans would help reduce carbon dioxide levels in the atmosphere.
Expert insights and speculations
According to Lindsay Turnbull, a plant ecologist at the University of Oxford, estimates that even if an adult woman had chlorophyll in her skin, it would only provide about 1% of her daily energy needs.
To meet all her energy needs through photosynthesis, she would need a surface area of green skin equivalent to a tennis court. Photosynthesis requires carbon dioxide, and humans would need porous skin to take it in.
This could lead to other issues, such as losing moisture through the skin.
Real-world analogies and inspirations
Some animals do have photosynthetic abilities. For instance, the pea aphid produces pigments that generate energy from sunlight, and the Oriental hornet uses a pigment in its exoskeleton to convert light to electricity.
The Elysia sea slug can even steal chloroplasts from algae it eats, allowing it to photosynthesize.
While these animals can photosynthesize, their energy needs are much lower than those of humans. A full-grown human needs between 1,600 and 2,400 calories per day, far more than what photosynthesis can provide.
To sum it up, the idea of humans photosynthesizing is not practical with our current understanding of biology and energy needs. However, it sparks curiosity and innovation, pushing us to explore the possibilities of genetic engineering and biotechnology.
Featured image credit: Peakpx
