02-09-2021, 12:00 PM
The winning combination for plants is photosynthesis combined with low-energy nutrients available for not too much expenditure of energy. IOW, leaves and roots.
The winning combination for animals is oxidation of much higher-energy food in much greater quantities. And access to nutrients suitable to release energy by oxidation requires mobility (instead of roots) and decisions about how to use energy.
It's not very easy to find a good combination or compromise between these strategies.
We can take the example of lifeforms very efficient in their use of energy. Cold-blooded reptiles get along on less than a tenth of the food mammals need for similar body mass.
Even so, if there are photosynthetic people, even highly efficient ones, I'd still expect it to be very minor as a source of energy. If they are acting like people - moving around and thinking, etc - I would expect that they still need to eat higher energy nutrients.
The winning combination for animals is oxidation of much higher-energy food in much greater quantities. And access to nutrients suitable to release energy by oxidation requires mobility (instead of roots) and decisions about how to use energy.
It's not very easy to find a good combination or compromise between these strategies.
We can take the example of lifeforms very efficient in their use of energy. Cold-blooded reptiles get along on less than a tenth of the food mammals need for similar body mass.
Even so, if there are photosynthetic people, even highly efficient ones, I'd still expect it to be very minor as a source of energy. If they are acting like people - moving around and thinking, etc - I would expect that they still need to eat higher energy nutrients.