• Question: Do you think that there is a way to enable humans to photosynthesise?

    Asked by Lulu to Cristiane, Nicki, Nikolai, Richard, Samuel on 11 Mar 2015.
    • Photo: Samuel Ellis

      Samuel Ellis answered on 11 Mar 2015:

      Great question. Probably not, or at least not without really changing how human biology works.

      However, there are a few examples of animals which can do photosynthesis similar to plants. My favourite I found is the Spotted Salamander, which has a close relationship with certain algae. Researchers then found that some salamander cells had acquired chloroplasts (the parts of plant cells which do the photosynthesis) from the algae, and could use them to make oxygen and carbohydrates for their own cells to use as fuel!

      This sort of thing wouldn’t work in humans for many reasons though, with a major issue being that our immune system would recognise the chloroplasts as non-human and attack them

    • Photo: Nikolai Adamski

      Nikolai Adamski answered on 11 Mar 2015:

      Not now, but I think that in the future it would be possible to get humans to do photosynthesis. However, as Sam also said, it would require massive changes to the human body. Would you be able to still call the resulting organism “human”? So this is more of an ethical question (should we do it?) rather than a technical one.

    • Photo: Cristiane Calixto

      Cristiane Calixto answered on 11 Mar 2015:

      What an excellent sci-fi question! It would be great if we could photosynthesise… They found an insect the other day that could sort of do photosynthesis. I think we would have to be genetically modified to acquire this ability, though. If one day we manage to do that, we’d still need to eat because the sun wouldn’t be able to give us all the energy we need in a day. So, we would never be like a plant…

    • Photo: Richard Simons

      Richard Simons answered on 13 Mar 2015:

      Since the other scientists have already answered this question very well, I’ll take it from another angle. Would you want to?
      The idea that humans would be able to synthesise their own food seems tempting at first, but could fall down when the actual mechanics of the problem are broken down.

      The suggested calorie intake for an adult is 200 kCal / day, that’s ~8,400 kJ/day.
      In the height of summer the average solar intensity is about 5 kWhr/m^2, giving a solar power of 1.4 W/m^2.
      The average surface area of an adult is between 1.6 and 2 m^2, but only half of that can ever face in one direction, so lets say 1 m^2 of skin which could see the sun.
      That would require an illumination time of nearly 17 hours each day! Even if we assume that we could convert all of that radiation into food that we could process.

      Given the brilliance of the things that we have developed I am sure that, in time, humans could develop a way to incorporate photosynthesis into our bodies. But, why bother, when plants do it so much better than us!

      Sources:
      http://www.nhs.uk/chq/pages/1126.aspx?categoryid=51
      http://www.pveducation.org/pvcdrom/properties-of-sunlight/average-solar-radiation
      http://www.medicinenet.com/script/main/art.asp?articlekey=39851

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