Question of the week: Can we eat aliens?

05 June 2018

Question

"If some-day we managed to travel to another planet and discovered aliens, what is the likelihood that we could eat them?"

Answer

Getting her teeth into an answer, Marika Ottman put this question to Dr Gareth Corbett, a gastroenterologist from Addenbrooke's Hospital in Cambridge...

Marika - Something about humanity is that when we come across something, we will usually try to eat it. Like pineapples, who first thought that was food? But could we eat alien life? On the forum, evan_au points out that there’s probably the same chance that aliens could eat us, as there is that we could eat them, but that doesn’t mean we could get nutrients from them. And Bored_chemist reminds us of an old, and very wise statement: "All mushrooms are edible...once.” But what if we found alien life on another planet? Would we even be able to make a dinner out of that? I put this question to Gareth Corbett, gastroenterologist at Addenbrooke’s Hospital in Cambridge to see if he had any food for thought...

Gareth - There are a number of theories regarding the basis of life on other planets.  It is almost inconceivable that given the vastness of the universe that there is not extraterrestrial life. On Earth, carbon is the key constituent of all life, due to the perfect conditions that allow the formation of long carbon chain molecules which make up all life as we know it. 

But there might be other ways to form life, with silicon and nitrogen being commonly cited as potential elements to base alien DNA around, due to their chemical bonding similarities to carbon.  However, it would be “life, Jim, but not as we know it!” If we were able to take them from their environment to eat the chemical structure of silicon based organic molecules would not be digestible by our digestive tracts, and indeed regular dosing of silicon would likely be toxic to our bodies.

If we were to encounter carbon based life that was like plants and animals we would be likely to be able to physically consume them.

Marika - The problem is, our bodies have evolved over millions of years on this planet, to be able to digest the very complex proteins that exist here. Some molecules can have the exact same elements in them, but are actually mirror images of one another, just like your left and right hand. Lemons and oranges both get their taste from mirror images of the same compound, limonene. All of our proteins and sugars have this property of handedness, and our digestive system has evolved to expect them to be that way.

Gareth - our enzymes might not be the right shape to combine with alien molecules, like a right hand trying to go in a left-handed glove.

However, just to finish, while discussing this with my father in law, he simplified the issue for us, “just pop in a bit of garlic butter and it will taste fine!”


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