When I was a student in the United States of America working towards obtaining my B.S. Degree, I used to walk outside my apartment to spend time thinking. One night, the verse,
"O' people! A parable is set forth (unto you) so listen unto it! Verily, those whom you call upon besides God can never create (even) a fly, even though they gather for it, and should the fly carry away any thing from them, they can not take it back from it; (how) weak the invoker and the invoked." (22: 73)
came to my mind, and caused me to stop. I said to myself, it is true that it is impossible that man kind create a being as much as a fly. Maybe it is possible to collect parts and pieces of a fly, and combine them together to make a fly, but it would be impossible to start from ground up using raw material to create one. I even remembered a science show on television which backed up my opinion.
Then I thought about the rest of the verse where Allah says,
"and should the fly carry away any thing from them, they can not take it back from it? "
God talks to us in this verse of our inability to extract from the fly what it has taken away (by feeding). Sure the fly cannot be created, but why wouldn't it be possible to take back from the fly what it had taken away, especially with the available tools that can dissect what is even smaller than a fly? With these tools we can definitely take back whatever a fly has ingested, and suppose that we don't have the technology to do that today, with the current advances wouldn't it be possible to do that in the future? That's when all my thoughts stopped, and I wanted to get out of this mind puzzle.
At the time, I didn't have a way to find the answer I was looking for. I didn't have the commentary books, and at that time it didn't occur to me to look into any scientific books either. That's why I decided to postpone the search until I went back home to Kuwait during summer. When I went to Kuwait, though, I would become so busy that I would forget to search into the subject matter, and as soon I travelled back to the USA I would remember the question and fall into the same dilemma.
Notice that the verse starts with a call to listen. According to the commentary of Taqreeb Al-Quran, this part of the verse is "an emphasis on attracting attention to awaken the mind." That is to say that this parable is very important, that was exactly why I was drawn to this verse this much, and that was the reason why I kept it in my mind for three years before I came to find the answer.
My father (may God protect my mother and him) is one of the people who loves any science involving animals, and he loved to see God's power manifest in such things. I remember, every time he would watch a show on the animal kingdom, he would look at me and say, look at this! My God what power does God have. Praise Allah? Praise Allah." Any person with wisdom would surely see the same.
One day, he called me to watch with him a show about insects, and as usual I had completely forgotten about the above verse. A small segment of the show was dedicated to the fly, and it talked specifically about the way a fly would take in its food.
When a fly needed to eat, it would extent its mouth to the surface of the desired food (I chose not use overly scientific words), creating a tube. If you would examine the tube closely you would see that the end that touches the surface of the food was wider, making it look like a vacuum cleaner's tube's end. After the fly had extended it's mouth, it would excrete enzymes that allowed it to break the food and convert it into liquid. That helped the fly draw the food into the its body.
After the show I set to look for more information in scientific books. I went to the library at Kuwait university, and in those books I found that a house fly (that is the formal name for it) had the ability to break down foods even outside of its body. That was the purpose for the enzyme as it was further explained to me by a professor at the university (you can read more about this in biology books yourself if you like).
What does this all mean? And what does the digestion process of the fly have to do with the parable mentioned in the verse? Notice carefully how the verse discusses this eternal disability. The problem with extracting the food does not come from the limitations of the tools, but rather in what is being extracted. Remember that the food that went into the body of the fly is not the same anymore. The food was broken down into molecules that makes it not longer what it was, and even it was taken back it would not be the same. Therefore it cannot be obtained again.
Notice also that even if we were to take back the food at the first point when it was just entering the mouth of the fly, it would still not help, because the food was digested even before that. Therefore, "they can not take it back from it" ever.