Nothing inatimate can reproduce itself, only living entities can do that. That is one of the reasons why biologists believe a strand of RNA was the first living life form. It was a chemical strand that could reproduce itself. It had no metabolism. It could only reproduce itself. Therefore, at that specific moment 3.5 billion years ago, the definition of life could only be a chemical compound that can reproduce itself. Nothing inatimate at that time could do this so therefore it must be alive. 3.5 billion years later, animals can live their whole life without reproducing and still be alive. So therefore no definition of life is applicable to all 3.5 billion years of life, assuming the RNA world hypothesis is correct. The answer to what life is seems to be applicable only to specific points in the history of life. Kind of like the slope of a curved line found with calculus. Slope is slope but the answer always changes on the line. A lack of reproduction in grizzly bears or humans will not cause death, so reproduction is not the force that drives life. Even the blueprint of life, DNA, is not a force of life. Currently the greatest force for life is clearly metabolism. Without the production of ATP, death would rapidly occur. So currently life is a controlled set of chemical reactions within a cell wall or cell membrane. Clearly, the definition of life has changed through time only if our theory about the first living being is correct. A true definition of life would have to be a definition ONLY from a specific time period, so it seems. Because we only know that metabolism drives life in this epoch, and we may never know the true first living being, the most accurate definition of what life is is metabolism. Interestingly, doctors have “clinically killed” patients for surgery. The doctors have essentially stopped the metabolism, but the Patient is still able to come back to life. So that actually questions whether metabolism is life. Overall, the true answer seems almost impossible.

Okay, so let’s assume life is metabolism. But then technically the first RNA is not alive because it lacks metabolism, even though it reproduces. But we know RNA HAD to be alive because nothing inatimate can reproduce. Something is DEFINETLY ALIVE if it reproduces, it has to be. So how in the world is the question answered? Is it really like calculus? Did the definition of life really change through time even though life is life? Overall I believe it is just like calculus. The definition of life always changes. I would ABSOLUTELY LOVE to hear everyone’s opinion.