Life is an immense topic of discussion, and not to mention, quite controversial as to how the origin of life first began. There are a number of theories that have been proposed, many of which seem like they could, in fact, be true.
It must have all started when some sort of replicating entity arose. Something that was considered as roughly equivalent to--what we know of today-- as a gene.
We know that it is genes that are passed on to the next generation of life, so it makes sense that life probably began-- some 4 billion years ago-- with an entity quite similar to a gene.
There are countless life forms today. But the real question remains, 'Does life exist elsewhere?'
My conjecture is that there is, in fact, life elsewhere in the universe. We are like a grain of sand in the grand scheme of things. The Milky Way Galaxy alone is estimated to contain anywhere from 100 billion--400 billion stars.
There are estimates that 100 billion galaxies exist in the universe. So it's almost unfathomable to wrap our heads around, simply based on the fact that there will never be a time in our generational existence that space exploration will reach a magnitude necessary to know the answer to this question.
Now, I'm not saying that space exploration isn't important or necessary-- it is very much so. What I mean is that the universe is so vast that it is highly unlikely that we will ever uncover whatever it may be that is truly out there.
Sure, maybe one day we will be fortunate enough to discover another entity which exists, but it will have to be in the Milky Way Galaxy. Unless that is, the entity itself travels to us.
Whatever life forms may be out there, I would be willing to bet that they follow suit with what Charles Darwin discovered back in the mid-1800s. Darwinian evolution has to be one of the greatest discoveries ever made, at least in my opinion.
Evolutionary theories were always such a tossup, but Darwin was able to pinpoint exactly how genes enter the next generation; an unbelievable discovery at that point in history.
If life really does exist elsewhere, then wouldn't it have to revolve around something similar to DNA? We don't know the answers to these kinds of questions. Most everything about this topic is purely educated hypotheses and conjectures based upon life on planet Earth.
It would be crazy to think that in a universe with some 1 billion trillion stars and billions of galaxies that we would stand alone.
There has to be life elsewhere, don't you think?