Some pop this question during discussions and the group usually get into a frenzy with various responses popping up from all corners.
Most theists will argue that the purpose of life is to fulfil God's Commandments, worship Him in the various manners prescribed, and live by His Books.
Others who have an opposing view will usually claim that we basically live in an environment of continuous events, each one triggered off by the previous one, all the way from and into eternity. The only unanswered question in this deduction is, How did the trigger begin, and Who started it. That's exactly where the religious lot jump in as shout in unison, God!
If science claims that everything began from a single cell, which divided itself and multiplied and then went on to become everything that we see around us now, then the religious gurus want to know where the cell came from. When the claim of God is put forward, the scientists then counter argue with the question of "who created God".
And hence spins an open ended dilemma that has gone on for centuries.