We do know how life originated on Earth. After the matter from the Big Bang was brought together by gravity, the earths' mass was created, after which single cell organisms began to spawn via abiogenesis, and gave rise to more complex multi-cellular organisms.
The Universe is the product of the rapid expansion of matter and energy caused by the Big Bang. We can accurately determine that at a finite time in the universes past all matter originated from a single point, a singularity where all matter was condensed.
Humanity is almost destined to join the %99 of species that have become extinct, on the universal timeline we have existed for barely a blink.
As for why I dont have faith;
Jehovah is only one God in a list of hundreds upon hundreds of mythological figures that cultures have sifted through over the centuries. The Greeks and the Mayans and the Romans were polytheistic, believing in many gods, each with their own sacred texts and idols and saviours supposed to have walked the earth. The Norse had Zeus, and his son Odin, saviour of mankind, who was granted the Secrets of the Runes after many days of self imposed suffering. After his death, Odin rose to Valhalla where he sits at the right hand of Zeus the Almighty. Hercules was supposed to have walked the earth and shared his stories with many men.
Each of these many religions has come and gone to be dismissed as myth and superstition by the cultures that came after them. Christianity is just another religion in the long list that has constantly been dispelled and laughed at by subsequent cultures. It is no different from any that have come before.
Extraordinary claims require extraordinary evidence, a 2000 year old mythological text written 30 years after it's supposed saviour walked the earth is not extraordinary evidence nor should it be treated as such. Remember that Jehovah had no qualms about appearing to thousands upon thousands of witnesses time and time again during biblical times, yet has suddenly become camera shy in the new age. Christians argue that faith is needed to appreciate and understand the story of Jehovah. However you must remember that it is called 'faith' because it is not knowledge. Faith is believing in something because you want it to be true, not because of any evidence.
We can explain the world we live in using evidence and history that does not agree with creationism. Christians have had 2000 years to come up with evidence but still fail, attempting to bend scientific finds to suit biblical ends, or downright ignoring them.
God does not exist, it's time to grow up instead of being born again.