I answered a question in the Lion's Den and thought my reply also belonged in this Science vs. Religion forum so I posted it here. It is true that a major problem fundamentalist Christians have with Evolution theory is that there is no abiogenesis theory within it. They rightfully ask how did life start? Science has many related theories but little or no real evidences so far to support any of these theories over the multitude of others. For this I think one should be familiar with some of these theories to explain the possibilities of abiogenesis to any who might be interested.
Justus quote: (from Lion's Den)
" ......I have 0% doubt they you don't know of any plausible theory for abiogenesis seeing that living matter can not evolve from non-living matter."
There are a great many different theories of abiogenisis. Nearly all mainstream related theories relate to life first evolving here on Earth roughly 3.8 billion years ago. The oldest fossilized microbial life was determined to be about 3.6 billion years old. The Earth itself has been determined to be about 4.543 billion years old. The most well known abiogenisis theory involves life forming from organic compound chemistry such as carbon, oxygen, nitrogen, water (H2O), carbon dioxide (CO2), methane, ammonia, hydrogen sulfide, etc.and other hydrogen compounds, the precursors of lipids (fatty cell walls), carbohydrates, (sugars, cellulose), amino acids (protein metabolism), and nucleic acids, the basis of RNA life -- viruses are a prime example. In some classifications viruses are not life because they cannot intake food or replicate without parasitic metabolism and proliferation inside cellular DNA life
The oldest abiogenisis theories related to life evolving in relatively quiet tidal pools having all the necessary chemistries of the oceans and atmosphere in those beginning times here on Earth. Some of these compounds accordingly rained down from atmospheric interactions involving lightning and combinations of atmospheric gases that do not exist in today's atmosphere. There are many variations of this theory. Another theory involves life evolving around volcanic vents involving sulfur and water, either on land, or in the ocean. These are a more modern theories.
The abiogenisis theory that I think is more likely involves life forming off the Earth within large comets, or inside matter within interstellar clouds, the precursors of the sun. These theories where the origin of life was created somewhere other than the Earth can collectively go by the name Panspermia, even if it was a more local rather than a universal occurrence. The advantage of these theories is that it allows much more time, billions of years longer, for life to have evolved within interstellar clouds so that beginning life already would have been long established in its most elementary form before it rained down on Earth during the formation of our solar system.
Another interesting abiogenesis theory that I like involves another planet the size of Mars that pre-existed the solar system in interstellar space. It would have been a primarily icy planet on its outside. Here life accordingly could have formed in its interior in a warmer region around a long-expired star or within interstellar clouds. It could have been a planet from a stellar system much older than the sun. The material from which it came coalesced to form our sun and solar system. Because this planet was far older than Earth, life could have first evolved on it, which could allow possibly twice as long for life to form and evolve in the first place. In the formation of our solar system this planet could have collided with the newly forming Earth, raining down its water and life onto the volcanic Earth's surface creating much of the surface oceans and seeding it with beginning life. The material from this collision formed the moon. Such a collision of a Mar's sized planet with the early Earth is now the prevailing theory concerning the formation of the moon. If this theory is valid evidence for early life should also exist on the moon's interior, far enough away from its surface where the sun's unblocked radiation could destroy it. Such evidence should also be found on the interior of Mars because it too is close enough to have been bombarded with some of this beginning life from such a relatively nearby collision. At that time Mars had water oceans and a thick atmosphere of carbon dioxide, fruital grounds for beginning DNA microbial life.
Even though possibly many theories in modern biology and physics may have flaws in them or be generally wrong, when you look at the odds for one of the major or minor theories of abiogenesis being valid, the odds go up greatly that one of the countless version of abiogenesis would be correct.
The god of the gaps just does not cut it.