When did life start?

Answer 1

The most widely endorsed view of the origin of life is that processes on Earth assembled inorganic molecules into larger organic molecules and ultimately into self replicating entities. This area of investigation is called Abiogenesis. (See related links.)

There are quite a number of alternative explanations, including the explanation that life was transported to Earth from some extraterrestrial source. The extraterrestrial view omits the need to explain how life started somewhere else. One can list approximately a dozen major theories with some scientific basis and the interested reader will find extensive resources that explain these. No one explanation is considered true or even highly likely. The scientific process of inquiry continues.

There are also nonscientific explanations of the origin of life, Earth, the Universe and all of evolution. The interested reader will find extensive resources that explain these. They may wish to start with the religious teachings of their own culture.

Answer 2

The oldest record of life on earth is determined by the age of stromatolites, the fossilization of microbe-like objects dated to be 3.5 Ga (billion years old), approximately one billion years after the formation of the Earth itself.

This was during the Paleo-Archean era.

Answer 3

There is no definite answer to the "why" question, as people's opinions vary widely on the subject. For the most part, scientists study the different questions of how life began and evolved.

The question of why life exists can be answered philosophically or religiously. Some people believe it has no apparent purpose. Others contend that everything was intentionally created by a deity of some kind. It all depends on your opinion, these are the kinds of questions that have no clear right or wrong answer.

Answer 4

According to the latest scientific findings, Earth life began somewhere around 3.5 billion years ago, most likely somewhere on the planet Earth.

Of course there are many different creation myths which have life beginning anywhere between billions of years ago (Vedic creationism) to a mere 7000 years ago (Biblical literalism according to James Ussher).

Answer 5

There are actually quite a few opinions on how exactly life originated. A very interesting and intriguing concept is the Big Band Theory concept.