Scientific consensus is that life occurred sometime between 4.4 and 3.5 billion years ago, the oldest evidence for life that has been preserved (and we have found) is in the 3,430-million-year-old Strelley Pool Chert from western Australia - obviously life must have started before this.
The oceans are thought to be the first resource on Earth, scientists, maybe about a year or two ago had just discovered one of the oldest living DNA from a life form 3,000 feet below the surface somewhere located on the Pacific, or was it the Atlantic? Anyways, when the diver returned to the location of the creatures to take pictures, they showed the pictures and videos of the ocean dwellers on the morning news. They looked like gigantic swarming germs about the size of the palm of your hand, and some the size of your thumb. Scientists are still researching the creatures today and they probably will be for a long time, they think that they have been on Earth at least 1,000 years before dinosaurs.
-Smarty (:
The earliest form of life on Earth appeared approximately 3.5 billion years ago in the form of single-celled microorganisms. These simple life forms evolved into more complex organisms over time through processes such as natural selection and genetic variation.
Cyanobacteria. was a late arrival.No one know what the first cells were nor do we understand their chemistry,but the most likely candidates were self reproducing proteins (like prions) somehow bound together.
The answer is debated amongst geologists, astrologists and palaeontologists - the earliest period in life's history is the Archean eon, when the first proto-cells were thought to have formed. The earliest period there, is the Eoarchean - 4200 - 4400 million years ago. However, the earliest eon is the Hadean, which encompasses the formation of the Earth as celestial body 4600 million years ago, up to 4200 million years ago. The earth was formed by accretion (gravitational attraction of smaller bodies, to form a central object of greater mass, thus attracting more smaller bodies, and so on), within 10 - 20 million years, so, other than describing this period of Earth's history as 'Proto-Earth', there isn't really a way of classifying even earlier stages, unless you are willing to look into the stages of accretion in forming planets. (The earliest stage would probably be a 'proto-planetary disk' stage, which was itself formed as a by-product of the formation of the sun, followed by a kilometre-wide planetisimal, and then a Mars sized 'embryo', growing progressively. In this sense, the Earth and the Sun are descended from the same Giant Molecular Cloud, or GMC.)
The Precambrian era was a geological period that spanned from about 4.6 billion years ago to around 541 million years ago. It encompasses the earliest part of Earth's history, including the formation of the planet and the evolution of life forms. The Precambrian era was followed by the Paleozoic era, which marked the beginning of complex life on Earth.
"life"
Stromatolites are one of the earliest known life forms; some fossils may date back 3.5 billion years - before Earth had any oxygen in it's atmosphere.
The earliest evidence of life on Earth comes from fossilized microorganisms that are approximately 3.5 billion years old. These microorganisms are simple bacteria-like organisms known as prokaryotes. They thrived in environments such as hydrothermal vents and shallow seas.
Cyanobacteria.
cyanobacteria
Cyanobacteria
The earliest ones still around are stromatolites, but there were lots of earlier life forms.
One example of a life-form in the Precambrian time was cyanobacteria, which are ancient photosynthetic bacteria thought to be one of the earliest forms of life on Earth. Cyanobacteria played a crucial role in the Great Oxygenation Event by producing oxygen as a byproduct of photosynthesis, which significantly altered Earth's atmosphere.
All land animals evolved from under the water. I would say fish and ammonites.
The prevailing theory of the origin of life on earth posits that it began in the oceans.
The earliest forms of life were microscopic autotrophs that lived in the great prehistoric oceans. Living under the water protected them from the deadly UV rays from the sun, as at this point Earth had not developed a suitable atmosphere. This is true everywhere but Kansas, where the earliest life forms were Adam and Eve. Zing!
It was to hot for rocks to form
The earliest lifeforms on Earth were likely single-celled organisms, such as bacteria and archaea. These organisms were simple in structure and relied on primitive forms of metabolism to survive. Over time, they evolved into more complex life forms.