Stromatolites recently found in Greenland suggest that life on the earth is 3.7 billion years old and that life sprang into existence on a fairly young earth.
How old is life?
Years of research and study of the age of rocks suggests that the earth is about 4.5 billion years old. The age of rocks is measured by radiometric age dating. During all these years the earth has undergone several changes in its layers, rock, and land formation. In the process of the evolution of earth, life originated at some point in time. Compared to the age of the earth, life is transient. One can only make suppositions based on certain evidence as to the beginning of life and the most ancient of organisms.
Life evolved along with the earth, and as layers of the earth underwent tremendous changes, it managed to preserve within its layers the remains of certain forms of life. These remains of life forms preserved among the layers of earth are called fossils. Fossils are preserved remains or traces of life. The remains are only part of the organism or signs of their existence.
Stromatolites are fossilized structures that provide ancient records of the time scale of life on earth. Stromatolites vary greatly in their structures and morphology from conical to stratiform, dome-shaped and columnar types, sometimes even branched. It is quite a challenge to identify if the suspected stromatolites have been created by biotic or abiotic factors. Stromatolites are structures formed by layers of biochemical accumulation, usually in shallow water when sediments get deposited in the biofilms formed by microorganisms. The stromatolites are formed when microbes living in communities lived as large mats that produced sticky biofilms that eventually trapped sand grains and minerals. The bacteria move upwards usually towards light leaving behind the sand and minerals to form layers with domes and mounds projecting out of the layers. These structures have been known to be formed by the most ancient of aerobic microorganisms the Cyanobacteria.
The oldest known stromatolites were found in Pilbara region of Western Australia and belonged to the Precambrian period during which stromatolites might have thrived in abundance. The stromatolites of the Precambrian period were as old as 3.48 billion years. Following the Precambrian period certain predators like snails caused the decline in stromatolites due to heavy grazing.
A couple of years ago, Australian geologists Vickie Bennett, Allen Nutman and Clark Friend were exploring the southwest part of Greenland, which is mostly barren except for moss and lichens. They noticed a few rocks from which the snow had recently fallen off owing to spring and on observation knew that it was no ordinary rock. The rock they saw had layers with conical humps rising out of them and they soon realized that these were stromatolites. Their research suggests that these stromatolites found in the Isua region of Southwest Greenland are as old as 3.7 billion years. This implies that the record of the existence of life sets back by 220 million years as compared to the earlier believed 3.4 billion years old stromatolites from Pilbara, Australia.
If this stands true, it also makes a huge implication that life on 4.5 billion years old earth began when the earth was very young as compared to older belief and evidence. The study may also be able to guide the determination of the existence of life on Mars as it has great similarities with the features of the earth.