The Earliest Evident of Life - Essay Example

The Earliest Evident of Life [Name] [Institutional Affiliation] Introduction There are several theories that have been put forward to explain and trace the origin of life on earth. These include the creation theory and the evolutionary theories. The latter bases its evidence on the evolution processes of both fossils and living things. In the evolutionary theory, both fossils and chemical evidence have been applied to identify signs of life on earth (Walter, 2007). Some of these approaches have been marred with controversies but the evidence they carry is worth relying on. The purpose of this essay is to review the earliest evidence for life on Earth. It begins by examining the various evidence for presence of life and where such evidence was found. In addition to this, the essay extensively discusses the controversies relating to some of this evidence. Finally, the essay sums up with a conclusion on the earliest date at which we can be confident that life was present on earth. Earliest evidence of life The earliest evidence of life on earth can be explained in two ways. One of them is fossil stromatolites and the other is carbon isotopes. This evidence has been discussed under the subheadings below. Fossils Geologists have found evidence in stromatolites to support evidence on early signs of life on earth. Stromatolites are circular in shape and often have a meter length with a smooth layering. These stromatolites are formed by prokaryotes which are photosynthetic materials. The photosynthetic material is found in water that is shallow. Over a period of time, they covered by particles and clay from the sediments. As a result of this, the photosynthetic materials move up so as to receive light from the sun. In doing so, such a upward movements of prokaryotes leaves behind dead layers just in the same way that trees leave an inner wood as they grow. Presence of stromatolites can be identified in the “ring of the tree” that serves to registers how the bacteria move. The oldest and first fossils that were used to justify the presence of life on earth date back to 3.7 million years ago (Walter, 2007). Graphite was discovered in ancient metasedimentary rocks in Western Greenland. Later on, microbial mat fossils were revealed in Western Australia at around 3.48 years ago. For over 3.8 million years ago, the microbial mats have been important in maintaining the ecosystem on planet Earth. The dominant form of microbial mats that existed in the ancient times are those that coexisted both bacteria and archaea. During the Archean years several crucial steps took place that had significant changes in the microbial mats. For instance, during the Archean period there was evolution of the photosynthesis process resulting to an influx of more oxygen in the atmosphere at around 2.4 Ga (Fenchel, 2002).At around 2.85, Ga eukaryotes appeared. These eukaryotes might have been present earlier on but the fact that they started using oxygen for metabolism, it catapulted a more accelerated diversification occurred. At around 1.7 Ga appearances of organisms with multiple cells happened. Animals that had both a back and front started to be seen at around 555 million years ago. The early signs of plants on the universe date back to around 450 years. A contrary evidence indicates that initial terrestrial ecosystems were created by microorganisms approximates 2.9 Ga. The very same microorganisms are the ones that gave way to formation of plants on earth. The growth and development of land plants was so intense that it is believed to have impacted on the Devonian extinction event. There are two major types of animals that emerged in the early years. The vertebrates first appeared around 525 million years ago while the invertebrates are believed to have come into existence during the Ediacaran period. In the period that preceded the Cambrian explosion, mammals are believed to have dominated the planet. One of these animals was the dinosaur. Chemical Evidence The other evidence for life on earth is chemical evidence. This evidence draws ideas from carbon isotopes. As Walter (2007). notes carbon exists in three distinct forms; 12C, 13C, and 14C.The first category has an equal of protons and neutrons. This is 6 protons and neutrons. The next two varieties-13C and 14C, have one or two more neutrons on top of the six. In chemistry, when an atoms has an equal number of protons but different number of neutrons it is said to be an isotope of that same element. The carbon varieties 12C and  13C last a little longer and are the one used by organisms. The 14C does not remain for long since it is radioactive. This means that 12C and  13C can be used to indicate the presence of living processes. Geologists have discovered these two forms of carbon in rocks thus justifying the presence of life on earth(Fenchel, 2002).Carbon rich in 12C was discovered in rocks in Greenland. These gave evidence of life and they date back to 3.85 billion years ago. This is first evidence of life on Earth. Controversies in the evidence of early life Despite that fact that both fossils and carbon have been ascertained as the most accurate form of evidence for life on earth, there are certain controversies that have faced them. The records that exist on the preserved rocks have been contested for a number of reasons. An immense number of the rocks are volcanic in nature. The processes that are seen today are as a result of complex processes. In most times, the rocks have gone through myriad changes over time and thus the rocks we see today are a result of a totally different process than what people observe today. No one can actually tell the exact time that life began on earth. On the other hand, there has been evidence to support that is only a small portion of the earth’s crust that has been preserved and this is preserved in Canada. More so, this portion only dates back to merely a few years ago. Microorganisms identified in the early years were very small and often featureless. This makes it hard for experts to study the organisms and be able to tell one organism and the other. The chemical evidence too has been marred with controversies. It has been proved that isotopes from other elements such as neodymium reveal that the interior of the earth had chemical mixing which was relatively slower that what scientist have recorded lately. Given these controversies, it is very difficult to tell exactly when the first evidence of life on earth was discovered. However, careful examination of both the fossil and chemical evidence reveals that life on earth traces back to 3.85 billion years ago. Despite the weaknesses in both theories and approaches, there is a common belief that life on earth can be justified by fossils and chemical evidence. Conclusion In conclusion, this essay reviews the earliest evidence for life on Earth. It begins by examining the various evidence for presence of life and where such evidence was found. The essay discusses the fossils and chemical evidence. In addition to this, the essay extensively discusses the controversies relating to some of this evidence. Finally, the essay sums up with a conclusion on the earliest date at which we can be confident that life was present on earth. References Walter, M. R. (2007). Earliest evidence of life on Earth. Amsterdam [u.a.], Elsevier. Fenchel, T. (2002). Origin and early evolution of life. Oxford, Oxford University Press. Read More