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Where did life first come from?
When did life begin on Earth?
What are the stages in the origin of life?
How long has life been on Earth?
Stages in the origin of life range from the well-understood, such as the habitable Earth and the abiotic synthesis of simple molecules, to the largely unknown, like the derivation of the last universal common ancestor (LUCA) with its complex molecular functionalities.
- Last Universal Common Ancestor
A tree of life, like this one from Charles Darwin's...
- History of life
The history of life on Earth traces the processes by which...
- Life
Life on Earth has existed for at least 3.5 billion years,...
- Last Universal Common Ancestor
- Fossil Record
- History of Studies Into The Origin of Life
- Early Conditions on Earth
- Current Models
- Origin of Organic Molecules
- Theories
- Panspermia
- Related Pages
Earliest claimed life on Earth
The earliest claimed lifeforms are fossilized microorganisms (or microfossils). They were found in iron and silica-rich rocks which were once hydrothermal vents in the Nuvvuagittuq greenstone belt of Quebec, Canada. These rocks are as old as 4.28 billion years. The tubular forms they contain are shown in a report. If this is the oldest record of life on Earth, it suggests "an almost instantaneous emergence of life" after oceans formed 4.4 billion years ago. According to Stephen Blair Hedges,...
Previous earliest
A scientific study from 2002 showed that geological formations of stromatolites 3.45 billion years old contain fossilized cyanobacteria. At the time it was widely agreed that stromatolites were the oldest known lifeforms on Earth which had left a record of its existence. Therefore, if life originated on Earth, this happened sometime between 4.4 billion years ago, when water vapor first liquefied,and 3.5 billion years ago. This is the background to the latest discovery discussed above. The ear...
Spontaneous generation
Until the early 19th century many people believed in the regular spontaneous generation of life from non-living matter. This was called spontaneous generation, and was disproved by Louis Pasteur. He showed that without spores no bacteria or viruses grew on sterilematerial.
Darwin
In a letter to Joseph Dalton Hooker on 11 February 1871, Charles Darwin proposed a natural processfor the origin of life. He suggested that the original spark of life may have begun in a "warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat, electricity, etc. A proteincompound was then chemically formed ready to undergo still more complex changes". He went on to explain that "at the present day such matter would be instantly devoured or absorbed, which would not have...
Haldane and Oparin
No real progress was made until 1924 when Alexander Oparin reasoned that atmospheric oxygen prevented the synthesis of the organic molecules. Organic molecules are the necessary building blocks for the evolution of life. In his The Origin of Life, Oparin argued that a "primordial soup" of organic molecules could be created in an oxygen-less atmosphere through the action of sunlight. These would combine in ever-more complex fashions until they formed droplets. These droplets would "grow" by fu...
There is almost no geological record from before 3.8 billion years ago. The environment that existed in the Hadean era was hostile to life, but how much so is not known. There was a time, between 3.8 and 4.1 billion years ago, which is known as the Late Heavy Bombardment. It is so named because many lunar craters are thought to have formed then. Th...
There is no "standard model" on how life started. Most accepted models are built on molecular biology and cell biology: 1. Because there are the right conditions, some basic small molecules are created. These are called monomers of life. Amino acids are one type of these molecules. This was proved by the Miller–Urey experiment by Stanley L. Miller ...
There are three sources of organic molecules on the early Earth: 1. organic synthesis by energy sources (such as ultraviolet light or electrical discharges). 2. delivery by extraterrestrial objects such as carbonaceous meteorites (chondrites); 3. organic synthesis driven by impact shocks. Estimates of these sources suggest that the heavy bombardmen...
RNA world hypothesis
In this hypothesis, RNA is said to work both as an enzyme and as a container of genes. Later, DNA took over its geneticrole. The RNA world hypothesis proposes that life based on ribonucleic acid (RNA) pre-dates the current world of life based on deoxyribonucleic acid (DNA), RNA and proteins. RNA is able both to store genetic information, like DNA, and to catalyze chemical reactions, like an enzyme. It may have supported pre-cellularlife and been a major step towards cellular life. There are s...
Metabolism and proteins
This idea suggests that proteins worked as enzymes first, producing metabolism. After that DNA and RNAbegan to work as containers of genes. This idea also has some evidences which supports this. 1. Protein as enzymeis essential for today's lives. 2. Some amino acids are formed from more basic chemicals in the Miller-Urey experiment. But proteins cannot copy themselves.
Lipids
In this scheme membranes made of lipid bilayersoccur early on. Once organic chemicals are enclosed, more complex biochemistry is then possible.
This is the idea suggested by Arrhenius, and developed by Fred Hoyle, that life developed elsewhere in the universe and arrived on Earth in the form of spores. This is not a theory of how life began, but a theory of how it might have spread. It may have spread, for example, by meteorites. Some propose that early Mars was a better place to start lif...
Sep 19, 2022 · The origin of life on Earth stands as one of the great mysteries of science. Various answers have been proposed, all of which remain unverified. To find out if we are alone in the galaxy, we will need to better understand what geochemical conditions nurtured the first life forms.
The origin of life is a result of a supernatural event—that is, one irretrievably beyond the descriptive powers of physics, chemistry, and other science. Life, particularly simple forms, spontaneously and readily arises from nonliving matter in short periods of time, today as in the past.
The earliest evidence of life on Earth comes from fossils discovered in Western Australia that date back to about 3.5 billion years ago. These fossils are of structures known as stromatolites, which are, in many cases, formed by the growth of layer upon layer of single-celled microbes, such as cyanobacteria.
