Origin of life
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|The science of life|
| The divine comedy|
“”So remember when you're feeling very small and insecure,
how amazingly unlikely is your birth!
And pray that there's intelligent life somewhere up in space,
'cause there's bugger all down here on Earth.
|—Eric Idle, Galaxy Song|
The origin of life is a much-debated topic that relates to how life began on this planet. Depending upon individual perspectives, there are a multitude of creation, design, and bizarre theories (those are more akin to a conjecture or hypothesis than a scientific theory) as to how life began. This article attempts to discuss the creation myths found in various religions. The last section covers the explanation derived by the scientific method (see also abiogenesis).
This particular creation story derives from Genesis, the first book of the Bible and of the Jewish Torah. The tale states that an unspecified God created the world, space, all the stars, and all known life over a series of six days, allowing Himself to rest on the seventh. While some creationists (intelligent design pushers) insist that this occurred roughly six to ten thousand years ago, and that the "days" were literal 24-hour days, nowhere does the Bible mention when the creation took place ("in the beginning" sounds like the intro of a myth, not like the precise dating one might expect from a historical account); nor does it discuss how long the days were. Some creationists do believe the Earth to be billions of years old.
Islam, rather than placing its entire myth in one book, spreads the myth of creation across the Qur'an. In the Islamic faith, the skies and Earth were made as one unit. Rather than taking six days, the Qur'an teaches creation took six long spans of time. Similar to the Bible, the Qur'an teaches that one God, Allah, created the world and everything, and that He made all organisms from a single drop of water. After which, He made angels, the Moon, the Sun, and all the other stars. The only thing not made by now was man.
Allah then took multiple types of soil, mixed them together, and made a man (it is not mentioned if it was in his image or another). God placed Adam in Paradise, then created Eve (in Islam, Hawa), from Adam’s side. Finished, God commanded all the angels to bow to Adam, than departed to the heavens. Iblis, believed to be the personification of Satan, refused to obey, and as in the Bible, tempted Eve, gave them the fruit, and got them expelled from Paradise.
One creation myth of the Aborigines of Australia focuses around the "dreamtime", a time around 10,000 years ago. In the beginning, everything already existed, save for life. The stars, planets, and everything else woke up, and burst through a surface, racing to their places. Two beings, however, formed themselves out of nothing. These beings are called the Ungambikula. Upon arriving to the Earth, they found masses of half-completed humans composed of animals and plants. To all extents, they were formless beings. The Ungambikula took a human of whose form they admired, and constructed all other humans in that way. The process of forming a human was not easy, requiring years of working with stone knives. At long last, every human in the world "existed" in a full and complete way. With their work done, the Ungambikula parted to below the surface, and went to sleep. The ground wherever they stepped, however, is holy, and marked by opals (Note: Opals play a VERY important role in Aborigine culture.)
The Norse creation myth begins with two separate realms of extreme hot (Muspelheim) and cold (Nifelheim) with a massive emptiness between them called Ginnungagap, under which lay a life-giving well called Hvergelmir. The water that flowed from the well was frozen by the icy north winds and the built-up ice created not the first human, but the first Frost Giant known as Ymir. Along with Ymir was a cow called Audumla who fed Ymir with her milk. Ymir drank the milk and fathered other Frost Giants from the shards that broke off of him and Audumla nourished herself by licking the ice around her, which was the frozen water from Hvergelmir.
After three days of licking, Audumla found a man in the ice: Burri, first of the Aesir (Norse gods). His son Borr married the giantess Bestla and they had three sons: Vili, Ve and Odin. The family fought against the evil Ymir and killed him, the water from his wounds drowning most of the Frost Giants, except for Bergelmir who made a sheltered boat to protect himself and his family from the flood (sound familiar?).
Using Ymir's body, the Aesir created Midgard, the world, and planted Yggdrasill, the Tree of Life, in order to hold the world steady with its roots and to hold up the sky with its branches. After creating the world, Odin created the first man and woman by making them out of driftwood and gave them souls; Vili gave them thought and feeling while Ve gave them hearing, sight and speech. Soon Midgard was filled with humans, but sorrow and pain came to them when the giants and other evil beings took the shape of humans and intermarried with humans, despite all that Odin did.
The origin of life continues to be an unsolved problem without any strong hypothesis about it, anything much beyond an origin from nonliving matter by natural causes, abiogenesis. Some prebiotic molecules ended up forming complexes that were able to make copies of themselves and transmit information about themselves, thus making the first organisms. However, it is a subject of active research, and impressive progress has been made. The research can be described as forward, from prebiotic environments, and backward, from existing organisms. These approaches may interact, as when forward-approach researchers try to produce what backward-approach researchers hypothesize. Interactions like Leslie Orgel's Prebiotic Chemistry and the Origin of the RNA World.
Typical of the forward approach is the Miller-Urey experiment and numerous similar experiments; there is now a sizable literature on prebiotic synthesis. One can get a great variety of organic molecules from simple precursors like water, ammonia, and methane, including biologically-important ones like amino acids and nucleic-acid bases. This results in a "primordial soup", but it is rather difficult for molecules to get together in it to form larger complexes. That has led to speculations about a "primordial pizza", origin from molecules on mineral surfaces, which can act as catalysts. Did Life Originate in a Mica Sandwich Sitting in Primordial Soup? | Astrobiology Web - Your Daily Source of Astrobiology News is typical.
The backward approach has made a surprising amount of progress, especially when one considers the great complexity of even the simplest autotrophic organisms, organisms like plants and algae and cyanobacteria and methanogens that can live independent of other organisms. Cellular organisms have a rather serious chicken-and-egg problem, where the "chicken" is the proteins and the "egg" is the nucleic acids. Nucleic acids must be built with protein enzymes, and proteins must be specified with nucleic-acid genes. Even the Last Universal Common Ancestor of all known cellular organisms had all these parts: DNA, RNA, and proteins.
But a remarkable hypothesis has emerged for this system's origin, one that has become a favored hypothesis of many early-evolution and origin-of-life researchers: the RNA world. It gets around the chicken-and-egg problem by proposing that the "chicken" and the "egg" were identical: RNA. It acted as both gene and enzyme (ribozyme). But it also recruited various other molecules to serve as coenzymes or helpers, and some of them were amino-acid chains. To make them, a RNA organism developed ribosomes, and eventually the amino-acid chains (proteins) took over many of the RNA enzymes' functions (Deconstructing the Ribosome - Origins). Likewise, it developed a modified form of RNA to serve as master copies of genetic information: DNA. To this day, organisms make DNA building blocks from RNA ones. This is one of several features that are reasonably interpreted as vestigial features of the RNA world, like coenzymes that use bits of RNA (NAD, FAD, Coenzyme A, ATP, etc.), ribozymes, the RNA in ribosomes, etc.
The main problem with the RNA world is the origin of the RNA. It is relatively difficult to make ribose prebiotically, and that has led to speculations like Peptide nucleic acids rather than RNA may have been the first genetic molecule. So the forward and backward approaches have still not met.