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The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day ...
Sep 19, 2022 · Earth is about 4.5 billion years old. Scientists think that by 4.3 billion years ago, Earth may have developed conditions suitable to support life. The oldest known fossils, however, are only 3.7 billion years old. During that 600 million-year window, life may have emerged repeatedly, only to be snuffed out by catastrophic collisions with ...
- Overview
- Hypotheses of origins
1.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.
2.Life, particularly simple forms, spontaneously and readily arises from nonliving matter in short periods of time, today as in the past.
3.Life is coeternal with matter and has no beginning; life arrived on Earth at the time of Earth’s origin or shortly thereafter.
4.Life arose on the early Earth by a series of progressive chemical reactions. Such reactions may have been likely or may have required one or more highly improbable chemical events.
Hypothesis 1, the traditional contention of theology and some philosophy, is in its most general form not inconsistent with contemporary scientific knowledge, although scientific knowledge is inconsistent with a literal interpretation of the biblical accounts given in chapters 1 and 2 of Genesis and in other religious writings. Hypothesis 2 (not of course inconsistent with 1) was the prevailing opinion for centuries. A typical 17th-century view follows:
[May one] doubt whether, in cheese and timber, worms are generated, or, if beetles and wasps, in cow’s dung, or if butterflies, locusts, shellfish, snails, eels, and suchlike be procreated of putrefied matter, which is apt to receive the form of that creature to which it is by the formative power disposed. To question this is to question reason, sense, and experience. If he doubts of this, let him go to Egypt, and there he will find the fields swarming with mice begot of the mud of the Nylus [Nile], to the great calamity of the inhabitants.
Perhaps the most fundamental and at the same time the least understood biological problem is the origin of life. It is central to many scientific and philosophical problems and to any consideration of extraterrestrial life. Most of the hypotheses of the origin of life will fall into one of four categories:
1.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.
2.Life, particularly simple forms, spontaneously and readily arises from nonliving matter in short periods of time, today as in the past.
3.Life is coeternal with matter and has no beginning; life arrived on Earth at the time of Earth’s origin or shortly thereafter.
4.Life arose on the early Earth by a series of progressive chemical reactions. Such reactions may have been likely or may have required one or more highly improbable chemical events.
Hypothesis 1, the traditional contention of theology and some philosophy, is in its most general form not inconsistent with contemporary scientific knowledge, although scientific knowledge is inconsistent with a literal interpretation of the biblical accounts given in chapters 1 and 2 of Genesis and in other religious writings. Hypothesis 2 (not of course inconsistent with 1) was the prevailing opinion for centuries. A typical 17th-century view follows:
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- Simple organic molecules were formed. Simple organic molecules, similar to the nucleotide shown below, are the building blocks of life and must have been involved in its origin.
- Replicating molecules evolved and began to undergo natural selection. All living things reproduce, copying their genetic material and passing it on to their offspring.
- Replicating molecules became enclosed within a cell membrane. The evolution of a membrane surrounding the genetic material provided two huge advantages: the products of the genetic material could be kept close by and the internal environment of this proto-cell could be different than the external environment.
- Some cells began to evolve modern metabolic processes and out-competed those with older forms of metabolism. Up until this point, life had probably relied on RNA for most jobs (as described in Step 2 above).
Photo courtesy of Verena Tunnicliffe, University of Victoria. Scientists are exploring several possible locations for the origin of life, including tide pools and hot springs. However, recently some scientists have narrowed in on the hypothesis that life originated near a deep sea hydrothermal vent. The chemicals found in these vents and the ...
Aug 1, 2024 · Where Did Life Come From, Exactly? The Answer Is Out There The latest research shows lightning, meteors, and far-off nebulae all played a role in assembling the ingredients for life on early Earth.
Oct 30, 2023 · HOW did life on Earth begin? Until 70 years ago, generations of scientists had failed to throw much light on biology’s murky beginnings. But then came three crucial findings in quick succession.
