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What is the Origin of Life?

Michael Anissimov
Michael Anissimov
Michael Anissimov
Michael Anissimov

The origin of life are thought to have occurred sometime between 4.4 billion years ago, when the oceans and continents were just starting to form, and 2.7 billion years ago, when it is widely accepted that microorganisms existed in vast numbers due to their influence over isotope ratios in the relevant strata. Where exactly in this 1.7 billion year range the true origin of life can be found is less certain. A controversial paper published in 2002 by the UCLA paleontologist William Schopf argued that wavy geological formations called stromalites in fact contain 3.5 billion year old fossilized algae microbes. Some paleontologists disagree with Schopf’s conclusions and estimate the first life at around 3.0 billion years of age instead of 3.5 billion.

Evidence from the Isua supercrustal belt in Western Greenland suggests an even earlier date for the origin of life – 3.85 billion years ago. S. Mojzis makes this estimate based on isotope concentrations. Because life preferentially uptakes the isotope Carbon-12, areas where life has existed contain a higher-than-normal ratio of Carbon-12 to its heavier isotope, Carbon-13. This is widely known, but the interpretation of sediments is less straightforward, and paleontologists do not always agree on their colleague’s conclusions.

Gradual change over the course of evolution led some dinosaurs to evolve into modern birds.
Gradual change over the course of evolution led some dinosaurs to evolve into modern birds.

We do not know the exact geological conditions of this planet 3 billion years ago, but we do have a rough idea, and can recreate these conditions in a laboratory. Stanley Miller and Harold Urey recreated these conditions in their famous 1953 investigation, the Miller-Urey experiment. Using a highly reduced (non-oxygenated) mixture of gases such as methane, ammonia, and hydrogen, these scientists synthesized basic organic monomers, such as amino acids, in a completely inorganic environment. Now, free-floating amino acids are a far-cry from self-replicating, metabolism-imbued microorganisms, but they at least give a suggestion as to how things might have gotten started.

Some scientists have speculated that the first lifeforms could have arrived on Earth aboard meteorites that came from elsewhere in the Solar System.
Some scientists have speculated that the first lifeforms could have arrived on Earth aboard meteorites that came from elsewhere in the Solar System.

In the large warm oceans of early Earth, quintillions of these molecules would randomly collide and combine, eventually making a rudimentary proto-genome of some sort. However, this hypothesis is confused by the fact that the environment created in the Miller-Urey experiment had high concentrations of chemicals that would have prevented the formation of complex polymers from the monomer building blocks.

In the 1950s and 1960s, another researcher, Sidney Fox, made an early-Earth-like environment in a lab and studied the dynamics. He observed the spontaneous formation of peptides from amino acid precursors, and saw these chemicals sometimes arranged themselves into microspheres, or closed spherical membranes, which he suggested were protocells. If certain microspheres formed which were capable of encouraging the growth of additional microspheres around them, it would amount to a primitive form of self-replication, and eventually Darwinian evolution would take over, creating effective self-replicators like today’s cyanobacteria.

Another popular school of thought about the origin of life, the “RNA world hypothesis,” suggests that life forms when primitive RNA molecules became capable of catalyzing their own replication. Evidence for this is that RNA can both store information and catalyze chemical reactions. Its foundational importance in modern life also suggests that life today may have evolved from all-RNA precursors.

The origin of life continues to be a hot topic for research and speculation. Maybe one day there will be enough evidence, or someone smart enough, that we'll learn how it actually happened.

Michael Anissimov
Michael Anissimov

Michael is a longtime WiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...
Michael Anissimov
Michael Anissimov

Michael is a longtime WiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...

Discussion Comments

anon1003490

Consider anything at all that obviously contains an intelligent pattern – say, a floral emblem such as may be found on decorated cloth. We are considering only the emblem – not the living flower that inspired it. The living flower is orders of magnitude more complex than the artistic pattern it inspired – but take the mere pattern – the artist’s impression -- as the design to be created.

There is a myth in modern "science" -- the universe of itself can produce life. Somehow, if you simply give enough materials enough time, they will assuredly and without fail come up with everything we see around us. Matter can produce life. A much safer god than many of those currently holding religious court in this overly superstitious world, but, for science, a poor fellow-traveller.

A high-school text-book shows why.

Processes in physics have to do with enthalpy, the heat content of a substance per unit mass; and entropy, the heat energy lost to the system for the purposes of doing work. This lost available energy is only lost in the sense that it is transferred into internal motion of molecules. Enthalpy is based on thermometer-type measurements and is expressed in heat content per unit mass. Entropy is calculated by reversing the process to determine the additional energy required to restore the system to its original configuration, and is expressed in heat content per degree Kelvin. To suggest that the two are potentially confusing is to state the obvious. Some popular explanations of entropy can only be classed as science fiction. Misunderstanding of these matters has fathered some weird notions. For instance, it has been authoritatively stated by some populist academics that, since cooling reduces the internal motion of molecules, cooling therefore reduces entropy, and thereby increases the organizational powers of matter. Following this reasoning, if we could get the universe down to absolute zero, instead of becoming effectively dead, it would become extremely creative!

To measure entropy, you must in practice or in theory set up a machine to fully reverse the process and thereby measure the energy made unavailable through that process. The extra energy expended in returning to original conditions, over and above the useful energy produced by the system, tells you the energy lost to that system as work-available energy. The extra work done in restoration is the measure of the work the system itself can no longer perform. Roll the ball down the slope; boost it back up to equal height; allow temperature of the apparatus to equalize; you have original configuration. Obviously, in this simple system, the extra energy required to get the ball back to equal height equals the friction-heat transferred into internal molecular motion during the ball’s travel.

Apply this to the floral pattern.

To produce a guaranteed pattern requires the creation of an artist to draw it. All the universe’s supernovae combined cannot guarantee a single floral pattern. They may chance it, perhaps more than once: but they can neither guarantee it nor exactly replicate it. If you don’t believe this, try looking in a telescope. Only artists draw flowers.

To measure the entropy involved in guaranteed production of one floral pattern – a step that does not even begin to qualify as life-building – you need to build an artist and also a machine that will "counter-build" your artist in such a way as to measure the "organizational effort" or entropy involved. Since no machine in existence can build a human being from inanimate materials, your task is impossible. It is impossible to compute the entropy involved in the production of even one intelligence-generated floral pattern.

Cageybird

I remember seeing a documentary on public television years ago that suggested life began with a lightning bolt. All of the raw ingredients mentioned in this article were in place, but it took something as powerful as lightning to make the jump from inanimate to animate.

There was another theory that life began when meteors struck the earth and in a sense "infected" it with life. The first living things then started spreading like a virus until the entire surface was covered in a primordial ooze, like moss growing on rocks.

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    • Gradual change over the course of evolution led some dinosaurs to evolve into modern birds.
      By: Bastos
      Gradual change over the course of evolution led some dinosaurs to evolve into modern birds.
    • Some scientists have speculated that the first lifeforms could have arrived on Earth aboard meteorites that came from elsewhere in the Solar System.
      By: Daevid
      Some scientists have speculated that the first lifeforms could have arrived on Earth aboard meteorites that came from elsewhere in the Solar System.