Origin of Man, from the Soup? (Evolution)

Member Name: Rainman44

Product:	Evolution
Date:	26/01/02 (469 review reads)
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Advantages: We don't know for sure

Disadvantages: We don't know for sure

Is there intelligent life on Earth?
Yes, but I’m only visiting.
- Quoted by Norman Shrapnel in the Guardian, 17 Oct. 1970

In the search for the answers to Evolution, one has to first understand how life originated on Earth and then use this basis of knowledge to extrapolate information about Evolution and its progress.

So this is part of my essay which won the UK based competition of Life in the Universe, so it must be good. I went to the finals in Geneva, last year, but I didn’t get through.

I am an atheist and in my opinion, I think that we all did develop by chance from mono-cellular organisms and evolved into what we are now. Other peoples’ reluctance to believe in such an idea probably stems from their own egocentric viewpoints and the denial of their own mortality, or maybe religious beliefs. I mean when you look at the options what would you rather believe, that you are specially made by a God that always loves you, or you are a random collection of atoms existing purely by dumb luck.
And there is the argument that the probability of humans existing is so small that they are neglible. However this mild corruption of the Proof of God by Design is flawed as can be seen with this analogy:
Imagine a madman ties you up and sets up a machine with a big handle in front of you with 52 shuffled decks of cards. And he tells you that when he pulls the handle, the machine will turn over the 52 top cards simultaneously and if they all show the Ace of Spades then the madman will let you go. However if even one card is not the Ace of Spades, then a bomb will explode immediately underneath your chair. So the madman pulls the handle, but can’t bear to look.
And then you open your eyes.
And see 52 Ace of Spades.
And the madman says ‘What did you expect to see?’

On the other hand, there is also ‘The Anthropic Cosmological Principle’, which is a book written by John
Barrow and Frank Tipler that details their Weak, Strong, Participatory and Final Anthropic Principles, (also known as WAP, SAP, PAP and FAP). These principles culminating in FAP, basically say that as no universe can exist in a strong sense unless it contains conscience observers, life on Earth will never be destroyed so removing the conscious observers as the Universe would cease to exist and the Universe wouldn’t do that to itself. So maybe life was inevitable and is taking the first steps to colonising the Universe. However according to Martin Gardner, the Final Anthropic Principle should be renamed CRAP – the Completely Ridiculous Anthropic Principle.
All we can know is that life did start whether it was ‘fated’ to do so or not.

Anyway enough philosophy, how about some science.

So how did life originate on Earth in the first place?

We do not know how life actually got started on Earth. There are many theories but they are very incomplete and untested. Modern scientific work still is unable to answer many very fundamental questions. It seems that the origin of life is one of these unanswered questions and the likelihood of scientists ever knowing exactly how life began on Earth is remote due to the complexity of the many different routes that life could have taken from the many different potential origin points.

Here are the most popular theories:

The Oparin-Haldane hypothesis

In the 1920s, Soviet scientist Alexander Oparin and English scientist J. B. S. Haldane independently proposed the first truly modern hypothesis on the origin of life, later known for its “primordial soup” idea.

The hypothesis can be summarized as follows:

1. When life began, Earth had an atmosphere that was composed of the mostly methane, ammonia, hydrogen, and water. There was no free molecular oxygen in the atmosphere.
2. Lightning, ultraviolet radiation from the sun, and
volcanic heat energized reactions involving the gases in the atmosphere. This led to the formation of carbon molecules (necessary for life).
3. As Haldane put it, these new molecules “must have accumulated until the primitive oceans reached the consistency of a hot dilute soup.”
4. Later changes amongst the molecules in the soup led to the formation of life.

This idea enjoyed widespread popularity in the 20th century. However, we now know it has problems that are probably fatal such as the discrepancy that the Earth’s early atmosphere was very different than the one proposed by Oparin-Haldane. That is, it was high in water vapor, carbon dioxide and nitrogen and not methane, ammonia or hydrogen which was proposed in the Oparin-Haldane hypothesis. There are additional questions regarding the longevity of the so-called prebiotic soup.

The Miller-Urey experiment

Stanley Miller was a graduate student at the University of Chicago in 1952. Under the guidance of his research advisor, Professor Harold Urey, Miller performed an experiment to test out the Oparin-Haldane hypothesis. An enclosed environment was set up with the correct gases and electrodes which simulated the lightning.

He let his experiment run for a week. After this period of time, he noticed a tarry substance coating the inside of the tube. When he analysed it for its contents, he found small amounts of two simple amino acids, alanine and glycine. Amino acids are the building block molecules for larger molecules called proteins (proteins are very important in living things).

However the main problems with this experiment are summarized below:

1. The initial gas mixture was based on the Oparin-Haldane atmosphere. This gas mixture in the early atmosphere now is thought to be highly improbable by geologists.
2. Only after extensive modifications did the apparatus produce the amino acids. So the sensitive eccentricity of the exp
erimental apparatus sheds doubt on the “inevitability” of the process on early Earth.
3. The presence of simple amino acids is not really relevant to the origin of life. This is because in order for life to work, molecules must be able to make copies of themselves. Nucleic acids, like DNA can do this. There is no evidence that amino acids or their protein constructs have any ability to self-replicate. If we cannot find copying abilities in amino acids, linking the Miller-Urey experiment to the origin of life issue is scientifically risky.

Leslie Orgel proposes that the first replicators may have been RNA

Leslie Orgel advocates the idea that RNA molecules (or similar variants) may have been the first replicators. The term, RNA, stands for “ribonucleic acid”. RNA is a cousin to DNA, the master replicator. Orgel’s vision is that RNA could have spontaneously assembled in the prebiotic world. However Orgel could not complete the total copying process without the benefit of enzymes (kinds of proteins). So the synthesis and replication of RNA today happens with the help of proteins (enzymes). Yet proteins are synthesized using the coded information in the RNA (or DNA). This situation represents a chicken-or-egg problem that may be impossible to overcome.
Yet RNA has the potential for being the first self-replicating molecule. Also RNA also can carry coded information and this in molecules like RNA (in particular, DNA) is used as a basis for making other chain-type molecules called proteins. Proteins are powerful molecules that have important functions in living things. So, if Orgel is correct, RNA was the first replicating and information-containing molecule possessing the two essential properties of life.
However the theory also requires the Oparin-Haldane atmosphere coupled with the problem with the proteins.


Sydney Fox proposed that cells made out of proteins came first

There is a proble
m with assuming that DNA was the first self-replicating molecule. This is because DNA, in addition to being absolutely huge, is also an immensely complicated molecule. So, it seems unlikely that the march of life on Earth was dependent upon the random synthesis of the first DNA molecule. The chances of this happening are extremely low. Professor Sydney Fox of the University of Miami believes he has the answer to DNA (or RNA) - protein paradox.
He thinks proteins came first where tiny bubble-like structures called microspheres were composed of a substance called proteinoids. These were molecules that were somewhat similar to proteins but not quite the same. In his model, the proteinoids catalyze chemical reactions and form outer surfaces that act like cell membranes. The chains of amino acids could self-replicate and, therefore, could evolve. In the process, they were able to produce nucleic acids like DNA and RNA. The DNA (or RNA) then began to evolve on its own.
There are many problems with Fox’s proposal, and most have to do with the natural chemical properties of amino acids and failed attempts to synthesize the proteinoids. So many biologists still find the theory incomplete.

Graham Cairns-Smith proposed a simpler idea less dependent on the atmosphere

Scottish chemist Graham Cairns-Smith suggested that perhaps the first living things on Earth were not based on carbon, as they are today. Instead, he proposed in the early 1980s that first life might have been a sort of clay crystal formed in the mud and made out of silicon dioxide crystals.
We know that mineral crystals have the ability to grow by simply adding on to an existing crystal. If a growing crystal breaks apart, the fragments of that crystal can continue to grow on their own. In a sense, this is self-replication, and it is a process that is essential for life. Certain kinds of clays called kaolinite have the interesting property of growing in thin layers. Cairns-Smit
h argues that the clay crystals began growing by adding layers to themselves, like adding pages to a book. The growing crystals competed with each other for resources as they grew. Some crystals would break apart, wash downstream and settle in a new area where they would continue their growth and later fragmentation.
In the early Earth proposed by this idea, the world would be populated by communities of competing clay “beings”. Eventually, these clay creations would begin to incorporate carbon-based molecules into their living apparatus. One way to do this would be the synthesis of DNA or RNA to augment clay-based genes. In time there would be a transition period where carbon based genetic material (DNA or RNA) would become a suitable alternative to clay-based genes. Then, the move to carbon-based life would be complete. DNA would have been created, and the march of organic life could begin.
In its favour, it makes no assumptions about the composition of Earth’s early atmosphere which is a major problem with other earth-based life hypotheses. It also is founded on the simplest of crystal properties, that they have the ability to grow and “reproduce”, by fragmentation. This property is a true nature of crystals, and can be easily demonstrated. Reproduction is an essential property of life.

However, Cairns-Smith argues that the clay idea provides a preparatory path for the ultimate synthesis of DNA or RNA. Yet he does not present a complete idea on how DNA came from clay.

Svante Arrhenius suggested that microorganisms were ejected from other life-bearing planets

The Swedish chemist Svante Arrhenius in the early part of the 20th century proposed that microorganisms were ejected from life-bearing planets and drifted through space. One of them encountered Earth quite by accident and started life here.
This idea fails for two main reasons:
The odds of a single microorganism happening upon Earth ar
e astronomically low. Also, there is the matter of surviving the journey. Radiation, vacuum and intense cold definitely would present major challenges to biological molecules traveling in space. If unprotected, large biological molecules would be destroyed. Yet if embedded deep inside a large rock, dormant microorganisms might have a chance. Of course, then there’s the problem of surviving the fiery entry through the Earth’s atmosphere.

Crick and Orgel proposed a dramatic idea called Directed Panspermia

A variation of the cosmic seed idea was presented by respected biologist Francis Crick and his colleague Leslie Orgel. Crick is the co-discoverer of the structure of DNA. In their idea called “Directed Panspermia”, Crick and Orgel proposed that life actually originated first on another planet outside our solar system a long time ago.
On this planet, a vast intelligent civilization was confronted with the realization that their sun soon would expand into a Red Giant and reduce their world to a burned out cinder. They failed in attempts to fly to other suitable worlds. The distances were too great and travel time in the thousands of years. So, instead of sending “people” (whatever they were), they decided to distribute the seeds of life itself, namely primitive bacteria. About 3.2 billion years ago, one of the ships from this ancient civilization reached earth and discharged its load of bacteria. The rest is history.
Ironically, even Crick himself believes his proposal is farfetched.

Hoyle and Wickramasinghe suggested that life originated elsewhere and colonized the comets of the solar system

Sir Fred Hoyle and Chandra Wickramasinghe have postulated a most complex cosmic connection. In the late 1970s, they proposed that life also originated elsewhere and it traveled to our part of the galaxy just as our solar system was forming. The Earth and the rest of the inner solar system were too ho
t then. So, microorganisms in the form of bacteria, viruses, and bits of genetic material survived in the cooler outer solar system. There, the bits of life became incorporated into comets whose orbits kept them on the outer fringes of the solar system.
From time to time a comet would break free and start its descent toward the sun. On its journey, the comet would strike Earth and deposit its long-held load of living material, establishing life on the planet. Then, throughout Earth’s history, later comets would deposit different kinds of living material, perhaps changing the course of the evolution of life.
Assessing this story is extremely difficult since it relies on speculative assumptions regarding the presence of organic substances in comets.

If we discover the one true origin theory, it will undoubtedly be one of the greatest accomplishments of humankind – to know how life here started. It might put some perspective on matters now and the debate of evolution.

Well thank you for reading all this, and Goodnight.

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