Primordial Soup: Theory & Model

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  • 0:00 What Is Primordial Soup?
  • 0:56 The Details
  • 2:01 The Miller-Urey Experiment
  • 3:22 Lesson Summary
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Lesson Transcript
Instructor: Joanne Abramson

Joanne has taught middle school and high school science for more than ten years and has a master's degree in education.

Curious where life came from on our planet? Learn about the Primordial Soup and the scientific studies that provide vital insight into the origin of life!

What Is Primordial Soup?

One of the main tenets of biology is that living things can only come from other living things. We are the product of our mother and father; we did not sprout out of a cabbage patch. However, at one point in time, many millions of years ago, there was no life on our planet. And now there is. So then, where did that life come from? The primordial soup is a theory that attempts to answer that question. The theory was generated separately in the 1920s by the Russian biologist Alexander Oparin and the English geneticist John Haldane. Basically, the theory states that when energy, in the form of lightning for example, was added to Earth's early atmosphere, the basic building blocks of life were created. These building blocks collected in certain areas, like along the shoreline of oceans, creating a soup of organic matter that eventually evolved into early forms of life.

The Details

Before life evolved on our planet, there was very little oxygen in the atmosphere. Instead, there were copious amounts gases like methane and ammonia. The theory of the primordial soup states that when energy is added to these gases in the form of heat, lightning or UV rays, monomers are formed. Monomer is from two Greek roots, monos, meaning 'one,' and meros, meaning 'part.' Monomers are the building blocks of more complex organic molecules called polymers. Polymer is from the Greek polus, meaning 'many.' So a monomer is 'one part.' Many monomers bonded together make 'many parts,' or a polymer.

Since scientists are pretty sure that life originated in the water, the theory goes on to state that the monomers gathered in areas such as tide pools, hot springs or deep sea ocean vents, creating a soup. Each of these areas contained a source of energy, which would allow the chemical reactions to continue. Tide pools had UV rays, which, in that early atmosphere, were mostly unfiltered. Hot springs and ocean vents had geothermal heat. Over time, the monomers bonded to form polymers and, eventually, the polymers joined to form life.

The Miller-Urey Experiment

In 1953, American scientists Stanley Miller and Harold Urey set out to test the theory of the primordial soup. They trapped methane, ammonia, hydrogen and water in a closed system. They then added continuous electrical sparks to simulate lightning strikes. After a day, the solution in the collection trap began to change color. After a week, the solution was tested, and over 25 amino acids had been formed, much more than the 20 essential amino acids required for life.

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