Abiogenesis: Definition, Theory & Evidence

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: The Origin of Life on Earth: Theories and Explanations

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:00 Definition/Primitive Earth
  • 1:15 The Miller Experiment
  • 1:56 RNA Came First
  • 2:54 The First Cells
  • 4:19 Other Hypotheses
  • 4:43 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Joseph Said
This lesson defines abiogenesis and discusses the evidence which supports the theory. This lesson will discuss primitive Earth and the possibilities of how the first life on Earth started from a purely scientific perspective.


How did life start on Earth? When did it start? These questions remained mysteries for thousands of years of human history. We know that the earth is about 4.5 billion years old and that bacteria could've been found on Earth as early as 3.5 billion years ago. The theory of evolution provides us with an explanation of how life started from a single-celled bacteria and diversified to the millions of species of animals, plants, fungi, and bacteria. But where did the first single cell come from?

Abiogenesis is a scientific theory which states that life arose on Earth via spontaneous natural means due to conditions present at the time. In other words, life came from non-living matter.

Primitive Earth

Imagine a lifeless Earth; violent volcanoes, lightning storms, nearly boiling oceans, frequent earthquakes, and an atmosphere with high levels of toxic gases. Primitive Earth was like that. Imagine an earth where the air consisted of high concentrations of methane, ammonia, hydrogen, and vaporized water.

So how and why did life start under these conditions? In the early 1950s, this question was debated by scientists looking for a coherent answer to this important question.

The Miller Experiment

In 1953, Stanley Miller sought out to answer the question of the origins of life on Earth. In his experiment, he used an apparatus with a flask filled with water and chemicals thought to exist on primitive Earth. What he found was these chemicals, under the right conditions, spontaneously formed organic molecules. This experiment suggests that organic molecules could have spontaneously formed on primitive Earth, giving way to the first living things.

Some scientists do not think the conditions of the Miller experiment were accurate to those on primitive Earth, but subsequent experiments with altered atmospheres have shown similar results of the spontaneous generation of amino acids, lipids, and nucleotides.

RNA Came First

For years it was debated among scientists if DNA, RNA, or proteins came first. DNA serves as the principle means to store genetic information, and proteins can catalyze reactions. RNA is nucleic acid that can act as a genetic library and catalyze reactions. This ability makes RNA the ideal candidate to have started the first life on Earth.

So where did RNA come from? Can RNA spontaneously form? First let us review the structure of RNA. RNA is composed of four nucleotide bases:

  1. Adenine
  2. Guanine
  3. Cytosine
  4. Uracil

These four nucleotides are the building blocks of RNA. If they can be synthesized spontaneously given the conditions on primitive Earth, then a large piece of the puzzle of how life started can be solved. Lo and behold, recently it was found that certain molecules can indeed form all four nucleotides in the presence of ultra violet light, or sunlight.

The First Cells

Okay, so if organic molecules and RNA can spontaneously form, what about cells? How are cell membranes made?

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account