Brief History and Science and Theories of Evolution

There are many scientific discoveries and ideas that shape the models that are presented today that attempt to explain the origin of life.

In 1859, Darwin published On the Origin of Species where he first introduced his theory about natural selection¹.  Since one of the theories of the origin of life involves the concept of evolution and natural selection, this is a topic that is relevant to our discussion.  According to Meyer (2009), Darwin gave a "plausible means by which organisms could gradually produce new structures and greater complexity by a purely undirected material process".  The word undirected is important in this concept because it shows that Darwin's theory does not line up with the creation science model for the origin of life.  This topic will be discussed in greater detail at a later time.

The first theories about the origin of life came before scientists fully understood the cell, the smallest unit of life.  Many scientists during the 19^th century believed that life came from non-living sources.  Thomas Henry Huxely and Ernst Haeckel were the first to create a theory of how life came from chemicals¹.

Although Huxely and Haeckel were the first to create a theory, there was not yet data to support such a claim.  In 1952, the Miller-Urey experiment showed that amino acids could be made from a chamber with a gas mixture (methane, ammonia, water and hydrogen) and lightening(as outlined in the picture on the left)¹.  Amino acids are the monomers, or the “building blocks”, in proteins.  Proteins are a molecule that is essential to life. 

Left-handed and Right-handed
enantiomers of alanine

In recent times, the applicability of the Miller-Urey experiment to modern theories of the origin of life has been questioned³.  There is a lack of oxygen (a common element in the environment in this experiment³.  This was because the scientists realized that oxygen would destroy the organic compounds made, if any were made⁴.  Evolutionary scientists claim that there would have been a "reducing environment" (in which oxygen would not be present) at the time that life originated, but recent experiments have shown that there was most likely oxygen in the environment at that time³.  This reducing environment would not be stable.  Also, very few amino acids were actually produced in these experiments (less than 2%).  Furthermore, the amino acids that were produced in this experiment were racemic, a mixture of both right-handed and left-handed amino acids (as illustrated in the S, left-handed, and R, right-handed, alanine enantiomers in the picture on the left)⁴.  In proteins, mostly left-handed amino acids are present⁴.  Therefore, there were even fewer amino acids in this mixture that would have actually produced proteins.

When discussing possible origins of life, a discussion of DNA is also pertinent². As this is a very detailed and lengthy topic, this will be left for another blog entry.

References:

1. Meyer, S. (2009). The Evolution of a Mystery and Why It Matters. Signature in the cell [Kindle version]. HarperCollins Publishers.

2. Scott, E. C. (2009). Evolution vs. creationism, an introduction. (2nd ed.). Westport, Conneticut: Greenwood Pub Group.

3. Miller/Urey Experiment. (n.d.). Retrieved from http://www.chem.duke.edu/~jds/cruise_chem/Exobiology/miller.html

4. Peet, J. (n.d.). Retrieved from http://www.truthinscience.org.uk/tis2/index.php/component/content/article/51.html
Reference of Pictures:
[Untitled photograph of Miller-Urey experiment]. (n.d.). Retrieved April 1, 2013, from      
      http://www.chem.duke.edu/~jds/cruise_chem/Exobiology/miller.html
[Untitled photograph of enantiomers]. (n.d.). Retrieved April 1, 2013, from      
       http://opiophilia.blogspot.com/2012/12/chirality-primer.html