Evolution What the Fossils Say and Why it Matters

Life’s Origins 159

Mosh Pits, Fool’s Gold, Kitty Litter, Black Smokers, and Mud

Their bacterial plight was pathetic

It’s hard to be unsympathetic

Volcanic heat diminished

Organic soup finished

Their solution was photosynthetic

—Richard Cowen, History of Life

For origin of life research, the biggest challenge is how to assemble longer and more complex
polymers, especially the long proteins that are so important for life. Most of the primordial
soup chemical experiments have produced only shorter proteins. But a number of scien-
tists have suggested that we’ve been going about it in the wrong way. Mixing chemicals
randomly in a beaker will only link things together so much. For a longer, more complex
polymer, you need a “scaffold” or “template,” some other material that will attract and line
up all the organic molecules in the same direction until they are closely packed like dancers

FIGURE 6.4. The next step in the origin of life is arranging the smaller building blocks into longer, more
complex chains (polymerization). The common reactions include linking together a number of amino acids
to form proteins, the basic building blocks of life; polymerizing simple sugars into complex carbohydrates,
the basic component of cell walls and also a critical energy source in metabolism; and linking together
sugars, phosphates, and nucleosides to make nucleic acids (DNA and RNA), the basic genetic code of all life.
(Modified from Schopf 1999: fig. 4.12)

Proteins

Amino

acid

A

Amino

acid

Dipeptide Protein (polypeptide)

H 2 OH 2 OH 2 OH 2 OH 2 O

• A A A A A A A A A

(A)

Carbohydrates

Sugar Sugar Disaccharide Carbohydrate (polysaccharide)

S S S S S S S S S S

H 2 OH 2 OH 2 OH 2 OH 2 O

(B)

Sugar Base Phosphate

Nucleoside Nucleotide Nucleic acid (polynucleotide)

Nucleic acids

S P

B

B S S S S S

B B B B

P P P P

H 2 OH 2 OH 2 OH 2 O

++

(C)

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