Page 38 - The Origin of Life and the Universe - International Conference 2016

The Origin of Life and the Universe

These are the five categories that we will be looking at: Chemical evo-
lution, microevolution, microbial evolution, speciation, and macro-
evolution. My colleague Fazale Rana just spoke to you in some detail
within 30 minutes about chemical evolution. So I will not spend too much
time on this topic and I will only highlight a couple of hurdles that
chemical evolution faces.
But chemical evolution as Fazale Rana said refers to the process of
generating life from non-life. It is sometimes called abiogenesis. And it is
synthesizing biogenic molecules from inorganic compounds. And these
are the building blocks for cells. It is, at the basis of the naturalistic
explanation for the origin of life. But the hurdles it faces are many. One of
them are the chemistries required for the syntheses of many of the
biogenic molecules. These chemistries are not compatible with one another.
So if you’re trying to generate a sugar, you’ll have a different chemistry
than if you’re trying to generate a fatty acid or a nucleic acid which is at
the heart of the DNA and RNA. But not only are the chemistries not com-
patible with one another, the chemistries are not compatible with early
earth conditions.
A second hurdle which I will spend a little more time on is the homo-
chirality of the sugars in RNA and DNA. And also the homo-chirality of
amino acids that are found in proteins. Chirality refers to the orientation
of a molecule, and is sometimes referred to as the "handedness" of a
molecule. If you think about your left hand and your right hand you can
see that they are mirror opposites of one another. Although both have a
palm, and thumbs, and four fingers you cannot superimpose one upon
the other because they’re mirror opposites. This is the problem of chirality.
It is true that the sugars in DNA and RNA, and the amino acids in all
proteins share only one orientation. Either a right-handedness for sugars
or a left-handedness for amino acids. But if you try to generate sugars or
amino acids through naturalistic processes in the laboratory, you don’t get
a single type of left handed molecule for amino acids or a single type of
right handed molecule for sugars. You get a mixture. That’s called a
racemic mixture. And a ratio is about %50 left handed and %50 right
handed sugars, %50 left handed and %50 right handed amino acids.