Theory of evolution cannot be denied

Letters to the Editor

On June 8, Mirror letter writer Thomas Harclerode made several misleading claims regarding Darwinian evolution.

Harclerode raises the fact that the fossil record is incomplete, that there is a “missing link.”

This tiresome argument is not sufficient to undermine evolution. The fossil record will always be incomplete. A specific series of events has to occur for a fossil to form.

Moreover, soft-bodied organisms are not preserved in the record.

Relative to the fossil record, molecular biology has provided a preponderance of evidence.

DNA, the nature of heredity, and structural biology were wholly unknown to Darwin and they profoundly confirm the reality of evolution.

We now understand how a change in DNA sequence — a mutation — can lead to changes in protein sequence. Contrary to the insinuation made by Harclerode, DNA polymerases are not flawless in their ability to proofread DNA for mutations.

DNA polymerases vary considerably in their fidelity.

This does not address the more error-prone RNA polymerases, which are roughly 1,000 times more error-prone.

In short, there is sufficient opportunity for mutations to arise and provide the raw material on which natural selection can act.

This raises another point: While mutations may occur randomly in a genome, the effects are non-random.

A mutation in a coding region will likely have a deleterious effect, whereas one in a non-coding region is likely to be silent and be passed on.

If one compares DNA sequences among various organisms, one will find that the degree of similarity is striking for certain genes.

Histone proteins are particularly well conserved from yeast to humans, for example.

Far from being a random process, evolution allows scientists to make predictions, and its success in this area shows that it is not just a theory.

Mark A. Frank

State College