DNA and genes and humans and chimpanzees

In this video, Simon Conway Morris talks about Convergent Evolution.

The fact that we share 98.8% of our DNA with chimpanzees gives rise to some strange conclusions. However, to avoid comparing apples and oranges, it needs to be noted at once that “DNA” does not mean the same thing as a “gene”. The significance of this point is drawn out by science writer and educator Maggie Ciskanik. This post drinks at the well of her enlightening article. She writes:

The DNA molecule is extraordinary. When stretched out, the length of DNA in one cell is close to 6 feet (almost 2 meters). Along its length are over 3 billion base pairs that make up the “rungs” of the DNA double helix. The Human Genome Project identified over 20,000 genes along its length.

Genes are functional sections of DNA which vary in the number and sequence of base pairs that make them up. Genes code for functional products, like structural proteins or enzymes; but there are large stretches of DNA for which there is no known function. Couple this “unmapped” region with the fact that a 0.1% difference in base pair sequences still leaves 3 million base pairs to make [each person] unique!

What About Similarity to Chimpanzees?

Let’s go to genetic similarity of humans to a different species, the chimpanzee. Being 98.8% similar in DNA to a chimpanzee can be misleading. This percentage is based on the similarity among base pairs on the same gene.

A good example is the gene that enables both species to see red. Since the gene’s function is the same in both species, this fact shouldn’t alarm us or surprise us. The percent similarity emphatically does not mean that we are 98.8% genetically the same as a chimpanzee. First, the size and number of chromosomes is different among species, and there are genes we do not share.

It is true that we do share many genes with other mammals, from those governing the production of functional and structural proteins to the development of the eye. The latter is used by paleontologist Simon Conway Morris as an example of convergent evolution. In this video, he compares the eye of an octopus and other mammals with the human eye. Fantastic!

It is unfortunate that genetic similarity statistics are used in what seems to be an assault on the unique characteristics of the human person, especially any characteristic that points to a transcendent origin and destiny. We must learn to ignore the more materialist interpretations of what these numbers mean and rejoice that this kind of order is in evidence throughout the created world.

Another take on the similarity and difference between humans and chimps (and bonobos):

Human and chimp DNA is so similar because the two species are so closely related. Humans, chimps and bonobos descended from a single ancestor species that lived six or seven million years ago. As humans and chimps gradually evolved from a common ancestor, their DNA, passed from generation to generation, changed too. In fact, many of these DNA changes led to differences between human and chimp appearance and behavior.

If human and chimp DNA is 98.8 percent the same, why are we so different? Numbers tell part of the story. Each human cell contains roughly three billion base pairs, or bits of information. Just 1.2 percent of that equals about 35 million differences. Some of these have a big impact, others don't. And even two identical stretches of DNA can work differently - they can be "turned on" in different amounts, in different places or at different times.

 Although humans and chimps have many identical genes, they often use them in different ways. A gene's activity, or expression, can be turned up or down like the volume on a radio. So the same gene can be turned up high in humans, but very low in chimps.

The same genes are expressed in the same brain regions in human, chimp and gorilla, but in different amounts. Thousands of differences like these affect brain development and function, and help explain why the human brain is larger and smarter.

See also: 70,000 Years Ago, What Made Us Human: The Origin of a Soul?