Date: March 2007
When it was announced a few years ago that humans shared 98% (or was it 95%?) of our genes with our nearest primate relatives the chimpanzees, many claimed that this questioned the Christian view of the uniqeness of humanity. Strangely, it was also believed that the main purpose of DNA was to code the production of proteins, and perhaps under 2% of DNA actually did this. I haven’t seen any figures as to the percentage of active DNA we share with chimps, nor any recognition that even tiny changes in DNA can produce mega effects in an organism’s function.
In reality we are still far from a good understanding of the whole process of DNA replication. In April 2003 was celebrated the essential completion of the sequencing of the chromosomes in the Human Genome Project (in charge of which was the devout Christian Francis Collins). Humans have around 3 billion base pairs of nucleotides – adenine-thymine and guanine-cytosine – bonded by hydrogen. These are grouped into genes which in turn are grouped into chromosomes. The DNA primary function is encoding to produce proteins, though only about 1.5% of the human genome actually does this. It was a surprise when the International Human Genome Sequencing Consortium in 2001 reduced previous estimates of around 100,000 to only about 30,000 to 40,000 protein-coding genes and by 2003-2004 the generally accepted number was only some 23,000, a staggeringly low number for our species. So only a low number of identified genes in a very small percentage of our genome have any obvious direct function. Another some 3.8% of genes are common in all mammals, suggesting that they have some vital function. What the other 95% or so do we don’t know. It is apparent, however, that the old notion that there was a “gene for everything” is wrong. Particular human characteristics are far more commonly caused by an interplay of effects of two or more genes.
Is it “junk”, ie unnecessary? Two facts suggest that at least some of it is. The first is that half of it contains “transposons”. These are repeated sequences for which the evolutionary explanation is a kind of internal competition to self-paste. Some apparent transposons in some animals have taken on a useful role, but this may not apply to all. The second fact is that a research team led by Edward Rubin in California has deleted two long sequences of non-coding DNA (some million pairs each) from some mice, without any apparent results in the resulting offspring. A year ago they deleted some from the ultra conserved regions of mice genomes, and the resulting animals seem still to be healthy.
Some non-coding DNA does have a regulatory function. We do not know, however, what percentage of DNA will turn out to have some function, and what percentage will have a significant function. Most current researches agree, however, that a largish percentage (probably over a half) will not.
A further complication is that the importance of RNA is also under discussion. RNA molecules were always seen as a kind of intermediate entities, used as go-betweens in the DNA production of proteins. Recent research has suggested that RNA may actually have a role in regulating what goes on in a cell – the operating system of the cell itself. In 2004 researchers in the Sir William Dunn School of Pathology found that RNA acts as an enzyme, catalysing specific chemical reactions or playing a role in gene regulation. More recent work has, indeed, indicated a much greater role for RNA than previously thought, controlling and directing gene expression and utilising some of the non-coding DNA. Some researchers think that a major paradigm change on this issue could becoming.
Where does all this leave our broader understanding of what it means to be human?
Firstly, however we are “programmed” we are not genetic determinists. We all are aware that we make choices, and our choices as well as our genetic make up affect who we become.
Secondly, the sheer complexity of it all makes us echo the Psalmist “we are fearfully and wonderfully made” (Psalm 139:14).
Thirdly, at this stage we cannot be too dogmatic about the mechanisms of genetics. We need a balance. There is much that we do not know, but there is also much that we do know about it. The pattern of the DNA code does seem to indicate that God used some evolutionary means to create it, rather than some kind of instant beginning. Yet the present level of knowledge about the code leaves us with little clue as to through what step in the incredibly complex process God could have given humans their distinctive language and morality. We should reject facile reductionist claims that a particular percentage of DNA in common with chimps (or for that matter with the pufferfish) removes our specialness as a species.