Did Scientists Really Discover the 'Gene That Makes Us Human'?
Now here's genetic research made for great headlines! A new research paper is being distilled into news articles along the lines of "scientists now believe the definitive difference between humans and other primates comes down to a single gene." Do they? Does it? If it does, what might that mean, if anything, for faith in Jesus Christ as redeemer of humanity?
He has set eternity in the hearts of men; yet they cannot fathom what God has done from the beginning to the end (Eccl. 3:11). This verse came to mind as I worked my way through the original research article, which is first rate work. Genetics has come so far, so fast. Most of the key discoveries that led to this work were themselves unforeseen until recently. How much more don't we know?
Biological life on Earth manages its daily affairs and reproduces using the molecules DNA and RNA. These are the information hardware and software of life, commonly called genes. Generally, the permanent versions of genes are written in DNA; temporary RNA copies are made for use as instructions to make the gene's product. You hopefully remember this foundation from somewhere. Each discovery since has added complexities. One is that genes often have their RNA cut and edited before the product is made. The cut out RNA pieces are called introns. Introns turn out to be not just throwaways, but sometimes essential genetic machinery.
Hai Yang Hu and his associates are studying microRNA (miRNA). These are very tiny strands of RNA that function as regulatory gene products, mostly to turn other genes off. Their existence as an essential part of genetics was only understood in the last 10 years. Thousands of miRNA have now been found. Some seem universal, and these are remarkably uniform among diverse forms of life.
Some miRNA, however, are unique to a single species: miR-941, which Hu et al. studied, seems to exist only in humans, and was present in each of 29 ethnically diverse human populations from every continent. No primates similar to humans—chimpanzees, gorillas, orangutans, or macaques (rhesus monkeys)—showed evidence of miR-941, nor did representative non-primate animals. In case you missed this, for some time scientists have been retrieving and sequencing DNA from the bones of extinct species or subspecies of humans, such as Neanderthals and Denisovans. Hu and his associates found that DNA sequences of Denisovans also possessed miR-941. (They did not examine Neanderthals.)
What might miR-941 do? It comes from an intron, in this case RNA cut out from a gene for a nerve cell protein. That protein has many functions in the brain, such as release of neurotransmitters allowing communication among nerve cells. Thus, miR-941 is a regulatory product of the very gene its RNA was cut from, and has diverse effects on brain functions. Hu et al. found expression of miR-941 in the prefrontal cortex and the cerebellum of human brains, but not chimpanzee or macaque brains. Since miR-941 is only in humans, it's reasonable to hypothesize it contributes directly to our unique brain and mental development. Some results indicated miR-941 could influence prenatal development. More speculatively, they suggest it might influence genes that aid humans to live longer than other primates.
What might these results mean? This is remarkable work, apparently uncovering an important genetic element unique to human life that wasn't even glimpsed a few years ago. It also isn't a "traditional" gene, producing one to a few protein products, but a tiny RNA that is part of a very complex program involving hundreds of other, different, tiny RNAs and proteins.
Does "the definitive difference" for being human then rest on a single gene? Well, no: that strikes me as journalistic hyperbole, for reasons scientific, philosophical, and theological.
First, this is recently published research (October 2012); it awaits others to independently test it, and offer their own interpretations, which could differ or lead in yet new directions.
Second, people have been tallying genetic similarities and differences between humans and other primates, especially chimpanzees, for some time; this is one more discovery.
Understanding of evolution came partly by observing family resemblance: i.e., the existence of a common ancestor. People spoke of the "cat family" or "dog family", because cats and lions and cougars, or dogs, wolves, and foxes, look and act more like each other than like other animals. So with primates: Linnaeus, father of scientific taxonomy in the 1700s, coined the category "Primates," and included humans because of obvious resemblance. As a Lutheran Christian, he believed we possess a soul that animals lack, but primates we still are. Not surprisingly, our physical similarity is reflected in greater similarities in our DNA, especially in the many genes we share with chimpanzees. It's not news that humans are more like monkeys than cows or cats.
Could the differences then reveal what it means to be human? One longstanding candidate is human chromosome 2, which is a fusion of chimpanzee chromosomes 12 and 13: We are the primate with 46 chromosomes instead of 48. Whenever that occurred, it set humans genetically apart from hybridizing with other primates. What else did it do to us? As DNA sequencing has become routine, genes that chimpanzees and humans don't share—genes unique to each—are being discovered. The miRNA sequence miR-941 is the newest addition.
But can human nature be defined by science alone? In the 1700s, building on the early success of modern science, philosophers like David Hume advocated empiricism: the study only of the measurable will lead us to all truth. Since God, beauty, meaning, and moral value cannot be measured, for empiricists, in theory these don't exist. However, people cannot live without making moral choices, nor without meaning, beauty, and a longing for spiritual answers. This double-mindedness is a root of much of the cultural chaos in our time. Further, when scientists study human nature, they are also part of the experiment: our beliefs and assumptions cannot be fully separated from our observations and conclusions.
In the 1940s, while geneticists were still debating whether genes were made of protein or DNA, C. S. Lewis argued that the moral sense we all carry could not have arisen merely as an emergent property from natural "instincts" (see "Some Objections" in Mere Christianity). Changing "instincts" to "behavioral genetics" makes his case just as relevant to us today.
Francis Collins, former head of the Human Genome Project, and now director of the National Institutes of Health, moved from atheism to faith in Christ partly through Lewis's argument. In an October 2001 interview with Christianity Today, he said:
The study of the genome will tell us a lot about our biological nature, about the parts of us that are mechanical, but I don't believe it will tell us why almost every human being has a sense of longing for God. I don't believe studying DNA will tell us where the sense of right and wrong we share comes from. I don't believe it will explain why we have this shared urge to do the right thing, even to the extent of putting our own lives in danger to save another, which would be exactly the opposite of what evolution would suggest we should do. All those aspects of humanity are some of the best evidence that there is more to us than chemicals and DNA, that there is a spiritual part to our nature.
If our sense of right and wrong shows that God made us different from other animals, when and how did this occur? Who were those extinct Neanderthals and Denisovans with whom we share 46 chromosomes? Lewis, again in the 1940s, pondered human evolution, our spiritual nature, and the Genesis account ("The Fall of Man", in The Problem of Pain). For Lewis, however and whenever God gave humanity a spirit—the ability to commune with God in a way other animals cannot—it would not have to be something visible: a different skull, or more durable artifacts, or perhaps not even a jump in intelligence.
As a Christian biologist, I'm intrigued by how those who trust in Jesus Christ become temples of God (1 Cor. 6:19). What a paradox! The lost potential was always evident, but we're darkened temples until God's presence comes. Then the transformation of all our weakness—our darkened spirit, our human psychology running from God in fear and shame, and the humble biology of a primate—begins to demonstrate God's glory.
Bless the LORD, O my soul, and all that is within me, bless his holy name—even the neuron proteins and microRNA.
Dave Unander is a professor of biology at Eastern University, St. Davids, Pennsylvania, and a member of Providence Church in West Chester.