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.