John Timmer was at the World Science Fest's panel on What It Means To Be Human, and gives a partial blow-by-blow. Usually these kinds of panels don't bother to include an anthropologist (after all, we study what it means to be human...), but this time, they invited Ian Tattersall, so that has to be an improvement.
Still, the "experts" in their various fields (Marvin Minsky, Daniel Dennett, Francis Collins, and others) didn't come to any consensus -- except apparently with this:
Collins got widespread agreement when he suggested that engineering or selecting genetic improvements was a non-starter: "it implies that someone knows what an improvement is, and our track record there is a little problematic." He also argued that we do basic improvements just fine without genetics through everything from vaccines to piano lessons. Everyone agreed that, at the genetic level, we simply don't know enough about how genes produce complex traits to start planning for them; given that environment plays a huge role, people should focus on parenting, which we do know a few things about.
So...nobody is different from each other in any important way, we have no idea why they might be different or how we might change them, and in any way that they actually are different, it's all because of their parents. Riiiight.
I found Timmer's account of the discussion interesting, just to see what kinds of points bubble up. I think it must have been a fascinating conversation -- ticket-buyers must have been very happy. But it doesn't appear they made much progress.
This is actually an exercise that I do with my undergraduate students on the first day of class -- what defines us as human? The thing is -- the students don't do any better (or, aside from a lack of big jargony words, very differently) from these experts. To be fair, "what it means" can encompass things besides a definition, but these experts seem to have been drawn to many non sequiturs. It almost leads you to think that people don't want an answer to the question.
For some reason, nobody ever thinks about humanity in a very inclusive sense. The wheelchair-bound are no less human just because they do not walk bipedally. Children with severe mental defects, or physical abnormalities are not less human, even if they do not develop into independent adults. People in different parts of the world are not more or less human than each other, despite their manifest genetic variety. A lack of speech does not make one subhuman. Not even a lack of parenting and socialization can do that: "Feral children" and other extreme cases of neglect are still human. And there are many people who not only will not "mate and produce fertile offspring," but are physically incapable of mating with another person. Yet they are human.
People clearly want to define humans in terms of some phenotype -- generally some socially valuable phenotype. Often they talk about "consciousness" -- without considering whether they would deny the humanity of the unconscious -- or grant humanity to the first conscious machine. Less often, people want to define humans in terms of some genotype. This effort never goes so far, because the genes that we know the most about tend to vary among people!
At the end of that first-day exercise, I always give the students the real answer. One thing is shared by all humans, and cannot be taken away: our evolutionary history. Each of us bears some -- but none has all -- of the marks of this history.
It is our history that connects us to our distant relatives, not our genes. Even with a close relative like a twentieth cousin, there is a decent likelihood that you will share no genes at all because of your shared kinship from your most recent common ancestor. By the fiftieth generation, it is a virtual certainty. You are a genetic stranger to your ancestors.
Within the span of fifty generations, a selected gene may completely transform a species, going from less than one percent to ubiquity. Indeed, a single genetic mutation may make you radically different from the rest of humanity, perhaps by restoring a thick coat of body fur, or making your tissues age at many times the average rate -- both characters that some people would make part of the definition of "human." Indeed, many such changes actually have happened in the past few thousand years.
Only history defines humanity, and will continue to define us no matter what we become in the future. We have not severed the genetic links between maize and teosinte, but they are tenuous enough to make the relationship difficult for the layman to see. We have intertwined several inbred strains, more than doubling grain production in a few decades. We regularly add genes from other organisms to our maize, subtly changing its phenotype. Yes, a good part of our corn now shares a history with Bacillus thuringiensis. But that does not deny its shared history with teosinte, or its unique history as a human domesticate. History is additive, inclusive -- not subtractive.
I like this view of human history -- the idea that evolution did not merely generate us, it defines us. To my way of thinking, this is why they study of evolution is central to the science of anthropology. You can see why this answer to the question may be unsatisfying -- it is not predictive. You can't take our shared history and make a prediction about the human future. You can't predict which genes or traits two people may share. You can't take this notion and apply it directly to a fossil hominid to tell whether it is a human.
But I don't see why that it is a weakness. The fact is, you can't place a statistical confidence interval around humanity based on a gene or a trait without leaving some people out. Unless the confidence interval is so wide that it includes some non-humans -- and it is not hard to define "human" in a way that leaves out many children but draws in Kanzi, the stone-tool-making and logogram-using bonobo. Our shared history brings us close to Kanzi, too -- but not the human part of our shared history.
These other things we do are tremendously interesting. It is not wrong to call them aspects of humanity, or parts of the human experience. Many of them have not only resulted from our shared history, they have driven it. Animal and plant domestication, the basis of agriculture, were accomplished by small groups of people working in different parts of the world. These innovations transformed human history in a fundamental way, a change to which we are still rapidly adapting. Agriculture would not have been possible without the social and linguistic changes that preceded them in the Late Pleistocene. These traits, borne by some (but not all) humans, changed the course of humanity.
We take what we have been given, we do things, maybe great things, and we might change the future. That is the individualism within our shared history.