The Great Migration: Tools Mark the Trail

Anatomically modern humans (AMH)—people who looked pretty much like us—migrated out of Africa tens of thousands of years ago and settled across Asia and Europe.

Just who were these people, how long ago did they migrate, and what route did they first take? These are some of the biggest questions in archeology. Now at last researchers seem to be closing in on concrete answers.

In a report published in the November 30 issue of the open-access journal PLoS ONE, an international research team led by Jeffrey Rose presents its analysis of recent work in southern Oman, located on the southeastern corner of the Arabian peninsula.

For years, researchers have debated with each other over the earliest migration route. Was it across the Red Sea to the Arabian boot heel (sea levels being much lower then)? Or was it north from Egypt along the Mediterranean?

Rose and his team found evidence suggesting that AMH residents of the Nile valley migrated—with their distinctive tool technology—to present day Oman. Their analysis of over 100 sites in Oman led researchers to believe that the tool culture was clearly the same in both settings. In other words, one culture spans two continents, clearly supporting the idea of human migration.

Scientists have long known about the Nile valley culture, which they call “Nubian.” The breakthrough reported here is the strong evidence that Nubian toolmakers made their way out of Africa to Arabia, bringing their characteristic stonecutting techniques with them.

The date of migration, according to the report, is at least 106,000 years ago, perhaps earlier.

No human remains were found with the stone tools. This leaves open the possibility that some other humans—“archaic” and not anatomically modern—may be responsible for the stone tools. The researchers dismiss this idea on the grounds that AMH seem to be the only form of humans present in North Africa at the time of the migration.

“After a decade of searching in southern Arabia for some clue that might help us understand early human expansion, at long last we've found the smoking gun of their exit from Africa,” according to Rose, a Research Fellow at the University of Birmingham.

Another surprise contained in the report is that the stone tools were found inland rather than right along the coast. “For a while,” remarks Rose, “South Arabia became a verdant paradise rich in resources – large game, plentiful freshwater, and high-quality flint with which to make stone tools,” according to a press release issued by PLoS One. One possibility is that the “southern route” out of Africa along the southern Arabian peninsula was not so much a coastal expressway to Asia and Europe as it was a settling of the interior of Arabia.

The report, “The Nubian Complex of Dhofar, Oman: An African Middle Stone Age Industry in Southern Arabia,” appears in the November 30, 2011 issue of PLoS ONE

Human Nature, Human Self-Creation

When I spoke at the University of South Florida-St Petersburg last week, I summarized various ways in which the Human Genome Project has opened new perspectives on recent human evolution.

Evidence is mounting the anatomically modern humans (AMH) interbred with archaic humans, such as Neandertals, within the past 80,000 years and perhaps as recently as 30,000 years ago. Not only that, but in the view of some experts, this interbreeding was widespread, possibly more the rule than the exception.

The title of my talk was “Finding the Human in the Genome.” I presented visual images of early human art, including the recent report of the discovery of the 100,000 “artist workshop” in South Africa.

Looking at ancient art can be inspiring and moving, but for us today, the question comes back more forcefully than ever. What are we? Where are we going as a species? Are we in danger of destroying ourselves, not by violence but by modification, by engineering future humans that are not exactly human anymore?

I suggested that our past is somewhat more complex than we thought. Our future, likewise, is a bit more open-ended. We are not clearly defined at either end, either in our origins or in our destiny. As science discovers a complex past, technology opens an uncharted future.

At that point in the talk, I turned to the prescient words of Giovanni Pico della Mirandola, the author of the Oration on the Dignity of Man. Writing in 1486, Pico praises the greatness of the Creator, the “Great Artisan,” who creates human beings with no defined or determinate nature, except the need for self-creation:

Finally, the Great Artisan mandated that this creature who would receive nothing proper to himself shall have joint possession of whatever nature had been given to any other creature. He made man a creature of indeterminate and indifferent nature, and, placing him in the middle of the world, said to him "Adam, we give you no fixed place to live, no form that is peculiar to you, nor any function that is yours alone. According to your desires and judgment, you will have and possess whatever place to live, whatever form, and whatever functions you yourself choose. All other things have a limited and fixed nature prescribed and bounded by our laws. You, with no limit or no bound, may choose for yourself the limits and bounds of your nature. We have placed you at the world's center so that you may survey everything else in the world. We have made you neither of heavenly nor of earthly stuff, neither mortal nor immortal, so that with free choice and dignity, you may fashion yourself into whatever form you choose. To you is granted the power of degrading yourself into the lower forms of life, the beasts, and to you is granted the power, contained in your intellect and judgment, to be reborn into the higher forms, the divine.

According to Pico, God speaks these words to the newly created Adam and Eve and, in effect, to all of us. Then Pico comments: “Imagine! The great generosity of God! The happiness of man! To man it is allowed to be whatever he chooses to be!”

Now, thanks in part to recent science, we can see just how far Pico was right.

Science and Human Mystery

I have been reading Bernard McGinn, a foremost expert on the history of Christian spirituality and mystical theology. In a recent essay, he comments on “the importance of recognizing the mystery of human existence.”

In Christian theology, the mystery of the human is grounded in the mystery of God. In the fourth century, St. Gregory of Nyssa observed that human beings are in the image of God. Our nature mirrors God’s nature. If God is inexhaustible mystery, then what we are must always remain a mystery to ourselves. Otherwise, our knowledge of ourselves would serve as something of a key for us to figure God out, a kind of theological Rosetta stone.

What does this have to do with recent science? Some think that science finds facts and dissolves mysteries. McGinn suggests as much. He thinks that theology’s insistence on human mystery serves as a useful check on the de-mystifying pretensions of science.

I agree with McGinn about the theology of essential human mystery. But I disagree that science has a tendency to erase mystery. Sure, many people see science that way. But look again. The more we learn about human origins, the more we find that any clear notion of a distinct human species seems to unravel. The more scientists merge human and nonhuman organisms or blur the distinction between human and machine, the more we make ourselves mysterious.

If I am right, science increases mystery. At least that’s what I tried to suggest in the brief article I contributed to Science last February. For more, see my post for October 12, below.

That’s why I think McGinn is not quite right when he say this:

“If God is the ultimate mystery, man’s image-nature implies an essentially negative horizon, or limit, to all that can be scientifically discovered about humanity, however original, illuminating, and productive these findings may be. From this viewpoint, growing scientific information (i.e. more and more facts) about human nature (biological, psychological, and sociological) will always be limited by the realization that the true meaning of human existence rests in its status as an inexhaustible mystery. Scientific contributions to the deeper understanding of human nature are welcome and often useful in the task of human self-realization, but they take on a different color when viewed from the sapiential perspective of the “learned ignorance” (docta ignorantia) that recognizes the limits of what can be known and quantified about humanity. This recognition of the limits of science may not be an easy message for contemporaries to appreciate, enamored as we are by the amazing discoveries about homo sapiens made during the past century; but it is one of the most significant challenges that image dei anthropology offers to the present.”

McGinn’s essay is entitled “Humans as Imago Dei: Mystical Anthropology Then and Now.” It appears in Sources of Transformation: Revitalising Christian Spirituality, 2010.

Still wondering..."What Defines Us?"

Last February the editors of Science marked the 10th anniversary of the publication of the complete human genome. They invited a dozen or so people to contribute short reflections on the meaning of this milestone.

I was given 250 words for my article, entitled “What Defines Us?” In that small space I tried to suggest two things. First I noted a simple irony: As we gain more scientific information about our genome and our evolution, the philosophical and religious concepts of humanity become blurred or defocused. Second, I suggested that this defocusing need not be a cause for discomfort. Precisely because we are humans—whatever exactly that means anymore—we switch almost immediately from discomfort to wonder and excitement. The quick switch is what makes us human. I ended by asking: “Who are we, and where will we go next?”

It is as if we are making ourselves up as we go along. Recent discoveries in human evolution intimate just such a view. Anatomically modern humans are now believed to have interbred with Neandertals and with the more recently discovered Denisovans. Many of us carry the DNA of these extinct forms of humanity in our own genome. In that sense they are not distinct at all but live on in every cell of our bodies. More recently, it has been suggested that similar interbreeding occurred in sub-Saharan Africa.

Interestingly, it has also been suggested that interbreeding enhanced us. In August, a research article in Science suggested that our immune systems are more resilient than they might have been. Why? Because our ancestors interbred with Neandertals and Denisovans.

The evolutionary tree of humanity is beginning to look less like a tree and more like a tangled vine. And now we are led to wonder whether it is the tangle that enhances us. What makes us less clearly Homo sapiens seems, paradoxically, to make us more extraordinary as a species. Well…we’re running far ahead of the science here, but (as I suggested in Science), wondering is what makes us human. It’s not just the DNA; it’s what we dare to do with it.

I have been thinking about this recently because I will be speaking on November 10 on this very topic at the University of South Florida Saint Petersburg. They have planned an exciting lecture series, Festival of the Genome: Celebrating the 10th Anniversary of the Sequencing of the Human Genome, showcasing various perspectives on human genome research.