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Thursday, Oct. 18, 2001
Tomb raiders for racial equality
By ROWAN HOOPER
Today, Oct. 18, is the feast day of Luke the Evangelist: physician, saint, author of the book of Acts and companion of Paul. It is thanks to Luke, the most literary of the four gospel writers, that we learn about the human aspects of Christ's life -- such as the enduring Nativity scene.
Most saints' bodies end up as relics, dispersed to shrines all over Christendom, but that believed to be Luke's, remarkably, stayed intact. More remarkable still, a genetic analysis of the corpse is published this week in the journal Proceedings of the National Academy of Sciences.
According to historical documents, Luke was born in Syria, lived to a ripe old age, died and was buried in Thebes (Greece) around A.D. 150. Almost 200 years later, his body was shuttled to Constantinople (now Istanbul). Moving again sometime before A.D. 1177, the body ended up in Padua, Italy.
Luke is a popular saint, and Christian scholars and historians have long sought to discover where he came from. The body in Padua is of unknown origin -- it might have been switched at some stage in its travels around the eastern Mediterranean. The new paper is an attempt, using molecular biology, to solve this historical mystery -- but it illuminates an essential, related issue: the myth that the human species is divided into races.
Biologists got the chance to analyze the saint's body after the magnificently named Vito Terribile Wiel Marin, of the University of Padua, was granted permission to open Luke's marble sarcophagus. It contained a lead coffin, the dimensions of which fit the tomb attributed to Luke in Thebes, and the skeleton of a man.
The skeleton showed signs of osteoporosis, indicating that the man had died at the age of 70 or older. (Interestingly, the pelvis showed damage from fly larvae, indicating that the body had decomposed in the coffin. Traditional piety holds that the bodies of saints are imperishable, immune to decay.)
A team led by Cristiano Vernesi of the University of Ferrara, Italy, first extracted DNA from the canine tooth of the body and bone from the femur for radiocarbon dating. They compared the ancient DNA to similar genetic sequences found in the DNA of modern people from Syria, Turkey and Greece.
The body said to be Luke's, the scientists can now confirm, is not that of a native of Greece. It contains DNA sequences that are most similar to those of modern-day Syrians, seeming to indicate that the body is indeed that of a Syrian.
But that's only the most likely explanation -- the presence of certain DNA sequences means that scientists can't exclude the possibility that the body comes from Turkey. The body was transferred to Turkey in the second year of the reign of the emperor Constantius (A.D. 338), and there is a chance that the corpse was switched there for that of a Turkish individual.
"Whether or not the body is that of the evangelist Luke is impossible to prove," said Guido Barbujani, an author of the paper and biologist at the University of Ferrara, in an e-mail interview. "However, the bishop of Padua, Antonio Mattiazzo, said explicitly that the cult of Saint Luke has nothing to do with the Padua body being his real body. That seems like a very sensible point."
There are two reasons for the inconclusive identification of the origin of the body. First, radiocarbon dating is imprecise when it comes to pinpointing time: The corpse purported to be that of Luke was dated to anywhere between A.D. 42 and A.D. 416. Second, and more important, there are relatively few genetic differences between "gene pools" (populations) in Syria and Turkey, so it is difficult to tell them apart with confidence. This is partly because Anatolia (the part of modern Turkey that is in Asia) is geographically close to Syria, but also because the whole concept of distinct human races is false.
"If the genetic difference between you and the most different human on earth is fixed to 100," said Barbujani, "then the difference between you and another member of your community (not a member of your family, of course) is not 10 but 85, on average."
What this means is that while each of our so-called racial groups may share genetic commonalities, the genetic diversity within groups is so great that it is impossible to draw dividing lines between them. The overlap and differences between individuals are too great.
Barbujani's figures come from a 1997 paper in which he and his colleagues analyzed human molecular diversity using 109 different DNA markers. Human DNA samples came from 16 populations around the world, including Mbuti pygmies from Zaire, several tribes from Brazil and also Cambodians, Japanese, Chinese and Europeans. Numerous other studies using different kinds of genetic markers also found high within-group diversity .
The conclusion is unambiguous: It is biologically meaningless to group humans according to perceived genetic differences, such as skin color.
"We differ genetically from each other, and it is not difficult to tell a Chinese from a Masai. However, it has so far been impossible to trace a line on the map, separating people who are genetically more like Masai from those who are more like Chinese," said Barbujani. "So the burden of proof is now on the supporters of a biological basis for human racial classification."
Until recently, anthropologists proposed anything from three to 200 distinct races for our species, based on physical differences. Among the rest of us, the concept of race will obviously take a long time to die. But die it will.
"Scientists can do a useful job by informing people that the supposedly deep racial differences among human groups are but a small fraction of human diversity, and therefore most perceived human differences are not based on genes. The reasons why we may feel different from, say, Afghanis or Eskimos, are not in our genes," said Barbujani.
Those perceived differences have been, and still are, hugely important in human history, but the new scientific work reminds us that they are artificial: Race is a cultural construct.
That's something that people of faith, even Saint Luke, dead for nearly 2,000 years, can still teach us.
E-mail Rowan Hooper at firstname.lastname@example.org