Neanderthal Man by Svante Pbo Read Free Book Online Page A

visits to Leningrad. It soon became clear that my host dreamed of visiting the capitalist West and that if he got the chance he would probably defect. To provide some perspective on working life in the West I suggested, as diplomatically as I could, that in the west if you drank on the job, you were likely to be fired—an unknown concept in socialism. Such sobering thoughts seemed not to detract from the allure of the opportunities my host imagined to abound in capitalism. In spite of the hours spent on these theoretical discussions, I managed to collect more than thirty mummy samples to take back to Sweden.
    At Uppsala, I prepared the samples for microscopy by soaking them in a salt solution to rehydrate them, then mounting them on glass slides and staining them with dyes that permitted visualization of cells. Then I looked for preserved cells in the tissues. I did this work on weekends and late at night, so as not to let it be widely known what I was doing. As I  peered through the microscope, the appearance of the ancient tissues depressed me. In muscle sections, I could barely discern the fibers, let alone any traces of cell nuclei where DNA might be preserved. I was almost despairing, until one night I looked at a section of cartilage from a mummified outer ear. In cartilage, as in bone, cells live in small holes, or lacunae, inside the compact, hard tissue. When I looked at the cartilage, I saw what appeared to be the remains of cells inside the lacunae. Excited, I stained the section for DNA. My hands were trembling as I put the slide under the microscope. Indeed, there was staining within the cellular remains in the cartilage (see Figure 2.1). There seemed to be DNA preserved inside!
    With renewed energy, I went on to process all of the remaining samples from Berlin. A few looked promising. In particular, the skin from the left leg of the mummy of a child showed what were clearly cell nuclei. When I stained a section of the skin for DNA, the cell nuclei lit up. Since this DNA was in the cell nuclei, where the cellular DNA is stored, it could not possibly be from bacteria or fungi because such DNA would appear at random in the tissue where the bacteria or fungi were growing. This was unambiguous evidence that DNA from the child herself was preserved. I took many photos through the microscope.

    Figure 2.1. Microscopic picture of cartilage tissue from an Egyptian mummy from Berlin. In some lacunae, cell remains light up suggesting that DNA may be preserved. Photo: S. Pääbo, Uppsala University.
    I found three mummies with staining of the cell nuclei showing the presence of DNA. The child seemed to have the largest number of well-preserved cells. But now doubt started to gnaw at me. How could I be sure that this mummy was really old? Modern corpses were sometimes falsified to look like ancient Egyptian mummies so that the perpetrators might earn a few dollars from tourists and collectors. Some of these mummies might later be donated to museums. The staff of the museum in Berlin had been unable to give me any records of the provenance of this particular mummy, perhaps because the relevant parts of the catalog had been destroyed in the war. The question of its age could be resolved only through carbon dating. Fortunately, Göran Possnert, an expert on carbon dating, worked at Uppsala University. He used an accelerator to determine the ages of tiny samples of ancient remains by measuring the ratios of carbon isotopes present. I asked him how much it would cost to date my mummy, worrying that I would not be able to afford it on my meager student stipend. He took pity on me and offered to date it for free, considerately not even mentioning the price, doubtless because it would have been well out of my range. I delivered a small piece of the mummy to Göran and waited to hear the results. For me, this exemplified one of the most frustrating situations in science, when your work depends crucially on the work of someone else