ABOVE: A Greenland shark
WIKIMEDIA, HEMMING1952
Jonas Frisén wanted to answer a question: How often, if at all, do brain cells in the hippocampus turn over in adult humans? But it was clear to him that the usual plan of attack for addressing such a question in lab animals—namely, feeding them a radioactive tracer and then examining their tissues postmortem—couldn’t be adapted to human subjects. “You will not be able to find a healthy volunteer to first drink a toxin and then donate the part of their brain to you, of course,” he explains.
Mulling over the problem, the stem cell researcher at the Karolinska Institute in Sweden considered how archeologists who also can’t feed their subjects radioactive tracers address dating of samples. Archaeologists often tests the ratio of carbon isotopes to determine approximate dates when an organism was alive, taking advantage of the fact that 14C decays at a measurable ...
