Bomb pulse dating
The premise of bomb pulse dating is fairly straightforward.
Most aboveground nuclear bomb testing happened between 19, and those detonations released untold numbers of neutrons into the atmosphere.
“It was precisely as revolting as it sounds,” she says.
Spalding would then spend hours chipping away to extract the necessary cells, a grisly procedure that was just the first in a decade-long stretch of hurdles she had to surmount.
But by the late 1960s and early 1970s, rodent studies led some experts like Fred Gage, a neuroscientist at the Salk Institute in La Jolla, California, to question this notion.
“We found stem cells in the hippocampus of adult mice and rats that could create new neurons,” Gage says.
These slammed into nitrogen atoms, causing their nuclei to eject a proton.
The human hippocampus, Spalding and Frisén discovered, was continually creating small numbers of neurons.The only time neuron numbers could increase was thought to be during fetal development and early childhood.Once the peak number was reached—usually around age four—it was all downhill.But she and her collaborators can’t waste any time.By 2050, Frisén and Spalding estimate, the bomb pulse will have completely dissipated.