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O n the morning of March 1,a hydrogen bomb went off in the middle of the Pacific Ocean. John Clark was only 20 miles away when he issued the order, huddled with his crew inside a windowless concrete blockhouse on Bikini Atoll.
Image: UPI Telephoto. Between andthe use of atomic bombs doubled the amount of carbon in our atmosphere. Carbon exists in the air, and plants breathe it in during photosynthesis. Animals eat those plants; we eat those animals; and carbon winds up in our bodies, incorporated into our tissues. Every eleven years, the amount of that carbon in the atmosphere would decrease by half.
Archaeologists often tests the ratio of carbon isotopes to determine approximate dates when an organism was alive, taking advantage of the fact that 14 C decays at a measurable and steady rate. So he worked with physicists who were able to increase the sensitivity of a method known as accelerator mass spectrometry.
Inthe group published its first studies using the technique. To date, researchers have used it to determine the ages of everything from classes of proteins to sharks to vintage wines—in some cases, overturning long-held assumptions.
He and collaborators have used 14 C to examine the dynamics of human heart muscle cellsadipocytesmicrogliaand more. While most of those cells do stay with us throughout our lifetimes, the researchers found, about one-third of hippocampal neurons belong to a subpopulation that does divide periodically, with about new neurons born in the region each day. By contrast, they later reported, humans do birth new neurons in an area called the striatumwhere new cells are rarely found in other Bomb spike dating brains.
More recently, the group found that the rate of turnover of myelin-generating oligodendrocytes in the brain was very different in people with multiple sclerosis compared with the turnover of these cells in animal models of the disease. The researchers have also found that in the immune system, the generation of new naive T cells slows with ageand the group identified molecular pathways associated with that slowdown.
Overall, they found, the age of these proteins does align with the year a person was born. Lynnerop says he and colleagues conducted the study with the idea that lens crystalline dating could help identify victims in situations such as mass casualty events. But its utility has turned out to be limited, he explains, partly because of the use of DNA testing to help make such identifications.
Lynnerop knows of only one case where the lens-dating technique has been used forensically, he says: to date the births and deaths of three newborns found in a freezer in Germany more than a decade ago. Although lens-crystalline dating has been little-used in forensics, the technique has been put to a very different use: revealing the age of sharks. So inwhen a Bomb spike dating of Copenhagen—based team set out to figure out how long the slow-growing Greenland shark lives, they analyzed 14 C levels in lens crystallines from 28 animals caught as bycatch.
Only the three smallest sharks from the sample had been born during or after the bomb pulsethe researchers reported. The positioned Greenland sharks as the longest-lived vertebrate known to science.
This technique has a pretty good record of turning population biology on its head for species that we thought we understood. Bomb pulse 14 C has revealed surprisingly long lifespans for some other aquatic species as well. By dating the core of an ear bone known as the otolith, for example, Allen H.
Anglers hunt the species using bows and arrows in some midwestern states, Bomb spike dating says—which, given its long lifespan, is cause for concern. Shawna Williams is a senior editor at The Scientist.
her at swilliams the-scientist. Andrews, University of Hawai'i at Manoa. Related Articles.