From the Guardian:
End of Neanderthals linked to flip of Earth’s magnetic poles, study suggests
Event 42,000 years ago combined with fall in solar activity potentially cataclysmic, researchers say
The flipping of the Earth’s magnetic poles together with a drop in solar activity 42,000 years ago could have generated an apocalyptic environment that may have played a role in a major events ranging from the extinction of megafauna to the end of the Neanderthals, researchers say.
The Earth’s magnetic field acts as a protective shield against damaging cosmic radiation, but when the poles switch, as has occurred many times in the past, the protective shield weakens dramatically and leaves the planet exposed to high energy particles.
One temporary flip of the poles, known as the Laschamps excursion, happened 42,000 years ago and lasted for about 1,000 years. Previous work found little evidence that the event had a profound impact on the planet, possibly because the focus had not been on the period during which the poles were actually shifting, researchers say.
Nowscientists say the flip, together with a period of low solar activity, could have been behind a vast array of climatic and environmental phenomena with dramatic ramifications. “It probably would have seemed like the end of days,” said Prof Chris Turney of the University of New South Wales and co-author of the study.
The team have collectively termed this period “the Adams event”, a nod to Douglas Adams, the author of the Hitchhiker’s Guide to the Galaxy in which 42 was said to be the “answer to the ultimate question of life, the universe and everything”.
Read the whole thing.
UPDATE: From AAAS’s Science magazine: (hat tip: Robert Black):
Ancient kauri trees capture last collapse of Earth’s magnetic field
Several years ago, workers breaking ground for a power plant in New Zealand unearthed a record of a lost time: a 60-ton trunk from a kauri tree, the largest tree species in New Zealand. The tree, which grew 42,000 years ago, was preserved in a bog and its rings spanned 1700 years, capturing a tumultuous time when the world was turned upside down—at least magnetically speaking.
Radiocarbon levels in this and several other pieces of wood chart a surge in radiation from space, as Earth’s protective magnetic field weakened and its poles flipped, a team of scientists reports today in Science. By modeling the effect of this radiation on the atmosphere, the team suggests Earth’s climate briefly shifted, perhaps contributing to the disappearance of large mammals in Australia and Neanderthals in Europe. “We’re only scratching the surface of what geomagnetic change has done,” says Alan Cooper, an ancient DNA researcher at the South Australian Museum and one of the lead authors of the study.
The study not only nails in fine detail the timing and magnitude of the magnetic swap, the most recent in Earth’s history, but is also among the first to make a credible, though speculative, case that these flips can affect the global climate, says Quentin Simon, a paleomagnetist at the European Center for Research and Teaching in Environmental Geoscience in Aix-en-Provence, France. But some paleoclimate scientists are skeptical of the team’s broader claims, saying other records show few traces of climate upheaval.
More at the link.