Sunscreen helped Homo sapiens outlive Neanderthals, study suggests
Neanderthals became extinct about 40,000 years ago, leaving modern humans as the sole-surviving hominin left on Earth.
Now a new theory suggests that the replacement could have been down to how the two groups responded to an increase in harmful UV radiation from space, sparked by an unusual flipping of the magnetic poles.
About 41,000 years ago, a temporary reversal of the poles occurred – known as the Laschamps excursion. It lasted about 1,000 years and weakened Earth's magnetic field to about 10 per cent of its current strength.
Earth's magnetic field protects the planet from harmful solar radiation and cosmic rays. Without it, populations can be dangerously exposed.
Scientists from the University of Michigan modelled the regions that were most vulnerable during the period and found they tallied with human activity in Europe and Asia.
Archaeological evidence shows that around the same time, Homo sapiens started making tailored clothes, dwelling in caves and using ochre as body paint – all of which would have screened them from the increased radiation.
'Having protection against solar radiation (from clothing) would have conferred significant advantage to anyone who possessed it,' said Dr Raven Garvey, associate professor of anthropology at the University of Michigan.
'There have been some experimental tests that show ochre has sunscreen-like properties. It's a pretty effective sunscreen, and there are also ethnographic populations that have used it primarily for that purpose.
'Its increased production and its association primarily with anatomically modern humans during the Laschamps is also suggestive of people having used it for this purpose as well.'
While clothing, ochre and cave dwelling could have protected Home sapiens, there is little evidence that Neanderthals had the same practices.
At sites associated with modern humans, archaeologists have found hide-scraping stones, as well as needles and awls, which were probably used for sewing, but these were absent from Neanderthal sites.
Tailored clothing, as well as protecting from UV rays, also brought warmth, meaning people could travel farther from their hearths and shelters in search of food.
Homo sapiens also probably stepped up their use of ochre, a naturally occurring pigment comprising iron oxide, clay and silica that has been used by many species to paint objects, cave walls and decorate their bodies
'I think it's important to note that these findings are correlational,' Dr Garvey added. 'But I think it is a fresh perspective on the data in light of the Laschamps excursion.'
Earth's magnetic field is created by the rotation of its molten iron core, which generates an electric field that forms around the globe.
This magnetic field has a north and south orientation, the North and South poles, but occasionally these poles wander from their traditional geographic positions, known as excursions.
The Laschamps excursion caused Earth's magnetic poles to drop down near the Equator and would have caused aurora to be seen all over Europe and into northern Africa. It coincided with a big shift for humanity.
'In the study, we combined all of the regions where the magnetic field would not have been connected, allowing cosmic radiation, or any kind of energetic particles from the sun, to seep all the way into the ground,' said Dr Agnit Mukhopadhyay, a climate, space sciences and engineering expert at the University of Michigan.
'Prehistoric sunscreen'
'We found that many of those regions actually match pretty closely with early human activity from 41,000 years ago, specifically an increase in the use of caves and an increase in the use of prehistoric sunscreen.'
Dr Mukhopadhyay added: 'If such an event were to happen today, we would see a complete blackout in several different sectors.
'Our communication satellites would not work. Many of our telecommunication arrays, which are on the ground, would be severely affected by the smallest of space weather events, not to mention the human impacts, which would also play a pretty massive role in our day-to-day lives.'
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