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Woolly mammoths and other ice age giants may not have been killed off by an asteroid or comet impact, according to new research.

A study by archaeologists at University College London and the University of California has cast doubt on a major piece of evidence that is used to support theories that an exploding space rock triggered an abrupt period of climate change at the end of the last ice age.

They have found that melted droplets of rock and soil, known as scoria, that were thought to have been scattered by the explosion were in fact created by human fires.

Woolly mammoths were once common across North America, northern Asia and Europe but they vanished around 10,000 years ago at the end of the Pleistocene when the climate underwent dramatic changes

By studying soil found at stone age archaeological sites in Syria, the researchers found the sites were scattered with spherical pieces of melted glass and carbon.

These are similar to other melted soil droplets that have been found scattered around the globe and were thought to have been caused by a meteorite impact. 

However, they claim that rather than being caused by the intense heat of from such an impact, they were created by much more modest temperatures.

Instead, they say that the melted droplets could have been created by fires in stone age buildings as the soil used to construct them melted.

The findings now lend support to other theories for what caused mammoths and other large animals to die out, such as over-hunting by humans and changes to their habitat.

Dr Peter Thy, a geologist at the University of California and lead author of the study, said: 'There is no evidence to suggest that siliceous scoria droplets result from very high temperature melting of soil and are the result of a cosmic event.'

A large asteroid or comet impact with the Earth is one theories for caused ice-age megafauna to die out

Researchers studied tiny droplets of melted debris found at archaeological sites in Syria and found that they appear to have been created by human induced fires as mud used to construct stone-age homes melted

Humans are known to have hunted ice-age giants like mammoths and the latest findings lend support to theories that it was the influx of human hunters into the northern hemisphere that led to the extinctions

The idea that an exploding comet or asteroid sparked the rapid cooling that occurred 12,900 years ago was first proposed by scientists in 2007.

An international team of researchers presented data suggesting carbon-rich black layers found in sediments at around that time were caused by a cosmic impact.

They say the exploding space rock created wildfires, hurricane force winds and lead to the collapse of the North American ice sheets, kickstarting a 1,300-year period of cold weather and drought known as the Younger Dryas cooling.

This lead to many of the large mammals - known as megafauna - that roamed the earth during the Pleistocene to die out.

The same team later claimed in 2013 that the impact spread more than 10 million tonnes of spherules of melted glass and carbon over an area of more than 50 million km across four continents of the Earth.

The latest study examined melted soil at archaeological sites around Syria and concluded it could not have been spread there by a large global wide explosion but was formed by fires within stone age houses

However, the new findings, published in the Journal of Archaeological Science, suggest this evidence may have in fact been caused by the melting of earth in fires created by humans.

The droplets studied appeared to be composed of material found in the local soil in Syria rather than matching soil from elsewhere in the world - which would be consistent with an meteorite impact.

They argue that earth used for constructing buildings was often made with silica rich materials that could melt at temperatures of around 800 and 1000°C.

Dr Thy added: '(Our) findings demonstrate that the presence of siliceous scoria droplets are independent of age and thus are not specific to the beginning of the Younger Dryas.

'Occurrences have not been reported from natural deposits, but are instead associated with buildings destroyed by fire and thus appear to be restricted to archaeological sites.

'We therefore conclude that melting of building earth in ancient settlements can occur during fires reaching modest temperatures.'

Previous research has suggested that an asteroid impact scattered melted droplets of soil around the globe