Nearby star exploding 8m years ago started human evolution

A nearby star exploding 8 million years ago could have triggered the evolution of our ancestors, new research suggests.

The supernova might have led to more lightning storms on Earth, which in turn set off wildfires across Africa.

These fires could explain the rise of the east African Savannah around that time, which experts think was key to the early evolution of hominins.

How the African savannas came to be eight million years ago has long been a mystery to scientists.

While the savannas are now dominated by plants called C4 grasses, these emerged 20 million years ago, long before they became the dominant species on the plains.

Some experts suggest the grass’s turnaround eight million years ago came thanks to a spate of wildfires.

Grasses typically regrow quickly after wildfires, while trees take longer to recover, meaning regular blazes would have expanded Africa’s savannas.

Now a team of US researchers led by experts at Washburn University in Kansas suggest a supernova triggered the savanna-broadening fires.

Deep sea sediments from the time contain high levels of the isotope iron-60, which is produced in larger stars.

The presence of iron-60 suggests there was at least one nearby supernova eight million years ago.

The researchers created a computer model detailing what would have happened if a supernova had exploded near Earth at the time. 

It suggested the explosion sent a pulse of high-energy cosmic rays across the planet.

A spate of wildfires eight million years ago could explain the rise of the east African Savannah, which experts think was key to the early evolution of hominins. These fires could have been caused by a supernova, scientists claim (stock image)

Some of these rays were energetic enough to ionise air particles in the planet’s lower atmosphere, the model found.

Scientists have previously linked this process to lightning formation.

The US team then used a vegetation model to calculate how a brief hike in the number of lightning storms over Africa would have changed its plantlife.

The storms could have cut tree cover on the plains by up to 10 per cent, the model found, enough to allow grasses to begin the formation of the savannas.

‘It’s one of these nice stories that all fits together, with the caveat that there’s some uncertainty in some of those linkages,’ lead researcher Dr Brian Thomas told New Scientist.

Dr Thomas will present the findings at the Geological Society of America annual meeting in Seattle, Washington, this month.

While recent evidence has suggested early hominins emerged in wooded environments, experts argue it’s too soon to discount the role of savannas in the rise of our ancient ancestors.

The first hominins would have evolved in Africa from an intermediate species between apes and humans roughly six million years ago.

Although they walked on two legs, the species had opposable thumbs and big toes which likely helped them climb trees.

The earliest hominins likely ate fruits and nuts from trees and bushes around the African plains.