'Rotten-egg smell delayed the evolution of animals'

The smell of rotten eggs is off-putting at the best of times, but now scientists believe the same chemical responsible for the awful smell may have held back the evolution of life.

Oceans polluted by hydrogen sulphide could explain why it took so long for life to develop on Earth. Around two billion years ago, deeper layers of the oceans contained high levels of the rotten egg chemical and little oxygen. The smelly poison would have placed a big obstacle in the path of biological evolution, say scientists.

Study leader Dr Simon Poulton, from the University of Newcastle, said: "It has traditionally been assumed that the first rise in atmospheric oxygen eventually led to oxygenation of the deep ocean around 1.8 billion years ago.

"This assumption has been called into question over recent years, and here we show that the ocean remained oxygen-free but became rich in toxic hydrogen sulphide over an area that extended more than 100 kilometres from the continents.

"It took a second major rise in atmospheric oxygen, around 580 million years ago, to oxygenate the deep ocean. This has major implications as it would have potentially restricted the evolution of higher life forms that require oxygen, explaining why animals appear so suddenly relatively late in the geological record."

Oxygen began to fill the Earth's atmosphere for the first time between 2.4 billion and 1.8 billion years ago, rising from nothing to about 5 per cent of present levels. But scientists have not been clear about what happened to oxygen in the oceans.

Early life first emerged in the oceans almost four billion years ago but did not progress beyond the stage of primitive single cells for nearly three billion years. More complex multi-cellular life evolved just over a billion years ago. Around 500 million years ago the "Cambrian Explosion" saw the creation of most of the animal groups that exist today. Soon after, dinosaurs and mammals appeared.

The new findings, reported in the journal Nature Geoscience, are based on an analysis of sedimentary rock samples from a region around Lake Superior in North America. They showed that while the ocean surface 1.8 billion years ago was oxygenated, middle depths extending a large distance from the shoreline were sulphide-rich and starved of oxygen.

Dr Poulton said: "What we have done with this study is to provide the first detailed evaluation of changes in ocean chemistry with water depth in the global ocean at this critical time. Earth scientists will need to consider the consequences of this oceanic structure when trying to piece together the co-evolution of life and the environment."

Suggested Topics
Arts and Entertainment
Dennis Stinchcombe, of Broad Plain Boys' Club in Bristol, by a Banksy artwork, titled 'Mobile Lovers', where the sale and handover have been completed at the Bristol Museum & Art Gallery, where it was on display to the public.
artHuge price will help to keep a 120-year-old youth club in Bristol open
News
i100'Geography can be tough'
News
newsVideo targets undecided voters
Arts and Entertainment
Singer Pixie Lott will take part in Strictly Come Dancing 2014, the BBC has confirmed
tv
PROMOTED VIDEO
Life and Style
Cooked up: reducing dietary animal fat might not be as healthy as government advice has led millions of people to believe
healthA look at how governments started advising incorrectly on diets
Life and Style
Evan Spiegel, the founder of Snapchat, dropped out of Stanford University just before graduation to develop his app
techAnd yes, it is quite a lot
News
REX/Eye Candy
science
News
A photo of Charles Belk being detained by police on Friday 22 August
news
News
i100
Arts and Entertainment
Amis: 'The racial situation in the US is as bad as it’s been since the Civil War'
booksAuthor says he might come back across Atlantic after all
News
ebooksAn evocation of the conflict through the eyes of those who lived through it
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Front-End Developer (JavaScript, HTML5, CSS3, C#, GUI)

£55000 - £70000 per annum + Benefits + Bonus: Harrington Starr: Front-End Deve...

Graduate C# Developer (.NET, WPF, SQL, Agile, C++) - London

£30000 - £40000 per annum + Benefits + Bonus: Harrington Starr: Graduate C# De...

DevOps Engineer - Linux, Shell, Bash, Solaris, UNIX, Salt-Stack

Negotiable: Harrington Starr: A fast growing Financial Services organisation b...

Trade Desk FIX Analyst - (FIX, SQL, Equities, Support)

£50000 - £60000 per annum + excellent benefits: Harrington Starr: An award-win...

Day In a Page

Israel-Gaza conflict: No victory for Israel despite weeks of death and devastation

Robert Fisk: No victory for Israel despite weeks of devastation

Palestinians have won: they are still in Gaza, and Hamas is still there
Mary Beard writes character reference for Twitter troll who called her a 'slut'

Unlikely friends: Mary Beard and the troll who called her a ‘filthy old slut’

The Cambridge University classicist even wrote the student a character reference
Could a later start to the school day be the most useful educational reform of all?

Should pupils get a lie in?

Doctors want a later start to the school day so that pupils can sleep later. Not because teenagers are lazy, explains Simon Usborne - it's all down to their circadian rhythms
Tony Jordan: 'I turned down the chance to research Charles Dickens for a TV series nine times ... then I found a kindred spirit'

Charles Dickens: A tale of two writers

Offered the chance to research Charles Dickens for a TV series, Tony Jordan turned it down. Nine times. The man behind EastEnders and Life on Mars didn’t feel right for the job. Finally, he gave in - and found an unexpected kindred spirit
Prepare for Jewish jokes – as Jewish comedians get their own festival

Prepare for Jewish jokes...

... as Jewish comedians get their own festival
10 best cycling bags for commuters

10 best cycling bags for commuters

Gear up for next week’s National Cycle to Work day with one of these practical backpacks and messenger bags
Kate Bush, Hammersmith Apollo music review: A preamble, then a coup de théâtre - and suddenly the long wait felt worth it

Kate Bush shows a voice untroubled by time

A preamble, then a coup de théâtre - and suddenly the long wait felt worth it
Robot sheepdog technology could be used to save people from burning buildings

The science of herding is cracked

Mathematical model would allow robots to be programmed to control crowds and save people from burning buildings
Tyrant: Is the world ready for a Middle Eastern 'Dallas'?

This tyrant doesn’t rule

It’s billed as a Middle Eastern ‘Dallas’, so why does Fox’s new drama have a white British star?
Rachael Lander interview: From strung out to playing strings

From strung out to playing strings

Award-winning cellist Rachael Lander’s career was almost destroyed by the alcohol she drank to fight stage fright. Now she’s playing with Elbow and Ellie Goulding
The science of saturated fat: A big fat surprise about nutrition?

A big fat surprise about nutrition?

The science linking saturated fats to heart disease and other health issues has never been sound. Nina Teicholz looks at how governments started advising incorrectly on diets
Emmys 2014 review: Can they genuinely compete with the Oscars

Can they genuinely compete with the Oscars?

The recent Emmy Awards are certainly glamorous, but they can't beat their movie cousins
On the road to nowhere: A Routemaster trip to remember

On the road to nowhere

A Routemaster trip to remember
Hotel India: Mumbai's Taj Mahal Palace leaves its darker days behind

Hotel India

Mumbai's Taj Mahal Palace leaves its darker days behind
10 best pencil cases

Back to school: 10 best pencil cases

Whether it’s their first day at school, uni or a new project, treat the student in your life to some smart stationery