Early humans and chimps may have interbred to create hybrid man

The close relationship between man and chimp has just got cosier, according to a study which suggests that ancestors of the two species interbred at some point in the distant past to form fertile hybrids.

It is well established that chimpanzees are the closest living relative of humans but this is the first time that scientists have found evidence for hybridisation through interbreeding.

The astonishing conclusion comes from an exhaustive analysis of the genomes of humans, chimps, gorillas and monkeys published in the journal Nature. The researchers were particularly interested in the point at which the last common ancestor of man and chimp split into two separate species - the process of speciation that gave rise to the chimp and human lineages.

"The study gave unexpected results, about how we separated from our closest relatives, the chimpanzees," David Reich, of the Broad Institute of Harvard and the Massachusetts Institute of Technology, said. "We found that the population structure that existed around the time of human-chimpanzee speciation was unlike any modern ape population," he said. "Something very unusual happened at the time of speciation."

A comparison of the entire DNA of chimps and humans suggests that they split apart no more than 6.3 million years ago,far more recently than previously thought. The study found that an original split was probably followed by a phase of interbreeding and hybridisation, possibly with fertile female hybrids cross-breeding with male chimps, before the final split occurred.

Hybridisation is a common feature of how plants split into different species but scientists have not seen it as being so important in the speciation of animals.

The suggestion could explain why an early human-like fossil known as Toumai or Chad Man appears to date back to seven million years ago, before the split between chimps and man, Nick Patterson, a member of the research team, said. "The fact that the Toumai fossil has human-like features suggests human-chimp speciation may have occurred over a long period with episodes of hybridisation between the emerging species," he said.

The human genome carries the genetic information for making a human being but it also acts as a source of evolutionary history. Some parts of the genome are known to be older than others, meaning that they could date back to the common ancestor of chimps and man.

Dr Reich and his colleagues looked at the variation in evolutionary history across the genomes of humans and chimps. They found that the time from the beginning to the completion of divergence between the two species ranges over more than four million years, much longer than expected. In particular, the study found that the X chromosome - which occurs twice in women and once in men - is the youngest part of the genome and was still being modified just before the final split occurred.

"A hybridisation event between human and chimpanzee ancestors could help to explain both the wide range of divergence times seen across our genomes as well as their relatively similar X chromosomes," Dr Reich said. "That such evolutionary events have not been seen more often in animal species may simply be due to the fact that we have not been looking for them."

Start your day with The Independent, sign up for daily news emails
PROMOTED VIDEO
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
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

Recruitment Genius: Account Manager

£20000 - £35000 per annum: Recruitment Genius: This full service social media ...

Recruitment Genius: Data Analyst - Online Marketing

£24000 - £35000 per annum: Recruitment Genius: We are 'Changemakers in retail'...

Austen Lloyd: Senior Residential Conveyancer

Very Competitive: Austen Lloyd: Senior Conveyancer - South West We are see...

Austen Lloyd: Residential / Commercial Property Solicitor

Excellent Salary: Austen Lloyd: DORSET MARKET TOWN - SENIOR PROPERTY SOLICITOR...

Day In a Page

Isis in Iraq: Yazidi girls killing themselves to escape rape and imprisonment by militants

'Jilan killed herself in the bathroom. She cut her wrists and hanged herself'

Yazidi girls killing themselves to escape rape and imprisonment
Ed Balls interview: 'If I think about the deficit when I'm playing the piano, it all goes wrong'

Ed Balls interview

'If I think about the deficit when I'm playing the piano, it all goes wrong'
He's behind you, dude!

US stars in UK panto

From David Hasselhoff to Jerry Hall
Grace Dent's Christmas Quiz: What are you – a festive curmudgeon or top of the tree?

Grace Dent's Christmas Quiz

What are you – a festive curmudgeon or top of the tree?
Nasa planning to build cloud cities in airships above Venus

Nasa planning to build cloud cities in airships above Venus

Planet’s surface is inhospitable to humans but 30 miles above it is almost perfect
Surrounded by high-rise flats is a little house filled with Lebanon’s history - clocks, rifles, frogmen’s uniforms and colonial helmets

Clocks, rifles, swords, frogmen’s uniforms

Surrounded by high-rise flats is a little house filled with Lebanon’s history
Return to Gaza: Four months on, the wounds left by Israel's bombardment have not yet healed

Four months after the bombardment, Gaza’s wounds are yet to heal

Kim Sengupta is reunited with a man whose plight mirrors the suffering of the Palestinian people
Gastric surgery: Is it really the answer to the UK's obesity epidemic?

Is gastric surgery really the answer to the UK's obesity epidemic?

Critics argue that it’s crazy to operate on healthy people just to stop them eating
Homeless Veterans appeal: Christmas charity auction Part 2 - now LIVE

Homeless Veterans appeal: Christmas charity auction

Bid on original art, or trips of a lifetime to Africa or the 'Corrie' set, and help Homeless Veterans
Pantomime rings the changes to welcome autistic theatre-goers

Autism-friendly theatre

Pantomime leads the pack in quest to welcome all
The week Hollywood got scared and had to grow up a bit

The week Hollywood got scared and had to grow up a bit

Sony suffered a chorus of disapproval after it withdrew 'The Interview', but it's not too late for it to take a stand, says Joan Smith
From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?

Panto dames: before and after

From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?
Thirties murder mystery novel is surprise runaway Christmas hit

Thirties murder mystery novel is surprise runaway Christmas hit

Booksellers say readers are turning away from dark modern thrillers and back to the golden age of crime writing
Anne-Marie Huby: 'Charities deserve the best,' says founder of JustGiving

Anne-Marie Huby: 'Charities deserve the best'

Ten million of us have used the JustGiving website to donate to good causes. Its co-founder says that being dynamic is as important as being kind
The botanist who hunts for giant trees at Kew Gardens

The man who hunts giants

A Kew Gardens botanist has found 25 new large tree species - and he's sure there are more out there