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."

Arts and Entertainment
The first film introduced Daniel Radcliffe to our screens, pictured here as he prepares to board the train to Hogwarts for the first time.
booksHow reading Harry Potter helps children grow up to be gay-friendly
Sport
Frank Lampard will pass Billy Wright and equal Bobby Charton’s caps tally of 106 caps against
sportFormer Chelsea midfielder in Etihad stopgap before New York contract
Arts and Entertainment
A scene from Aladdin is performed at the Tony Awards in New York in June
theatreBrit producer Lythgoe makes kids' musical comedy a Los Angeles hit
Sport
Usain Bolt of Jamaica smiles and shakes hands with a competitor after Jamaica won their first heat in the men's 4x100m relay
sport
PROMOTED VIDEO
News
ebookA unique anthology of reporting and analysis of a crucial period of history
News
Chancellor George Osborne, along with the Prime Minister, have been 'complacently claiming the economy is now fixed', according to shadow Chancellor Ed Balls
i100... which is awkward, because he is their boss, after all
News
i100
Arts and Entertainment
Adèle Exarchopoulos and Léa Seydoux play teeneage lovers in the French erotic drama 'Blue Is The Warmest Colour' - The survey found four times as many women admitting to same-sex experiences than 20 years ago
filmBlue Is The Warmest Colour, Bojack Horseman and Hobbit on the way
News
Kenny Ireland, pictured in 2010.
peopleBenidorm actor was just 68
Arts and Entertainment
Preparations begin for Edinburgh Festival 2014
Edinburgh festivalAll the best shows to see at Edinburgh this year
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

(Senior) IT Support Engineer - 1st-3rd Line Support

£40000 per annum: Ashdown Group: A successful IT service provider that has bee...

Wind Farm Civil Design Engineer

£55000 - £65000 Per Annum: The Green Recruitment Company: The Green Recruitmen...

Principal Marine Mechanical Engineer

£60000 - £70000 Per Annum: The Green Recruitment Company: The Green Recruitmen...

Principle Geotechnical Engineer

£55000 - £65000 Per Annum: The Green Recruitment Company: The Green Recruitmen...

Day In a Page

Dress the Gaza situation up all you like, but the truth hurts

Robert Fisk on Gaza conflict

Dress the situation up all you like, but the truth hurts
Save the tiger: Tiger, tiger burning less brightly as numbers plummet

Tiger, tiger burning less brightly

When William Blake wrote his famous poem there were probably more than 100,000 tigers in the wild. These days they probably number around 3,200
5 News's Andy Bell retraces his grandfather's steps on the First World War battlefields

In grandfather's footsteps

5 News's political editor Andy Bell only knows his grandfather from the compelling diary he kept during WWI. But when he returned to the killing fields where Edwin Vaughan suffered so much, his ancestor came to life
Lifestyle guru Martha Stewart reveals she has flying robot ... to take photos of her farm

Martha Stewart has flying robot

The lifestyle guru used the drone to get a bird's eye view her 153-acre farm in Bedford, New York
Former Labour minister Meg Hillier has demanded 'pootling lanes' for women cyclists

Do women cyclists need 'pootling lanes'?

Simon Usborne (who's more of a hurtler) explains why winning the space race is key to happy riding
A tale of two presidents: George W Bush downs his paintbrush to pen father’s life story

A tale of two presidents

George W Bush downs his paintbrush to pen father’s life story
Restaurateur Mitch Tonks has given the Great Western Pullman dining car a makeover

The dining car makes a comeback

Restaurateur Mitch Tonks has given the Great Western Pullman dining car a makeover
Gallery rage: How are institutions tackling the discomfort of overcrowding this summer?

Gallery rage

How are institutions tackling the discomfort of overcrowding this summer?
Louis van Gaal has £500,000 video surveillance system installed to monitor Manchester United players

Eye on the prize

Louis van Gaal has £500,000 video surveillance system installed to monitor Manchester United players
Women's rugby: Tamara Taylor adds fuel to the ire in quest to land World Cup

Women's rugby

Tamara Taylor adds fuel to the ire in quest to land World Cup
Save the tiger: The day America’s love of backyard tigers led to a horrific bloodbath

The day America’s love of backyard tigers led to a horrific bloodbath

With only six per cent of the US population of these amazing big cats held in zoos, the Zanesville incident in 2011 was inevitable
Samuel Beckett's biographer reveals secrets of the writer's time as a French Resistance spy

How Samuel Beckett became a French Resistance spy

As this year's Samuel Beckett festival opens in Enniskillen, James Knowlson, recalls how the Irish writer risked his life for liberty and narrowly escaped capture by the Gestapo
We will remember them: relatives still honour those who fought in the Great War

We will remember them

Relatives still honour those who fought in the Great War
Star Wars Episode VII is being shot on film - and now Kodak is launching a last-ditch bid to keep celluloid alive

Kodak's last-ditch bid to keep celluloid alive

Director J J Abrams and a few digital refuseniks shoot movies on film. Simon Usborne wonders what the fuss is about
Once stilted and melodramatic, Hollywood is giving acting in video games a makeover

Acting in video games gets a makeover

David Crookes meets two of the genre's most popular voices