The smell of fear can be inherited, scientists prove

Study shows scents associated with terror may be passed on for two male generations

Scientists have shown for the first time that fear can be transmitted from a father to his offspring through his sperm alone in a ground-breaking study into a new kind of genetic inheritance.

Experiments on mice have demonstrated that they can be trained to associate a particular kind of smell to a fearful memory and that this fear can be passed down through subsequent generations via chemical changes to a father’s sperm cells.

The findings raise questions over whether a similar kind of inheritance occurs in humans, for example whether men exposed to the psychological trauma of a foreign war zone can pass on this fearful behavioural experience in their sperm to their children and grandchildren conceived at home.

The researchers emphasised that their carefully controlled study was carried out on laboratory mice and there are still many unanswered questions, but they do not discount the possibility that something similar may also be possible in people.

“I think there is increasing evidence from a number of studies that what we inherit from out parents is very complex and that the gametes – the sperm and eggs – may be a possible mechanism of conserving as much information as possible from a previous generation,” said Kerry Ressler, professor of psychiatry at Emory School of Medicine in Atlanta, Georgia.

“The biggest interpretation of this research, if it holds up across mammals, is that it may be possible for certain traits such as the fearful experience of a parent to be transmitted to subsequent generations,” Professor Ressler said.

The findings also lend some support to a discredited theory known as the "inheritance of acquired characteristics", promulgated by Jean-Baptiste Lamarck in the late 18th Century. Lamarck postulated that organisms can pass on physical features they developed during their lifetime to their offspring, such as the long neck of giraffes which stretched to reach the highest leaves on a tree.

Butt this idea was later supplanted by Charles Darwin's theory of natural selection, which was further supported by the discovery of genes and Mendelian inheritance. The latest study, however, shows that a kind of Lamarckism may in fact exist in nature as a result of environmental influences directly affecting epigenetic changes to an organism's DNA.

The study, published in the journal Nature Neuroscience, trained male mice to associate the smell of the chemical acetophenone, which smells like cherry blossom, with a mild electric shock. These mice soon displayed fear whenever they were exposed to acetophenone on its own.

Breeding experiments showed that this fear of acetophenone could be transmitted to two further generations, the sons and grandsons of the original male mice. This inheritance must have passed on in sperm as the original males were not allowed to come into contact with their offspring.

Further experiments involving the fertilisation of mouse eggs using IVF techniques confirmed that the fear trait, which was resulted in specific changes to the brains of the mice involve the sense of smell, was transmitted in the sperm as “epigenetic” changes to the proteins surrounding the DNA of the sperm cells.

“While the sequence of the gene encoding the receptor that responds to the odour is unchanged, the way that gene is regulated may be affected,” Professor Ressler said.

“There is some evidence that some of the generalized effects of diet and hormone changes, as well as trauma, can be transmitted epigenetically,” he said.

“The difference here is that the odour-sensitivity-learning process is affecting the nervous system – and, apparently, reproductive cells too – in such a specific way,” he added

Similar studies on female mice, where their pups were immediately fostered by other females, showed that the same kind of mechanism may also occur through egg cells. However, it is more difficult in this instance to eliminate the possibility that the changes occurred in the foetus rather than in the DNA of the females’ eggs.

The study concluded that “ancestral experience before conception” may be an under-appreciated influence on the behaviour of adults, particularly when psychological conditions such as post-traumatic stress disorder, phobias and anxieties are involved.

“Knowing how the experiences of parents influence their descendants helps us to understand psychiatric disorders that may have a trans-generational basis, and possibly to design therapeutic strategies,” Professor Ressler said.

Professor Marcus Pembrey, a paediatric geneticist at University College London, said that the study is important because it provides compelling evidence for the biological transmission of the “memory” of a fearful ancestral experience.

“It is high time public health researchers took human trans-generational responses seriously. I suspect we will not understand the rise in neuropsychiatric disorders or obesity, diabetes and metabolic disruptions generally without taking a multi-generational approach,” Professor Pembrey said.

Professor Wolf Reik, head of epigenetics at the Babraham Institute in Cambridge, said: “These types of results are encouraging as they suggest that trans-generational inheritance exists and is mediated by epigenetics, but more careful mechanistic study of animal models is needed before extrapolating such findings to humans.”

Sport
The sun rises over St Andrews golf course, but will it be a new dawn for the Royal and Ancient Golf Club?
sportAnd it's Yes to women (at the R&A)
Arts and Entertainment
Friends is celebrating its 20th anniversary this year
tvSeries celebrates 20th anniversary
Sport
Yaya Touré (left) and Bayern Munich’s Spanish defender Juan Bernat
footballToure's lack of defensive work is big problem for City
Voices
voicesApple continually kill off smaller app developers, and that's no good for anyone
PROMOTED VIDEO
Arts and Entertainment
Liam Neeson said he wouldn't
tv

Liam Neeson's Downton dreams

Sport
Wembley Stadium
footballNews follows deal with Germany
Arts and Entertainment
A spell in the sun: Emma Stone and Colin Firth star in ‘Magic in the Moonlight’
filmReview: Magic In The Moonlight
News
ebooksAn unforgettable anthology of contemporary reportage
Sport
A 'Sir Alex Feguson' tattoo
football

Arts and Entertainment
Ben Whishaw is replacing Colin Firth as the voice of Paddington Bear
tv

Thriller is set in the secret world of British espionage

Life and Style
life

News
ScienceGallery: Otherwise known as 'the best damn photos of space you'll see till 2015'
Life and Style
fashion

Bomber jacket worn by Mary Berry sells out within an hour

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

Volunteer your expertise as Trustee for The Society of Experimental Biology

Unpaid Voluntary Position : Reach Volunteering: Promising volunteer Trustee op...

Email Designer

£30000 - £35000 Per Annum: Clearwater People Solutions Ltd: Our client is curr...

Psychology Teacher

£110 - £130 per hour: Randstad Education Reading: Psychology Teacher needed fo...

Food Technology Teacher

£85 - £120 per day: Randstad Education Cheshire: Randstad Education are curren...

Day In a Page

Mystery of the Ground Zero wedding photo

A shot in the dark

Mystery of the wedding photo from Ground Zero
His life, the universe and everything

His life, the universe and everything

New biography sheds light on comic genius of Douglas Adams
Save us from small screen superheroes

Save us from small screen superheroes

Shows like Agents of S.H.I.E.L.D are little more than marketing tools
Reach for the skies

Reach for the skies

From pools to football pitches, rooftop living is looking up
These are the 12 best hotel spas in the UK

12 best hotel spas in the UK

Some hotels go all out on facilities; others stand out for the sheer quality of treatments
These Iranian-controlled Shia militias used to specialise in killing American soldiers. Now they are fighting Isis, backed up by US airstrikes

Widespread fear of Isis is producing strange bedfellows

Iranian-controlled Shia militias that used to kill American soldiers are now fighting Isis, helped by US airstrikes
Topshop goes part Athena poster, part last spring Prada

Topshop goes part Athena poster, part last spring Prada

Shoppers don't come to Topshop for the unique
How to make a Lego masterpiece

How to make a Lego masterpiece

Toy breaks out of the nursery and heads for the gallery
Meet the ‘Endies’ – city dwellers who are too poor to have fun

Meet the ‘Endies’ – city dwellers who are too poor to have fun

Urbanites are cursed with an acronym pointing to Employed but No Disposable Income or Savings
Paisley’s decision to make peace with IRA enemies might remind the Arabs of Sadat

Ian Paisley’s decision to make peace with his IRA enemies

His Save Ulster from Sodomy campaign would surely have been supported by many a Sunni imam
'She was a singer, a superstar, an addict, but to me, her mother, she is simply Amy'

'She was a singer, a superstar, an addict, but to me, her mother, she is simply Amy'

Exclusive extract from Janis Winehouse's poignant new memoir
Is this the role to win Cumberbatch an Oscar?

Is this the role to win Cumberbatch an Oscar?

The Imitation Game, film review
England and Roy Hodgson take a joint step towards redemption in Basel

England and Hodgson take a joint step towards redemption

Welbeck double puts England on the road to Euro 2016
Relatives fight over Vivian Maier’s rare photos

Relatives fight over Vivian Maier’s rare photos

Pictures removed from public view as courts decide ownership
‘Fashion has to be fun. It’s a big business, not a cure for cancer’

‘Fashion has to be fun. It’s a big business, not a cure for cancer’

Donatella Versace at New York Fashion Week