DID you hear the one about how the giraffe got its neck? Aeons ago there was an animal that walked along a dusty path to a watering hole every morning. Halfway, she would spot a patch of trees with the tastiest, most succulent leaves on the savannah. Stretch as she might, she couldn鈥檛 quite reach them. Then one day the stretching paid off, and she suddenly had a mouthful of juicy fronds. Years passed, and the giraffe had babies. Over the generations they became spindlier and spindlier, reaching ever higher into the treetops.
It could be one of Rudyard Kipling鈥檚 Just So Stories, and you can see its charm: keep studying, training and eating healthily, and you can change yourself for the better. Not only that, but your efforts will endure and future generations will benefit, too.
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It鈥檚 just a shame that scientists from Darwin onwards have said that this picture is flat-out wrong. Random mutations in DNA, corralled by the forces of natural selection, fuel evolutionary change.
There鈥檚 no change in that basic picture, but some recent research suggests that elements of our giraffe story might not be so wide of the mark after all. Far from being a rigid instruction manual, our DNA is flexible and responsive 鈥� and we might be able to change much more than we thought.
Almost all your cells hold the same 20,000 or so genes, but each type of cell uses a unique suite of them. Genes have to be turned on and off at the right time in the right place. The mechanisms by which this happens are referred to as 鈥渆辫颈驳别苍别迟颈肠鈥�, acting over and above the genetic code.
Epigenetic information is written into our genes through a series of biological marks that don鈥檛 affect the underlying DNA sequence. A dazzling array of chemical tags can be stuck onto the proteins that package DNA, or even DNA itself, masking certain parts of our genomes from the cell鈥檚 gene-reading machinery or making them more enticing. Crucially, our cells can rub out and rewrite these epigenetic marks to turn genes on or off.
, supping on green tea and that have been linked to changing our epigenetic marks for the better. And it works the other way too: some researchers lay the blame for ailments ranging from allergies to cancer to Alzheimer鈥檚 disease at the door of dodgy epigenetic switches.
Things start to get really interesting when we ask whether epigenetic changes can be passed down the generations. If true, it would mean that the behaviour of a parent could affect how their babies, and even those of their children, develop, and even influence the diseases they might succumb to later in life.
For this to happen, epigenetic marks would need to be written into the DNA of eggs or sperm and preserved in the resulting offspring. There are mechanisms to wipe the epigenetic slate clean between generations, but some studies hint that this .
And there are some intriguing examples of the experiences of past generations seeming to affect subsequent ones. In a famous case known as the Dutch Hunger Winter, the children of women who conceived during the famine caused by the second world war were born smaller than average 鈥� as were their grandchildren, even though they were living at a time of post-war plenty.
For now, solid examples of this happening in humans are rare, but the evidence is growing. It鈥檚 certainly one to keep your eye on: if your gym habit, penchant for pizza or caffeine addiction is going to have cascading effects on your unborn children, you ought to know about it.
Like this? Read: 鈥�Get smarter: 9 ideas to make your life better鈥�
(Image: Denis-Huot/naturepl.com)
This article appeared in print under the headline 鈥淣eed to know: Epigenetics鈥�
