In 2013, an obese man went to Hvidovre Hospital in Denmark to have his stomach stapled. All in all, it was ordinary bariatric surgery — with one big exception.
A week before the operation, the man provided a sperm sample to Danish scientists. A week after the procedure, he did so again. A year later, he donated a third sample.
Scientists were investigating a tantalizing but controversial hypothesis: that a man’s experiences can alter his sperm, and that those changes in turn may alter his children.
That idea runs counter to standard thinking about heredity: that parents pass down only genes to their children. People inherit genes that predispose them to obesity, or stress, or cancer — or they don’t. Whether one’s parents actually were obese or constantly anxious doesn’t rewrite those genes.
Yet a number of animal experiments in recent years have challenged conventional thinking on heredity, suggesting that something more is at work.
[For more of this story, written by Carl Zimmer, go to http://www.nytimes.com/2015/12...ectionfront&_r=2]
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