Epigenetic inheritance
There is lots of evidence, both from human and animal research, which shows a correlation between what the father consumes and his child's health, especially metabolism and weight. Among the best- documented evidence is the research conducted in a Swedish village called Överkalix. Researchers studied the history and found that, if a grandfather had plenty of food in his childhood, his grandchildren were more likely to be afflicted with health conditions like diabetes. If he had suffered through famines, his grandchildren lived longer. This resulted in the implication that a man's diet somehow affected his grandchildren's health, even though he hadn't raised them himself (Pembrey et al., 2006). But the best evidence comes from controlled animal lab tests. In one key study, scientists fed male father mice a diet rich in fat to make them obese. The obese mice then gave birth to offsprings that themselves were prone to problems with blood sugar and weight gain, even though their offspring were on a normal, healthy diet. When they looked at the sperm of the obese father mice, they found that the epigenetic tags (the methylation) on genes controlling appetite and metabolism were different. In simpler words, this showed that the father’s unhealthy eating had somehow had an effect and programmed his sperm to transmit the message of ‘storing more fat’ (Ng et al., 2010). It is not just about eating too much either. Studies have shown that low-protein diets have the same effect – as if a father's body can use epigenetics to prepare his children for the kind of world he grew up in. If food was scarce, the children might be primed to store calories, which is helpful in a famine but makes them obese if there is a lot of food. As Carey puts it, this means parents do not just pass on genes; they might also pass a ‘biological memory’ of their environment. A father's sperm is not a blank page; it comes with notes scribbled in the margins from his own life. Science is also beginning to show that a father's stress can even affect his children's brains and how they deal with anxiety. In a large study, male mice were subjected to stressful experiences every day, such as the smell of a predator. Those stressed-out mice then went on to have more anxious and hyperactive offspring. The mice babies also shared different stress hormones – their bodies overreacted to scary situations. To help ensure this was from the sperm and not because the fathers were just not good parents, the scientists turned to IVF. They took sperm from stressed-out fathers, used IVF to fertilize an egg in a lab, and implanted it in a mellow, unstressed female mouse. The babies still showed the same anxiety and stress hormone problems: the effect was passed on in the sperm itself (Dias & Ressler, 2014). RNA in the sperm seems to play a crucial role here. Researchers took the RNA from the stressed father mouse sperm and injected it into normal eggs. The babies were anxious. But if they removed the RNA from stressed sperm first, the effect vanished. This was significant as it showed that the RNA messages were directly leading to the alteration in the offspring's brain development (Rodgers et al., 2015). This has huge implications as it suggests that a father's mindset when mating matters. Trauma, chronic stress, or anxiety can not only affect him, but biologically increase his future children's risk of depression and anxiety. While the science I have been describing is exciting, it is important to remember that a father’s epigenetic influence is only one part of a much bigger picture. The biggest other factor is the extensive contribution of the mother. A father contributes one cell – a sperm. A mother, however, contributes not only an egg—which is much larger and contains its own vital molecules and nutrients—but also the entire nine-month incubator: her womb. Her health, stress levels, and diet all directly influence the developing foetus. Carey (2012) uses the example of the Dutch Hunger Winter to illustrate how malnutrition affected two generations. The results showed that when a mother was malnourished only
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