The Biological Burdens

Written by Lilly Tozer Photography by Noemi Duroux

The concept of biological inheritance as we know it today was famously ‘discovered’ by Austrian monk George Mendel and his peas in 1865. This came shortly after the publishing of the even more famous work of Charles Darwin, On the Origin of Species, in 1859. The crucial imaginings of these previously unknown geneticists quickly reverberated throughout the world; concepts that are now so ingrained in our society and understanding of modern biology that it is hard to imagine otherwise. What would our world look like without the concept of Mendelian inheritance or Darwinian evolution? Without nature or nurture?

It goes without saying that the supposed discovery of a wholly new way of passing down biological information caused quite a stir in the scientific community. Starting as a subsection of genetics, the field now known as epigenetics has been studied rather quietly for the better part of six decades. Unlike traditional genetic inheritance, where the code of the DNA itself is passed down through generations, epigenetic inheritance describes the chemical and structural modifications made to DNA in response to our environment, without changing the code itself. The idea of this ‘soft’ inheritance – the passing down of traits acquired during one’s lifetime – has been around for a long time: it was even proposed in the theories of Aristotle himself. Although his hypothesis that a foetus’ sex can be determined by the weather wasn’t exactly correct, the idea that more than just genetic code can be biologically inherited from parent to child is one that has permeated through society since his time.

An explosion of attention ignited interest in the field when a handful of studies linked the inheritance of epigenetic modifications to the passing down of intergenerational trauma. Despite criticisms, the claims still filled headlines. Children exposed to famine during the Dutch Hunger Winter of 1944-45 in early pregnancy were more likely to develop obesity later in life due to epigenetic marks that changed the function of a gene involved in growth. The offspring of Holocaust survivors were found to have inherited a different epigenetic pattern to those who hadn’t, which increased their vulnerability to PTSD and depression. The hypothesis goes that these adaptations are passed down as a result of the response to these extreme conditions to improve the odds for survival; conditions which no longer pose a threat to the children born from them. Considering the immense psychological and emotional toll that these people have endured, it does not sound so far-fetched to think that these biological scars would pass down to the next generation.

While believers signalled a new paradigm shift to the very foundation of biology, cautionary critics still debated its validity. Problems arose as quickly as the praise: a reasonable reaction to such bold claims. Issues like the experimental methods they used, the small sample sizes, and the inability to exclude other explanations for the findings were - and still areused to argue against its possibility. One major issue with accepting epigenetic inheritance in humans is that no one has quite managed to explain exactly how it happens. When fertilised eggs begin to grow in mammals, DNA undergoes what is known as reprogramming, where all the modifications made to it are removed. For these marks to be passed onto offspring they would have to somehow avoid this reprogramming or somehow be reinstated afterwards. Our knowledge from studying other species may give us some suggestions – zebrafish embryos only remove the maternal epigenetic pattern and retain the paternal one; whereas in fruit flies, there are molecules which guide the cell to where to reinstate these markers after reprogramming. However, how this might work in mammals, let alone in humans, remains a mystery.

Valid criticisms aside, the fact that epigenetics plays a role in the inheritance of traits for other organisms, like plants and simpler vertebrates, means it isn’t implausible that it might affect us too. But would the inheritance of our parents’, grandparents’, and even great-grandparents’ experiences change the way we look at the age-old question of nature vs nurture? These marks are our bodies’ way of trying to protect against the hardships faced by our predecessors, despite the fact that it can seemingly turn against us and cause our own problems as a result. In some ways it is not too dissimilar from the way our upbringings affect us. If what the research shows is true, inherited epigenetic modifications might be the bridge that binds the two together, as the experiences of our lifetimes would be passed down not only through ourselves but through our biology.

As we move towards considering both in combination, it seems that most people today would accept that it is no longer a question of nature vs nurture, but rather to what extent both influence our lives both physically and mentally. It is somewhat too easy to use science like this to explain it all away. In a similar way to the popularisation of genetic research in the early 2000s, sensationalist claims about finding the gene for criminality or homosexuality were made without much consideration for the nuances of the science. It would seem as if people were too eager to find biological answers to societal questions; to feel like these things are predetermined by our biological script. But, in reality, our lived experience is just as important. So, despite the line between nature and nurture seemingly thinning, there remains some realms for which we should not look to science to provide all the answers.

Written by Conor Walsh

Photography by Noemi Duroux