We really do have ‘green’ genes
(This post updates material in Chapter 11 of Connect with Nature.) In 2013, choosing to call my blog, Our Green genes, was something of an act of faith. I was inspired to call it that by Edward O Wilson’s biophilia ‘hypothesis’ that humans are innately or genetically disposed to be interested in and attracted to nature.
As a biologist, he was deeply aware of the central part that evolution plays in adapting species, including our own, to the environments they occupy. It would be astonishing, Wilson argued, if evolution had not fashioned humans to be attracted to the natural world, as nature has been humanity’s home for the best part of 300,000 years.
Wilson derived his hypothesis from such observations as:
- people the world over seek to stay connected with nature regardless of their ethnic, racial or cultural backgrounds
- people prefer views and images of natural rather than urban scenery
- an interest in living things appears very early in life, independently, it seems, of learning
- natural creatures, objects and phenomena have the power to evoke powerful emotions, predominantly positive ones, notably pleasure, awe and wonder
- severe deprivation of nature experiences can be detrimental to health and well-being.
While compelling, this observational or ‘indirect’ evidence does not show conclusively that genes play a part in how we humans respond to nature. The evidence is consistent with that possibility. It is what you would expect if the hypothesis is valid. But the evidence does not rule out other explanations – that learning alone determines how we respond to nature, for example.
Nevertheless, I chose to ‘stick my neck out’ and write a blog based on the assumption that Wilson was correct: that we humans do have ‘green’ genes – genes that dispose us to connect mentally and emotionally with nature.
But in February 2022, a report was published of a study providing (at last) direct evidence that biophilia is genetic, in part at least. My step of faith has been vindicated: we humans do have ‘green’ genes.
The study used 1,153 pairs of adult twins, 764 pairs of identical (ID) twins, 380 pairs of non-identical (NID) twins, and 9 non-identical opposite sex twins. All the twins were UK residents, although the researchers were affiliated with universities from outside as well as within the UK.
The genes of ID twins are 100% the same, while only 50% of the genes of NID twins are shared. By comparing the nature affiliation of the two groups, the researchers were able to assess how much genes contributed to differences in nature affiliation. If there is a substantial genetic contribution, they reasoned, then ID twins should be more alike in their nature affiliation than NID ones.
This is just what the study revealed.
ID twins were significantly more alike than NID twins on four of five measures of nature affiliation:
- Preference for and openness to natural environments
- Frequency of visits to domestic (their own) gardens
- Duration of visits to domestic gardens
- Frequency of visits to public nature spaces
Their data enabled the researchers to calculate how much of nature affiliation could be attributed to genes (how ‘heritable’ it is) and how much to experience – upbringing, urbanisation of home district, encounters with nature, etc.
The heritability measures ranged from 34% for frequency of garden visits to 46% for preference and openness to natural environments and 48% for frequency of visits to public nature spaces.
I can almost hear Edward O Wilson saying: ‘These are the sort of figures I expected’. He maintained from the start that the human desire to affiliate with nature (biophilia) was influenced but not governed by our genes. The ongoing strength of that influence is subject, in fact, to life experiences and circumstances. Wilson went so far as to say that biophilia is a ‘fragile trait’. In so doing he underscored the importance of nurturing our biophilia – by having regular, frequent and rewarding contacts with nature.
The findings of the twin study reinforce that message. Yes, they indicate that biophilia has a genetic component as Wilson predicted, but they also tell us that other factors actually shape most of our affinity to nature. These factors include experiences of nature in childhood, upbringing, family, social and cultural background, education, and socio-economic circumstances.
As Professor Richard Fuller, one of the authors of the study, says: ‘This is good news, because many of these things are under our own control’.