When it comes to political debate, few topics stir passionate rhetoric more than immigration. Recently on these pages, Prof William Reville highlighted a facet of this long-running discourse, arguing that the higher birth rate of immigrants might be a cause for concern. In his piece, Reville called for "vibrant public debate" and in that spirit I'm compelled to argue precisely the opposite position to his.
It is undoubtedly true that European birth rates have fallen, and certainly birth rates below replacement level have implications for future stability. Yet such decreases aren't surprising – high female literacy is associated with lower birth rates and greater contraceptive use. Higher female educational attainment decreases the number of children a woman is likely to bear, defined as the total fertility rate (TFR). This effect is stark – in Ghana, women with second-level education have a TFR of two-three, whereas TFR for those without education is six. The impact of education is hard to overstate; a study in Nigeria found increasing female education by just one year reduced TFR substantially.
Concerns that immigrant populations will overrun indigenous culture is not new – this fear was voiced in 1860s America, where the higher birth rate of the influx of immigrants (the Irish chief among them) raised concerns that foreigners would rapidly outbreed those already settled. Yet this alarm was ill-founded because by the second generation immigrant birth rate had already dropped substantially, trending towards the norm. This isn’t surprising, as socioeconomic and educational factors have far more bearing on reproductive rates than any intrinsic virility. Indeed, we need only consider the evolution of Irish family size over the last century to observe this.
Sadly, misguided fears haven't subsided over centuries, as evidenced by the anti-immigrant sentiment that underpinned both Donald Trump's election and the Brexit referendum. There's a clear irony in white Americans of the 1800s being concerned about immigrants, and interestingly sources from the period attest the Irish were considered a distinct race, a notion we'd consider daft today. But this curious demarcation prompts a question – what do we mean by race? While a socially loaded term, it's not scientifically meaningful. The entirety of human life is one species – Homo sapiens. The Human Genome project has confirmed that genetically, humans differ minimally, articulated by Prof Micheal Yudell's observation that "genetic methods do not support the classification of humans into discrete races".
The essentialist mindset that there is some genetic or intrinsic trait that defines an ethnic group or culture has no scientific basis. Indeed, there is abundant evidence that variation within ethnic groups far outstrips those between groups. Genetic characteristics might be associated with certain populations but these characteristics are not in any way exclusive to it. The lines of demarcation are entirely arbitrary – from a scientific perspective, “race” is so nebulous a term as to be useless.
Even if we were to try and find essential traits that define some culture, it would be a Sisyphean task. Even white skin is a relatively recent mutation – dark skin was the norm across central Europe for most of prehistory, with white skin confined to the northern-most part of the continent. The first farmers from the Near East carried genes for both light and dark skin. They reproduced with local hunter-gatherers, and it was only 5,800 years ago that the depigmentation gene variant known as SLC24A5, once rare, exploded in frequency across the continent. Far from being an essentialist trait, the emergence of white skin as a common phenotype required the sustained interbreeding of many cultures. Incidentally, this, of course, makes the spectacle of white supremacists touting racial purity as deluded as it is disgusting.
Even with the minimal genetic variation across humans, increased genetic diversity maximises our collective fitness. Without this modicum of external influence, the alternative is sustained inbreeding and deleterious recessive traits. Cystic fibrosis is an example, passed on if both parents carry a mutated gene copy. In Ireland's island population, this gene mutation is carried by one in 19 people, resulting in Ireland having the world's highest rate of cystic fibrosis. Exclusive in-group breeding can only be circumvented by population diversity.
The reality is that there is precious little difference between us, and no need to fear being bred out of existence, or loss of our culture. The notion of hard divisions between groups is largely fictitious, and acting on this misguided belief has had hateful consequences. We have always been a curious, promiscuous species – a trait that stands to our success.
David Robert Grimes is a physicist, cancer researcher and science writer