People's intuition about how "human genetics" works (how DNA variation is distributed around people around the world) and how it relates to "ethnicity" (the boxes people tick when asked to self identify in different societies) is really off beam.
Ethnicity, a box ticking process on surveys and gestalt assessment by other people, involves a mixture of cultural (in particular mother tongue language) and some aspects of visual human attributes, most notably skin colour but also things like facial features.
These physical attributes vary between people and much of that variation is due to variation in the genetics underlying these attributes. However the vast majority of human genetics is nowhere "near" (in a genetics sense) the genetics of skin colour and facial features
Although these physical attributes that we blend into the box ticking of our ethnicity *are* genetic, the opposite inference is not true - the boxes you tick (or the gestalt identification of someone else's ethnicity) tells you surprisingly little about your - or their - genetics
Added on top of this human population genetics is so gloriously messy in its history it really will never, ever fit into a small (or even large!) number of boxes to tick.
We are a super-young species - we exploded out of Africa only a heartbeat ago from an evolutionary perspective. We all too quickly colonised the world due to our amazing flexibility in "tool making" and "society" - passing this down through generations - "culture" + "teaching"
We are quite a remarkable and unique species because of this. Our genetics, which is standard issue mammalian genetics, looks pretty much like... a small group of apes (smaller than Chimpanzees) from quite a small part of Africa (these days not quite sure where beyond "Africa")
As we've travelled around the world we invented new things (new ways to hunt, agriculture, cheese, dogs, riding horses, writing, metallurgy...internet) and we delighted in sharing and trading these inventions with ourselves and just moving around the world. We like to explore.
Unsurprisingly for one species when we did these movements (as groups and as individuals) we ... fell in love, had sex, and had children. This means our genetics has all this glorious complexity all through our history. These histories are cruel and sad and lovely and amazing.
Using the trace in our genetics we can unpick movements that happened before written records; the historical space of archeology. It is brilliant, fun to learn about and integrate with "traditional" archeology, but the main thing to realise is that it is super messy and complex.
This never stopped, and goes on today at both population movement levels (sometimes for sad reasons, such as refugees) but far more as individuals - the big cosmopolitan cities of the world are a testament to this.
Because of all of this, ethnicity is just ... boxes people tick with some aspects linked to some very small part of people's genomes. Don't be fooled by your certainty of how you tick your box, or your agreement in gestalt assessments of others that this is a proxy for genetics.
It just... doesn't work this way. It is far cleaner to separate out the ethnicity "box ticking" process away from human genetics and consider them two entirely different things than confound them together (despite this small overlap in skin colour and facial features).
All of this to lead up when we use these boxes - indeed collections of boxes in the case "BAME" in the UK context ("Non-white" in the US context sometimes) and we find things which are different in these groups we know it cannot be mainly "due to genetics"
("European American" or "white" or "White European" is also a surprisingly to most people more genetically complex grouping of people - this is due to the complex history of humans in Europe; basically every part the world has a more complex history than most people realise).
Genetics can - and does - have strong effects on individuals from genetic disease (cystic fibrosis) to far more complex things - some complex things which are easy to measure - height - and some complex things which are complex - eg schizophrenia.
But these strong genetic effects are not well summarised by ethnicity. Separate them out in your mind. The boxes you tick and your gestalt assessment of other people are nowhere near a good representation of the DNA you or they have.
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