Many visible characteristics (skin colour, eye shape etc) of humans is largely genetic. Some - like clothing, makeup, jewelery is very much not genetic. Just to say, despite the confident self assignment of people into race/ethnicity groups, it is actually impossible to have hard criteria for this.
For genetics every generation shuffles and halves the genome information they pass on (our chromosomes - how are DNA is stored - come in pairs; in our eggs or sperm we shuffle the genome between the pair on each chromosome and hand over half to our children).
Each generation back you double the number of ancestors, 2, 4, 8, 16, 32 etc - meaning very quickly you have *alot* of ancestors. Because of the halving not every bit of DNA in the ancestors makes it the next generation.
Go far enough back (~7 generations) you will have ancestors which did not contribute DNA to you (but might have to your sister or brother or cousin).
The next thing to realise is that humans are (a) a very young species (we're crazy young) and (b) some of us have big wanderlust - as individuals and as groups. Sometimes the travelling is also forced on people (the most horrific being the transatlantic slave trade).
There are two things going on in human populations - many people stay relatively close to where they are born, and many people move. Because of those movements we mix *all the time* - in pre-history (we can see this in DNA), in ancient history and now.
This mixing proportion means that the small part of the genome behind visible characterisitics - skin colour, eye shape - moves around, and these visible characterisitics, although genetically determined is ... a very small part of the genome.
Because someone has black skin means there are about ~30 places on the genome where you could have a good guess of their genome (though skin colour is surprisingly complex genetics at these 30 places) but it doesn't mean you can easily predict other places in their genome
There are (crudely - it is rather more complex than this) 300,000 different parts of the genome to be shuffled - like a deck of cards with 300,000 numbers/picture cards (1 to 300,000 if you like) and each card comes in 2 to (top end) 100 different suits
Everyone gets delt (via their parents) one card of each number (1 to 300,000) from each parent - your "genetic hand" are these cards twice - one from dad, one from mum. For this thought experiment, let's imagine the cards come in 4 suits (though this is not how it works in real life)
So I might have a 1 of hearts and 1 of clubs at the start of chromosome 1, and then for the next position, the "2", perhaps I got a 2 of diamonds from both parents, and then the 3 I got a diamond and a club ... etc for 300,000 (split into 23 chromosomes, with special rules on sex chromosomes)
There is no real reason for ppl to look at themselves back so far. Unless for health, physical/or emotional, there is no logical or spiritual need to go so far back. I don’t get it. No health benefit, the social context so vastly different then, that it’s useless to us now except as awareness. Why?