I once read somewhere (online, forgot where) that all humans are more or less 20th cousins of eachother, less of hidden away tribes. I have never heard this again. I have read that cheetahs are all cousins pretty much because they got down to a super small population. But with humans on average oh closely related would two random people be?
I heard 50th cousins, but yours sounds closer - if you go back 20 generations (500-700 years) you have a million ancestors, and probably share a common ancestor with nearly everyone on earth. I read another stat that a native British person is related to 80% of the people alive at the time of the signing of the Magna Carta.
There are approximately 10 to 30 million SNPs (single nucleotide polymorphisms, or a difference at a single base pair in your genome), and 3 billion base pairs in the human genome. Which means if you differ from the average person in 10 million places, you are 0.33% different from them at the genetic level, ignoring any epigenetic modifications and any major deletions/insertions. If you happened to have all 30 million SNPs different from someone else (highly unlikely) you’d be 1% different at the DNA level. You also have 2 alleles, so you might actually be closer or further, maybe someone else can help out with the math.
Keep in mind the majority of these SNPs don’t affect you at all, so even if you’re 0.33% different genetically, at the RNA/protein expression level you are definitely going to be more similar. So at the cellular level I’d say you are less than a quarter of a percent different from everyone on earth. One thing I’ve learned from molecular biology is how similar we all really are.
Same thread from 2 weeks ago:
That would have to depend on your definition of “related.” In the 1200s, there hadn’t been much contact–much less interbreeding–between the British and the vast majority of Asia, so it’s unlikely your average native British person would have had Chinese blood unless you went back a hundred generations or more.
What about a Chinese and an English person having a common ancestor from somewhere in the middle? You must have heard of the Silk Road. It wouldn’t take 100 generations, all it would take is a merchant or diplomat or soldier on a distant journey fathering a child on a local woman.
Examples:
Charlemagne is known to have sent a mission to Baghdad in 799.
Alexander the Greek’s army made it to Afghanistan which is most of the way to China. Presumably some of them left children.
Brad Templeton wrote in his blog on this topic.
I heard this too – from Cecil!