It is strange but verifiably true from our DNA that everyone alive has a common relative about 3,400 years ago. This makes us all cousins.
Think about it.
With everyone alive being about 100th cousins, there are some shocking things you can claim that are completely true. A few examples:
- You and I are related
- You are related to royalty
- Every war is a family feud
- If you have ever kissed someone, you are kissing a cousin
- I have a family member of every nationality
- I have a very large family that owns land on every continent
- I have a billionaire cousin and I also have a homeless cousin
- I have a family member practicing every current religion on Earth
- You are part of the bloodline that includes every US president, from John Hanson to the current one
- You are related to the Pope
- My family is multiracial
- I know a guy who thinks members of his own family are not human
- You are related to Elvis, the Beatles and Marylin Monroe
- We are both related to Martin Luther King Jr.
- You are related to Gandhi and to the Dahli Llama
- Several family members of mine claim to have walked on the moon
- Every meeting is a family get together
What other wild sounding but true claims come to mind for you based on the fact of human relativity or cousinality?
Share yours in comments.
Here is how we know we are all cousins:
… “The length of a shared DNA sequence shows how closely, or distantly, two people are related … Thus DNA sequences shared with parents are the longest, those shared with grandparents are half as long and those shared with great-grandparents half as long again and so on.
“So the longer ago an ancestor is, the shorter the chunk is likely to be.”
“Our research confirmed what Chang suspected—that everybody who was alive in Europe a thousand years ago and who had children, is an ancestor of everyone alive today who has some European ancestry,” Ralph said.
Ralph and Coop calculated that these shared segments showed ancestors stretching back some 3,000 years, or 100 generations. This lends support to Chang’s calculation that by expanding his model from living Europeans to everyone alive on Earth, an all-ancestor generation would have occurred some 3,400 years ago. 
Does this mean we came from the same two ancestors 3,400 years ago?
No. It means that of the people alive 3,400 years ago, you and I had a common ancestor in that pool of people. A third person alive today may not have that same common ancestor as both you and I, but she would have some common ancestor from that pool with each of us. That is the meaning of an all-ancestor generation.
It still makes us all cousins. Think of it this way:
“The fact that everyone has two parents means that the number of ancestors for each individual doubles every generation,” Ralph said. “By using basic mathematics, we can calculate that ten generations ago each individual had a thousand ancestors, and 20 generations ago they had a million and so on.
“But when we get to 40 generations ago, in the time of Charlemagne, we arrive at a trillion ancestors and that is a problem because we now have more ancestors than there were people. Thus one can deduce that a lot of those ancestors must be the same person.” 
The result is:
No matter the languages we speak or the color of our skin, we share ancestors who planted rice on the banks of the Yangtze, who first domesticated horses on the steppes of the Ukraine, who hunted giant sloths in the forests of North and South America, and who labored to build the Great Pyramid of Khufu. 
Perhaps you see a flaw in this conclusion, after all, we know humans migrated to the various continents 10s of thousands of years ago.
Surely isolated populations alive today must be excluded as relatives, otherwise some humans from 3,400 years ago must have gone everywhere humans are alive now?
Right, they did.
The data says all isolated populations had at least one person from the all-ancestor generation or after it reproduce in the population causing a genetic line that persisted.
How does it feel to be related to 7.5 billion people? Will you now see every poet, priest, politician, super model, dictator, neighbor, blogger, … everyone, in a new way?
This fact should unite humanity, but knowing my thick headed relatives, it may take a threat from a truly non-human intelligence to end our long and bloody history of self-loathing, to get so many estranged family members back on good terms.