# Can Two People in the World be Identical?

There are a lot of people who live in this world; 6,987,000,000 to be exact (as of 2011).  Seven billion is a huge, huge number, and I was wondering if two people out of that seven billion could be genetically identical.  I understand that not every single person has a doppelgänger, but I want to know if there is just a single pair of people who are identical.  With 7 billion people, I think there has to be at least one pair.  This is a very interesting topic to me, because I really wonder if there is another me walking around planet Earth.  Throughout my blog, I will determine if there has ever been two identical people, and if it is even genetically possible for that to happen.

There is a common saying that there are seven people on planet Earth that look exactly like you.  This, I find very hard to believe.  I’m sure there are several people who resemble me, but to say there are seven who look exactly like me is just blasphemous.  Each human being is separated by 6.4 million base pairs.  This means that the chance that two people are genetically identical is 1/(2^6,400,000), such a small number that it is essentially zero.  Think about it this way: the chance of two people being genetically identical is the same chance of getting heads 6.4 million straight tosses of a fair coin.

Another researcher talks about how it is very possible for two strangers to look practically identical.  A team of friends started the Twin Strangers Project, which is a mission to find two strangers who look identical in appearance.  Throughout this project, the group of friends found some extremely similar looking people (pictured below).  Human’s share 99.5 percent of the same DNA, so the only thing that separates human beings is .5 percent, which still makes up for many million different base pairs of DNA.  It is a known fact that you are more likely to look more similar to a relative than to a complete stranger.  Of the .5 percent of DNA where humans defer, identical twins share nearly all of that.  Siblings share half of that 5 percent, meaning they defer by only .25 percent of their DNA.  Cousins share some of that .5 percent, but not nearly as much as siblings.  Arthur Beaded, a geneticist for the University of Baylor, says that people who live in the same region or area are more likely to look the same than people who live further away from each other.  The reason behind this is because people who live closer to each other are more likely to be distant relatives, and we know that relatives are more likely to look the same than strangers.  Dr. Beaded believes that there is a good chance that we have seven people who look exactly like us, and possibly more if we live in a highly populated area.

Twins are a very interesting subject.  Identical twins are thought of by people as being literally identical, but this is not the case.  For the longest time, people believed that the only thing that made identical twins different was environmental conditions, but this theory has recently been challenged.  One main component that scientists have used to determine that identical twins could indeed be genetically different is genetic diseases.  Schizophrenia is a disease that is passed through by genetics.  If one twin had Schizophrenia, and twins shared the same DNA, it would mean that the other would have to have it as well.  This is not the case.  It is very common for one twin to have a genetic disease while the other does not.  19 identical twins were studied, and in every case, one twin’s DNA was different than the others at a specific point of the genome.

Yes, it is very likely that two human can look very similar, possibly even identical, but they will never be genetically identical.  The odds of this happening are so as close to zero as you can get.  Yes, it is possible for two humans to be genetically identical, but so slim that our world may never see.

## 3 thoughts on “Can Two People in the World be Identical?”

1. Alexandra Kaminsky

I really like this post because I have always thought so many people look identical to others. I’m curious as to how this can happen though. Studies on ancestors would provide good proof of this topic because we would be able to look for variables to measure when it comes to the two people and their ancestors.

2. Lucille Laubenstein

Going along with what you said about the seven people around the world who look similar to one another notion, do you think that there is some distant common ancestors shared between all of those people? The source you provided from Women’s Health Magazine said that they shared 99.5% of DNA, is there another blood test which could have determined common ancestry, or would it be too minuscule to even detect? I was not able to find any such test, the only ones I found were blood testing for ancestral ethnicity.

3. Katherine Yuen

Hi Matthew! Your post got me thinking about what the science is behind having twins. I found this article about the genetics behind having twins, both identical and fraternal. Apparently the best way to know that you have good chances of having fraternal twin girls is simply to have a mom, aunt, or grandmother who is a fraternal twin!