What we can learn from the clones that walk among us

Genetically speaking, identical twins ought to be two copies of the same person. Environmentally speaking, if the twins grow up together, they ought to even be influenced by the same things. But if you actually pay attention to identical twins, they aren't identical in personality or interests. How do naturally occurring clones become individual people? That's the subject of a mouse study that Scicurious writes about on her blog. Fascinating stuff.


  1. Perhaps I’m seeing the study in a different way, but the entire article seems to be looking for reasons to say that the differences are non-environmental. The assumption that  she makes in the beginning (That “Identical twins reared together” is the same as “Identical environment”) seems a bit off to me- The sum total of the environmental experiences can vary right from the womb, before the individual exists. 
    And what the mouse study seems to show is that in the same setting, two individuals can experience very different environments.

    But, perhaps it’s a perception thing- What I’m seeing as emergent behaviour creating different environments in the same setting may be interpreted as something else entirely, something that doesn’t need to have the unfashionable tag “environment” attached to it.

  2. It gets a lot more freaky when you look at twins raised separately (not knowing about each other). They can wind up with identical careers, and married to women with the same first name, etc. Very odd.

    1. That may just be due to the fact  in a country of 300 million people there are bound to be a few such cases, though I don’t doubt that identical genotypes might play some role here.

  3. They’re not always identical physically.  I had a twin roommate in SF, and he and his identical twin had obviously different hair textures, despite otherwise looking alike.

    1. Identical twins may have the same genome, but some genes may be expressed at different times due to environment. It’s not an area that’s well understood yet, but as it turns out, actual clones are usually very different from their original, for this reason, and often not very healthy.

      It’s a good argument against human cloning: if Dolly the sheep #147 has a defective heart, scientists can just destroy her. Not so simple if she was human.

    2. My identical twin sister and I look very similar but also very different… The closer to 20 and beyond we got, the less alike we looked.  As kids, though, you couldn’t tell us apart.

  4. Well so… the 40 mice all had different exploration-patterns in the cage. It’s not as if, they’d be able to have identical exploration patterns anyway. Big whoop.

    I’d be more interested in the study looking at exploration patterns of 40 identical mice with 40 identical enriched environments. Manipulation of similarity between the individual elements in the cages might be a way of determening how identical these identical mice actually are.

  5. Seriously? You’re asking how people are different beyond physiological explanations?

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