You can have genetically identical siblings. They have the same genome. They lay right next to each other in the womb. They're born, and at the moment they're born, they're already different. Before any experience has accrued at all. Why shouldn't they be just the same?

This question and more are discussed in today’s episode on individuality, variability, heritability and epigenetics. 

Our guest is David Linden. He is a professor of neuroscience at Johns Hopkins University. He is also at the Kavli Neuroscience Discovery Institute. His most recent book is Unique: The New Science of Human Individuality.

Episode Quotes:

On Variability:

“The other thing that's important to realize is sometimes it's a lot easier to kind of break a process than it is to make a process function to a greater degree.”

On memory:

A lot of our memory has to do with things that we can't recall. Like when you practice a sport and you get better at it. You can recall maybe your tennis lessons, but you don't really recall how to hit the ball better. It is a subconscious experience. Likewise, you may have been traumatized as a child by an aggressive dog. And now as an adult, every time you see a dog, your heart races. And it's not like you necessarily remember the experience as a child, but that reaction, that association, that fear learning is there at a subconscious level. All these things form us as individuals.

On OkCupid traits and preferences:

If you really like to eat lutefisk, that probably came because you grew up liking it because there's just about no other way to like it. It doesn't seem to be genetic related and it doesn't seem to have to do with what taste or smell receptor variants you have. It’s something that's socially encoded in your experience. Likewise, if you were to say, well, I've always been an early bird all my life. Well, that is heavily genetically infected. That's a highly heritable trait and we know a lot about the genes that contribute to people who like to rise earlier or rise late.

On food preference:

Generally speaking, food preference has some heritable things that we can trace mostly to your odorant receptors and a few of them to your taste receptors. But most of it is socially determined. You go to Thailand, it's pretty hard to find someone who doesn't like chili peppers. Whereas, if you're walking around Baltimore, you'll find plenty of people that don't like chili peppers.

Show Links:

Guest Profile:

• Faculty Profile at John Hopkins School of Medicine
• Professional Profile at Kavli Neuroscience Discovery Institute
• David Linden’s Website
• David Linden on Twitter
• David Linden on TEDXUNC

His work:

• David Linden on Google Scholar
• Unique: The New Science of Human Individuality Kindle Edition
• The Accidental Mind: How Brain Evolution Has Given Us Love, Memory, Dreams, and God
• The Compass of Pleasure: How Our Brains Make Fatty Foods, Orgasm, Exercise, Marijuana, Generosity, Vodka, Learning, and Gambling Feel So Good
• Touch: The Science of the Hand, Heart, and Mind