Why we prefer people just like us. And why that may be dangerous.

In general, birds of a feather do tend to flock together.

Nicholas Christakis: Preferentially attaching yourself to people that you resemble or who have similar interests that you do-- for instance, a similar tolerance for heat and cold, or similar taste in foods, for example-- actually could confer a fitness advantage. So if you are following around another person who gets cold at the same temperature that you get cold, that person might build a fire. And if they build a fire, they create this positive externality. They create this benefit for you. It would be better for you to be near such a person than near a person who had a different heat tolerance than you did. Or for example, if there were different kinds of foods in the environment, some of which made you sick, being with people who resembled you in their tolerance for those foods would be advantageous, because they would go to an environment where they could eat the food and so could you eat the food.

So hanging out with people you resemble is a kind of a way of probing your match with the environment. If you preferentially attach to people that you resemble, you will therefore be more likely to be in an environment which is good for you. Another idea has to do with a kind of multiplicative advantages of certain kinds of genotypes. What do I mean by that? Well, imagine a kind of toy idea, a kind of toy model, in which you are the first person on the planet to evolve the capacity for speech.

There's a big debate right now about a particular gene called FOXP2. Some people think it plays a role in our evolution or speech, some don't, but imagine that it does, for the sake of argument. Imagine you are the first person on the planet to have a mutation in this gene which confers on you the capacity for speech. This mutation would be useless to you unless you were connected to someone you could talk to. It would be a little bit like being the first person on the planet to get an email address. The email address is useless to you unless you have someone to email. Then, all of a sudden, it becomes very advantageous.

So this example, too, is an example of why we might have evolved the capacity or the interest in preferentially hanging out with people that we resemble. And there are a number of advantages and disadvantages to this tendency once it arises. The advantages include some of the things we've already talked about, but they also include the ability of a group of people of shared abilities and interests to bond and work together to achieve common objectives. So for example, if I can hang out with people I resemble who have similar tastes and abilities that I do, I kind of know on what to count on. You know, if we're going out to hunt big game and we all can run at the same speed, I kind of know that this group can move at this pace, for instance.

But there are disadvantages as well, because once you form a group of people who all resemble each other, you have no heterogeneity in skills. Maybe what you really need is a group where one person can see far and can spot the prey, and another person is strong and can spear the prey. Or maybe you want heterogeneity of information. When you have groups that are all very similar to each other, when groups form, you get a kind of redundancy of information and no novelty. Everyone is like, do you know where the prey item is? Do you know where the prey item is? Everyone has the same information. But you would rather have a group of people with different knowledge and different skills, who might be able to work together to achieve common objectives.

So natural selection across our evolution has taken account of these advantages and has shaped us to in general prefer homophily. But we don't always prefer homophily. There's this notion of 'birds of a feather flock togehter'. But we also have in our language this notion of opposites attract. So we are also equipped with the capacity to define the borders of our group. And one of the ways to push back against tribalism is to step up from the tribalism and to broaden the focus of our concern, to redefine the group as being even bigger.

And if you think about this politically in the United States, for example, one of the kind of political agendas in our country since its founding, with respect to the American project, has been to believe and claim-- I think rightly so-- that anyone can be an American. The focus of our tribalism becomes our shared Americanism. So you can step up from individual groups and sort of be united by our common humanity-- or in this case our common nationality-- and broaden the focus. But in addition we have this other ability. We have this ability to step down and look at the level of individuals. In that we have the capacity to express and detect individual identity. We do this with our faces.

Every human knows that they can look at 1,000 faces and tell one person from the other. We signal our individuality with our faces. Our faces have evolved to be incredibly different-- unlike our hands, for example. You can't tell your friends apart by looking at their hands. But you can tell them instantly apart by looking at their faces. And the fact that we can do this, the fact that we can see individuals as unique, is very important if you are, for instance, a baby and you want to communicate to your mother or your father, this is me, not someone else, care for me. Or if you want to support cooperation-- you want the ability to remember who is nice to you and who is not nice to you.

The capacity for signaling and detecting individual identity is crucial for maintaining cooperation in social systems. Same for friendship. It's crucial. To tell your friends apart or to tell friends from strangers, you need to be able to signal individual identity. So individual identity exists in our group, in our species, it plays a role in all of these things I'm discussing, and it gives us another way of counteracting tribalism. Because now, instead of stepping up a level To redefine the groups to be bigger, we can also step down a level And now look at individuals not as members of groups but as unique human beings. So we don't need to rely on this heuristic. We don't need to rely on this sort of convenient tool of saying, who should I befriend? Oh, I should befriend Or people who are members of my own group. We can either say, I'm open to befriending anybody, or we can say, I'm going to assess each person as a unique human being when deciding whether to hang out with them or not.

  • It's common for people to form groups of like minded individuals who also have similar abilities.
  • Evolution confers advantages on heterogeneous groups of people and groups with diverse talent sets.
  • Prizing individual identity ahead of group identity also helps counteract tribalistic politics.


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Meet Dr. Jennifer Doudna: she's leading the biotech revolution

She helped create CRISPR, a gene-editing technology that is changing the way we treat genetic diseases and even how we produce food.

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Technology & Innovation

This article was originally published on our sister site, Freethink.

Last year, Jennifer Doudna and Emmanuelle Charpentier became the first all-woman team to win the Nobel Prize in Chemistry for their work developing CRISPR-Cas9, the gene-editing technology. The technology was invented in 2012 — and nine years later, it's truly revolutionizing how we treat genetic diseases and even how we produce food.

CRISPR allows scientists to alter DNA by using proteins that are naturally found in bacteria. They use these proteins, called Cas9, to naturally fend off viruses, destroying the virus' DNA and cutting it out of their genes. CRISPR allows scientists to co-opt this function, redirecting the proteins toward disease-causing mutations in our DNA.

So far, gene-editing technology is showing promise in treating sickle cell disease and genetic blindness — and it could eventually be used to treat all sorts of genetic diseases, from cancer to Huntington's Disease.

The biotech revolution is just getting started — and CRISPR is leading the charge. We talked with Doudna about what we can expect from genetic engineering in the future.

This interview has been lightly edited and condensed for clarity.

Freethink: You've said that your journey to becoming a scientist had humble beginnings — in your teenage bedroom when you discovered The Double Helix by Jim Watson. Back then, there weren't a lot of women scientists — what was your breakthrough moment in realizing you could pursue this as a career?

Dr. Jennifer Doudna: There is a moment that I often think back to from high school in Hilo, Hawaii, when I first heard the word "biochemistry." A researcher from the UH Cancer Center on Oahu came and gave a talk on her work studying cancer cells.

I didn't understand much of her talk, but it still made a huge impact on me. You didn't see professional women scientists in popular culture at the time, and it really opened my eyes to new possibilities. She was very impressive.

I remember thinking right then that I wanted to do what she does, and that's what set me off on the journey that became my career in science.

Freethink: The term "CRISPR" is everywhere in the media these days but it's a really complicated tool to describe. What is the one thing that you wish people understood about CRISPR that they usually get wrong?

Dr. Jennifer Doudna: People should know that CRISPR technology has revolutionized scientific research and will make a positive difference to their lives.

Researchers are gaining incredible new understanding of the nature of disease, evolution, and are developing CRISPR-based strategies to tackle our greatest health, food, and sustainability challenges.

Freethink: You previously wrote in Wired that this year, 2021, is going to be a big year for CRISPR. What exciting new developments should we be on the lookout for?

Dr. Jennifer Doudna: Before the COVID-19 pandemic, there were multiple teams around the world, including my lab and colleagues at the Innovative Genomics Institute, working on developing CRISPR-based diagnostics.

Traits that we could select for using traditional breeding methods, that might take decades, we can now engineer precisely in a much shorter time. — DR. JENNIFER DOUDNA

When the pandemic hit, we pivoted our work to focus these tools on SARS-CoV-2. The benefit of these new diagnostics is that they're fast, cheap, can be done anywhere without the need for a lab, and they can be quickly modified to detect different pathogens. I'm excited about the future of diagnostics, and not just for pandemics.

We'll also be seeing more CRISPR applications in agriculture to help combat hunger, reduce the need for toxic pesticides and fertilizers, fight plant diseases and help crops adapt to a changing climate.

Traits that we could select for using traditional breeding methods, that might take decades, we can now engineer precisely in a much shorter time.

Freethink: Curing genetic diseases isn't a pipedream anymore, but there are still some hurdles to cross before we're able to say for certain that we can do this. What are those hurdles and how close do you think we are to crossing them?

Dr. Jennifer Doudna: There are people today, like Victoria Gray, who have been successfully treated for sickle cell disease. This is just the tip of the iceberg.

There are absolutely still many hurdles. We don't currently have ways to deliver genome-editing enzymes to all types of tissues, but delivery is a hot area of research for this very reason.

We also need to continue improving on the first wave of CRISPR therapies, as well as making them more affordable and accessible.

Freethink: Another big challenge is making this technology widely available to everyone and not just the really wealthy. You've previously said that this challenge starts with the scientists.

Dr. Jennifer Doudna: A sickle cell disease cure that is 100 percent effective but can't be accessed by most of the people in need is not really a full cure.

This is one of the insights that led me to found the Innovative Genomics Institute back in 2014. It's not enough to develop a therapy, prove that it works, and move on. You have to develop a therapy that actually meets the real-world need.

Too often, scientists don't fully incorporate issues of equity and accessibility into their research, and the incentives of the pharmaceutical industry tend to run in the opposite direction. If the world needs affordable therapy, you have to work toward that goal from the beginning.

Freethink: You've expressed some concern about the ethics of using CRISPR. Do you think there is a meaningful difference between enhancing human abilities — for example, using gene therapy to become stronger or more intelligent — versus correcting deficiencies, like Type 1 diabetes or Huntington's?

Dr. Jennifer Doudna: There is a meaningful distinction between enhancement and treatment, but that doesn't mean that the line is always clear. It isn't.

There's always a gray area when it comes to complex ethical issues like this, and our thinking on this is undoubtedly going to evolve over time.

What we need is to find an appropriate balance between preventing misuse and promoting beneficial innovation.

Freethink: What if it turns out that being physically stronger helps you live a longer life — if that's the case, are there some ways of improving health that we should simply rule out?

Dr. Jennifer Doudna: The concept of improving the "healthspan" of individuals is an area of considerable interest. Eliminating neurodegenerative disease will not only massively reduce suffering around the world, but it will also meaningfully increase the healthy years for millions of individuals.

There is a meaningful distinction between enhancement and treatment, but that doesn't mean that the line is always clear. It isn't. — DR. JENNIFER DOUDNA

There will also be knock-on effects, such as increased economic output, but also increased impact on the planet.

When you think about increasing lifespans just so certain people can live longer, then not only do those knock-on effects become more central, you also have to ask who is benefiting and who isn't? Is it possible to develop this technology so the benefits are shared equitably? Is it environmentally sustainable to go down this road?

Freethink: Where do you see it going from here?

Dr. Jennifer Doudna: The bio revolution will allow us to create breakthroughs in treating not just a few but whole classes of previously unaddressed genetic diseases.

We're also likely to see genome editing play a role not just in climate adaptation, but in climate change solutions as well. There will be challenges along the way both expected and unexpected, but also great leaps in progress and benefits that will move society forward. It's an exciting time to be a scientist.

Freethink: If you had to guess, what is the first disease you think we are most likely to cure, in the real world, with CRISPR?

Dr. Jennifer Doudna: Because of the progress that has already been made, sickle cell disease and beta-thalassemia are likely to be the first diseases with a CRISPR cure, but we're closely following the developments of other CRISPR clinical trials for types of cancer, a form of congenital blindness, chronic infection, and some rare genetic disorders.

The pace of clinical trials is picking up, and the list will be longer next year.

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