The New Science Of Why Men & Women Cheat - Macken Murphy - #825

**Chris Williamson** (0:00)
What's happening people? Welcome back to the show. My guest today is Macken Murphy. He's an evolutionary biologist at the University of Melbourne, a writer and a podcaster. Why do people cheat? Is it just the allure of novelty, dissatisfaction in their current relationship, fear of being left, retaliation for their partner cheating? Macken's brand new study gives so many fascinating answers to all of these questions. Expect to learn what the evolutionary drivers behind men's and women's infidelity are, what this new science says about the dual mating and mate-switching hypotheses, the top three reasons why women and men both cheat, whether cheating is heritable, if there is such a thing as one and done cheating, the most common behaviors of someone who is being unfaithful and much more. This episode is brought to you by 8 Sleep. I am currently dying in Austin because it's too hot all the time and I'm being kept alive by my 8 Sleep pod cover. It actively cools and heats each different side of the bed, so if you sleep hot or if you sleep cold, this fixes the problem. It is an absolute game changer. If you find yourself waking up in the middle of the night or feeling extra groggy in the morning, temperature is almost always to blame. Also, it tracks your sleep, tells you how long you've been asleep. It gives you advice about how to get to sleep better. It'll even adjust the temperature of your bed as your sleep stages change throughout the night. On top of all of that, there is a 90 day money back guarantee so you can buy it and sleep on it for 89 days. And if you do not like it, they will give you your money back. Head to 8sleep.com/modernwisdom to save $150 or 150 pounds on the pod cover. That's the best offer that you will find, but you must go to eightsleep.com/modernwisdom. This episode is brought to you by Manscaped. It is the best ball and body hair trimmer ever created. It's got a cutting edge ceramic blade which reduce grooming accidents, a 90-minute battery so that you can take a longer shave, waterproof technology which allows you to groom in the shower, and an LED light which illuminates grooming areas for a closer and more precise trim or if you're just a particularly crevice-y human. They've also got a 7,000 RPM motor with quiet stroke technology and a wireless charging system that helps the battery to last even longer. So if you or the man in your life is hairier than you would like them to be, this is a fantastic gift to get yourself or someone else. Head to manscaped.com/modernwisdom and use the code modern wisdom at checkout for 20% off plus free shipping worldwide. That's manscaped.com/modernwisdom and modern wisdom at checkout. This episode is brought to you by Shopify. Shopify is the global commerce platform that helps you sell at every stage of your business. From the launch your online shop stage to the first real life store stage, all the way to the did we just hit a million orders stage, Shopify is there to help you grow. Whether you're selling scented soap or offering outdoor outfits, Shopify helps you sell everywhere. From that all-in-one e-commerce platform to their in-person POS system, wherever and whatever you're selling, Shopify has got you covered. Shopify helps you turn browsers into buyers with the internet's best converting checkout. 36% better on average compared to other leading commerce platforms. You would be amazed at how many massive brands you love use Shopify. Gymshark, perhaps one of the biggest independent sportswear companies in the world uses Shopify. And if it is good enough for them, it is good enough for you. So if you are looking to get started at selling something online, Shopify is the easiest, quickest and most convenient way to do it. Plus, you can sign up for a $1 per month trial period at shopify.com/modernwisdom, all lowercase, that's shopify.com/modernwisdom, to grow your business no matter what stage you're in. But now, ladies and gentlemen, please welcome Macken Murphy.
You have caused some drama in the world of evolutionary psychology.

**Macken Murphy** (4:13)
A little bit of drama. I try not to get in trouble, but certainly this last publication might be a little controversial within the field, sure.

**Chris Williamson** (4:21)
What have you done? What's the current state of the leading infidelity hypotheses?

**Macken Murphy** (4:28)
Well, I mean, I guess we've got time to get into it, but it is a bit of a long story. So I would say that the background to know for someone who's just completely entry level here and has not heard about the evo-infidelity debate is that there's been a long running debate as to the evolutionary drivers of women's infidelity, female infidelity in humans. During the late 90s and the early 2000s, and to an extent, the 2010s as well, I would say that most evolutionary psychologists would have said that the primary driver of women's infidelity from an evolutionary perspective is the powerful benefit of being able to obtain better genes, right? Better in a fitness sense, obviously not in a moral sense. We might end up saying the phrase good genes quite a bit on this show, and every time it's always good in a fitness sense. But in any case, the mainstream idea was that infidelity is a conditional strategy that women sometimes employ in order to obtain better genes for their offspring, right? So to pair the genetic benefits of one male with the parental investment benefits of another male. So everyone, when we're looking for mates, there are two things that they can give our offspring. They can give our offspring genes, obviously, or they can give our offspring investment. And normally, women get genes and investment from the same person. But the idea was is that women's infidelity allows them to get genes from one person and parenting from another. Let's say if they're with a mate who is very high investment, right? They love them, they've got lots of resources, but they don't necessarily have the heritable traits that a woman might want to pass on. So that was the mainstream idea for a very long time, almost 20 years. And then in the late 2010s, there was a bit of a reckoning, right? Which stemmed from the facts that during the 2010s, the original suite of experiments that were used to evidence this idea, which from here on, we'll call the dual mating hypothesis. In this case, I mean, there's a few ways to use that term. I'm using it to describe that specific strategy.