David Raichlen is a professor of biological sciences at the University of Southern California whose research examines how human evolution, physical activity, and brain health are linked across the lifespan. In this conversation, Zoë and Brendan talk with David about what's actually happening in your brain when you go from couch to consistently active, why exercise might be the closest thing we have to a dementia preventative, and why his research on the runner's high, which famously involved humans, dogs, and ferrets, suggests it evolved as something more useful than feeling good.

They also get into what hunter-gatherers like the Hadza can (and can't) tell us about how to live, why "more is better" hits diminishing returns at the high end, the trouble with paleo prescriptions, and whether sitting really is the new smoking. Plus: Brendan tries to figure out if his rock-climbing mom or his golfing dad is doing better cognitive work than he is.

This episode is brought to you by Running Warehouse, the one-stop shop for all things trail running, with gear guides and expert resources to help you figure out what actually works for you. Use code TRAILHEAD for free two-day shipping on orders over $50.

Our featured race is the Sonoma Fall Classic, the inaugural fall festival in the heart of California wine country featuring a 100-miler, the original Lake Sonoma 50 returning to its 2008 point-to-point roots from South Lake Trailhead, a trail marathon, and four-person relays. Sixteen miles of buttery single track, sweeping lake views, swimmable water crossings, and free on-site camping. Registration closes Monday, October 12. Sign up at UltraSignup.com.

The Trailhead is part of the UltraSignup Podcast Network.