Your ancestors mastered circadian rhythms for millennia without blue light glasses or $300 sleep trackers—here's how to tap into that same biological wisdom. # Picture this: It's 50,000 BC. Your great-great-great (add about 2,000 more "greats") grandmother is living her best cave life. No ring light for her morning selfies, no blackout curtains imported from Sweden, and definitely no app tracking her REM cycles. Yet somehow, she slept like a baby mammoth and woke up refreshed enough to outrun saber-toothed tigers. Meanwhile, you're over here with a bedroom that looks like a NASA control center, spending more on sleep optimization gadgets than most people spend on rent, and you still wake up feeling like you've been hit by a woolly rhinoceros. What gives? Did evolution somehow forget to program us for good sleep in the modern era? Or have we just gotten really, really good at ignoring the biological operating system we've been running on for millions of years? sleep

# Spoiler alert: It's the latter. And today, we're going to hack that system using nothing but the free resources your ancestors relied on—light, temperature, timing, and a healthy dose of common sense. # The $0 Circadian Reset: A Day in the Life of Perfect Sleep ## 6:00 AM - The Dawn Patrol: Light Hacking 101 What the Gadgets Promise: Blue light blocking glasses, sunrise alarm clocks, and light therapy boxes that cost more than your first car. What Your Ancestors Did: Went outside. Revolutionary stuff, really. ## The Science: Natural sunlight is especially powerful. In addition to being magnitudes brighter than indoor light, retinal nerves can detect the time of day based on the ratio of blue to yellow light. Research shows that light in the morning (about 1 hour before and after usual wake-up time) can shift the circadian system about 1 hour earlier per day. ### Your Free Biohack: The "Caveman Sunrise Protocol" 1. Within 30 minutes of waking, get outside for 10-15 minutes 2. Face east (where the sun is, genius) without sunglasses 3. If it's cloudy, stay out longer—clouds reduce light intensity but don't eliminate it 4. If you live in a dungeon (aka a windowless apartment), at least open your blinds and stand by the brightest window ### Pro Tip: Can't get outside? Stand by an open window with no glass between you and the morning light. Glass filters out some of the beneficial wavelengths your brain needs to kickstart its daily rhythm. The Results: Office workers got more bright morning light for 5 days. They found it easier to make decisions and scored 79% higher on cognitive tests. Not bad for something that costs absolutely nothing. ## 8:00 AM - 12:00 PM: The Productivity Plateau What the Gadgets Promise: Standing desks, light therapy panels, and productivity apps that track your every keystroke. What Your Ancestors Did: Worked outside or near windows, took advantage of natural energy rhythms. The Science: In the morning and until the midafternoon, use bright overhead lights to facilitate the release of dopamine, norepinephrine, epinephrine (molecules associated with motivation, attention and drive) and optimal amounts of cortisol to maximize your alertness and focus. ### Your Free Biohack: The "Hunter-Gatherer Workday" 1. Position your workspace near the brightest available light source 2. Take "light breaks" every 2 hours—step outside or near a window for 5 minutes 3. Use the natural energy peak for your most challenging tasks 4. If you're stuck under fluorescent lights (my condolences), supplement with brief outdoor walks ## Troubleshooting: If you work night shifts, you'll need to reverse this protocol. Use bright lights during your "day" (night shift) and darkness during your "night" (actual day). Your circadian system doesn't care about society's schedule—it cares about consistent light/dark cycles. ## 12:00 PM - 2:00 PM: The Afternoon Dip (And Why Fighting It Is Futile) What the Gadgets Promise: Caffeine timing apps, power nap optimization devices, and energy drinks that taste like regret. What Your Ancestors Did: Had a siesta. Not because they were lazy, but because they understood biology. The Science: The post-lunch dip isn't caused by lunch—it's a natural circadian rhythm that occurs regardless of meal timing. Fighting it is like trying to stop your heart from beating: technically possible, but not advisable. ### Your Free Biohack: The "Strategic Surrender" 1. If possible, take a 10-20 minute power nap between 1-3 PM 2. Keep it short—longer naps will mess with nighttime sleep 3. If napping isn't possible, do low-energy tasks during this window 4. Avoid caffeine after 2 PM (your future self will thank you) The Genius Move: Schedule boring tasks (like answering emails or organizing files) during your natural energy dip. Save creative or complex work for your peak hours. ## 3:00 PM - 6:00 PM: The Second Wind What the Gadgets Promise: More caffeine, energy supplements, and productivity hacks. What Your Ancestors Did: Took advantage of the natural energy uptick for gathering, socializing, and preparing for evening. ### Your Free Biohack: The "Afternoon Renaissance" 1. This is your second peak energy window—use it wisely 2. Schedule physical activity during this time if possible 3. Handle challenging conversations or decisions while your brain is sharp 4. Begin winding down activities after 6 PM to prepare for sleep ## 6:00 PM - 8:00 PM: The Temperature Surfing Hour What the Gadgets Promise: Smart thermostats, cooling mattresses, and temperature-controlled pajamas that cost more than most people's wedding dresses. What Your Ancestors Did: Worked with natural temperature changes instead of against them. The Science: When our core and brain temperatures are in rapid decline we are most likely to choose to sleep, and if we dissociate from this cycle of body cooling we experience insomnia. Research shows that the thermal environment is one of the most important factors that can affect human sleep. ### Your Free Biohack: "Temperature Surfing" 1. Take a warm shower or bath 1-2 hours before bedtime 2. The warm water raises your core temperature temporarily 3. When you get out, your body temperature drops rapidly, triggering sleepiness 4. Keep your bedroom cool (65-68°F if possible) 5. Wear minimal clothing to bed to help heat dissipation The Counterintuitive Truth: Warming up helps you cool down faster. It's like metabolic jiu-jitsu. ## 8:00 PM - 10:00 PM: The Digital Sunset What the Gadgets Promise: Blue light blocking glasses, special light bulbs, and apps that filter your screens. What Your Ancestors Did: When the sun went down, so did the light. Wild concept, I know. The Science: Light in the evening (about 2 hours before and after usual bedtime) can shift the circadian system about 2 hours later per day. Even small amounts of light can suppress melatonin production and delay sleep onset. sleep

### Your Free Biohack: "The Caveman Evening Protocol" 1. Dim all lights in your home after sunset 2. Use lamps instead of overhead lighting 3. If you must use screens, keep them as dim as possible 4. Better yet, read a physical book or practice actual human conversation 5. Avoid bright bathroom lights—use a nightlight for evening routines The Reality Check: Yes, blue light blocking glasses can help, but they're treating a symptom, not the cause. The real issue is that we're flooding our eyes with artificial light when our biology expects darkness. ## 10:00 PM - 6:00 AM: The Sleep Sanctuary What the Gadgets Promise: Sleep trackers, white noise machines, weighted blankets, and mattresses that cost more than a used car. What Your Ancestors Did: Found a safe, dark, quiet place and slept until dawn. Sometimes they even slept on the ground and were fine. ### Your Free Biohack: "The Paleo Bedroom" 1. Darkness: Make your room as dark as possible. Cover LED lights, use curtains or eye masks 2. Silence: Minimize noise or use consistent background noise (a fan works great) 3. Cool: Keep the room temperature between 65-68°F 4. Consistency: Go to bed and wake up at the same time every day (yes, even weekends) 5. Phone Exile: Charge your phone outside the bedroom The Hard Truth: Your bedroom shouldn't be an entertainment center, office, or social media scrolling lounge. It should be a sleep cave. # Seasonal Adjustments: Because Your Body Isn't Stupid Your ancestors didn't live in perpetual spring. They adapted to seasonal changes, and so should you. Winter: More sleep (up to 9 hours), earlier bedtime, extra morning light exposure Summer: Less sleep needed (7-8 hours), later bedtime, more evening activity Spring/Fall: Gradual transitions between winter and summer patterns ## Troubleshooting Common Issues "I'm a Night Owl!" You might be, but you might also be suffering from "social jet lag"—living on a schedule that doesn't match your biology. Try the morning light protocol for 2 weeks before declaring yourself nocturnal. "I Travel Constantly!" Use light as your primary tool. Seek bright light at your destination's morning time and avoid light at your destination's evening time. Your circadian system adjusts to light faster than any other cue. "I Work Shifts!" You'll need to create an artificial day/night cycle using light and darkness. Bright lights during your "day" (work hours), complete darkness during your "night" (sleep hours), regardless of what the sun is doing. "I Live in a Cave (Apartment)!" Prioritize outdoor time whenever possible. Even 10 minutes of natural light is better than hours of artificial light. Consider a brief morning walk or eating lunch outside. # The Gadget Reality Check Don't get me wrong—some sleep gadgets can be helpful. But here's what they're actually measuring and how to get the same benefits for free: ## Sleep Trackers: They track movement and estimate sleep stages. You can do the same by noting how you feel upon waking. Refreshed = good sleep. Groggy = not so good. ## Light Therapy Boxes: They provide bright light at specific times. The sun does this better and includes vitamin D synthesis as a bonus. ## Smart Thermostats: They regulate temperature. You can manually adjust your thermostat or open/close windows. ## White Noise Machines: They mask disruptive sounds. A fan costs $20 and works just as well. ## Blue Light Glasses: They filter blue light in the evening. Dimming your lights and avoiding screens works better. # The 30-Day Challenge: Your Circadian Reset Week 1: Morning light exposure and evening light reduction Week 2: Add temperature manipulation (warm shower before bed) Week 3: Incorporate consistent sleep/wake times Week 4: Fine-tune based on what works for your lifestyle Track your energy levels, mood, and sleep quality without fancy gadgets. Use a simple 1-10 scale in a notebook or phone note. # The Bottom Line: Sometimes Simple Is Genius Your ancestors weren't sleep-deprived zombies shuffling around the savanna. They worked with their biology instead of against it, used environmental cues that evolution had perfectly calibrated, and somehow managed to function without a PhD in sleep science. The irony is delicious: while we've been busy trying to hack our way to better sleep with increasingly complex and expensive solutions, the most effective methods have been free and available all along. Light, temperature, and timing—the same circadian cues humans have used for hundreds of thousands of years. Your smartphone might be smarter than you, but it's not smarter than millions of years of evolution. Trust your biology, work with your natural rhythms, and save your money for something more useful—like a vacation where you can practice these techniques on a beach somewhere. Sweet dreams, and remember: the best sleep tracker is how you feel when you wake up. If cave dwellers could figure this out, so can you. ## Resources & Research: •

Huberman Lab: Using Light for Health

•

Sleep Foundation: Light and Sleep

•

PMC Research: Effects of Light on Circadian Rhythms

•

CDC: Effects of Light on Circadian Rhythms

•

PMC Research: Temperature and Sleep

•

Frontiers: Temperature Dependence of Sleep

NumiEarth Blog