16/05/2025
Ever wondered why you aren't sleeping well? Or your kids are always tired? Read this short article that was stolen with permission from my good friend Billy Craig - enjoy.
How to get 🔥 sleep!
The evolutionary use of fire profoundly impacted human physiology, behavior, and even brain development. Fire wasn't just a tool for cooking—it reshaped our environment, our circadian rhythms, and our metabolic priorities. Here's how this ties into evolutionary safety, rest, brain development, and even how fire’s red light spectrum might still help us today:
🔥 1. Fire as an Evolutionary Catalyst
The control of fire was arguably one of the most transformative evolutionary events. Its influence went far beyond cooking:
🔐 A Shield Against Predators
Fire provided safety at night, reducing the need for hypervigilance.
This allowed early humans to sleep more deeply, especially in groups, knowing the fire deterred animals.
Deeper, more restorative sleep supported memory consolidation, immune repair, and neurodevelopment.
🧠 Energy Reallocation
Cooking food made nutrients more bioavailable and digestion less energy-intensive.
This freed metabolic energy that could be redirected toward brain expansion and complexity (supporting the "expensive tissue hypothesis").
Less time was needed for foraging and digesting raw food, giving time for social bonding, planning, and cultural development.
🛌 Extended Wakefulness Under Safer Conditions
Firelight extended the day in a gentle way. Rather than harsh sunlight, the low-intensity, red-dominant glow of fire allowed humans to stay awake longer without fully disrupting melatonin production.
This may have contributed to group bonding, storytelling, and tool-making during low-energy nighttime hours.
🌅 2. Firelight and the Red Spectrum: A Circadian Match
Human biology is tuned to natural light cycles. Firelight aligns closely with the evening spectral environment, especially in contrast to blue light:
🔴 Red and Amber Light Support Sleep
Fire emits mostly longer wavelengths (red/orange), which do not suppress melatonin significantly.
In contrast, blue light (from screens, LEDs, etc.) strongly suppresses melatonin, disrupting sleep timing and depth.
🧠 Calm Brain State Induction
Red/orange light creates a visually calming environment, reducing cognitive stimulation and sympathetic nervous activity.
This mimics twilight conditions, signaling safety and rest rather than alertness or threat.
🛑 Modern Disruption
Artificial lighting—especially cool white or blue-rich LEDs—is the opposite of firelight.
It tricks the brain into “daytime mode,” contributing to insomnia, anxiety, metabolic dysfunction, and circadian misalignment.
🧬 3. Evolutionary Implications for Sleep and Growth
The safety and light provided by fire may have:
Reduced the energetic cost of fear (by calming the amygdala through perceived safety).
Enabled longer, consolidated sleep and thus more REM and deep sleep, both essential for memory, learning, and cellular repair.
Supported a more efficient metabolism, reducing stress hormone output and supporting hormonal regulation.
Created a social, cooperative space—key for language development and shared knowledge.
🌙 Takeaway: Can Firelight Still Help Us Today?
Yes. Mimicking firelight in modern environments can help recreate the ancestral cues our brains and bodies evolved to rely on:
Use red or amber light bulbs after sunset to support melatonin and calm.
Avoid screens or use blue light filters in the evening.
Consider candlelight or infrared lamps to ease the nervous system before sleep.
Reconnect with natural firelight when possible—campfires, fireplaces, even just being outdoors at dusk.
