When did meat become important?

Contrary to some implied beliefs, the Ice Age did not make the whole world carnivorous — it just forced latitude-based divergence in diets.

1. When did meat become important?

• Savanna shift (~2.5 mya):Climate drying in Africa turned forests into grasslands. Early Homo species (habilis, erectus) began scavenging and later hunting medium-to-large herbivores.

  • Brain–gut trade-off (“expensive tissue hypothesis”): This was enabled by higher nutrient density (meat + marrow + some tubers). Brains grew, guts shrank.

  • Fire (~1 mya, maybe earlier): Controlled fire made it easier to digest both tubers (detoxifying starches) and meat (softening, reducing pathogens). This was a force multiplier, but evidence suggests meat eating preceded controlled fire. Fire allowed greater reliance, but did not start the trend.

  • So: The brain-gut morphology shift was already underway before the Ice Age — linked to omnivory, not purely carnivory.

2. What was the Ice Age’s role?

• The “Ice Age” wasn’t a single frozen Earth — it refers to glacial cycles between ~2.5 mya and 12k years ago.

• Effect on diet:

  • Equator & tropics: Still supported plants, fruits, tubers, fish → omnivorous diets with heavy plant reliance.

  • Temperate zones: Seasonal plant shortages → greater seasonal animal reliance.

  • High latitudes (Europe, Siberia, Beringia): Plants scarce for much of the year → humans survived mainly on megafauna, fish, and fat.

• Therefore: The Ice Age did not “make humans carnivores” across the board. It regionalized diets: meat-heavy in the north, plant-rich near the equator.

3. Did the whole world freeze?

• No.

  • Ice sheets covered northern continents (North America, northern Europe, Siberia).

  • Equatorial Africa, SE Asia, and parts of South America remained habitable with tropical and savanna ecosystems.

  • In fact, Africa remained the refuge for much of humanity — continuous human habitation, ongoing use of tubers, fruits, legumes.

• Global cooling and drying happened, but ecosystems varied by latitude.

4. So where do meat and archetypes fit?

• Pre-Ice Age (Savanna, 2.5–1 mya):Omnivory already established → brain-gut shift.

• During Ice Age (1 mya–12k ya):Diets diverged regionally:

  • Equator: Plant-heavy omnivores.

  • Mid-latitudes: Seasonal omnivores.

  • High latitudes: Meat- and fat-dominant.

• Takeaway:

  • The major evolutionary shift (brain growth, gut reduction, higher energy metabolism) was already in place before the Ice Age.

  • The Ice Age primarily shaped regional archetypes, not the global human template.

5. Modern Implications for Archetypes

• People with ancestry from high latitudes may carry adaptations for higher fat/meat reliance (e.g., FADS gene variants).

• People with ancestry from equatorial/tropical regions often have stronger starch digestion (AMY1 copies) and different micronutrient metabolism.

• This explains why a “universal carnivore” or “universal plant” model doesn’t fit — different archetypes trace back to these Ice Age regional divergences.

✅ Summary:

• Meat eating + brain-gut morphology began before the Ice Age.

• Fire amplified meat and tuber use, but meat was already in play.

• The Ice Age did not make the whole world carnivorous — it just forced latitude-based divergence in diets.

• Equatorial populations kept eating plants; northern groups relied heavily on meat and fat.