Comparative Anatomy and Physiology Brought Up to Date

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T A B L E   O F   C O N T E N T S   F O R

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PART 4
Intelligence, Evolution of the
Human Brain, and Diet

• Introduction: claims of the comparative "proofs"
  
  • Human intelligence ignored or rationalized
    
  • Brain size discounted
    
  • Hidden, contradictory views on the value of intelligence
    
  • Recent evolutionary research now emphasizes the interaction of diet and brain development

• Encephalization
  
  • "Expected" vs. actual brain size
    
  • Kleiber's Law
    
  • Brain and digestive system compete for limited share of metabolic energy budget
    
  • A comparative anatomy analysis of primate brains
    
    • Humans at top of primate scale
      
    • Large gap between humans and great apes
      
    • Brain enlargement disproportional

• Factors in encephalization: energy (metabolism) and diet
  
  • Extensive energy required for brain growth
    
  • Dietary quality is correlated with brain size
    
  • Dietary shift beginning with Homo
    
  • How dietary quality relates to the brain's share of total metabolic budget
    
    • Dramatic changes in last 4 million years
      
    • Human brain's metabolic budget significantly different from apes
      
    • Human brain MR (metabolic rate) 3.5 times higher than apes
      
    • Humans depart from normal dietary quality (DQ)/body-weight relationship
      
  • The paradox: Where does the energy for the large human brain come from?

• The relationship of dietary quality and gut efficiency to brain size
  • The expensive tissue hypothesis of Aiello and Wheeler
    
    • Large brain compensated for by decreased gut size
      
    • Less energy-intensive gut associated with higher dietary quality
      
  • Recent brain-size decreases in humans as further evidence of the brain/diet connection
    
    • Why has brain size decreased 11% in the last 35,000 years and 8% in the last 10,000?
      
    • Far-reaching dietary changes over the last 10,000 years
      
    • Brain growth dependent on preformed long-chain fatty acids such as DHA
      
    • Rate of synthesis of DHA from plant-food precursors does not equal amounts available in animal foods

• Fruitarian evolution: science fact or science fiction?
  
  • Vague claims about an ancient frugivorous primate ancestor
    
  • Crank science and logical fallacies used in support of claims of fruitarian evolution
    
  • Fruitarian denial of physiological evolution/adaptation

• Analysis of the fruitarian claims
  
  • Claim: Morphological evolution is "easy," physiological evolution is nearly impossible.
    
  • Claim: The digestive system is extremely complex. For it to evolve in a mere 2.5 million years is simply not possible.
    
  • Claim: (twisted quote) Expert opinion is that physiological evolution is highly unlikely.
    
  • Claim: There is no convincing teleonomy proof that humans have adapted to a diet that includes meat!
    
  • Claim: There are no examples of animals evolving backwards from a vegetarian to an omnivorous diet!
    
  • Claim: If humans are adapted to eating meat, what exactly are those adaptations?

• Further evidence against the claims of fruitarian evolution
  
  • Quadrupedal vs. bipedal adaptations and tree-climbing/fruit-picking
    
  • Actual fruit availability/dependability fluctuates with location and time
    
  • Different adaptations, different tradeoffs
    
  • Adaptations must be interpreted in context
    
  • Body size and tree-climbing
    
  • Fruitarian nutrition vs. brain evolution
    
    • Vitamins, minerals, and fats
      
    • Evolution/survival on pure fruit diets not possible in nature given fluctuations in fruit availability

• Synopsis and section summary

SEE REFERENCE LIST

SEE TABLE OF CONTENTS FOR:
PART 1 PART 2 PART 3 PART 4 PART 5 PART 6 PART 7 PART 8 PART 9

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GO TO PART 1 - Brief Overview: What is the Relevance of Comparative Anatomical and Physiological "Proofs"?

GO TO PART 2 - Looking at Ape Diets: Myths, Realities, and Rationalizations

GO TO PART 3 - The Fossil-Record Evidence about Human Diet

GO TO PART 4 - Intelligence, Evolution of the Human Brain, and Diet

GO TO PART 5 - Limitations on Comparative Dietary Proofs

GO TO PART 6 - What Comparative Anatomy Does and Doesn't Tell Us about Human Diet

GO TO PART 7 - Insights about Human Nutrition & Digestion from Comparative Physiology

GO TO PART 8 - Further Issues in the Debate over Omnivorous vs. Vegetarian Diets

GO TO PART 9 - Conclusions: The End, or The Beginning of a New Approach to Your Diet?

Back to Research-Based Appraisals of Alternative Diet Lore