Question

1. read the list of human vestigial structures shown in table 1 below. suggest a possible function for each structure and explain why it became vestigial.

table 1.

Explanation:

• Wisdom teeth:
• Possible function: In ancestors, they helped grind tough plant materials.
• Why vestigial: Modern diet (softer foods) and smaller jaws make them often impacted or unnecessary.
• Little toe:
• Possible function: Helped with balance and grasping in tree - dwelling ancestors (arboreal locomotion).
• Why vestigial: Bipedal locomotion on flat surfaces (like ground) and footwear reduce its functional importance.
• Muscles that make hair stand up (arrector pili muscles):
• Possible function: In animals (and ancestral humans), makes the animal look larger (for threat display) or provides insulation (fluffing up fur).
• Why vestigial: Humans have less body hair, and social communication (not visual threat display via hair) and artificial insulation (clothing) make this muscle - related function less useful.
• Muscles that move ears (auricular muscles):
• Possible function: In some animals, helps in localizing sound sources (by moving ears to better capture sound).
• Why vestigial: Human ear structure and neck mobility (to turn head for sound localization) make these muscles less necessary for most people (though some can still move ears slightly).
• Appendix (in koalas, it digests leaves):
• Possible function (in human ancestors): May have been involved in digestion of plant - based diets (like cellulose - rich foods), similar to its role in some herbivores.
• Why vestigial: Human diet (less reliance on tough plant fibers) and gut microbiome changes have reduced its digestive function.

Answer:

• Wisdom teeth:
• Function: Grind tough plant materials (ancestral).
• Vestigial: Modern diet and jaw size.
• Little toe:
• Function: Balance/grasping (arboreal ancestors).
• Vestigial: Bipedalism and footwear.
• Muscles for hair standing:
• Function: Threat display/insulation (ancestral/animals).
• Vestigial: Less hair and social/clothing substitutes.
• Ear - moving muscles:
• Function: Sound localization (some animals).
• Vestigial: Ear structure and neck mobility.
• Appendix:
• Function: Plant - diet digestion (ancestral).
• Vestigial: Diet and gut microbiome changes.