What evolutionary consequence is linked to upright posture and altriciality?

• A. Decreased parental care
• B. Increased infant care and pair-bonding
• C. Smaller brain size
• D. Fewer social bonds

Answer: (B)

Upright posture together with altricial offspring promotes greater parental investment and social cooperation. When offspring are born relatively undeveloped and dependent, parents must invest more time and resources to ensure their survival. Bipedalism makes it easier for a caregiver to carry and tend a helpless infant while foraging or guarding, which increases offspring survival and supports a longer developmental period. To sustain this extended care, families benefit from coordinated efforts and stable pairings, leading to pair-bonding as a social strategy. This combination naturally yields more infant care and stronger social bonds. An option suggesting decreased parental care doesn’t fit with altricial young; a smaller brain size isn’t aligned with the extended development and social complexity; and fewer social bonds contradicts the need for cooperative care.