Passage Summary: Usually, the bigger a primate's brain, the bigger their social group, and the more they groom each other to stay friendly. Early humans had the brains for big groups, but they didn't actually groom each other.

Reasoning: While primates generally use social grooming to maintain cohesion in large groups, and early humans likely lived in large groups based on their brain size, evidence shows early humans did not engage in social grooming.

Analysis: We have a classic paradox here: if early humans had the large social groups associated with their large neocortices, how did they maintain social cohesion without the standard primate tool of grooming? To resolve this, we need to find an alternative mechanism that served the same social function as grooming but was more efficient or simply different. Look for an answer choice that introduces a new behavior—perhaps something uniquely human—that could keep a large group together without requiring hours of picking through each other's fur. It's all about finding a 'grooming substitute' that fits the human context.