Final answer:
Primates are more vulnerable to infanticide due to the investment of time and resources by females, complex social dynamics, and physical characteristics that make them susceptible to attacks.
Step-by-step explanation:
Primates are more vulnerable to infanticide due to several factors. First, because primate females invest more time and resources in caring for their young, killing infants from rival males can be a strategy to eliminate potential competitors for resources. Second, the complex social dynamics among primates create competition for resources and mates, which can lead to infanticide as a form of aggression. Third, the presence of forward-facing eyes and grasping hands in primates may have evolved as adaptations for hunting small prey, but these characteristics also make primates vulnerable to infanticidal attacks.