Final answer:
The case of Romanian orphans and other similar cases demonstrated humans' biological need for social interaction, as research studies showed the significant challenges faced by those lacking social interaction and emotional care.
Step-by-step explanation:
The case of Romanian orphans, as well as other similar cases, demonstrated humans' biological need for social interaction. Research studies on Romanian orphans showed that those who lacked social interaction and emotional care experienced significant developmental and social challenges. For example, the Harlow experiments with rhesus monkeys highlighted the importance of social comfort over basic physical needs. These cases emphasize that social interactions are crucial for our emotional, cognitive, and social development.