The correct option is statements 1 and 2 only. In an elephant herd, the matriarch, typically the oldest and most experienced female, leads the group, showcasing the social structure of elephants that emphasizes female leadership. Additionally, elephants have a notably lengthy gestation period, which can indeed last up to 22 months, highlighting their reproductive biology. However, statement 3 is misleading; elephants can continue to reproduce beyond the age of 40, while statement 4 is inaccurate as Karnataka, not Kerala, has the highest elephant population in India, reflecting more recent conservation and habitat dynamics. Understanding these aspects of elephant behavior and demographics is crucial for the UPSC Prelims as it combines ecology, human-animal conflict, and wildlife conservation.