Explanation:

- Option 1: Technological innovations

Technological advancements can improve productivity but were not directly linked by Rousseau to the emergence of inequality.

- Option 2: Specialization

Specialization refers to individuals focusing on specific tasks, leading to improved efficiency but not directly tied by Rousseau to initial inequality.

- Option 3: Division of labour

Division of labour involves splitting work into distinct tasks, leading to interdependence but isn't directly pointed out by Rousseau as the start of inequality.

- Option 4: Individual property

Rousseau emphasized that the concept of personal property marked the beginning of inequality, as it introduced wealth disparities and social stratification.

- Correct Answer: Option 4 - Individual property