Which one among the following is the earliest text ?

Ashtadhyayi, the great Sanskrit grammatical treatise composed by Panini, is the earliest among these texts, dated to approximately the 6th–5th century BCE. The Sushruta Samhita (medical treatise) is dated to around the 6th century BCE in its earliest form but the extant version is later. The Manusmriti was composed between the 2nd century BCE and 3rd century CE, and Bharata's Natyashastra is dated between the 2nd century BCE and the 2nd century CE. Therefore, the Ashtadhyayi is the oldest of the listed works.