Isvarakrsna’s Samkhyakarika is the important source of information on the Samkhya system; he is generally placed in the fifth century A.D., because the Samkhyakarika was translated into Chinese between A.D. 557 and A.D. 567. But the Samkhya system is much older—Chanakya’s Arthashastra, which is dated to B.C. 300, has references to the Samkhya, Yoga, and Lokayata systems.
The other Hindu systems — Nayaya, Vaisesika, Mimamsa, and Vedanta — came after the Samkhya, Yoga, and Lokayata were systematized.
There are striking similarities between Samkhya and Buddhist systems—for instance, both systems react against the Vedic sacrifices, ritualism, and belief in god; they preach that life is a web of pain and ignorance, and liberation (salvation) can be attained through knowledge; they reject self-torture and have an emphasis on becoming and change. The Samkhya position on Kalvalya (the ultimate raja yoga which stands for "solitude", "detachment" or "isolation") is similar to the Buddhist nirvana.
The ancient texts on systematic Samkhya are no longer extant and most references to sage Kapila, the historical founder Samkhya, are mythological, but the unity in the Samkhya system indicates that it can be the work of one philosopher. Since the name of the birthplace of Buddha (Gautama) is Kapilavastu, it’s believed that this is the region where sage Kapila did his work.