Megaliths, the ancient burial monuments, of Kerala belong to the Iron Age and generally date from 500 BCE to the early centuries of the Common Era. Grave goods comprising iron weapons and agricultural tools, pots and pans, etc, represent the religio-funerary beliefs and customs of the people. They are primitive tombs erected to honor the dead, indicating belief in life after death as well as spirit worship.
Megalithic burials are of various types. Dolmenoid cists (grave structures of two or more upright stones supporting a horizontal slab), urn burials and menhirs (single-shaped, upright stones) etc., are found in other parts of South India, too, but rock-cut tombs, kudakklas (umbrella stones) and topiikkals (hat stones) are peculiar only to Kerala.
The rock cut tombs are found in the lateritic zone of the districts of Thrissur, Malappuram and Kannur. They are known locally as pandukulis or pandukuzhi meaning pits of the Pandavas. They are roughly oblong or circular in plan and divided into chambers. The caves usually face east. Umbrella stones resemble the handle-less umbrellas of palm leaf, commonly used in Kerala. Hat stones consist of a circular capstone with a dome-like profile, place on a shaft made up of three or four stones.
At Porkalam, a number of burial urns, umbrella stones, dolmenoid cists and rock-cut tombs have been found in a vast area. Significantly, some of the South India megaliths exhibit a remarkable similarity to megaliths found in the lands bordering the Mediterranean and Atlantic.
The practice of erecting megaliths apparently disappeared after cremation became the order of the day.
Megalithic types of South India in Ancient India Vol V (1949) – V D Krishnaswami – Archaeological Survey of India – New Delhi
Issues in Kerala Historiography, (2003) KK Kusuman – International Centre of Kerala Studies, University Of Kerala
Encyclopedia of Hinduism Volume II page 129 – 130 – Rupa IHRF