Embryo development stages described in Bhagavata Purana, Mahabharata, Aitareya Upanishad
Embryology is the science of development of an embryo from the fertilization of the ovum to the fetus stage.
The earliest scientific approach is credited to Aristotle (384 – 322 BC), but indians have done a lot of scientific work, long before Aristotle. Kapil Muni was probably the first man who studied embryo. The epic Mahabharata written around 3100 BCE and the Bhagawata Purana composed around 1800 BCE have recorded lot of scientific information about embryology.
Ancient Indian rishis had discovered the body secretions, which reproduce and called them Raja (ovum) and Reta (sperm).
The Mahabharata, Shanti Parva, 301, 320, 331, 356, and the Bhagawata 3/31 state that one fine particle of Shukra conjugates with that of Shonit during copulation. The fine particles are sperm and ovum. They termed the conjugate product as ‘Kalala’, whereas modern science terms it as ‘Zygote’ or fertilized ovum.
Bhagawata states that only in one night, which means 12 hours’ time, from the coitus, Kalala forms. Science admits that an ovum remains fertilizable for a short time, measured in hours, after its release from ovary.