প্রাক্-ক্যাম্ব্রিয়ান কালের আবির্ভাব কত বছর আগে হয়েছিল ?
The Precambrian (colored green in the timeline figure) is an informal unit of geologic time, subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago (Ga) to the beginning of the Cambrian Period, about million years ago (Ma), when hard-shelled creatures first appeared in abundance.
4.6 billion