ancient lineage - working hard or hardly working?

While our species seems to be about 150K years old, our genus stretches back ~2.4 million years and our subtribus to more than 4.4 Mya.
This is a good occasion to recall my nagging question,if the species - or H. sapiens sapiens - is 150K years old, why did they  develop writing and beyond only in the past six to seven thousand years?

update:
- possible resolution vectors,
   - the most obvious, or simplest answer is that writing probably existed much longer b/f that, but like our predilection nowadays, their media failed to outlast them, and thus the beginnings of our widely accepted "written history" got pushed back by God knows how many millenia. -- 19.viii.xiv.

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