Exponential growth. That first 195,000 years was every tribe figuring out super basic stuff we take for granted, then gradually building upon that with other basic stuff we take for granted. Even before agriculture, pottery, metallurgy, herbal medicine, the basic knowledge these were built from took millennia to work out and pass down.

The real secret sauce was communication. Once tribes started sharing knowledge, suddenly the base of knowledge to built on got higher, and broader. Written language, better means of travel, this sped up the process. Electronic communication has made that knowledge base pretty much universally accessible and combinable.

Progress is faster when you’re not limited to what your direct tribal ancestors figured out and passed down.