Technological advancement is cummulative. You can't build steam engines with rocks, you can't build electrical grids with wood, you can't operate factories if 90% of the population is subsistance farming. The history of technological change is one of building on previous successes.

The biggest boom came during the industrial and scientific revolutions, which were dependent on one another. Improvements in agriculture during the late middle ages enabled more and more people to work in jobs other than farming. And this set the stage for early factory production and then power assisted manufacturing (with water wheels then steam power then electricity). At the same time, socio-cultural !nd economic changes enabled and rewarded greater intellectual curiosity and gave rise to systems of thought designed to maximize the return of knowledge from such curiosity. Which is not to say that nothing similar had existed before. The transition during the stone/iron age from farming to also producing secondary products (like pottery, olive oil, cloth, etc.) and several periods of scientific curiosity (such as with the ionian greeks) came before, but with the industrial/scientific revolution these things were on a much more massive scale and able to be capitalized to a much greater degree.

Once there is a strong and tight feedback loop between scientific investigation/invention and commercial application then the pace of advancement accelerates dramatically. During the pre-industrial age of artisan manufacturing it was very expensive and risky to attempt to experiment with things in order to try to improve them. By the industrial age it was possible for folks who experimented with improving inventions to be able to do so as a job, and to become wealthy doing so.

The technological clock starts about 12,000 years ago with the Neolithic Revolution or the Agricultural Revolution. Prior to this there wasn't enough of a caloric surplus in humans food sources to allow of specialization of skills and the nature of food generation (i.e. hunting and gathering) placed limit ability for people to be settled for anything length of time, and thus have the opportunity to start to change their environment. The last glacial period also ended about 12,000 years and there are theories about climate change driving the Neolithic Revolution.

The Last Glacial Period ran from about 110,000 - 12,000 thousand years ago. When humans left Africa is a little more confused, but the earliest date is 125,000 year ago, and some of the more recent are 60 thousand years ago. So one theory is the humans spent the last ice age mucking about doing the Hominid thing, then the climate changed dramatically forcing many groups to adopt new survival and food generation strategies, some that resulted in the domestication of select plants and animals. As these newly domesticated organisms eventually merged together into a agricultural packages, that enabled villages, towns and eventually cities.

One the the theories about why this didn't happen sooner, is that the labor involved is much higher and the quality of diet is much poorer, especially when only a fraction of the overall agricultural package is available. Communities would only adopt farming as their primary means of food production as a last resort. It wasn't until later, that farming practices started providing a surplus and became a real competitive advantage.