The origin of cumulative culture

https://www.sciencedaily.com/releases/2024/06/240617173730.htm
The PNAS article is paywalled:
https://www.pnas.org/doi/10.1073/pnas.2319175121
When did we acquire our current ability to assimilate and build on cultural innovations?  We obviously started building on a bipedal culture around the time we suffered the hip deformations that forced our ancestors into a more upright stance.  Monkeys and chimps have a crude culture passed down across generations, and to some extent some of the behavior isn't learned buy instinctive, but there is some learning and passing survival behaviors down the generations like tool use.  It takes monkeys and chimps years to adapt and learn behaviors that they observe others of their species performing.  Humans excel at accumulating and using technological innovations.  When did we advance to our current ability from the slow hard won efforts to learn simple advantageous behaviors to being able to rapidly and effectively understand, and build a culture requiring multiple advantageous learned behaviors?
These researchers looked at stone tool manufacture.  From 3 to 1.8 million years ago we didn't do much more than the pebble tool complexity.  From 1.8 to 600,000 years ago stone tools started to exceed the initial baseline, within the last 600,000 years tools started a marked acceleration in manufacturing technology.  They believe that this indicates that humans had reached the mental ability to transmit more cultural behaviors efficiently.  They needed to learn multiple steps needed to make the stone tools.
This might explain why it took Neanderthals so long to adopt blade technology.  It was a much more efficient use of stone that sometimes had to be transported for hundreds of kilometers to where it was used. For some reason Neanderthals did not adopt the technology until just before they went extinct when they had been interacting with modern humans for over 20,000 years.  The DNA difference indicates that Neanderthals and Denisovans may have left Africa around 800,000 years ago, and they took the older stone tool tech with them.  The ability to efficiently assimilate cultural innovations would not have been a common ability in Africa until a couple hundred thousand years after Neanderthals and Denisovans had left Africa.
Ron Okimoto