the very first few generations are hard to pinpoint, as much has been lost.
the generations are cycles of time, but they are not always the same length.
the cycle we are in, the modern cycle, started around 1960. it will likely last until around 2100. this is the cycle of modern technological advancement, which is bad, but also of realizations. realizations about climate change and how we need to stop pumping carbon into the air, realizations about the evils that technologies have brought, realizations about how racism is wrong, etc. we dont know it the realizations or the technology will be the defining trait of the next cycle.
the next cycle will likely start around 2100. but we dont know if it will be a time where technology destroys the earth, our souls, and the realizations, or if it will be a time of spiritual awakening and the fixing of problems, where we stop putting carbon in the air, where we stop developing technology, where we stop anti-spiritual thought, where we stop poisoning ourselves and the earth.
the last cycle started around 1800 and ended around 1960. it was the cycle of mindless technological advancement, as well as a time of wars. both world wars were in that cycle, as was the industrial revelution. it was a very bad cycle. this was when we started destroying nature.