Without agriculture there is no civilzation.
Except that fossils that were Argon dated at 160,000 years old, were found with lots of tools. This article from Berkley says they knew how to exploit plants. Maybe by exploit they don't mean agriculture. But still.
They had tools. They would have been at the top of the food chain. War, famine, pestilence could serve as limits to their population growth. But then again, pestilence would be less in a less populated world with less travel. Famine would be less in a less populated world.
There is absolutely no reason to believe man would be limited in his population growth.
It's a lot easier to believe that the argon test was wrong (and we now know that new rock can test very old due to excess argon), than it is to believe that man made no progress for 300,000 years and left almost no record.