Scatter-gather society

A variation of hunter gather. These folks gathered seed and scattered it the next sprung. This culture was post glacial, thrived up to 9000 years ago, these came settled ag. All their ag avcivity got washed away during holocene, they were like the south and  central american native cultures.  In asia, the holocene period arrived and settled ag came everywhere would have wiped out traces, except underwater archeology. We see at least large grain warehouses in one spot.

Such a culture must have  filled the gap of rising temperature and melting ice. A highly migratory social structure. From Wiki:

At the end of the last ice age, the North Sea was a great plain, and anthropological material, as well as the remains of animals such as mammoths, are sometimes recovered by trawlers. Also, because human societies have always made use of water, sometimes the remains of structures that these societies built underwater still exist (such as the foundations of crannogs,^[8] bridges and harbours) when traces on dry land have been lost. 

The sea rose fairly slow in human time. They started as migratory scatter gather with migration routes.  Then began to be crowded by the sea and learned settled ag. A hard Malthusian life.  The skill is elementary, kids can do it. So, given a few great springs in a row, we get this huge attack on atmospheric co2, a sudden drop in production. Ag camps expand, we get eight kids per parents, almost unlimited expansion each spring as climate warms, then suddenly the co2 is down, the the glacial cycle gets stuck. Stopping the warming left glacial ice sheets, the up lifting of crust failed and volcanic released ceased, mantle crust cooled just enough.