Mailbag: The Eemian: what gives?

I wandered into your site after searching for Eemian and human evolution. The general consensus is that anatomically modern humans were in Africa 150-200K year ago. During the Eemian interglacial these humans presumably had similar opportunities to migrate and develop agriculture as humans did during the Holocene. Yet apparently they didn't. Do have any thoughts on why this is so? Of course, a smaller population base at the beginning of the Eemian than at the beginning of the Holocene might account for this but I would think that with favorable climatic conditions a small population at the start would rapidly increase. Another reason might be that anatomically modern humans at the beginning of the Eemian lacked something in the neurological wiring to build modern culture.

Thanks for writing. Indeed, this very question has interested archaeologists for a long time. The multiple independent origins of domestication and agriculture seem to have a demographic explanation. That means that the Eemian, with its environmental profile so similar to the Holocene, might be expected to have given rise to the same events. Surely Eemian west Asia was more similar to Holocene west Asia than the latter was to Holocene Mexico.

Archaeologists’ explanations are basically as you describe, although I could add a few:

  1. Maybe the Eemian wasn’t really so similar to the Holocene, despite appearances.
  2. The technology in pre-Eemian times may not have allowed population growth in response to the ameliorating climate to the extent that Upper Paleolithic-era technologies did prior to the Holocene.
  3. The cognitive abilities of Eemian-era humans may not have enabled effective response to changing climate.
  4. The cultural systems of pre-Eemian times may have been more highly based on population regulation/limits to growth, thereby enabling the population to respond without the overgrowth that necessitated sedentism and ultimately domestication of plants.
  5. Demographic intensification in Africa and resulting mass migration DID happen in the Eemian, and we call this the out-of-Africa event.

I will note that there is now some evidence of intensive collection of cereals in tropical Africa before the Eemian, so this problem may yet become more complex. One of the reasons I follow the Holocene domestication literature so closely is to try to perceive what social dynamics were shared among terminal Pleistocene peoples – because some critical factors must have been absent pre-Eemian, but we don’t know which!