The cultural progress of the Species encountered impediments along the way. Overpopulation was a constant problem: as soon as the capacity of the local environment to support the population began to suffer, so individuals began to retreat from specialisation and exchange into defensive self-sufficiency, broadening their production and narrowing their consumption. This reduced the collective intelligence they could draw upon, which reduced the size of the niche they occupied, putting further pressure on population. So there were crashes, even local extinctions.