A phylogenetic split ∼7.5 Ma (million years ago) separated paninan ancestors that were unlike today's chimpanzees, from homininan ancestors that were unlike Homo sapiens today; neither had evolved into their modern physical and behavioural forms. Those paninans gave rise to the mainly frugivorous woodland-dwelling chimpanzees (Pan troglodytes), whose multifemale-multimale troops have social hierarchies where prominent parts are played by promiscuous males whose female offspring have little choice after menarche but to seek sexual partners in other troops, hostility between troops notwithstanding, whilst male promiscuity is incompatible with paternal interest in their offspring, interest being provided mainly by mothers or female alloparents. Contrary to widespread conjecture that the social arrangements of Pan were those of primaeval homininans, it is proposed here that ∼4 Ma the nature of the mosaic landscapes (of grasslands and stands of trees) that were the habitat of australopithecine homininans, had 4 consequences that impinged on homininan evolution, differentiating it from that of woodland-dwelling paninans: (1) The diversity of whatever was available to eat was not the same in adjoining habitats of homininan social units, each of which may have been constrained by whatever mostly could be foraged, scavenged, eaten, or carried away, within perhaps a 2-hour walk; (2) Whatever was forageable, scavengeable, and edible within that distance likely was limited at any period of the year, so social units were increasingly omnivorous and necessarily small; (3) Smallness demanded cognitive ingenuity and transmissibility of existential information acquired by active inference generated by self-evidencing through enacted neuroethological behavioural responses, in line with the free energy principle, thanks to the cognitive broadening of homininan "zones of bounded surprisal" (ZBS) with respect to paninans' ZBS, both within each homininan "small-world" social unit and between nearby homininan units spreading out, in space and time, as budding very small-world information networks; (4) The existential continuity of small homininan social units depended on cooperation and sporadic collaboration between social units with mixed-sex philopatry (perhaps present ∼4 Ma among Australopithecus anamensis), behaviour which, together with (a) the generation of information within each unit that is enhanced by the intimate proximity to toddlers and children of older females and males in small mixed-sex social units, and (b) mixed-sex dispersal of sexually-active partners establishing mixed-sex social units at newly-formed localities nearby, was behaviour that maintained not only heterozygosity, but also, crucial cognitive awareness of kinship links favouring transmissibility of information and cooperation and collaboration (rather than hostility) between neighbouring social units, and was behaviour that represented evolutionary cognitive and social divergence from paninans. The vulnerability of small fragile social units implies there were hundreds of false dawns between ∼4 Ma and ∼40,000 BCE when even Homo neanderthalensis had vanished, leaving only our prehistoric Homo sapiens ancestors bearing "Homo informatio's" highly-evolved hierarchically mechanistic mind with its unequalled wide cognitive "zone of bounded surprisal" (ZBS) grounded in active inference in accord with the free energy principle.