The Rise of Modern Humans

摘要

Human beings are distinguished most strikingly by their unique “symbolic” way of processing information about the world. Although based on a long evolutionary history, the modern human cognitive style is not predicted by that history. It is not the product of a process of incremental refinement but is instead “emergent,” representing an entirely distinct level of complexity. Physically, Homo sapiens is very distinctive, its peculiarities clearly resulting from a significant developmental reorganization with numerous skeletal ramifications and quite plausibly others as well. It seems reasonable to suppose that the structural underpinnings of symbolic thought were acquired in this reorganization. Still, the fossil and archaeological records indicate that the first anatomically recognizable members of the species predated the first humans who behaved in a demonstrably symbolic manner. So while the biological potential for symbolic thinking most likely arose in the morphogenetic event that gave rise to H. sapiens as a distinctive anatomical entity, this new capacity was evidently exaptive, in the sense that it had to await its “discovery” and expression, clearly through a cultural stimulus that was plausibly the invention of language. One manifestation of symbolic reasoning is the adoption of technological change in response to environmental challenges, in contrast to earlier responses that typically used existing technologies in new ways. As climates changed at the end of the last Ice Age, this new technophile proclivity was expressed in a shift toward agriculture and sedentary lifestyles, precipitating a fundamentally new (and potentially self-destructive) relationship with Nature. Both of the two most radical and fateful evolutionary innovations in the history of life (symbolic thinking and sedentary lifestyles) were thus very recent occurrences, well within the short tenure of H. sapiens.