Becoming Modern Homo sapiens

Abstract

Human beings are unusual in many ways but perhaps most strikingly in their unique symbolic form of processing information about the world around them. Although based on a long and essential evolutionary history, the modern human cognitive style is not predicted by that history: it is emergent rather than the product of an incremental process of refinement. Homo sapiens is physically very distinctive and is clearly the result of a significant developmental reorganization with ramifications throughout the skeleton and presumably beyond. It is reasonable to suppose that the neural underpinnings of symbolic thought were acquired in this reorganization. However, the fossil and archeological records indicate that the first anatomically recognizable members of the species substantially predated its first members who behaved in a demonstrably symbolic manner. Thus, 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 release through a cultural stimulus. Plausibly, this stimulus was the invention of language. One expression of symbolic reasoning is the adoption of technological change in response to environmental challenges, contrasting with earlier responses that typically involved using existing technologies in new ways. As climates changed at the end of the last Ice Age, the new technophile proclivity was expressed in a shift toward agriculture and sedentary lifestyles: a shift that precipitated a fundamentally new (and potentially self-destructive) relationship with nature. Thus, both of what are arguably the two most radical (and certainly the most fateful) evolutionary innovations in the history of life (symbolic thinking and sedentary lifestyles) were both very recent occurrences, well within the (so far rather short) tenure of H. sapiens.

The Evolution of Human Genetic and Phenotypic Variation in Africa

“…The earliest known suite of derived traits associated with anatomically modern humans was identified in fossil remains from East Africa dating to around 195–150 kya [7–9]. Thus, the basic morphology of modern humans was established in Africa about 200 kya [10]. Other early anatomically modern humans, with a more full set of modern features, also appear in Africa before 100 kya and in the Near East around 100 kya [11–13], followed by the more recent expansion of anatomically modern humans into Eurasia within the past 40,000–80,000 years [1, 2](Figure 2).…”

Quest for breathing: proliferation of alveolar type 1 cells

“…Exaptation is defined as existing structures that now enhance fitness but were not produced by natural (or sexual) selection for their current role (Gould and Vrba 1982 ; Tattersall 2009 ). There is much evidence to indicate that the vertebrate lung originated from a progenitor structure present in bony fish (Randall et al 1981 ; Graham 1997 ; Nelson and Dehn 2011 ; Hoffman et al 2016 ), but crucial structures for the evolution of air breathing were present in the vertebrate ancestors (lungless) prior to the evolution of the lung (Sullivan et al 1998 ; Hoffman et al 2016 ).…”

“…There is much evidence to indicate that the vertebrate lung originated from a progenitor structure present in bony fish (Randall et al 1981 ; Graham 1997 ; Nelson and Dehn 2011 ; Hoffman et al 2016 ), but crucial structures for the evolution of air breathing were present in the vertebrate ancestors (lungless) prior to the evolution of the lung (Sullivan et al 1998 ; Hoffman et al 2016 ). In 2016, Hoffman and co-authors proposed a completely novel hypothesis, namely that the evolution of air breathing in all vertebrates occurred through exaptations (Gould and Vrba 1982 ; Tattersall 2009 ; 2014 ) derived from critical basic elements (Hoffman et al 2016 ). One of them is the central rhythm generator sensitive to CO 2 /pH present in lamprey—a lungless vertebrate (Hoffman et al 2016 ).…”

“…According to Tattersall, exaptations, combined with “critical factors,” constitute a powerful evolutionary mechanism, and they are the driving force of development. On the other hand, all new genomic variants must arise as exaptations, mutations occur at random, and new functions cannot be adopted without prior new structures (Tattersall 2006 ; 2009 ; 2014 ).…”

How the Adaptation Got its Start

“…In an article in this issue (Becoming Modern Homo sapiens), Ian Tattersall (2009) addresses a concept that gets at the evolutionary history of currently useful traits: exaptation, a feature that performs a function but that was not produced by natural (or sexual) selection for its current use. Tattersall's discussion focuses on the human capacity for symbolic thinking, but the idea applies broadly throughout the living world.…”