Population structure and the evolution of Homo sapiens in Africa

Abstract

It has been proposed that a multiregional model could describe how Homo sapiens evolved in Africa beginning 300,000 years ago. Multiregionalism would require enduring morphological or behavioral differences among African regions and morphological or behavioral continuity within each. African fossils, archeology, and genetics do not comply with either requirement and are unlikely to, because climatic change periodically disrupted continuity and reshuffled populations. As an alternative to multiregionalism, I suggest that reshuffling produced novel gene constellations, including one in which the additive or cumulative effect of newly associated genes enhanced cognitive or communicative potential. Eventual fixation of such a constellation in the lineage leading to modern H. sapiens would explain the abrupt appearance of the African Later Stone Age 50–45 thousand years ago, its nearly simultaneous expansion to Eurasia in the form of the Upper Paleolithic, and the ability of fully modern Upper Paleolithic people to swamp or replace non‐modern Eurasians.

Four-Field Co-evolutionary Model for Human Cognition: Variation in the Middle Stone Age/Middle Palaeolithic

“…For post-50 ka populations, we argue that what is represented in the Eurasian archaeological record is probably the product of mixed populations (to a larger or lesser extent), instead of belonging solely to either the Neanderthals or to H. sapiens. Klein (2019) suggests that novel gene constellations post-50 ka gave rise to 'fully modern' people and the Later Stone Age in Africa. The fact that the precuneus in its current form is, however, already visible in the palaeoneurological record from1 00 ka during the MSA, reveals a different scenario.…”

“…Some have suggested that this latter development occurred with a single sudden mutation or novel gene constellations at post-50 ka (e.g. Klein 2000Klein , 2019. It is our take, however, that human cognitive evolution is a long, incremental, multi-faceted, and continuous process.…”

The Middle/Later Stone Age transition and cultural dynamics of late Pleistocene East Africa

“…The MSA/LSA transition was integrated into broader discussions of the evolution of H. sapiens only in the 1970s and achieved prominence in the late 1980s–1990s under the Human Revolution model, which, through the important and influential work of Klein and others, posited a single origin point for “modern” human behavior that arose as a genetic mutation somewhere in Africa, coincident with the appearance of LSA sites. Under this model and later variants of it, the mutation rapidly spread across and out of Africa ~40–50 ka through population contact or dispersal . Indeed, Klein's work in particular has been central to drawing attention to the MSA/LSA transition.…”

“…Addressing any of these questions can proceed only with a well‐defined archeological record and a detailed understanding of the timing, tempo, and nature of the transition. While hypotheses related to genetic changes are important, they are not easily addressed with archaeological data, and are not my focus here.…”

“…Under this model and later variants of it, the mutation rapidly spread across and out of Africã 40-50 ka through population contact or dispersal. 29,30 Indeed, Klein's work in particular has been central to drawing attention to the MSA/LSA transition.…”