One of GEITP’s (many) ongoing themes is the Great Human Diaspora –– i.e. when and how the Homo genus arose, when and how at least 25 different “fits and starts” of new branches arose/diverged and lived for tens of thousands of years before becoming extinct (and how much did the climate and diet affect their genomes along the way), and when and how the Neaderthals, Denisovans, Homo sapiens (“modern humans”) and (perhaps other sublines?) arose and migrated out of (and sometimes back into) Africa, constantly being challenged by their environment (climate, diet, social conflicts, cross-breeding). GEITP has stayed almost exclusively with molecular biology and genetics (DNA sequence) and epigenetics. Therefore, these articles [attached as one continuous file] are a bit divergent from that theme because these data are in the field of paleo-anthropology and anatomy.
Modern Homo sapiens share certain skeletal features that can also be recognized in fossil remains –– these include “a high, rounded braincase (the part of the skull surrounding the brain), a small face tucked beneath it, and small, separated brow ridges (bone ridges above the eye socket).” Our understanding of episodes in human evolution is mainly based on fossils, radicarbon- and thermoluminescence-dating of nearby rocks/soil, and available DNA for sequencing. However, gaps in our knowledge remain, as far as when and where H. sapiens evolved from ancestral humans within the genus Homo. Authors (in the first of the two full-length attached articles) describe the earliest known H. sapiens fossils, and present an analysis of the size and shape of these remains. Accompanying thermoluminescence-dating evidence is provided by authors (in second of the two full-length articles), which underscore data in the first article.
The fossils, excavated with associated stone tools, provide crucial information about early steps in the evolution of H. sapiens. Fossil remains indicate that early modern
H. sapiens were present in Africa from about 200,000 years ago, and these individuals had an anatomy similar to that of humans today. However, DNA analyses of living people and fossils suggest that our lineage diverged from that of our closest relatives –– the Eurasian Neanderthals and Denisovans –– more than 500,000 years ago (i.e. considerably earlier than the first recognizable early modern H. sapiens). This could imply that earlier members of the H. sapiens lineage existed, members that had features predating emergence of the full suite of modern skeletal traits, and that instead had a preponderance of primitive, rather than modern, features. Until now, it has been difficult to identify such fossils.
Human fossils, recovered from Morocco in 1961 and 1962, had been called “African Neanderthals” and were estimated to be about 40,000 years old. One skull was reported in 1970s, however, to be quite distinct from that of Neanderthals and more closely resembled that of H. sapiens. A child’s jaw was found at the site in 1968, and analysis of the teeth indicated a modern-looking growth pattern; this was significant because modern humans mature more slowly, and over a longer period of time, than was the case for primitive humans such as Homo erectus and Neanderthals. Furthermore, this specimen was dated to ~160,000 years ago. Because more-modern-looking human fossils had been found in East African sites of similar age, the view had persisted that the Jebel Irhoud (Morocco) fossils were “marginal in their location in Africa and peripheral to the origins of H. sapiens.”
Authors of both full-length papers calculated the richest African Middle-Stone-Age hominin site to have an age of 315 ± 34 thousand years ago, also showing that the evolutionary processes behind the emergence of H. sapiens involved the entire African continent. Further support is obtained through the recalculated uranium series with electron spin resonance date of 286 ± 32 thousand years ago for a tooth from one Irhoud hominin mandible. These ages are also consistent with the fauna and microfauna assemblages and almost double the previous age estimates for the lower part of these deposits. The emergence of our species, and emergence of the Middle Stone Age, appear to be close in time, and these data suggest a larger scale –– potentially pan-African –– origin for both.
Nature 8 June 2o17; 546: 289–292, 293–296 (full articles) and 212–214 (News-N-Views)