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Homo sapiens are primates of the Family Hominidae and are the only living species of their genus. This lineage originated 200 thousand years ago in Eastern Africa and have since spread to all corners of the world.

	HOMO SAPIENS


HOMO SAPIENS / HOMO SAPIENS SAPIENS



Genus:		Homo

Species:		Homo sapiens / sapiens sapiens

Other Names:		• Modern Humans • Cro-Magnon • Omo

Time Period:		• Homo sapiens • 200,000 - 50,000 years ago • Homo sapiens sapiens • 50,000 years ago to Present

Characteristics:		Modern, Migration, Art, More Gracile, Technological

Fossil Evidence:		Fossil Specimens, Europe, Worldwide

Website Links:		Journey of Mankind

Bradshaw Foundation

The ORIGIN OF MODERN HUMANS

by Cassandra Turcotte
Center for the Advanced Study of Hominid Paleobiology (CASHP)

Several lines of evidence support a single African origin for Homo sapiens. For example, analysis of mitochondrial DNA has demonstrated that the greatest level of genetic diversity in modern humans occurs within the African continent, represented by the mtDNA macro-haplogroup L (Ingman et al. 2000). Mitochondrial DNA, of course, is passed from mother to daughter without recombination and thereby preserves a record of female descent to the matrilineal most recent common ancestor - the woman from whom all humans alive today descend (see Pakendorf and Stoneking 2005; van Oven and Kayser 2008).

Homo sapiens Mitochondrial DNA Modern Humans

Mitochondrial DNA has demonstrated that the greatest level of genetic diversity in modern humans occurs within the African continent

This woman, nicknamed Mitochondrial Eve, lived some time between 99 and 200 kyr in East Africa (Cann et al. 1987; Ayala 1995; Jorde et al. 1998). Her descendants gave rise to all present-day variation. Today, there are seven primary subclades of the L haplogroup (L0-L6), all of which present primarily in Africa. Diversity in all non-Africans, including Europeans, Asians and Native Americans, is a subset of the L3 haplogroup (Jorde et al. 1998; van Oven and Kayser 2008).

The earliest human fossils also come from Africa. More specifically, these fossils are found in Ethiopia. The fossil skulls at Omo Kibish attributed to modern Homo sapiens (Day 1969) date all the way back to ~195 kyr (McDougall et al. 2005). Additional finds from Herto Bouri, Ethiopia, dated to ~160 kyr, were characterized as morphologically primitive anatomically modern humans (White et al. 2003; Clark et al. 2003), which the authors refer to as Homo sapiens idaltu to differentiate them from later Homo sapiens sensu stricto. Both are part of the same species, though earlier H. s. idaltu is thought to preserve more archaic morphology such as increased robusticity, prognathism and lack of chin (White et al. 2003; McBrearty and Brooks 2000). H. sapiens are defined in contrast to earlier specimens by a more globular cranium, prevailing orthognathism, and skeletal gracility on top of behavioral modernity (McBrearty and Brooks 2000).

Homo sapiens Modern Humans Homo neanderthalensis Neanderthal Neanderthals

Anatomical comparison of the skulls of Homo sapiens sapiens
(modern humans) and Homo neanderthalensis (right)

EXPANSION

Mitochondrial DNA supports an initial dispersal of the L3 haplogroup from Africa into the Near East up to 70 kyr (Behar et al. 2008; Soares et al. 2012), with the possibility of subsequent dispersals across the Red Sea or through the Sinai. The timing of this expansion has been tied to an improvement in Central and Eastern African climate after 70 kyr (Soares et al. 2012). The earliest fossil evidence of modern humans outside of Africa occur in the Levant, where specimens in Skhul and Qafzeh, Israel date to around ~115 kyr. The disconnect between the early appearance of fossils outside of Africa and the relatively late mtDNA divergence suggests that, while humans made it out of Africa ~100-130 kyr, successful migrations did not occur until much later.

Indeed, human presence in the Levant is a tricky business, with transitions from Neanderthal (e.g., in Tabun Cave) occupancy to modern human and back again (see Stringer 2001). The nature of the interactions between modern humans and Neanderthals remains a hot topic in paleoanthropology today, with genetic evidence suggesting that the two may indeed have interbred (see Sankararaman 2012; Prüfer et al. 2014; Sankararaman 2014).

Skeletal evidence places modern humans in Australia possibly ca. 60 kyr in the Lake Mungo region (Stringer 1999; Thorne et al. 1999; Balme 2013; Long et al. 2014), and in China’s Tianyuan Cave by 40 kyr (Tong et al. 2004; Shang and Trinkaus 2010). Definitive evidence of modern humans in Central Asia and Europe, however, is complicated by a fragmentary fossil record and the presence of similar-looking Neanderthal specimens. Recent work has identified ~45 kyr molars from Grotta del Cavallo in Italy as the first such remains of Homo sapiens in the region (Benazzi et al. 2011), followed by revised dates for the Kent’s Cavern, UK modern humans, placed to ~44 kyr (Higham et al. 2011). Settlement of the Americas occurred relatively late in the scheme of human evolution, delayed by the physical barrier of the Pacific Ocean until glacial periods lowered the sea level enough to expose a land bridge connecting modern day Siberia to Alaska (See Achilli et al. 2013; Meiri et al. 2014; Raff and Bolnick 2014).

An Out of Africa perspective on modern human origins and expansion contrasts what is known as the Multiregional model, where humans are believed to have evolved from specimens of H. erectus in situ around the world. In this way, regional differences accrued but species cohesion was maintained through genetic drift (Stringer and Andrews 1988; Wolpoff et al. 1994). This model expects transitional fossils outside of Africa and regional continuity in morphology. While there is some evidence of genetic admixture (Currat and Excoffier 2011; Prüfer et al. 2014), the long genetic and fossil history of H. sapiens in Africa paints a strong Multiregional view of modern human origins as problematic and the Out of Africa model a better fit of current evidence.

BEHAVIORAL MODERNITY

Traditionally, modern human behavior was thought to arise suddenly and at once across Europe 40-50 kyr, implying quite a long lag between anatomical and behavioral modernity. On top of unfairly portraying preceding human populations as primitive, however, this view is inaccurate. Indeed, the components of behavioral modernity appear within the African Middle Stone Age (McBrearty and Brooks 2000). These activities represent manifestations of advanced cognitive behaviors: abstract thinking, planning, innovation, an appreciation of symbolism.

Indeed, modern humans developed a mastery of their environment and of technology beyond anything observed in earlier species (see McBrearty and Brooks 2000). As discussed, H. sapiens expanded out of Africa and across the world. Given the distribution of this species, it’s no surprise that they developed regional variation in their tools and cultural artifacts, whether it’s the traditional Acheulean handaxes of Stillbay, South Africa (Goodwin 1929) or the hafted points that characterize the Aterian in modern-day Morocco (Debénath 1994). Modern humans made novel use of new materials for their tools, such as bone and horn (Leakey 1971; Blackwell et al. 2008; Brooks et al. 1995; possibly Singer and Wymer 1982), and better lithic sources (e.g. Singer and Wymer 1982). These people engaged in different kinds of resource management, such as more specialized hunting (Klein 1994; Milo 1998) and the extraction of aquatic resources (Robbins et al. 1994). Human in Africa and beyond have also made extensive use of ornamentation and the production of symbolic artifacts. In the African Late Stone Age, for example, ostrich eggshell beads in South Africa are exceedingly common from at least 26 kyr (White Paintings Rock Shelter: Kokis et al. 1998; Robbins 1999). The same kind of beads are observed in Kenya and Tanzania from 37-40 kyr (Ambrose 1998), and pigmented bone ornaments can be found from Blombos, South Africa by 73 kyr (Henshilwood and Sealey 1997). This foundation of behavioral advancement can be seen in all the regions that modern humans eventually occupied.

One of the more familiar examples comes from the Upper Paleolithic of Europe, where early human settlers left behind a rich assemblage of cultural artifacts. Because the first such specimen was discovered in the Abri de Cro-Magnon rock shelter in Les Eyzies-de-Tayac-Sireuil in southwestern France, these humans were nicknamed Cro-Magnons and were responsible for well-known ancient works of art such as the paintings of Lascaux, the Venus figurines, and the Aurignacian technocomplex.

Of course, humans still exist today, pushing the envelope of cultural and technological evolution to ever more spectacular limits. The physical and behavioral modernity of this species have their roots in Africa and subsequently spread around the globe, replacing earlier hominins either through competition or hybridization. The implications of a single successful exit are highly significant, and lie at the core of the Journey of Mankind Genetic Map.

The question of course is now ‘will the Homo genus keep evolving?’ Moreover, what other discoveries will help explain the ‘untidy tree’ of evolution?

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