The Face of History: Fossil Evidence of the Earliest Modern Human Outside Africa
By Kirsten Meltesen
Edited by: Katherine Hill
Who would have thought that one small piece of bone could change our entire perception of human evolution? A discovery by Dr. Israel Hershkovitz and his colleagues recently did just that. In January of 2018, the researchers revealed in the journal Science that they had uncovered a left hemimaxilla belonging to none other than Homo sapiens while excavating an Early Middle Paleolithic site in Misliya Cave, Israel. The fossil, pictured right, is a piece of bone corresponding to the upper left jaw of a skull. Even more exciting, the fossil’s teeth were all almost perfectly preserved. The fossil itself was dated to be between 177,000 to 194,000 years old¹. This age makes this skull fragment, nicknamed Misliya-1, evidence of the earliest anatomically modern human outside of Africa to date.
Prior to this discovery, the earliest evidence of modern humans outside of Africa came from the sites of Skhul and Qafzeh, both of which are also located in Israel. Fossils from these sites were dated to 120 thousand years ago and 100–90 thousand years ago respectively. Their discovery outside of Africa provided evidence that early modern humans left Africa via the Northern Route, moving through the Sinai Peninsula and across the Levant region of the Middle East². The Levant is the region of land in southwestern Asia which connects Africa to Asia, encompassing the western coastline of the Middle East along the Mediterranean to the eastern deserts³. Additional genetic analysis of African and Near Eastern populations also support the idea that migration between Africa and Eurasia occured primarily via the Levant². Thus, Misliya-1 is consistent with previous theories of human dispersal patterns
What is unique about Misliya-1, however, is its age. To determine how old the fragment was, three independent laboratories conducted radiometric dating of both the fossil’s teeth and of archaeological material associated with the fossil at the site¹. By comparing ages estimated from three different types of dating methods, the researchers were able to conclude that Misliya-1 was approximately 131 to 227 thousand years old, markedly older than either the Skhul or Qafzeh discoveries discussed above¹.
In addition to dating the fossil, the scientists also needed to show that the skull fragment belonged to a modern human. To do so, Hershkovitz and his team compared the shape of the jaw bone and the shapes of the teeth to other known modern humans and their ancestors using a computer program. The results of their analyses, depicted left, show that Misliya-1 (highlighted in red) is located in the lower right hand corner along with other known recent modern humans (indicated in gray). It is distinct from Neandertals (indicated in black) and early middle Pleistocene hominins (indicated in purple). Because Misliya-1 was associated with other early modern humans, this analysis provided evidence that the skull fragment did belong to a modern human. Furthermore, the characteristics of the teeth as determined through the Arizona State University Dental Anthropology System were found to be consistent with recent modern humans as well.
In addition to discovering the hemimaxilla, Hershkovitz and his colleagues also discovered well-defined hearths, stone-based tools, animal remains, and indications of the use of Levallois technology, a unique stone-knapping technique used to create tools1,4. These findings suggest that the emergence of Levallois technology in the Levant may be associated with the introduction of early modern humans to the region. The Levallois technique is a distinctive method that doesn’t vary too much in the regions where it has been discovered5. Because of this, anthropologists in recent years have hypothesized that this method of tool creation requires individuals to actively teach one another the technique in order for it to be replicated so consistently5. Thus, the association of early modern humans with Levallois technology presents new evidence that early modern humans possessed the capacity for social learning.
Despite all of this new information, there is always more to learn. The discovery of Misliya-1 has pushed back the date of human dispersal out of Africa by nearly 40,000 years, leaving scientists with plenty of new questions about early human migration. Was there a single dispersal event or many waves of dispersals? Did early modern humans interact with Neandertal populations living in the Levant at the same time? Could humans have left Africa at an even earlier date? If we want to find out, we’ll have to keep digging.
Works Cited
¹Hershkovitz, Israel, et al. “The earliest modern humans outside Africa.” Science, vol. 459, no. January, 2018, pp. 456–59, doi:10.1126/science.aap8369
²López, Saioa, et al. “Human Dispersal out of Africa: A Lasting Debate.” Evolutionary Bioinformatics, vol. 11, no. S2, 2015, pp. 57–68, doi:10.4137/EBo.s33489.
³Killebrew, Ann E., and Margreet L. Steiner. The Oxford Handbook of the Archaeology of the Levant: C. 8000–332 BCE. OUP Oxford, 2014. Accessed February 17, 2018.
4Adler, D. S., et al. “Early Levallois Technology and the Lower to Middle Palaeolithic Transition in the Southern Caucasus.” Science, vol. 345, no. 6204, 2014, pp. 1609–14.
5Lycett, Stephen J., et al. “Levallois: Potential Implications for Learning and Cultural Transmission Capacities.” Lithic Technology, vol. 41, no.1, 2016, pp. 19–38.
