Evolution of Human Innovation

Pushing Back Evolutionary Timeline

Evidence of Innovation Dates to a Period When Humans Faced an Unpredictable and Uncertain Environment, According to Three New Studies

The early roots of stone tool innovation, exchange between distant hominin groups, and the use of coloring material are reported in three papers in the journal Science on March 15, 2018. These milestones in the technological, ecological, and social evolution of the human species date back to 320,000 years ago, roughly coinciding with the oldest ages for fossils attributed to Homo sapiens, and 120,000 years earlier than the oldest fossils of our species in eastern Africa. The discoveries include clues to environmental change at the time of these milestones and to the possible factors behind these key developments in human evolution. The publications stem from research in the Olorgesailie Basin, southern Kenya, a multi-decade project of the Smithsonian Institution’s Human Origins Program in collaboration with the National Museums of Kenya. 

Three Olorgesailie Achulean handaxes varying in size from 1.2 millions years ago to 500,000 years ago displayed on the left side of the image. Middle Stone Age Innovations such as points and pigments of varying size and color from 320,000 to 305, 000 years ago displayed on the right side of the image.
(© Copyright Human Origins Program, Smithsonian Institution)

The Olorgesailie project is led by Dr. Rick Potts, director of the Smithsonian’s Human Origins Program, National Museum of Natural History, Washington, DC. Potts co-authored the three papers with long-term collaborators Dr. Alison Brooks (George Washington University and the NMNH Human Origins Program), Dr. Alan Deino (Berkeley Geochronology Center), Dr. Kay Behrensmeyer (NMNH), Dr. John Yellen (National Science Foundation and the Human Origins Program) and 19 additional researchers.

A 3/4 aerial view of Locaility B, Olorgesailie Basin in southern Kenya.
(© Copyright Smithsonian Institution)
A bird’s eye view of the Olorgesailie Basin in southern Kenya. The sediment layers exposed in the eroded landscape provides evidence of an environmental shift between 500,000 years ago, which marks the last known evidence of the handaxe toolmakers in the Olorgesailie Basin, and the more recent sediments dated 320,000 years and younger, which preserve the Middle Stone Age evidence, including the color pigments and sophisticated tools made from obsidian. White and light brown sections of the landscape indicate the ancient lake and lakeside environment associated with older handaxe technology. Middle Stone Age archeological sites occur in the darker brown sediments, which mark the end of the stable lake environment and the onset of dramatic environmental unpredictability and uncertainty in the region marked by fluctuations between wet and dry conditions.
 
The first evidence of human life in the Olorgesailie Basin comes from about 1.2 million years ago. For hundreds of thousands of years, people living there made and used large stone-cutting tools called handaxes. Based on archeological excavations that began in 2002, the three new studies show that, between 500,000 and 320,000 years ago, early humans in East Africa had begun using color pigments and manufacturing more sophisticated tools than those of the Early Stone Age handaxes, tens of thousands of years earlier than previous evidence has shown in eastern Africa. The sophisticated tools were carefully crafted and more specialized than the large, all-purpose handaxes. Many were points designed to be attached to a shaft and potentially used as projectile weapons, while others were shaped as scrapers or awls.
 
Middle Stone Age stone tools and pigments
(© Copyright Smithsonian Institution)
The Smithsonian team found small stone points made of non-local obsidian, a glassy black volcanic rock, at their Middle Stone Age sites. The team also found larger, unshaped pieces of the sharp-edged volcanic stone at Olorgesailie, which has no obsidian source of its own. The diverse chemical composition of the artifacts matches that of a wide range of obsidian sources in multiple directions 15 to 55 miles away, suggesting exchange networks were in place to move significant quantities of the valuable stone across the ancient landscape.
 
A central finding of the research is that large quantities of obsidian, valuable for its sharp edges, were found at the MSA sites in contrast to earlier handaxe sites. Chemical matching of the excavated artifacts to obsidian sources in central and southern Kenya shows that large pieces of obsidian raw material were carried from multiple directions of at least 25-95 kilometers (15-55 miles) straight-line distance, and involved far longer travel considering the rugged terrain of the Kenya rift valley. These distant sources were likely occupied by other groups such that the extent of obsidian transfer represents a significant expansion in how hominin groups related to one another. According to the research team, the movement of obsidian implies an early development of social networks, which connect members of our species in larger numbers and across longer distances than small bands typically travel in a day. Hunter-gatherer societies show that such networks are crucial for survival in patchy or unpredictable environments. Creating and sustaining these networks requires considerable social and cognitive complexity. Our papers provide the earliest evidence of extensive human contacts across larger landscapes than in earlier hominins. These oldest known social networks reflect a change in how early humans related to and kept track of a larger social world.
 
 
Middle Stone Age point and core fit together. The point is positioned directly on top of the middle portion of the core.
(© Copyright Smithsonian Institution)
MSA refit point and core side by side. Core on the left. Point on the right.
(© Copyright Smithsonian Institution)
The MSA at Olorgesailie included novel forms of technology compared with earlier times. Small stone points made on obsidian, which is not available in the immediate vicinity, were produced using prepared core techniques in which flakes of a desired shape and thickness were struck from the core, suggesting complex planning compared with the older handaxe technology. The small, triangular-shaped points were an especially important development. The widest areas opposite the pointed ends were sometimes modified to allow hafting to shafts. The emergence of this potential for projectile technology was ultimately important in the development of hunting, especially of fast or dangerous prey struck at a distance with reduced danger to the hunter.
 
 
Equally surprising is that black and red rocks that served as coloring material were present at these archeological sites. Concretions streaked with black manganese were clustered at one site, while red ocher was altered and processed at others. The use of coloring material may be a hallmark of symbolic behavior; the ability to use symbolic communication may have been important in maintaining ties among distant social groups.
 
Two Middle Stone Age pigments. Manganese on bottom and Ocher on top from Olorgesailie, Kenya
(© Copyright Smithsonian Institution)
The research team also discovered black and red rocks—manganese and ocher—at the sites, along with evidence that the rocks had been processed for use as coloring material. “We don’t know what the coloring was used on, but coloring is often taken by archeologists as the root of complex symbolic communication,” Potts said. “Just as color is used today in clothing or flags to express identity, these pigments may have helped people communicate membership in alliances and maintain ties with distant groups.”
 
 
Previous thinking pitted the idea of a later, rapid evolution of modern human behavior beginning around 60,000 years ago (the so-called “creative explosion”, which gave rise to sophisticated cave art) versus a far earlier and lengthier period of development of modern behavior based in Africa. In the latter view, MSA behaviors emerged slowly and piecemeal beginning roughly 280,000 years ago. The new findings depict a relatively intricate suite of behaviors – social networks, the use of pigments, and new technology - which emerged considerably earlier than previously known. The finding that such sophisticated behavior had evolved by around 320,000 years ago suggests that emerging cognitive, social, and technological complexity helped to distinguish the earliest Homo sapiens from other hominin species.
 
Crew members excavating at MSA site GOK-1
(© Copyright Smithsonian Institution)
In this Olorgesailie Basin excavation site, red ocher pigments were found with Middle Stone Age artifacts. The light brown and gray layers provide evidence of ancient soils and of landscapes affected by earthquakes and other seismic activity, factors that rapidly altered the environment and resources on which human ancestors depended for survival.
 
 
A question addressed in the papers is how and why these shifts in the behavior of human ancestors took place. What factors spurred their evolution? The research team investigated the survival conditions connected to these fundamental evolutionary changes. The major shift in early human behavior coincided with a massive (~85%) change in mammal species and a prolonged period of strong climatic and landscape change. A unique combination of geological, geochemical, paleobotanical, and faunal evidence suggests that the earliest MSA southern Kenya took hold during an era of pronounced resource instability and episodes of scarcity. In settings of unstable resources, the expansion of human social networks may have become an important survival tool.
 
photo of labeled cliff faces of Labeled photo cliff faces of the Oltulelei Formation and the underlying Olorgesailie Formation.
(© Copyright Smithsonian Institution)
View of part of the Oltulelei Formation and the underlying Olorgesailie Formation.  The dark “Oltulelei Tuff” was deposited on the Olorgesailie Fm. about 225,000 years ago.  Then a deep valley was eroded into the earlier deposits and filled by the red-brown Oltepesi Member sediments, which are ~103,000 years old. The light tan sediments in the upper right are ~50,000 years old.  The sediments and the dates thus show geologically rapid changes in the landscape where MSA artifacts were made and used by early Homo.
 
 
In a related paper published March 15, 2018 in the Geological Society of America Bulletin, the Smithsonian team added further evidence that Middle Stone Age humans faced rapidly shifting environments. Interest in human evolution has stimulated geological work in the Olorgesailie Basin of southern Kenya. The sediments of the newly named Oltulelei Formation in the basin preserve the Middle Stone Age evidence, which "makes sense when we understand the geology of the enclosing rocks," says lead author Anna K. Behrensmeyer, "particularly the age of the strata and the nature of the paleoenvironments associated with archeological and fossil sites." The synthesized result is a picture of geological change in which both tectonics and climate altered the East African landscape inhabited by early populations near the origin of Homo sapiens. 
 
Crew members excavating MSA Site  BOK-1
(© Copyright Smithsonian Institution)
At this Olorgesailie Basin excavation site, the Smithsonian team discovered key artifacts and pigments. Fossil bones found at the site also showed that a significant change in the kinds of animals in this region occurred around the same time as the transitions in human behavior. This turnover signaled that environmental conditions significantly changed and affected which animals could thrive in the region.
 
 
In excavations focused on the later phases of the Acheulean, the team also uncovered shifts in this older way of life that entailed making smaller tools, using distant stone materials, and expanding the area of movement by groups. These new behavioral patterns, dating between 615,000 and 500,000 years ago, may have offered the foundation for later evolutionary possibilities resulting in the origin of the MSA. The period between 615,000 and 320,000 years ago thus represents a critical era in the emergence of Homo sapiens.
 

The research teams for the three studies published in Science include collaborators from the following institutions: the Smithsonian Institution, the National Museums of Kenya, George Washington University, the Berkeley Geochronology Center, the National Science Foundation, the University of Illinois at Urbana-Champaign, the University of Missouri, the University of Bordeaux (Centre National de la Recherche Scientifique), the University of Utah, Harvard University, Santa Monica College, the University of Michigan, the University of Connecticut, Emory University, the University of Bergen, Hong Kong Baptist University and the University of Saskatchewan.

Funding for this research was provided by the Smithsonian, the National Science Foundation, and George Washington University.

 

Summary of the papers:

The paper by Alison S. Brooks, John E. Yellen, Richard Potts, and 12 coauthors announces the oldest known evidence of the technology and behaviors linked to the emergence of the human species. The article focuses on early evidence of resource exchange, or trade, between distant groups of ancestral humans, and the use of coloring materials, which is a form of symbolic behavior typical of our species.

Brooks, A.S., Yellen, J.E., Potts, R., Behrensmeyer, A.K., Deino, A.L., Leslie, D.E., Ambrose, S.H., Ferguson, J., d’Errico, F. Zipkin, A.M., Whittaker, S., Post, J., Veatch, E.G., Foecke, K., Clark, J.B., 2018. Long-distance stone transport and pigment use in the earliest Middle Stone Age, Science. http://science.sciencemag.org/cgi/doi/10.1126/science.aao2646

 

The paper by Richard Potts, Anna K. Behrensmeyer, and 13 coauthors identifies the adaptive challenges during this critical phase in African human evolution. Integrating diverse sources of environmental data, the article advances the idea that changing landscapes and climate throughout the region prompted the evolutionary shift by favoring technological innovation, longer distance movements, and greater connectivity among social groups as a means of adjusting to scarce and unpredictable resources.

Potts, R., Behrensmeyer, A.K., Faith, J.T., Tryon, C.A., Brooks, A.S., Yellen, J.E., Deino, A.L., Kinyanjui, R., Clark, J.B., Haradon, C., Levin, N.E., Meijer, H.J.M., Veatch, E.G., Owen, R.B., Renaut, R.W., 2018. Environmental dynamics during the onset of the Middle Stone Age in eastern Africa, Science. http://science.sciencemag.org/cgi/doi/10.1126/science.aao2200 

 

The paper by Anna K. Behrensmeyer, Alan Deino and Richard Potts presents the results of more than 15 years of field research on the last 500 thousand years of geological history in the southern Kenya rift system.  The team worked together to integrate the geology, the absolute ages, and the archeological sites to synthesize a detailed history of rapid environmental changes that affected the landscape inhabited by early populations of our genus, Homo."

Behrensmeyer, A.K., Potts, R., Deino, A., The Oltulelei Formation of the southern Kenyan Rift Valley: A chronicle of rapid landscape transformation over the last 500 k.y., 2018. Geological Society of America Bulletin. https://pubs.geoscienceworld.org/gsa/gsabulletin/article/529628/the-oltulelei-formation-of-the-southern-kenyan

 

The paper by Alan Deino and 5 coauthors provides the chronology for the discoveries described in the accompanying papers, and documents one of the oldest known and most securely-dated sequences for the African Middle Stone Age, between 320,000 and 295,000 years ago. The article relies on the latest developments in 40Ar/39Ar dating, integrates U-series analyses carried out at the Berkeley Geochronology Center, and offers a synthesis of dates for late Acheulean and early Middle Stone Age archeological sites throughout Africa.

Deino, A.L., Behrensmeyer, A.K., Brooks, A.S., Yellen, J.E., Sharp, W.D., Potts, R., 2018. Chronology of the Acheulean to Middle Stone Age Transition in Eastern Africa, Science. http://science.sciencemag.org/content/early/2018/03/14/science.aao2216

 

Related news:

"A Cultural Leap at the Dawn of Humanity - New finds from Kenya suggest that humans used long-distance trade networks, sophisticated tools, and symbolic pigments right from the dawn of our species"  https://www.theatlantic.com/science/archive/2018/03/a-deeper-origin-of-complex-human-cultures/555674/

"Signs of symbolic behavior emerged at the dawn of our species in Africa"  (great video on this page) http://www.sciencemag.org/news/2018/03/signs-symbolic-behavior-emerged-dawn-our-species-africa

"Ancient climate shifts may have sparked human ingenuity and networking" https://www.sciencenews.org/article/ancient-climate-shifts-may-have-sparked-human-ingenuity-and-networking

"Colored Pigments and Complex Tools Suggest Humans Were Trading 100,000 Years Earlier Than Previously Believed - Transformations in climate and landscape may have spurred these key technological innovations" https://www.smithsonianmag.com/science-nature/colored-pigments-and-complex-tools-suggest-human-trade-100000-years-earlier-previously-believed-180968499/

“New Understanding of Kenyan Paleoenvironments Opens Window on Human Evolution in the Area"  http://www.geosociety.org/GSA/News/pr/2018/18-10.aspx

“Changing environment influenced human evolution” http://www.bbc.com/news/science-environment-43401157

“Unstable climate forced early humans to be more social and creative - when times got tough, early humans got craftier, more social, and eventually brainier“ https://www.arstechnica.com/science/2018/03/unstable-climate-forced-early-humans-to-be-more-social-and-creative/