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What's a prehistoric toolkit and how could it rewrite human history?

Exactly how, when and in at what point of evolution humans left Africa remains a point of hot debate in a number of academic fields.
Exactly how, when and in at what point of evolution humans left Africa remains a point of hot debate in a number of academic fields.
George Diebold/The Image Bank/Getty Images

Researchers that study humanity's past have developed something of a mission, if not an obsession, with charting the course that humans took from the African cradle of our species. The ideas that shape the debate are often contentious: Did a great many people leave Africa at once and spread out to populate the rest of the world? Did successive waves take place, with different groups going in different directions? Did humans evolve in Africa and then leave or did an ancestral hominid exit and evolve into regional races after becoming separated geographically?

These questions plague researchers of human origin theories. To investigate these questions, science has deployed a wide array of disciplines. Linguists track the evolution of words and languages to chart the course of human development. Geneticists look for evidence of population bottlenecks -- points where the population has dramatically decreased and genetic diversity along with it -- in the genetic codes of modern humans. And anthropologists search out toolkits.

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Toolkits are the types of tools used by humans in a given period, to a given culture or in a certain area and style. It's a common description -- and an important one; the Iron, Bronze and Stone Ages all describe the materials people used to make tools. Not only time, but entire cultures, may be marked by toolkits. The mysterious Clovis people of North America are identified by the fluted arrow and spear heads unique to their toolkit.

There is a lot of value in using toolkits to describe, identify, date and track humans. Because they're made of hard materials like stone or metal, tools can withstand the ravages of time. They also tend to illustrate human craftsmanship, since tools like axe heads, arrows and hammers must be honed, sharpened and shaped. While employed as-is rather than shaped by humans, the earliest tools -- the Oldowan toolkit of about 2.6 million years ago -- still show signs of use, like batter marks on hammerstones [source: Smithsonian].

Humans leave behind evidence of their presence in a given place through their tools. By using chemical techniques for dating of the particles found in the soil surrounding the tools or in the tools themselves, anthropologists can also determine the approximate time the tools came to rest at the place they were found.

This is why a 125,000-year-old toolkit recently found in the United Arab Emirates could rewrite human history. We'll explain on the next page.

An example of a Stone Age axe head.
An example of a Stone Age axe head.

In 2006, researchers discovered a rock shelter in a mountainous area at Jebel Faya, about 62 miles (100 kilometers) from the Persian Gulf. As anthropologists began excavating, the site yielded evidence of human presence. Several different assemblages (in this case, groups of tools and artifacts on a single site that belonged to people of different eras) were uncovered from the Bronze and Stone ages. The oldest of these assemblages included axes, scrapers and denticulates (toothed tools used as saws) [source: Switek].

The researchers at the Jebel Faya site used a process called luminescence dating to come up with a rough idea of when the tools were last exposed to light. Crystalline materials found in rock store radiation from sunlight. When they're covered up by soil or sediment, the rocks maintain this radiation, which can be released and measured. The amount of luminescence generated when the radiation is released can be converted into an approximate age. The more luminous the radiation, the longer it's been since the rock was exposed to sunlight.

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The luminescence dating showed the oldest tools found at the Jebel Faya site had last been exposed to sunlight between 100,000 and 125,000 years ago. What's more, the researchers found the tools were produced with the same methods used by groups living in East Africa around that time.

This isn't supposed to be. According to popular belief, humans didn't enter the Middle East until 65,000 years after these early tools were made [source: Reuters]. And they certainly weren't thought to have entered the area through East Africa. Human origin theories place these migrating humans not only later in history, but also coming from a different direction -- from North Africa into Asia.

Yet, these tools, along with recent remains dated from about the same period uncovered in modern-day Israel, suggest the migration of modern humans took place far earlier and along different routes than previously thought [source: Switek].

The Jebel Faya researchers point to recent evidence that the Arabian Peninsula during the era was lusher than it is today, offering migrating humans sustenance through vegetation and eating other animals. The Red Sea, which separates the peninsula from eastern Africa, may have also flowed at a lower level than today, which would allow for easier passage of humans.

Perhaps the biggest challenge to the Jebel Faya site is the lack of human remains associated with the tools. Without associated remains, it's equally possible that the discovery means we'll rewrite our understanding of tool making, rather than human migration.

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Sources

  • Archaeology Wordsmith. "Assemblage." (Accessed January 31, 2011) http://www.archaeologywordsmith.com/lookup.php?category=&where=headword&terms=assemblage
  • Callaway, Ewen. "Early human migration written in stone tools." Nature News. January 27, 2011. (Accessed January 31, 2011)http://www.nature.com/news/2011/110127/full/news.2011.55.html
  • Harmon, Katherine. "Middle Eastern Stone Age tools mark earlier date for human migration out of Africa." Scientific American. January 27, 2011. (Accessed January 31, 2011) http://www.scientificamerican.com/article.cfm?id=middle-eastern-stone-age-tools&page=2
  • Hawks, John. "Jebel Faya and early-state reduction." John Hawks Weblog. January 29, 2011. http://johnhawks.net/weblog/reviews/archaeology/middle/jebel-faya-2011.html
  • Johanson, Donald. "Origins of modern humans: multiregional or out of Africa?" Action Bioscience. 2001. (Accessed January 31, 2011)   http://www.actionbioscience.org/evolution/johanson.html
  • Krock, Lexi. "Stone age toolkit." Nova. March 1, 2009. (Accessed January 31, 2011)http://www.pbs.org/wgbh/nova/ancient/stone-age-toolkit.html
  • Smithsonian National Museum of Natural History. "Early stone age tools." (Accessed January 31, 2011) http://humanorigins.si.edu/evidence/behavior/tools/early-tools
  • Switek, Brian. "Ancient tools may mark earlier path out of Africa." Wired. January 27, 2011.                                                          http://www.wired.com/wiredscience/2011/01/new-out-of-africa/
  • U.S. Geological Service. "What is luminescence dating?" October 28, 2010. (Accessed January 31, 2011)http://crustal.usgs.gov/laboratories/luminescence_dating/what_is_tl.html

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