Heat Treated Stone Helps Endangered Humans Survive

August 20th, 2010 by James L. Sweaney, CGA, FGA. GG
There' No Place Like Home

There's No Place Like Home

The desire and ability to exploit our environment and to utilize and improve the natural materials we find is rooted in our deepest past, and is in fact, part of the reason we are here today.

I was absolutely fascinated by an article in the August 2010 Scientific American, When the Sea Saved Humanity, that describes findings from an archaeological dig on the Horn of Africa. According to author Curtis W. Marean, his excavations in caves near Capetown show the presence of a small band of early humans during the Ice Age known as Marine Isotope Stage 6 (MIS6).  Somewhere between ~195,00 to ~123,000 years ago, because of the cold dry climate, early Homo sapiens on the mother continent of Africa suffered a severe population crash– the population plummeted from more than 10,000 to a few hundred breeding individuals.

This small endangered band was able to survive along the coast because of the unique ecology of the area, known as the Cape Floral Region, which is characterized by two ready and dependable sources of food. First, this ecology has over 9000 plant species found mainly in two unique vegetative regions known as fynbos & renosterveld, which produce tubers, bulbs and corms that are rich in high quality carbohydrates. These rich sources of calories are easily harvested with digging sticks year round.

The second critical source of food can still be found in the tidal zones along the coast. Here cold highly oxygenated water mixes with plankton-rich warm currents to nourish dense beds of shellfish. This accessible abundance provides a very high quality supply of protein and omega-3 fatty acids. Marean’s excavations show that these early humans enjoyed lots of these critters– perhaps on the half shell?!

With these dependable and abundant food resources, these precious few humans were able to survive this Ice Age that rendered the rest of the African continent uninhabitable. Studies of the DNA of modern-day populations indicate that everyone alive today is descended from this group of people, these few survivors of a calamitous time.

What I found particularly interesting was the author’s discovery of stone tools that had been heat treated! Silcrete, a form of silica and sand, is a common material that is easily obtained but not suitable to make sharp stone tools. When it’s heated and cooled carefully, it transforms into stone that flakes much like flint. Marean and his colleagues excavated numerous sharp tools and bladelets of silcrete that showed evidence of heat treatment. The number of tools indicates that they were an important part of the lives of these early men.

This technology marks two important intellectual developments in these primal humans. First, these people recognized that they could alter a raw material to make it useful. Second, they could carry out the process of gathering and sorting the raw material, preparing the site, and consistently changing the properties of the stone, indicating a capacity for foresight, planning, and organization.

The true significance of this discovery is that these advanced cognitive abilities existed at a much earlier time than previously thought. Other discoveries of heat treatment of silcrete in prehistoric Africa date only to 60,000 to 80,000 BC– these tools were created perhaps 100,000 years earlier!

As a gemologist and jeweler, I was further delighted to read that these humans may have heated yellow ocher, turning it red. The color red has always been associated with the life force and  power. Carvings of this ocher indicate the material may have been valued as symbols in religious/cultural ceremonies, and/or for social identity and personal adornment– humans with a taste for jewelry, even then!

While we know that these findings are subject to review and revision, it is enthralling to see a window into the past that shows the mind of our forbears. They were thinking symbolically and engineering raw materials long before they had the ability to record a history of their culture.

These survival skills are with us today as we struggle to develop and strengthen our culture in a complex and changing world. As a professional jeweler, I’m heartened to see that elements of the skills and craft I love have been an important part of our progression since the time of man began. Further, this discovery of the early use of heat to alter minerals adds a good perspective to today’s debate over the merits or not of heat treating gems.

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One Response to “Heat Treated Stone Helps Endangered Humans Survive”

  1. Randy Hays Says:

    Fascinating topic. Bet it didn’t take long for a pretty seashell to end up on a piece of cord around someones neck.

    I have heard of these finds before. I remember that it was pointed out that gradual migration of just 5 to 10 miles a generation was enough to repopulate nearly all the coastal areas on the planet.

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