Unit 3 - Task 3 - the one about when Geology is Archeology and Isotrope is Isotope ...

"You will have to read one of the following articles. Some have already been allocated, so tell me in advance through a mail which is the one you are going to work with. Once chosen, read it and take some notes, as you will be making a c. 10 minute presentation next week were you will explain us part (or all) of said article.

GEOLOGY - JAVIER

-ISOTROPE TESTING IN BEADS

https://www.the-scientist.com/notebook/eggshell-beads-point-to-far-flung-relationships-in-southern-africa-67715

"

So, just before Manolo posted this task in Moodle, I was trying to find anything in google to do with the teaser I got in class. The four keywords I wrote down were: Geology, Isotropic, Beads, Africa.

And I could not find much!

It turns out that the article is not about Geology at all, but rather Anthropological Archeology.

They both usually find stuff in the ground, but are not the same at all!

Another confusing term: Isotropic vs Isotopic ... just one consonant apart, but it makes a huge difference!

Anyway, this is the link to the article proper:

Ancient Beads Point to Far-Flung Relationships in Southern Africa 

So, first of all, what are eggshell beads?

They are beads, like the ones on necklace jewelry, made of eggshell and in this particular case, ostrich eggshell.

Just for comparison, these are typical egg shell thicknesses: Chicken eggshell is 0.3 mm and ostrich is 3.5 mm in average, or about 10 to 11 times thicker.

So, it turns out that ostrich eggshell beads are fairly common in parts of Southern Africa and in some parts of Asia, and are still in use to this day by some African tribes.

They have been found in archeological sites in Africa and in quite significant numbers in caves in Lesotho, dating back up to tens of thousands of years old. Incidentally, ostriches were quite unlikely to be living in Lesotho, since it is pretty much mountain country, not the preferred habitat of the ostrich.

The theory is that the beads found in those caves in Lesotho were brought in or exchanged with other tribes.

The problem and the question is: Can scientists prove that? Where did the beads come from?

It turns out that the ratios of strontium isotopes in eggshells (and bones) closely match the ratios in the rocks and soils where the animals lived.

So, archeologists from the University of Michigan are running isotope analysis on the beads to compare them to other bones and rock analysis and try to pinpoint where the eggshells originated from.

There were some difficulties at the start, as the researchers needed a large number of reference samples from multiple locations to be able to compare their eggshell samples. But fortunately, there are loads of animal teeth and bones available in all the small natural history museums of the region.

After a lot of work, the first thing the researchers concluded was that the eggshells from the Lesotho caves did not originate from there, but at least 100 km away, since the strontium signatures did not match the local bones or rocks. About 20% of the beads were from at least 200 or 250 km away. Some from even much further away.

The oldest eggshell bead dated from about 33000 years and it came from further away than 250 km.

So it seems that ostrich eggshell beads were part of a very old tradition to create and strengthen trading and social networks.

How the beads got to the caves in Lesotho is another question altogether. Were they exchanged from tribe to tribe or did they travel with traders from far away? Were there seasonal human migrations?

One thing is for sure, the eggshell beads are evidence of long distance relationships between tribes. The early homo sapiens groups likely used the beads as gifts to build relationships with other groups.