(and other secrets from the world’s oldest man-made material)
The world’s oldest man-made material is probably more familiar than you’d think. Although humans invented this technological marvel about 12,000 years ago, we still use it today!
Concrete is everywhere! It paves our sidewalks, supports our skyscrapers, and dams our rivers. It might be the most consumed synthetic material on the planet today, but concrete (and its fine-grained version, plaster) still has ancient secrets for archaeologists to reveal. In my PhD thesis, I’m working to discover those secrets! Here are 3 things I’ve learned so far:
1. Tiny sea creatures built an ancient city
Although starfish wearing hardhats and wielding hammers sounds pretty fun, these ancient sea creatures were much, much smaller. So, how did they build an ancient city?
The sticky ingredient in concrete and plaster, called lime, is made from rocks rich in the mineral calcite (CaCO3). Some rocks get their calcite from the ocean. The fossils of tiny sea creatures called foraminifera are often made of calcite—it’s these teeny-tiny marine fossils that made much of the lime for the ancient city Alashiya!
Alashiya was a city on the Mediterranean island of Cyprus during the Bronze Age (3300 BCE to 1200 BCE). It’s called Kalavasos-Ayios Dhimitrios today. Ancient Alashiya was a hip and exciting city for its time, with houses, roads, storage buildings for olive oil, and even a drainage system—it had all the essential amenities for your Bronze Age needs!
Many of Alashiya’s luxury structures were built from lime concrete. Using techniques from the geological sciences, I’ve learned that much of the city’s concrete was made with rocks packed with LOTS of tiny sea fossils.
Interestingly, archaeological research shows that this fossil-rich stone (called chalk) wasn’t the only calcite source available to ancient Alashiya. So, why was chalk filled with tiny sea creatures chosen to build this city? Stay tuned–my future research might give us the answer.
2. Ancient concrete reveals ancient recycling
Another secret I’ve learned from ancient concrete: “going green” isn’t such a new concept. People have been making concrete with reused materials for thousands of years!
When chunks of ancient plaster came loose from buildings, those scraps (along with bits of brick and sometimes even broken pottery) were scooped up and mixed into the next batch of lime concrete. These recycled tidbits added extra strength and support to new material, without consuming new resources.
Modern construction is experimenting with using recycled concrete in buildings today. Who knew that we’d have the same ideas as ancient builders? Maybe ancient concrete can give us some more tips on sustainable construction in the future.
3. Making concrete is making (ancient) magic!
Your concrete sidewalks might not seem very supernatural, but stick with me, here: in ancient times, making concrete was magical. Before we had Home Depot, humans made our construction materials by hand. Making synthetic stuff like metal, pottery, and plaster usually required the maker to heat specific rocks or clays with very hot fires–as hot as 1,100℃!
Imagine–what might ancient people have thought when they saw a scorching-hot fire transform rocks into a shapeable form for the very first time? Without our modern knowledge of chemistry, making ancient concrete might have looked like magic.
Archaeological evidence supports the idea that ancient people may have viewed the transformation from limestone to plaster and concrete in a religious or magical way. In the Neolithic Period (about 10,000 BCE to 4,500 BCE), ancient people in the Middle East decorated the skulls of the deceased in plaster, paint, and shells, to ritually transform the skulls into the faces of their loved ones.
Every day, modern humans repeat this magical act to build the world around us. Although its sense of mystical transformation may be lost to the ages, using concrete connects us to 12,000 years of human innovation. That’s pretty magical, when you think about it.
Hannah M. Herrick - Archaeologist 