R is for Rubber

Rubber isn’t an Ancient Invention, is it? Wasn’t rubber invented by Charles Goodrich (or was it Goodyear?) Or the Michelin Man? Historians seem to think so. A 2021 textbook on material culture history starts: “Rubber began its global bouncing career in the late 15th century.” Another says : “Columbus discovered rubber!” (Columbus discovered a prison cell is what Columbus discovered. ) Or: “Goodyear invented vulcanized rubber!” (Goodyear.com seems to think so.)

Some encyclopedias rightly credit the Mesoamerican cultures with discovering the properties of rubber, though usually they get two sentences, while Anglo-Europeans like Joseph Priestley, Charles Condamine, and Goodyear get several paragraphs. Let’s be clear. The Olmecs , Mayans, and Aztecs, starting as far back as 1600 BCE, cultivated and used rubber. They understand how to use it, what to use it for, and how to improve it. They were proficient with polymer chemistry–vulcanization–to extend its functionality They also invented sports in ways that would seem eerily familiar to us.

Given that we use rubber every darned day, I thought the Mesoamericans deserved a little more credit than always being the fifth oh, and... culture that I include. I thought they deserved their own post.

This post, therefore, deserves its own three questions:

1. What are the origins of Rubber?
2. How did the ancient civilizations with access to Rubber use it?
3. How are these early practices echoed in modern-day Rubber use?

The Rubber People and Their Mesoamerican Neighbors

Olmecs meant “rubber people.” At least that’s what the Aztecs called them in their language, Nahautl,: Ōlmēcah. Although this is where confusion and mistranslation reigns. Olmecs is what the Aztecs called the people who lived in the Gulf lowlands when the Spanish showed up in the highlands of Mexico.

Let’s back up a little further. And use a map. Here’s a little primer on Mesoamerica.

The Olmec culture, the earliest of Mesoamerican “civilizations,” from 1600-400 BCE. They were primarily located in the “Gulf lowlands,” meaning the less-hilly area directly south of the Gulf of Mexico. (MEXICO. Not Gulf of America.) Researchers don’t know why the Olmec “disappeared” around 400 BCE other than climate change and other usual threats to survival. (See Anasazi). Although they had a writing system, we don’t know what they called themselves.

The Mayans lived to the east, primarily spreading up and over the Yucatan peninsula. While Mayans were planting crops and growing communities by 2000 BCE, their greatest cultural period began with the development of cities like Chichen Itza @750 BCE. The Mayans began to dwindle by 900 CE–again, climate change and environmental threats–and the one remaining city was wiped out by the Spanish invaders in 1697 CE. The Mayans had the longest time to develop and perhaps “invent” things, but there was little left when the Spanish came.

After the dwindling of the Olmec central cities, people still lived in the Gulf Lowlands and to the west in the Mexican highlands, but in smaller groups. Meanwhile, a group of Nahua-speaking people spread south from northern Mexico, from desert to hills and a better climate, roughly beginning in the 200-400 CE range. Over time, these cultures created city-states in the north and west as well as moving to the east in former Olmec territory. The city-states in what is Northern and Central Mexico today were highly sophisticated by the European Middle Ages. Tenochtitlan had 400,000 people. Along with Tetzcoco and Tlacopan, the three cities shared a language and strong trade alliances. During the 12th-14th centuries, they banded together into an alliance known as the Aztecs, and those were the folks that Cortes encountered in the 1500s.

All of these had access to rubber, so that now seems like a good time to discuss polymer chemistry.

Mesoamerican Chemistry

Rubber is the sap of the Hevea brasiliensis tree, a tree which originated in Brazil, but had spread broadly across much of South and Central America by the time the Olmecs and Mayans came along. The sap is naturally stretchy. The Aztecs called it olli; the Mayans referred to it as k’ik’ che’.

What happens with rubber molecules is that they are loosely arranged in an unstretched state, then lined up when latex is stretched. However, when the sap dries, most of its stretchiness goes away. It becomes brittle and breaks when stretched. The hard brown rubber can be “flaked,” which is why untreated rubber, or India rubber, was first used as pencil erases. (Hence, the applied name “rubber” meaning to “rub out.”)

Today, most of what we know as stretchy rubber has been vulcanized. It’s worth noting here that this is a hilarious word, since it refers to the Roman blacksmith god but was applied by an American scientist to a Mesoamerican sap. The Mesoamericans didn’t call the process vulcanization, but they knew how to do it.

We know they knew how to treat rubber by the time the Spanish arrived because the invaders noted that the people wore black sandals and used a pliable black substance. That substance was on axe handles, headdresses, straps, and balls. Brittle natural rubber dries brown and can’t be used in any of these ways, so the Mesoamericans already knew how to vulcanize rubber.

Treating rubber takes several steps. First, the sap needs to have its water removed, preferably with something acid-like. Before it dries to the brittle state, it the needs to be mixed with the right kind of liquid and heated. Goodyear used magnesium. The Mesoamericans used the juice of the morning glory plant.

When rubber is mixed with the right liquid substance, heated, cooled, and dried, it becomes stretchy, bouncy, pliant, and waterproof. Both the Olmecs and Mayans knew how to do this by 1600 BCE.

The Excitement of an Attached Axe Haft

The Spanish reported that the Aztecs (et al) employed black rubber, so clearly this heating/morning glory process was known by 1520. But archaeologists have much older implements with treated rubber. Hafting an axe–that is, rapping rubber around the wood handle helps it absorb shocks better.

Treated rubber was also used as an adhesive. In its liquid form, rubber acts like glue, causing things to tightly adhere to each other. Dried rubber rubber wrapped around natural substances–say wood and ceramics–makes them less breakable as well as sticking them together.

Treated rubber made into sandals would make them waterproof. It’s fairly wet in the jungle, so anything to help gain traction would be useful. Forming a long “rope” of rubber could work for everything from flinging arrows to holding bags.

Furthermore, these cultures didn’t just create treated rubber. They varied the formula according to the needs of the item. Hard black sandals likely used one part rubber to three parts juice. Balls for bouncing would be more equal parts. There’s no evidence that the Olmecs discussed it with their Mayan neighbors, in international chemistry conferences, but they might have shared trade secrets. Somehow these cultures all figured out how to transform and customize latex to maximize the usefulness of its chemical properties.

What should now dawn on you, as it did finally to me, is that the Europeans didn’t find out how to treat the rubber before they enslaved and massacred all the indigenous people They had to wait another 300 years for an American chemist to “rediscover” vulcanization. Maybe they should have asked more questions before destroying all the Mayan and Aztec people, monuments, and buildings. Hindsight’s 20/20.

The Good Ol’ American Ball Game

The Olmecs, Aztecs, and Mayans all played ball. Not with the Spanish–at least not to the satisfaction of the Spanish. It’s hard to say, since the Aztecs “invited” Cortes in, hoping he would help them kill a rival tribe, and it turns out Cortes killed them and took their stuff. So they chose poorly. Anyway, the Mesoamerican cultures all had versions of games that used a bouncing ball, a ball unlike anything that had been seen by Europeans before.

The Olmecs, the oldest of the Mesoamericans, played a game now referred to as ulama. This is the game painted by Charles Weiditz (see top). Players wore nearly nothing and points were scored for how and where the ball was hit. There might be a wall, but not necessarily, and ther was no ring. The players primarily used their hips, as feet and hands were off limits.

The game was exceedingly popular, in that some 2500 stone ball courts were built throughout Olmec territory. Artists of the day also painted and sculpted examples of the games, with spectators. It seems eerily familiar. Is that a referee or a bookie standing front right?

The Mayans also created their version of a game, pok-te-pok, with courts and a ball. But they took it a few steps further. First, they incorporated the game in religious rituals, describing the game as ordained by gods. Players might have to be purified before and after playing, perhaps saying a prayer in the huddle or kneeling before the play. No, sorry, that’s American football.

The courts, like the one in Chichen Itza, were more elaborate. In one formation, there was a sideways “hoop” high on the wall. The goal involved scoring against the wall with varying rules. Getting the ball through the hoop was rare, more like capturing the quidditch if your remember your Harry Potter. This game was a little more physical, which meant that players wore padding. The ball was also twice as heavy, even though it did bounce.

Certainly, they were other variations. Another indigenous group called the Zapotecs used a small mitt made out of stone–what biceps!–to hit the ball. In some cities, the losing team captain might have been executed (I would say something about a sacrifice fly… but no…)

What They Didn’t Invent and Why They Don’t Still Have Rubber

I had long read speculation that severed heads were used as balls, but this now seems somewhat stupid. These games were designed around balls chemically altered to have a lot of bounce. Heads wouldn’t score points. I say nix to the idea of severed heads. The 12th century Arabs, now, played soccer with their enemies’ severed heads, but I’ll save that story for the Silk Road Alphabet.

Columbus brought back–likely not especially willing–ballplayers, which is how the Europeans learned about these games. They surely found the balls intriguing. Since 1523, ball games have obsessed sports fans worldwide. England and Scotland are given credit for creating the original versions of rugby and soccer (folkball), so I’m not saying the Mesoamericans invented modern sports, but they did invent the balls.

Strangely enough, the Mesoamericans definitely did not influence tires. They didn’t use wheels. It baffled historians that the Mesoamericans seemed to know what the wheel was, since they had it on toys, but didn’t actually have carts with wheels, rubber or otherwise. This curious fact was long used as evidence that the Meso cultures were simply not very advanced. However, researchers now think that the lack of draft animals in the region coupled with the jungle and hilly terrain made wheels impractical. You try pushing that cart with wheels up the hills of the Sierra Madres or through the jungle. Good luck.

It’s well documented how the Europeans–Spanish primarily–enslaved the indigenous Mesoamericans, massacring some, killing others with disease. Researchers think some 90% of the entire American populace died from smallpox brought by the Europeans. They did, however, like the rubber trees and, though it took more than a century, finally managed to bring rubber seeds back. This turns out to be ironic.

As part of the attempt to broadly exploit the natural resources of the region, rubber plantations in Central and South America were planted by the Spanish from the 17th to the 19th centuries, on an increasing scale, once Goodyear “invented” vulcanization and the auto manufacturers began to demand tires. However, by 1904, concern started to mount as manufacturers noticed the rubber trees dying. A leaf blight spread through the crops, exacerbated by the industrialization of large crop fields.

The Brazilian and Amazonian rubber trees died out. Today, 90% of the world’s rubber is harvested in Southeast Asia, which has no leaf blight. Yet.