Posted in History & Literature


In the 1790’s, an Oxford University student by the name of William Buckland pulled an unusual prank. One night, he took buckets of bat guano and spread it on the Oxford College lawn, spelling out “GUANO” with the material. For those who have never heard of guano, it is the excrement of a bird or bat. You could imagine the shock of Oxford authorities the next day at the sight of poop on their prestigious lawn.

The guano was cleaned up immediately. But after a while, a mysterious phenomenon occurred. Everyone could see “GUANO” clearly spelled out on the lawn in tall, luscious grass, rising above the surrounding grass. Even after it was freshly mowed, the letters kept growing back, thicker and faster than the other grass.

The reasoning behind this is that guano is an excellent fertiliser. Animal excrements have long been used in farming as a fertiliser, as they contain vital nutrients such as nitrogen, phosphate and potassium that plants need to grow. Bat and bird poop in particular contain large concentrations of these nutrients.

Guano had been used as a fertiliser for over a millenium in the Americas, such as by the Incans. It was known to the West by the 1700’s, but the thought of applying poop to prestigious English gardens did not sit right, therefore it was not widely used for a long time.

But by the 1800’s, many European scientists noted the potent ability of guano in transforming sterile fields into plentiful farmlands in Peru. Demand for guano rose rapidly as people caught on to how guano could drastically improve crop output and food production.

Ramon Castilla, the president of Peru, capitalised on this by exporting large quantities of guano to Europe. Peru had some of the largest deposits of high-quality guano thanks to its native seabird population, with entire mountains and islands of guano being available for mining. The massive spike in guano trade resulted in Peru’s greatest age of prosperity – known as the Guano Era. Peru used this newfound economic boom to abolish slavery, eliminate head taxes on indigeneous populations and started a public education system.

This sounds like a success story, where a developing nation enjoys dramatic growth with improved quality of life for its citizens thanks to good timing and natural resources. However, the guano story has a far darker side.

To have better access to guano deposits, wars were fought and genocide committed. Chile invaded Bolivia to seize control of Guano Islands, while the USA and Britain started colonising and annexing Pacific islands to access guano reserves. Aggressive mining of guano disrupted natural habitats of seabirds and bats, resulting in destruction of entire ecosystems dependent on guano for nutrients. In the late 1800’s, approximately 53 million seabirds lived on the Guano Islands, whereas only 4.2 million lived there by 2011. Many people were forced into slavery or exploited to decrease costs of mining guano, with miners often working in horrific conditions.

Guano dominated global economics and politics of the 19th century, but its reign ended in 1913 when German chemists Fritz Haber and Carl Bosch successfully started mass-producing ammonia using a novel chemical process (Haber-Bosch process), fixing nitrogen from the air to cheaply produce nitrogen-based fertiliser. This ended the need for guano as a source of nitrogen, while dramatically improving agriculture and food supplies around the world.

Isn’t it fascinating to see how much impact bird poop has had on world history?

Posted in Psychology & Medicine

Viscera: Large Intestine

(Learn more about the organs of the human bodies in other posts in the Viscera series here:

The final destination of food travelling through the digestive tract is the large intestine, or colon. It is the site where digested food is transformed into faeces, ready for excretion. The large intestine is much shorter than the small intestine – roughly 1.5m in length. Unlike the small intestine which is relatively free and mobile, the colon is fixed to the abdominal wall. It starts in the lower-right corner of the abdomen in a pouch called the caecum (connected to the small bowel). This is where the appendix is located. The colon then ascends the right-side of the abdomen (ascending colon) all the way to the diaphragm, does a 90-degree turn to the left (transverse colon) until it hits the spleen, then goes downwards to the lower-left corner (descending colon). Here, the colon bends into an S-shape towards the centre (sigmoid colon) until it ends as the rectum, which opens out to the anus. The colon essentially frames the contents of the abdomen.

The colon’s main function is the absorption of water and salts from the food that has been processed by the small bowel. As it sucks out the water in this liquid, it becomes more and more solidified. The brown colour of normal stool comes from bile and bilirubin (from the breakdown of red blood cells) secreted by the liver into the duodenum. For this reason, biliary obstruction (e.g. due to gallstones) causes pale stool and dark urine (overflow). Stool also contains undigested material like fibre, giving it bulk. Because it is at the end of the digestive tract, stool can be used to diagnose many diseases, such as an infection in the gut (bacterial, viral or parasitic).

The colon is a common site for cancer to occur in. Because there is room to grow, colon cancers are often found late when they have already spread and is incurable. The key symptoms of colon cancer are bloody stool (although this can be due to many reasons such as haemorrhoids), worsening constipation, anaemia (from blood loss causing iron deficiency), change in bowel habit and general symptoms of cancer (e.g. weight loss, fatigue).

(Appearance of colon cancer on colonoscopy)