CAMBRIDGE, England, July 22 (UPI) -- Infectious disease traveled along the Silk Road as early as 2,000 years ago. Feces collected from an ancient latrine in northwestern China proves traders carried intestinal parasites as well as goods.
The latrine is thought to have been first erected during the Han Dynasty, around 111 B.C., and was used as late as A.D. 109. In ancient feces collected from the site, scientists identified the eggs of four parasitic worm species: roundworm, whipworm, tapeworm and Chinese liver fluke.
The presence of Chinese liver fluke is proof that travelers picked up and carried parasites from disparate regions. Chinese liver fluke, Clonorchis sinensis, requires wet marshland to complete its life cycle. The ancient latrine was located within the arid Tamrin Basin, on the outskirts of the Taklamakan Desert, where the parasitic flatworm could not have survived outside human intestines.
Today, the Chinese liver fluke's closest native habitat is nearly 1,000 miles from the site of the ancient latrine.
"When I first saw the Chinese liver fluke egg down the microscope I knew that we had made a momentous discovery," researcher Hui-Yuan Yeh, an archaeologist at the University of Cambridge, said in a news release. "Our study is the first to use archaeological evidence from a site on the Silk Road to demonstrate that travellers were taking infectious diseases with them over these huge distances."
Rush hour on the Silk Road stretched from 202 B.C. to A.D. 220. The trade route connected merchants, explorers, politicians and soldiers from the Middle East and Mediterranean with their peers in East Asia.
"Finding evidence for this species in the latrine indicates that a traveller had come here from a region of China with plenty of water, where the parasite was endemic," said study leader Piers Mitchell. "This proves for the first time that travellers along the Silk Road really were responsible for the spread of infectious disease along this route in the past."
The findings were published this week in the Journal of Archaeological Science: Reports.
Researchers also recovered personal artifacts from the latrine, as well as "hygiene sticks" -- long rods with cloth tied one end, an ancient version of toilet paper.
CAMBRIDGE, England, July 22 (UPI) -- Scribbled pages in a notebook of Leonardo da Vinci, previously dismissed as nonsense, have been revealed as the polymath's earliest musings on the laws of friction.
Leonardo is widely considered the founder of tribology, a branch of mechanical engineering and materials science that deals with the principles of friction.
Now, scientists have a better understanding of when Leonardo first began to understand the laws of friction. In the years following these early scribbles, Leonardo would expand on the role of friction in engineering and the development of machines.
The significance of the scribbles was discovered by Ian Hutchings, a professor engineering at the University of Cambridge.
"The sketches and text show Leonardo understood the fundamentals of friction in 1493," Hutchings said in a news release.
Art historians had previously dismissed the scribbles as nonsense, focusing instead on the significance of a sketch of a woman some suggest is Helen of Troy. Beneath the woman figure is a quote: "cosa bella mortal passa e non dura," or "mortal beauty passes and does not last."
Next to his thoughts on the principles of friction are a series of sketched diagrams, one depicting a pulley system with a series of blocks supporting a rope tied to a heavy weight.
"He knew that the force of friction acting between two sliding surfaces is proportional to the load pressing the surfaces together and that friction is independent of the apparent area of contact between the two surfaces," Hutchings said.
Until now, science historians have credited French scientist Guillaume Amontons with first describing the laws of friction -- 200 years after Leonardo first put them on paper.
"Leonardo's 20-year study of friction, which incorporated his empirical understanding into models for several mechanical systems, confirms his position as a remarkable and inspirational pioneer of tribology," Hutchings concluded.
Hutchings' analysis of Leonardo's early ideas on friction is detailed in a new paper, published this week in the journal Wear.
Leonardo's groundbreaking notebook is currently on display at the Victoria and Albert Museum in London.