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The cooperative pulling paradigm is an experimental design in which animals cooperate to pull food towards themselves. Researchers use these experiments to try to understand how cooperation works and how and when it may have evolved. Meredith Crawford ran the first such experiment in 1937, attaching two ropes to a rolling platform that was too heavy to be pulled by a single chimpanzee. In another design, a rope comes loose if only one animal pulls it, and the platform can no longer be retrieved. Researchers look for signs of cooperation, such as when an animal waits for another animal's actions before pulling the rope. Chimpanzees, bonobos, orangutans, capuchins, tamarins, wolves, elephants, ravens, and keas appear to understand the requirements of the task, and other animals sometimes manage to retrieve the food. The superior scale and range of human cooperation comes mainly from the ability to use language to exchange social information. (Full article...)

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Chrysler Turbine Car

... that the Chrysler Turbine Car (pictured) could burn a variety of unusual fuels, ranging from furnace, peanut, and soybean oils to tequila?
... that in healthy adults, HMB has been shown to increase exercise-induced gains in muscle size, muscle strength, and lean body mass, reduce muscle damage, and speed recovery from exercise?
... that the fireflies Aquatica ficta and Aquatica hydrophila both have aquatic larvae that are unable to swim?
... that prior to creating Booker T. Washington State Park, West Virginia's Conservation Commission justified its segregation policy by explaining that "our Negro citizens would feel ill at ease" using parks alongside whites?
... that the tropical tree Axinaea sclerophylla is pollinated by birds such as the masked flowerpiercer?
... that Zhang Shengmin led a thousand troops to participate in the reconstruction work after the 2010 Yushu earthquake?
... that the Texas Capitol View Corridors protect views of the state capitol from a cemetery, an air traffic control tower, an interstate highway, and a University of Texas practice field?
... that Hainan Island is dominated by rocks that crystallized from melts?
... that functional accounts of emotion suggest that the function of anger is to correct injustice?
... that Chinese classical musician Lui Tsun-Yuen adapted the English ballad "Greensleeves" for the pipa?

In the news

Kim Jong-un and Donald Trump

An earthquake strikes Hualien, Taiwan, killing at least 10 people and injuring more than 260 others.
The SpaceX launch vehicle Falcon Heavy makes its maiden flight, carrying Elon Musk's Tesla Roadster as a dummy payload.
U.S. President Donald Trump and North Korean leader Kim Jong-un meet (pictured) in Singapore.
Archaeologists announce the discovery using LiDAR of approximately 60,000 Mayan structures in the Maya Biosphere Reserve, Guatemala.
A total lunar eclipse occurs, close to perigee and also the second full moon in a month, a coincidence of events not seen for 35 years.

On this day...

July 27: Tu B'Av (Judaism, 2018)

Signing of the Korean War armistice agreement at P’anmunjŏm, Korea

678 – Sclaveni attackers were forced to give up their siege of the Byzantine city of Thessalonica, being unable to penetrate the city's defenses.
1214 – Philip II of France decisively won the Battle of Bouvines, the conclusive battle of the 1213–1214 Anglo-French War.
1949 – The de Havilland Comet, the world's first commercial jet airliner to reach production, made its maiden flight.
1953 – An armistice was signed (pictured) to end hostilities in the Korean War, officially making the division of Korea indefinite by creating an approximately 4 km (2.5 mi) wide demilitarized zone across the Korean Peninsula.
2002 – A Ukrainian Air Force Sukhoi Su-27 aircraft crashed during an aerobatics presentation at an airshow near Lviv, Ukraine, killing 77 people and injuring over 500 others.

Conrad II of Italy (d. 1101) Elizabeth Plankinton (b. 1853) Alfred Duraiappah (d. 1975)

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A design by Chief Engraver of the United States Mint Frank Gasparro for the Susan B. Anthony dollar, a dollar coin minted from 1979 to 1981 and again in 1999. Proposed as a smaller replacement for the cumbersome Eisenhower dollar, the coin was initially intended to depict an allegorical representation of Liberty. However, legislative and popular demand led to the likeness of social reformer and women's rights activist Susan B. Anthony being used instead. In 1978, Gasparro began preparing a design, going through multiple versions depicting Anthony at various stages of her life before settling on an approximation of her at age 50. After the final design was approved, the dollar was first struck in 1978.

Illustration: Frank Gasparro

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