A man from the Dani tribe cuts the head of a pig after cooked by traditional way which is use burned hot stones at Obia Village on August 9, 2014 in Wamena, Papua, Indonesia. The stone-age Dani tribe live a traditional existence in the Baliem Valley, which is situated 1600 metres above sea level in the heart of the Cyclops Mountains. (Photo by Agung Parameswara/Getty Images)

A man helps another make his way through deep mud at the site of a landslide at the Koslanda tea plantation near Haldummulla October 30, 2014. Hopes of finding survivors under the mud and rubble of a landslide in south-central Sri Lanka had run out by first light on Thursday, though a government minister cut the estimated death toll to more than 100 from 300 the previous night. (Photo by Dinuka Liyanawatte/Reuters)

A miner with a donkey makes his way through the low and narrow tunnel leading out of a coal mine in Choa Saidan Shah in Punjab province, April 29, 2014. Workers at this mine in Choa Saidan Shah dig coal with pick axes, break it up and load it onto donkeys to be transported to the surface. Employed by private contractors, a team of four workers can dig about a ton of coal a day, for which they earn around $10 to be split between them. The coalmine is in the heart of Punjab, Pakistan's most populous and richest province, but the labourers mostly come from the poorer neighbouring region of Khyber Pakhtunkhwa. (Photo by Sara Farid/Reuters)

In this May 2, 2015 photo, skywriter Nathan Hammond releases smoke as he writes messages of hope and love over New Orleans, during the New Orleans Jazz & Heritage Festival. Hammond was commissioned by local entrepreneur, Frank Scurlock, who said the messages were simply his way of reminding people that goodness can still flourish in a world that seems increasingly marred by violence. (Photo by Gerald Herbert/AP Photo)

A man wearing a face mask walks his dog as he pulls a trolley after shopping in Beijing on February 13, 2020. The number of deaths and new cases from China's COVID-19 coronavirus outbreak spiked dramatically on February 13 after authorities changed the way they count infections in a move that will likely fuel speculation that the severity of the outbreak has been under-reported. (Photo by AFP Photo/China Stringer Network)

Brain-on-a-chip. Dazzling in green and magenta this image shows the nerve fibres (in green) produced by neural stem cells (in magenta) as they grow on a synthetic gel. Captured by a technique known as confocal microscopy, the image is part of research shedding light on how tinkering with the environment can affect the way in which nerve fibres grow. (Photo by Collin Edington and Iris Lee/Massachusetts Institute of Technology/Wellcome Images)

In a July 14, 1967 file photo, left, National Guardsmen make their way along Market Street in Newark, N.J, after an evening of deadly rioting and looting in what came to be known as the Newark riots. In a June 16, 2017 photo, right, an ambulance drives on the same block 50 years later. (Photo by AP Photo/File, left; Julio Cortez, right)

A student aims a stick of wood at Bolivarian National Police officers during clashes outside the Central University in Caracas, Venezuela, Thursday, June 9, 2016. Students had planned to march from Venezuela's top university to elections headquarters, but hundreds of police in riot gear blocked the way. Students covered their faces with Venezuelan flags and threw bottles, stones and sticks while police lobbed tear gas. (Photo by Fernando Llano/AP Photo)