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(left to right): JOAO LAET/AFP via Getty Images; TOM BJÖRKLUND; OMAR FRANO

Top stories: Breakthrough of the Year, 6000-year-old chewing gum, and a monarch mystery solved

2019 Breakthrough of the Year

Every year, Science assembles a lineup of the most significant advances across scientific disciplines—and a list of what went wrong. Here are our picks, including the very first image of a black hole, a peek into the biology of the mysterious Denisovans, and the raging fires that devastated the Amazon earlier this year.

Nearly 6000-year-old chewing gum reveals life of ancient girl

More than 5700 years ago, a girl spat out a wad of chewing gum at what is now an archaeological site in Denmark. Today, researchers report in Nature Communications that they have sequenced a full genome from that gum, the first time they have extracted so much information from anything other than ancient bones or teeth. The DNA in the gum was so well preserved that researchers were able to offer a glimpse of the girl who had chewed it and a snapshot of her life.

Mysterious monarch migrations may be triggered by the angle of the Sun

Over 20 years, citizen scientists across North America tagged more than 1 million monarch butterflies as they flitted their way southward on one of nature’s more mysterious migrations. Now, scientists analyzing data from those journeys have discovered what may trigger them: the angle of the high noon Sun—which changes over time and as one moves closer to the equator.

Chimps create ‘rock music’ by throwing stones at trees

In forests across West Africa, scientists have caught some grown male chimpanzees engaging in a strange behavior: They pick up a rock, hoot, throw the stone at a tree, and run away. The reason for this odd activity is still a mystery, but a new study reveals a clue: The chimps seem to prefer to throw rocks at trees that create a richer, longer lasting sound when struck. This suggests the chimps are chucking the stones either as a method of communication—or simply because they like the sound.

Final 2020 spending bill is kind to U.S. research

Legislators released details today of how they plan to fund each federal agency for the 2020 fiscal year that ends on 30 September. In almost every case involving science, Congress agreed to give the agency an absolute increase—and much more money than the cuts President Donald Trump had sought for some in his 2020 budget request in February.