Hominid hunting requires a lot of hard work and determination. Paleoanthropologists can spend months surveying a landscape, studying the fine details of a geologic formation and sifting through mounds of sediments. But sometimes all it takes is dumb luck. Here’s a look at five hominid fossil discoveries that were complete accidents.

Neanderthal 1 (1856): While quarrying limestone, workers unearthed some bones in Feldhofer Cave in Germany’s Neander Valley. The men thought they had found the remains of an old bear and tossed the fossils aside. The quarry’s owner gave one of the bones, a skullcap, to schoolteacher Johann Fuhlrott. Although the skull had thick browridges and a sloping forehead, Fuhlrott recognized the fossil was more human than bear and turned it over to Hermann Schaffhausen, an anatomist at the University of Bonn who concluded the skull belonged to an ancient human race. In 1864, Irish geologist William King pointed out that the cave sediments in which the fossil was found dated to more than 30,000 years ago. Due to the great antiquity, he suggested the skullcap belonged to an extinct species of human, one that he named Homo neanderthalensis. This was the first time anyone had recognized a fossil as being a part of an extinct hominid species. But Neanderthal 1, as the skullcap is now called, wasn’t the first Neanderthal ever found. A skull discovered in Belgium in 1829 and another one found in Gibraltar in 1848 were later classified as Neanderthals.

Cro-Magnon (1868): Clearing a path for a road in southern France, construction workers exposed the entrance to a limestone rock shelter. The cave was named Cro-Magnon and inside workers found the skeletons of four adult Homo sapiens and one infant, in addition to stone tools and perforated shell beads. Researchers realized these humans were quite old because their bones were found in association with the remains of mammoths and lions. (Radiocarbon dating in the 1950s confirmed that these people lived roughly 30,000 years ago.) The name Cro-Magnon eventually became synonymous with early Europeans from this time period.

Kabwe 1 (1921): At the Broken Hill (now Kabwe) iron and zinc mine in Zambia, Swiss miner Tom Zwiglaar came across several fossils, including a skull, jaw and leg bones. The specimens looked human, but the skull also had features that didn’t resemble any modern people, such as heart-shaped browridges and a sloping forehead. The bones were sent to British paleontologist Arthur Smith Woodward. He decided the fossils represented an extinct hominid species he called Homo rhodesiensis (Zambia was once part of the British colony Northern Rhodesia). Today, the Kabwe 1 skull, dating to 300,000 to 125,000 years ago, is classified in the species Homo heidelbergensis, which some paleoanthropologists think was the common ancestor of Neanderthals and modern humans.

Taung Child (1924): Clearly, mines are a great place to stumble across hominid fossils. The discovery of the Taung Child is no exception. In 1924, a mining official noticed a monkey skull lodged in a chunk of limestone that had been blasted from a quarry near Taung, South Africa. The official brought the skull home, and his son later showed to it Raymond Dart, an anatomy professor at the University of the Witwatersrand. Intrigued by the specimen, Dart had the quarry send over some more rubble that might contain fossils. Inside was a promising rock that looked like the surface of a brain. Careful scraping with a pair of knitting needles allowed Dart to liberate the brain’s corresponding face from another piece of rock. The face looked like an ape, but Dart recognized that aspects of its brain looked like a human’s. He believed the fossil represented an intermediate species between apes and humans, and named it Australopithecus africanus. It was the first discovery of an Australopithecus, and it spurred other hominid hunters to start looking for our ancestors in Africa.

Australopithecus sediba (2008): This discovery wasn’t completely unexpected, but the finder of the fossil was. Lee Berger of the University of the Witwatersrand was surveying South Africa’s Malapa Cave with his Witwatersrand colleague Job Kibii when Berger’s 9-year-old son Matthew announced he had found something: a rock with a hominid collar bone sticking out. Additional excavation led to the recovery of two hominid skeletons dating to nearly two million years ago. The older Berger decided the skeletons represented a new species, Australopithecus sediba, which is a leading candidate for ancestor of the genus Homo.