Piltdown Man was the name given to fossilised hominid bones discovered in gravel pits near the Sussex village of Piltdown in 1912. The discoverer was amateur geologist Charles Dawson and he notified the Natural History Museum. Dawson and geologist from the NHM Arthur Smith-Woodward, made further discoveries and were able to put together skull, teeth and jaw fragments and declared it was around 500k years old and therefore a 'Missing Link' between humans and ape-like ancestors. It seemed to have a human-like cranium with an ape-like jaw confirming existing speculation that a large brain had evolved before a less strong jaw and teeth.
From the beginning however there was dispute amongst doctors, and paleontologists about the reconstruction. Some dismissed it as flawed while others accepted the findings. Later fossil discoveries over the decades - such as Tuang Child and Peking Man differed quite considerably so that Piltdown stood out as an aberration. It meant that these later discoveries were dismissed for some time.
In 1953, Time magazine published a study showing the skull was made from three distinct species: a medieval human skull, an orangutan jaw and filed down chimpanzee teeth. All had been stained with an acid and iron solution. A study in 2016 by The Royal Society concluded that Dawson was the forger. He had forged a number of other artifacts over the years in an effort to leave a scientific legacy but whether he worked alone is not known. The impact of Piltdown Man was to set back human origin study for several decades and even now it is trotted out by creationists to show why science is bunk. Forgetting that it was scientists that debunked it.