Here is a list of possible frauds. It is uncomfortable, but the hypothesis of fraud must be mentioned in order to be tested.
Eugene Dubois, Dutch anatomist and fossil collector. By reading Ernst Haeckel, Dubois was convinced that humans evolved in southeast Asia, where orangutans and gibbons live. In 1888 Dubois moved there, telling others that he would return with proof of the missing link. In 1894 he returned to Amsterdam with Java Man fossils, the first specimens of Homo erectus. He became professor of geology. He prevented his fossil materials from being carefully inspected or chemically tested.
Robert Elliott, English amateur archeologist. For two years, he regularly visited a chalk quarry near Kent, asking workers to sell him any prehistoric stone tools they might find in ice-age gravels that overlie the chalk. In 1888, the workers showed him a human skeleton, which he excavated. In 1894 these bones were studied by a professional, and became known as the Galley Hill Man. The bones were subjected to fluorine testing 50 years later, and shown to be modern, not fossils. That testing was done by Kenneth Oakley. Soon after, Oakley debunked Piltdown Man and a skeleton from Olduvai gorge using fluorine analysis. Fluorine analysis and other chemical tests are no longer carried out on hominid fossils.
Otto Schoetensack, German geologist. He studied ice-age deposits near Heidelberg. For twenty years, he kept asking the owner of the Mauer gravel pit to be on the lookout for bones of prehistoric man. In 1907 the owner found him a lower jaw. The following year, Schoetensack published a monograph establishing the new species Homo heidelbergensis. (Arthur Keith showed in 1915 that this jaw was remarkably like a female orangutan.)
Arthur Keith, English anatomist and paleoanthropologist. He wrote a book in 1915 The Antiquity of Man, which I think hints at many fossil hoaxes, including his own. From reading about Java Man, Galley Hill Man, and Homo heidelbergensis, I think that Keith realized how successful fossil falsification could be. He decided to carry out the Piltdown Man hoax. He carefully prepared broken orangutan jaw pieces and human cranium pieces, which he gave to Charles Dawson to fool paleontologist Arthur Smith Woodward. Keith, Woodward, and G. Elliot Smith then became famous for their study of Piltdown Man.
Charles Dawson, English solicitor and amateur fossil collector. Either alone or with Keith, he planted the Piltdown pieces and then led Woodward to discover them in 1912. This species, with ape-like jaw and human-like cranium, was named Eoanthropus dawsoni in his honor.
Davidson Black, Canadian physician and anatomist. He worked and studied in Arthur Keith’s laboratory in England in 1914. He then decided he would find human fossils himself. He moved to China in 1919 and obtained two human teeth and some chipped stones from a cave. He announced that these were from a missing link, and received funding to excavate more. Human-like bones were then found, and these became known as Peking Man (Homo erectus). All fossil originals later disappeared and were never recovered.
Unknown Nazi workmen. They dug up a jawbone with one tooth in the city of Athens in 1944. This fossil became known as Graecopithecus. (Racist Nazis were opposed to the model of humans having originated in Africa.)
Tom Gray, American Ph.D student. Together with his advisor, professor Donald C. Johanson, Gray stole a leg bone from a family tomb in Hadar, Ethiopia in 1973. The next year he led Johanson to the place where they discovered the "Lucy" bones (Australopithecus) lying loose on the ground.
Richard Hay, American geology professor. He interpreted geologic relationships in Olduvai Gorge and Serengeti Plain, concluding that bipedal Laetoli fossil footprints had been made in newly fallen volcanic ash. I think the footprints were not in ash, but in water-lain lake muds, and that they were made by Homo sapiens, not Australopithecus. Hay collected minerals to be dated, and arranged for the dating of the footprints. His claim that the layers are volcanic ash makes the footprints to be millions of years old, the same age as the minerals dated.
Mary Leakey, professional paleoanthropologist. She described the Laetoli footprints together with geology professor Richard Hay in 1978. Then in 1979, they had the footprint layer covered by dirt and boulders. This prevented visiting geologists from reinterpreting the footprint layer as lake sediment.
Richard Leakey, professional paleoanthropologist, and American anatomist Alan Walker. They collected and announced the Turkana Boy (Nariokotome Homo erectus skeleton) in 1984. I claim that the bone fragments are not fossils at all. They are recent bones, first broken and buried in recent river gravels, and then discovered. Leakey and Walker saturated the bone fragments in vinyl acetate solution to strengthen them. This made them hard and heavy like fossils, and prevented carbon-14 dating or chemical analysis. The fragments were first collected in loose river sediments, and during the next few years, excavations were made in much older rock layers nearby, leading paleoanthropologists to believe that the fossils came from there.