Les Animaux dénaturés

The novel was adapted into the motion picture Skullduggery (1970), starring Burt Reynolds and Susan Clark.

What they find is not a fossil, but an actual population of ape-like creatures, called Paranthropus greamiensis after the discoverer, and dubbed Tropis.

They try to use the criterion of interfertility, but it appears that Tropi females can be impregnated by sperm from both man and ape, making it impossible to decide before the offspring reach reproductive age.

[1] P. Schuyler Miller received the novel favorably, noting that it handled its theme "more quietly, less emotionally [and] less melodramatically" than familiar genre treatments of the subject.

[3] Time magazine found it to be a "pungent" satire, '"more supple than subtle", but faulted its "halfhearted love story" and concluded it was "more a polemic than a novel".