Sir Wilfrid Le Gros Clark was one of the primatologists who developed the idea of trends in primate evolution and the methodology of arranging the living members of an order into an " ascending series " leading to humans.
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It is an inconspicuous species, often first located by its song, an accelerating and ascending series of musical notes " cuew-cuew-cuew-cue-cue-cue-cu-cu-cu-cu ", or the call, a snarled " churrrr ".
