Ian, Picasso's innovation far surpass bis building upon African art. While he was the central figure of Modernism in the visual arts, in many ways he was a precursor of Post-Modernism building upon a broad array of art history and rejecting the notion of loyalty to a single style.
Let's look at what is likely his single most revolutionary painting (one that shocked even Matisse): Les Demoiselles d'Avignon
The impact of African art upon this painting is quite overstated. The first influence was Cezanne:
The general theme and the cluster of female giantesses was drawn from Cezanne's painting, the Large Bathers
... which itself drew inspiration in part from Renoir's Large Bathers
The shattered landscape behind the figures comes from Spanish art... specifically El Greco's View of Toledo
The distorted expressionistic figures come from a variety of sources. In 1906 Picasso journeyed to the ancient Catalan village of Gósol , high in the Pyrenees. A friend had tipped him off about this “magnificent” mountain refuge, which was notorious for its smugglers. There, he was struck by several art works that would alter his approach to art-making. Among these was the "Virgin of Gósol":
He was also struck by other medieval Spanish/Catalan sculpture and fresco paintings:
The "Virgin of Gósol" would serve as the primary source for Picasso's painting, The Woman with Loaves
“Picasso, before those incomparable fragments of early Catalan art, admired [their] power, intensity and skill … and he stated without hesitation that our Romanesque Museum will be something unique in the world, an indispensable resource for anyone who wishes to know the origins of Western art, an invaluable lesson for the moderns.”
Picasso... and Joan Miro, another Spanish Modernist, were both profoundly impacted by the experience of their native Spanish/Catalan Romanesque art. They had a sense that the ‘primitive’ was more authentic and purer than sophisticated Western art of the Renaissance and post-Renaissance periods. There’s a strong element of anti-naturalism at its core, and also anti-academicism. Picasso drew from the imagery of the wide eyes, dramatic gestures, and "simple" symbolism.
The impact of Picasso's experience with Medieval art would not be forgotten. It clearly shows in his later masterwork, Guernica
Returning to Les Demoiselles d'Avignon
, we find more examples of just how Picasso was all over the place... drawing inspiration from the whole of Art History. The figure to the left is built upon ancient archaic Greek Kouroi and Kourai figures:
To all of these influences, yes, Picasso added the imagery inspired by African masks to the two figures on the right.
It is no more reasonable to suggest that Picasso did no more than steal the style of African art (even if that were true) than it is to suggest that Degas did nothing more than steal ideas from Japanese Ukiyo-e prints... or that Stravinsky's Rite of Spring
is no more than a rip-off of Russian folk music. Picasso absorbed his various influences and transformed them into something new. At the same time, Picasso's, Van Gogh's, Degas' and endless other Western artist's admiration of Non-Western and "Outsider" art helped bring recognition of the merit of art long ignored in Post-Renaissance Western culture. By recognizing the "genius" and impact of Picasso, we are in no way undermining the "genius" of African Art, Egyptian Art, Archaic Greek Art, Japanese Ukiyo-e, etc...