Complex sentence: Leakey's primary interest was in the arena of physical anthropology so his interest in the shell midden sites waned upon the find "Proconsul africanus" on Rusinga Island, Lake Victoria, in 1948.
Split into simpler sentences: Leakey's primary interest was in the arena of physical anthropology. His interest in the shell midden sites waned upon the find "Proconsul africanus" on Rusinga Island, Lake Victoria, in 1948.