Extracts from a current paper on the Darwin - Wallace Controversy.
"Though Darwin never acknowledged the Sarawak Law paper , a graduate student, Lewis McKinney (1966) found a copy of it in his collected papers. It had been heavily annotated by Darwin who had obviously recognized its importance....
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"... This completed Wallace’s theory of evolution; he wrote it out and posted it to Darwin from the island of Ternate on 9 March  when the first available ship arrived. McKinney (1966) has drawn attention to another letter, which still exists, and was sent by Wallace on the same boat, on the same day, to Frederick Bates (figure 3). The letter corroborates the dates of posting; it carries the cancellation marks for the various stages of its journey from Ternate and arrived in the Leicester post office for delivery on 3 June.
"The letter to Darwin should therefore have been delivered on the same day or very soon after, but he claimed not to have received it until 18 June. The fact that he had, in the meantime, written to Hooker on 8 June to say that he had finally solved the frustrating problem of how species diverged in nature, looks a little suspicious in these circumstances.
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"That Wallace almost certainly solved the problem of divergence before Darwin did is, perhaps, not surprising. Wallace had much the greater experience in the field of biogeography, which was so fundamental to unravelling the relationships between species. But, even more importantly, he had the advantage that, unlike Darwin, he was looking actively for evidence of evolution while in the field, and
could therefore tailor his data collection appropriately.
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It appears [i.e., it's not proven] that Wallace's contributions enabled Darwin to overcome his conceptual logjams and provided him with some key insights that were integral to his theory as finally published subsequent to Wallace's published papers and letters to Darwin. Darwin finally acknowledged Wallace, but not in the first edition of the Origin, and not in its second.
Extracted from J. Biosci. 35(3), September 2010 ePublication: 30 June 2010
DAVID LLOYD*, JULIAN WIMPENNY and ALFRED VENABLES