Oh! Oh! Oh! I can answer this, since I just read "Longbow: A Social and Military History" by Robert Hardy! Your definition of a "longbow" may be too narrow if you restrict it to bows that are about 6' long, made of yew (both heart and sap wood) and have a D-shaped cross-section.
They have the remains of bows, that would have been approximately 6 ft. in length, that they dug up in Somerset, England. These two bows date to around 2,400 B.C. He also cited examples of longbows from Egypt, other parts of Africa, Asia and, most relevantly to this thread, the cold Nordic regions.
These longbows differed, in many respects (length, wood used and cross-section, for example), to the longbows used by Henry V to obliterate the French at Agincourt, but that weapon itself had evolved from the time Edward I faced the Welsh longbow, a century earlier and those bows were probably different, in some ways, to the examples pulled from the wreck of the "Mary Rose" of 1545.
Interestingly, there was speculation that the Vikings may have re-introduced the longbow to Britain during their occupation of parts of that island.
Thanks for the info on the longbow....so it was around much earlier than what the “Conventional Wisdom” states?