claim: Species distribution can be understood only through speciation.
evidence: Doug McAvoy -LRB- born 1939 -RRB- is a retired British trade union leader .. British. British people. trade union. trade union. He was General Secretary of the National Union of Teachers from 1989 to 2004 .. National Union of Teachers. National Union of Teachers. A teacher , McAvoy was secretary of Newcastle-upon-Tyne NUT and became a member of the National Executive of the Union in 1970 .. Newcastle-upon-Tyne. Newcastle-upon-Tyne. He was appointed Deputy General-Secretary designate in 1974 , a post he held until 1989 when he became the first directly elected General Secretary in 1989 .