TITLE: generators of Out(F_n) and homology
QUESTION [8 upvotes]: It is known that the mapping class group of a closed (orientable) surface is generated by elements of finite order. Is this also known to be true for $Out(F_n)?$ A related question is the following: The mapping class group is known to be a perfect group for $g\geq 3,$ that is, it is equal to its commutator. Is this known for $Out(F_n)?$ I can find references to the effect that the rational homology is trivial in low dimensions, but that's not quite the same...

REPLY [6 votes]: In Bridson's "A condition that prevents groups from acting nontrivially on trees" 
it is shown that for $n\geq 3$, $Aut (F_n)$ is generated by subgroups $A_1,A_2,A_3$ such that $\langle A_i,A_j \rangle$ is finite for $i,j=1,2,3$. This answers your question and moreover implies (via Helly's theorem) that for $n\geq 3$, any action of $Aut (F_n)$ on a tree fixes a point. 
Beautiful stuff!