An evolutionary “simple” muscle would be?

Answer 1

Since this is not my area of expertise, I searched Google under the key words "evolutionary 'simple muscle'" to get these possible sources:

http://jeb.biologists.org/cgi/reprint/202/7/867.pdf
http://www.shadmehrlab.org/book/musclemodel.pdf

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.

I hope this helps. Thanks for asking.