Pg 1 of the guide reveals ". . .  an utterly insignificant blue-green planet whose ape-descended life forms are so amazingly primitive . . ."  So since it is later revealed that he is  descended from the Golgafinrcham we can also guess  that the Golgafinrcham are "ape-descended life forms." Alternatlely we can assume that this entry in the guide is one of those where ". . . it has many omissions and contains much that is apocryphal or at least wildly inaccurate. . ." 
 

Ok... probably partially descended from Golgafrinchans.

I think Arthur descended from a bunch of telephone sanitizers, marketing consultants, hairdressers and other middle men from Golgafrincham. :)
Apart from that it's a nice piece... although I have to agree with Opacus. If you for example try to stand in Arthur or Ford's pose you'll notice if you lean backward your hips will automatically move forward.

I love it! It would be cool to put these guys in a 2D platformer game!

Fantastic work, what a great idea.

What really bugs me is that all characters are out of balance. If they'd stand that way as real persons, they'd fall over.

Haha, very cool. I really like this :)