Why are rat thumbs atrophied ?

I don’t understand why the moderators permit this sort of vicious rant!

Because they don’t play enough Nintendo.

@ratboy Get a grip! Oh, sorry, you have no usable thumbs.

Just thank Darwin that they don’t. (That would be Charles Darwin, not our beloved Flutherite) If rats had thumbs, then we would probably be extinct. They’d be building man traps baited with computer software and/or porn links.

This reminds me of the observation that if spiders were as big as housecats, humankind would be extinct.

Animals don’t evolve things just because they want to. Rat hands do what rats need them to do very well, so there is no selective pressure to change their hand structure. The animals that have evolved opposable thumbs (or the equivalent, like the giant panda which has a thumblike sesamoid bone) use them to exploit niches where an opposable thumb is a big advantage to survival.

Sorry I should be more precise: If they don’t need thumbs, then why do they have a 1/4 thumb? It should be all or nothing, not in between.