Well they have noted their bodies don't function like those of humans, being much denser for one, and of course supernaturally strong.i have figured it out
their titties have an anti-gravity field that's why it's always perky and doesnt flop down
that might mean that they also have gravitational pull which can attract objects to them
and that explains why the shirts always fit the titties perfectly
this theory may apply to gera's ass too
Then again, the sheer ridiculous upper body mass of that one guy makes me wonder if the humans are themselves abnormal in this series.