Well, lets see, on the island in my present pysical condition I'd have to do something that was low key, low stress. What could a weakling such as I contribute to the common weal?
Tend the fire at night, make sure it doesen't go out. Get it cranked up at sunrise by stoking and have it ready for morning meal. Gather small loads of firewood, sort them for building said fire. Stire the food pot, make sure it doesen't boil over. Baby sit any kids that may have survived, in order to free those with stronger abilities to do the grunt work, on and on, and on. In otherwords somehow, someway make myself usefull in order to have a place at the table. That's called having a work ethic.
What does a parisite do? Nothing, but they make themselves seem they are doing. Using any kind of deception in their tool box. Some parisites hide out. When the dinner gong bangs their they are elbowing their seat at the table.
To me it's not the strong verses the weak, it's rather those who are willing to contrbute whatever they can verses the true parisite.