Other apes still share, especially our closest relatives, chimps and bonabos. Back when humans still lived as part of nature (i.e., hunter/gatherers) it remained the most viable mode of human survival, the only strategy that made sense; the tribe combed its territory as a group, when someone found a tree full of ripe fruit, there was a party. Recall that the most American of holidays, Thanksgiving, is entirely a celebration of the generosity of native people (hunter/gatherers) who shared what they had with the starving white settlers who would later steal their land.
Jefferson understood the need to share, advocating both a progressive tax structure and the redistribution of land. And for a brief period near the end of the Civil War, there was a short-lived experiment in redistribution when human beings who had been treated as property themselves (i.e., former slaves) were given 40 acres and a mule to provide for their families.
Perhaps the greatest recognition of the need for sharing in a civilization was realized by Jewish brilliance; the Jews understood that some people were greedier than others and some of the greedy ones were sharp enough to amass great wealth at the expense of the rest of the community. So every 49 years there was a year of Jubilee, where not only land was redistributed back to families who had lost it over the previous 49 years, but all debts were also forgiven and all slaves freed; everyone started over with a clean slate and on equal footing.
Given that there are now more than 7,000,000,000 humans drawing their existence from 1 fragile planet (which has a finite and limited carrying capacity), the sanctification of greed and the vilification of sharing are a sure recipe for destroying the only life support system which we (and millions of species of fellow earthlings) will ever know. Granted, sharing can be taken too far; there once was a Jewish heretic who, for instance, told his followers: "If a man asks for your shirt, give him your coat also…” but even if we've given up on "WWJD?" surely we could at least behave as generously as those terrible communists suggested: "From each according to ability, to each according to need".
Keep up the Good World........