Yesterday was the 125th anniversary of the slaughter of hundreds of defenseless Native People – men, women, and children – at Wounded Knee on the Pine Ridge Reservation in 1890.

While this atrocity was the work of the Seventh U.S. Cavalry, its genesis lies in the policy of genocide and dispossession practiced by European colonial powers from the day of their arrival in the Americas four centuries earlier. Moreover, these practices were sanctioned by racist ideology and acquired extraordinary force and tempo as they evolved and maturated in the “whirlpool,” to use Marx’s word, of an emerging and expanding capitalist economy.

If I had forgotten about this horrific episode and era of history, I have Roxanne Dunbar-Ortiz to thank for recalling it for me. Her new book, “An Indigenous People’s History of the United States,” is a vivid, incisive, passionate, and unforgiving accounting of the nation-building practices of the European settlers and the heroic resistance of indigenous peoples at Wounded Knee and in countless other encounters, across the continent and the centuries. Page after page the author shows how the voracious appetite for land, natural resources, and political and cultural dominance of the settlers was coupled with a ruthless determination and superior weaponry to crush the far older civilizations that had occupied the land long before them.

At any rate, yesterday’s commemoration (as well as Dunbar-Ortiz’s book) should remind us not only of a far more complicated historical narrative — actually counter narrative — about our nation’s origins, shaped as it turns out in the cauldron of systematic dispossession and genocide of indigenous people, not to mention the more widely acknowledged brutal system of slavery and ferocious class exploitation. It should also cause us to extend a hand of solidarity to indigenous people in their present-day struggles for justice, equality, sovereignty, sacred sites, and land rights.

But we should do so not only out of a new moral clarity too long obscured and sense of justice too long denied, compelling as they undeniably are. Such solidarity should also spring from an understanding that a sustained struggle against genocide, dispossession, and oppression of Native peoples in particular – and racial and gender inequality in general – is at the core of a people’s, working class-based alliance that is durable and muscular enough to confront our foes and create a livable and peaceful future for all. In other words, our common future depends on the readiness of each of us to join the struggle to undo (to the extent possible) the crimes of the past – genocide, dispossession, and slavery – and the racial and gender inequalities of the present.

One final word: earlier this year, Ta-Nehisi Coates wrote an essay in The Atlantic making a persuasive case for reparations to compensate for the horrors and long-term impact of slavery on African Americans. It seems to me that a similar though not identical case, which Dunbar-Ortiz does, can be made for reparations for indigenous peoples, who have almost miraculously survived and yet continue to face a denial of their rights to economic security, equality, full sovereignty, and dignity.

Reparations cannot make up for hundreds of years of genocide and dispossession any more than they can compensate for slavery, but they would begin to undo some of the injustices of the past and present and are necessary if our imperfect union is to become a more perfect one and our country to measure up to its proclaimed ideals.