When Richard Dawkins' book 'The Selfish Gene' was published in 1976, it caused an outrage on the left. Marxists, feminists and others took the book to be a celebration of laissez-faire economics and competitive individualism. But when we look at the versions of Darwinism which had prevailed in the previous period, it becomes clear that 'selfish gene' theory represented a major scientific advance. Far from justifying selfishness, the new Darwinism explains in a convincing way why instincts of solidarity and generosity are commonplace throughout the natural world. Today, one of the major figures in human evolutionary theory is the feminist thinker and 'selfish gene' pioneer Sarah Hrdy, whose book 'Mothers and Others' explains how cooperative childcare was the critical factor which gave rise to our species. Hrdy's work represents a modern scientific vindication of the traditional Marxist theory, popularized by Frederick Engels, that early human kinship and family life was based on collective rather than individual parenthood. This talk will review the catalogue of misunderstandings which led the left across most of the western world to respond to a scientific controversy by tragically backing the wrong side.