William MacAskill: ‘There are 80 trillion people yet to come. They need us to start protecting them’

The moral philosopher gives most of his earnings to charity, says we need more not less economic growth to tackle global heating, and in a striking new book argues that it's our duty to ensure the wellbeing of our distant descendants

Although most cultures, particularly in the west, provide a great many commemorations of distant ancestors - statues, portraits, buildings - we are much less willing to consider our far-off descendants. We might invoke grandchildren, at a push great-grandchildren, but after that, it all becomes a bit vague and, well, unimaginable.

And while we look with awe and fascination at the Egyptian pyramids, built 5,000 years ago, we seem incapable of thinking, or even contemplating, 5,000 years in the future. That lies in the realm of science fiction, which is tantamount to fantasy. But the chances are, barring a global catastrophe, humanity will still be very much around in 5,000 years, and going by the average existence of mammal species, should still be thriving in 500,000 years. If we play our cards right, we could even be here in 5m or 500m years, which means that there may be thousands or even millions times more human beings to come than have already existed.