What if we could honour everyone - the estimated 110 billion or so humans who have ever lived?
Of course, our most urgent challenge right now is to keep working towards the goal of giving everyone alive right now access to basic needs - to water and food, security, health, education etc - and it's painfully clear that, with e.g. growing numbers of orphans around the world, we still have a huge task still ahead of us. (And yes, let's unashamedly say "us", rather than fall back on the third person, abstract term "humanity" that somehow suggests it's someone else's problem.)
However, what if at the same time, as Theodore Zeldin puts it, we could see all the people who've ever lived and honour their memory? If everyone - all 7.8+ billion of us alive now - were allocated, at random (to encourage diversity and understanding) about 15 "ancestors" about whom we would try and find out something - a name, a likely lifespan or job etc. - and for whom we would light a candle, wear a flower, say a prayer...whatever...how much more might we feel part of the same family, regardless of race, creed or gender?
For this, we'd need to join up all the records, histories and anthropological studies that give us clues about our ancestors.