We can't say that when x happens we get a mass extinction. To the extent we understand mass extinction, one has been caused by glaciation event, one has been caused by a massive climate change, and one has been caused by an asteroid. These events turn out to have no precedent.
Elizabeth KolbertFor a long time, science has gone in the direction of sort of putting people in their place. We learned that the sun doesn't revolve around the Earth, the Earth revolves around the sun; we learned that we're just another species, evolved, like all other species, so we're just another animal, really.
Elizabeth KolbertSomewhere in our DNA must lie the key mutation (or, more probably, mutations) that set us apartโthe mutations that make us the sort of creature that could wipe out its nearest relative, then dig up its bones and reassemble its genome.
Elizabeth KolbertMitochondrial DNA, which is a sort of abridged version of DNA, is passed directly from mother to child, so it's something that can be looked at to trace matrilineal descent.
Elizabeth Kolbert