One planet, one experiment15.' If this book has a lesson, it is that we are awfully lucky to be here - and by 'we' I mean every living thing. To attain any kind of life at all in this universe of ours appears to be quite an achievement. As humans we are doubly lucky, of course. We enjoy not only the privilege of existence, but also the singular ability to appreciate it and even, in a multitude of ways, to make it better. It is a trick we have only just begun to grasp. We have arrived at this position of eminence in a stunningly short time. Behaviourally modern humans have been around for less than 0.01 per cent of Earth's history - almost nothing, really - but even existing for that little while has required a nearly endless string of good fortune. We really are at the beginning of it all. The trick, of course, is to make sure we never find the end. And that, almost certainly, will require a lot more than lucky breaks.