" We have both been given the same wish to survive, We are all, you see, toys of the life-force. It made you numerically stronger, but mentally undeveloped. It made us mentally strong but physically weak: now it has set us at one another, to see what will happen. A cruel sport perhaps, from both our points of view, but a very very old one. Cruelty is as old as life itself. There is some improvement: humour and compassion are the most important of human inventions; but they are not very firmly established yet, though promising well. But the life-force is a lot stronger than they are; and it won't be denied its blood-sports. "

― John Wyndham , The Midwich Cuckoos