I think you'll have to explain why you think evolution is the central theme of life.
As I said, I think it's the central theme in the sense that it's the underlying principle which ultimately describes the physical characteristics and development of all life on Earth. But if you think that doesn't make it the central theme of life, fair enough. I have no problem with that.
I'd say it's more central than the idea that Nature is all about bloodshed. But, again, that's just my opinion.
Name one reputable biologist who has said that evolution is the central theme of life.
I guess I could try googling some. If I can't find a quote in which they use the exact words: "I declare that Evolution is the central theme of life" are you going to quibble?
Charles Darwin (starting with the easy one)
Stephen Jay Gould
Richard Dawkins
Ernst Mayr
J.B.S. Haldane
Theodosius Dobzhansky
etc.
I kind of cheated and googled "evolutionary biologists" on the assumption that such people, by definition, think of Evolution as being pretty central.