Existence can devalue human life. What is infinitely special to us as individuals is infinitely worthless to the universe and just slightly above completely meaningless in terms of our own planet. (an individual's life, that is)
So at best, I would say Darwinism may highlight this.
But even then, one can make the argument that is improves the value of human life as the life of 1 individual is sort of like a stepping stone, and a learning process, for the whole human society. This makes the value of a human's life pretty high as many humans down the line may benefit from what has happened with earlier human lives, giving them long lasting value that cascades out into infinite.... ok somewhat too dramatic but you get my point.