If we are nothing more than our bodies, then we can create a conscious machine simply by finding something that simulates neurons, connecting enough of them in the right configuration, and training the neuron collection properly. But I have a hard time believing that we are nothing more than our bodies.

Why? Well, for one thing, it becomes impossible to escape from some kind of determinism (possibly with some quantum noise at the lowest levels). In particular, in the materialist view, you cannot have any free will or any kind of ability to make a non-determined choice. It's just determinism all the way down - the laws of neurology, which are built on the laws of biochemistry, which are built on the laws of atomic physics. At no level is there a place for a free will.

And if that's gone, then everything we think of as making us human is also gone. Love? You can't love in the highest sense of the word, of choosing to do what's best for another, because you can't choose anything. And even if love just means sex, that's just a matter of deterministic neurological and biochemical responses to stimuli.

Morals? If humans have no ability to choose what they do, how can you say that any action is moral or immoral? You don't say that a rock behaved morally when it followed Newton's laws of motion.

Meaning? If all you are is a deterministic machine, what kind of meaning in life is possible?

So either I'm a machine produced at random by an unfeeling universe, which by a horrible turn of fate has aspirations of being more than a machine, but can never fulfill those aspirations... or the fact that I find that vision horrifying is in fact evidence that I'm more than that.

tl;dr: Materialism is the dominant epistemology of scientists, but it is not anything that science has proven or can prove. If it's wrong, then perhaps human consciousness/thought/mind cannot be reproduced by any algorithm or machine.