Proteins are the machinery of living tissue that builds the structures and carries out the chemical reactions necessary for life.

It was a shock to people of the nineteenth century when they discovered, from observations science had made, that many features of the biological world could be ascribed to the elegant principle of natural selection.

Despite some remaining puzzles, there's no reason to doubt that Darwin had this point right, that all creatures on earth are biological relatives

Throughout history there have been many other examples, similar to that of Haeckel, Huxley and the cell, where a key piece of a particular scientific puzzle was beyond the understanding of the age.

I find the idea of common descent (that all organisms share a common ancestor) fairly convincing, and have no particular reason to doubt it.

Since natural selection requires a function to select, an irreducibly complex biological system, if there is such a thing, would have to arise as an integrated unit for natural selection to have anything to act on.

We can look high or we can look low in books or in journals, but the result is the same. The scientific literature has no answers to the question of the origin of the immune system.