For example, both humans and chimps have a broken copy of a gene that in other mammals helps make vitamin C. ... It's hard to imagine how there could be stronger evidence for common ancestry of chimps and humans. ... 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.

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.

As commonly understood, creationism involves belief in an earth formed only about ten thousand years ago, an interpretation of the Bible that is still very popular. For the record, I have no reason to doubt that the universe is the billions of years old that physicists say it is. Further, I find the idea of common descent (that all organisms share a common ancestor) fairly convincing, and have no particular reason to doubt it.

The conclusion of design flows naturally from the data; we should not shrink from it; we should embrace it and build on it.

Thus it seemed to Haeckel that such simple life could easily be produced from inanimate material.

The basic structure of proteins is quite simple: they are formed by hooking together in a chain discrete subunits called amino acids.