Tom's original question as to the evidence that man has inherent rights is an important one that I've been thinking about since he first posed it. The concept of innate rights was mostly conceived of during the Enlightenment. During that time the "evidence" was even more hidden. Man lived under mostly an absolute monarchy, where rulers were divinely granted rule over mankind. Organized religion was used as a tool for tyrants to rule over the populace.

To me, Tom's question just brings up more questions. Despite the lack of "evidence" of innate rights, Locke's viewpoints took hold and ignited a transformation in political thought. Perhaps the driving factor was morality and the lack of morality of the ruling class? Perhaps these innate rights became evident because the ruling class disregarded these rights.

What will wake up the world today? Perhaps the evidence of innate rights becomes more apparent when those rights are violated, like the need for water is apparent when water is not around.

Jay and Kevin,
If one believes in the Bible, and that God created man in his image, then it is easy to believe that men are "endowed by their Creator with certain unalienable rights", although at the time the Constitution was written He hadn't yet extended those rights to women or Blacks.
If one doesn't believe that rights are God-given, then they are much more difficult to explain. I think that Dr. Murray Rothbard was the greatest libertarian of the 20th century, but in his book The Ethics of Liberty his explanation of how humans acquired the rights to life, liberty, and property seem to fail. I parsed his sentences very carefully, and all I can come up with is that because human beings think, they therefore have rights which other animals do not possess. But other animals think to some degree. A coyote that has lost toes in a steel trap will not be trapped again. When one tries to corner a pig in a barn the pig sees the problem and responds. Dr. Rothbard could have made the case that since rights do not exist, that no group of people calling themselves a majority have a right to coerce anyone else, and that Rousseau's "Social Contract" is nonsense unless someone voluntarily signs it.
This does not mean that we are not hardwired with some natural ethics. We recognize babies and find them cute and are protective of them, at least partially due to the disproportionately large head size, and we find baby elephants cute although they are very large. On the "bad" side of natural ethics is our innate tribablism in which we feel that it is not nearly as bad to kill and maim people of other tribes as it is our own, but this is lessening as modern communication and transportation increases the size of our tribes.
There is also a relatively new philosophical field called "rational ethics". I think that Mark Twain anticipated this ethics when he said "When you tell the truth, you don't have to remember anything." Being honest is an easier way to live. Contrast this with Aquinas' statement that lying is a misuse of God's gift of speech in his defense of the Ten Commandments.
Tom

As noted previously, if you fool a pig or a coyote once, you are unlikely to fool them again. This may be one of the major diffences between pigs, coyotes, and your average voter.