Equal how?

In an interview, of sorts Bill Gates was ask why his foundation primarily helps third world countries. His answer begins, "Melinda and I started our foundation because we believe all lives have equal value." I am consternated by this idea; the idea of universal human equality. At Anderson we had to take a class of half-assed philosophy and one day we discussed human value. The teacher asked me, "Don't you think each human life is valuable, is equal?" My reply? "Equal how?"

In what way are all human beings equal? Human beings have different sexes, different abilities, different preferences, different physical and mental capabilities. Some human beings have no legs, no arms. Some human beings do not even have their own bodies, but share a body with another human being.

We can say that all human beings are equal; we can embrace egalitarianism. But what is the foundation for our doing so? What do we mean by this sort of equality? Because, yes, we can say that all human beings are equal, just as we can describe unicorns. But are we actually talking about anything? And if so, what?

The idea is even further complicated by applying this notion of equality to human embryos. What quality do human embryos have which cow, pig, or dog embryos lack? And what quality do human embryos share with octogenarian human beings?

If we ignore the declaration of this equality as self-evidently true, what is its foundation? And if there is none why do people still use it?

Keep in mind that Plato was wrong.