Let me respond to a frequently asked question. The question usually goes something like this: if we know that adult stem cells can do everything that embryonic stem cells can do, why waste time pursuing sources that would supposedly offer the equivalent of human embryonic stem cells? In response, I say that my experience over the past five years working closely with both pro-life and secular scientists and experts in the field of stem cell biology tells me the following:

• Adult stem cell research has proffered hundreds of positive and promising clinical trials on human subjects (something embryonic stem cell research is years from commencing). That is marvelous and it should be pursued and promoted by all possible means.
• Notwithstanding those inroads, adult stem cell research is still at a very early stage; and embryonic stem cell research for its part is at an even earlier stage of development as a science.
• With regard to any eventual therapies, both camps are still very much in the realm of speculation, both sides to often guilty of hyping their cause-and aggravating the ethical divide which afflicts our country.
• It is also clear to me that we are now entering the era of developmental biology. In that realm, biologists want to do basic scientific research on human embryos and the cells that compose them at very early stages so as to harness the science of cell differentiation-the science of how stem cells generate more specialized tissues. They want embryonic stem cells or their functional equivalent. A large percentage of these scientists want these, not for the sake of cures, but for the sake of basic scientific knowledge. For them, the whole project of seeking therapeutic advances using human adult stem cells, noble enough in itself, is largely a side show, having little or no impact on their endeavors. · In this sense, adult stem cell research will never assuage the scientific interest in human embryos.
• And as far as I can confirm in dialogue with some of the best and most honest scientists in the field-and not withstanding a growing body of scientific literature on potentially pluripotent types of adult stem cells-there is no conclusive evidence of a sure source of pluripotent adult stem cells. This means it is has not been demonstrated that human adult stem cells can do, or will be able to do, all that science hopes to do-in terms of therapies and cures-with embryonic stem cells. And remember- it's not all about cures.

That's why I continue to promote research into scientifically viable alternative sources of embryonic-like cells through methods such as altered nuclear transfer and direct cell reprogramming.

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Fr. Thomas Berg is Executive Director of the Westchester Institute for Ethics and the Human Person.