The NY Times today has a profile on Shinya Yamanaka, the senior author on one of the recent papers reporting the creation of pluripotent stem cells by expressing 4 transcription factor genes in adult fibroblasts. Yamanaka (who "is known on campus for refusing to join colleagues for lunch, choosing to eat by himself so he can keep working" - unfortunate, since informal conversations with colleagues can really be quite useful) has without question achieved something significant by successfully creating stem cells, first from mice and then from human fibroblasts. However I take issue with Yamanaka's outlook on the ethics: "Dr. Yamanaka was an assistant professor of pharmacology doing research involving embryonic stem cells when he made the social call to the clinic about eight years ago. At the friend’s invitation, he looked down the microscope at one of the human embryos stored at the clinic. The glimpse changed his scientific career. 'When I saw the embryo, I suddenly realized there was such a small difference between it and my daughters,' said Dr. Yamanaka, 45, a father of two and now a professor at the Institute for Integrated Cell-Material Sciences at Kyoto University. 'I thought, we can’t keep destroying embryos for our research. There must be another way.'" You might expect Dr. Yamanaka to be concerned about the much greater destruction of embryos that takes place in fertilization clinics - far more human embryos are destroyed there than in research labs. A petri dish is not exactly the most natural environment for an embryo, and the very act of creating embryos in vitro puts those embryos at risk. While I'm not belittling Dr. Yamanaka for his views, and realize that he's just giving his impression and not necessarily making a strong ethical statement, I do think we should realize that his reaction is not universal. I've seen human embryos as well - and two of them became my youngest daughters. Several others never made it that far. I don't feel traces of sorrow for those lost embryos. I suspect most physicians who work in fertility clinics feel the same way. Many, if not most scientists whose views I personally know, share this persepctive. We're happy for the ones that become human beings, but we don't lose sleep over the millions of little clusters of cells that are lost each year, both in and outside of IVF clinics.