|See parts 1 and 2 of V's guest commentary.|
So what does this tell us about pre-implantation embryos? These percentages do not reflect life as we know it. Life is tenacious. Life is greedy. Life hates not to endure. Life employs multiple backup strategies to ensure that it will propagate itself. Life, as a rule, does not go gently into that good night. Of course, this is a bit different in old age, although even then it really doesn’t just give up. Our survival and fitness drive is geared towards successful reproduction anyways. Once you reproduce, (or are past reproductive age) life has begun to run out its course. But before, and through, the reproductive years, life clings with dogged determination. Let us take, for instance, a time point that everyone can agree upon as 'life'----the birth of a child. At this stage, our makeup as human beings ensures that our survival is not left to a wishy-washy 15-30% implantation-like chance. This is clearly reflected in the myriad ways we are programmed to survive---like our innate fight-or-flight response, in our exquisite immune-defense systems, in the fact that breathing and circulation are more reflexes than conscious actions, and so on. Even in the darkest days of human history, I don’t think that there ever was a 70-85% (or even 25-35%) mortality rate due to natural causes (we're not counting wars or genocides here) of children and youth. Admittedly, historical mortality rates are hard to interpret because in many countries, children did (and still do) die due to starvation, rampant disease or violence. So a better comparison would be to see what the survival rates are under the best of circumstances. In these technologically sophisticated times, the failure rate with IVF embryos is at least 65%, and the failure rate with natural embryos has been estimated to be in that range. If, however, you look at infant mortality rates (due to all causes combined), it is around 20 per 1000 (or about 2%) in our country, i.e. the failure rate is 2%. Thus, given every chance to survive, pre-implantation embryos fail 65-85% of then time, while life (as we all agree upon) succeeds well over 95% of the time. The point I'm trying to emphasize here is that the incredible drive and program for survival is not just any other trait, but rather is a defining feature of life. This feature is not very evident in pre-implantation embryos.
Tomorrow: The conclusion.
Tags: Stem Cells, Science, Politics, IVF, Bush, Tony Snow, Snowflake babies