Irish doctor with too many thoughts, too little time and a blog that's supposed to check in on reality.

Sunday, March 19, 2006

The More You See the Less You Know

The more we learn about genetics, embryology and the happenings of that dark, warm haven of the womb, the less we seem to be sure of.
I posted on the recent case involving a couple’s dispute over their IVF created embryos last week.
Sarah Carey has an article up about it today  - just 1 point about it –  she says -
If there was a genuine consensus that life starts from the moment of conception, the morning-after pill would be banned. When you see a blue line on the pregnancy test, the embryo is implanted and then, and only then, are you pregnant. If a fertilised egg doesn’t implant, you were never pregnant.
Implantation is even murkier than conception as (an arbitrary) starting point for human life. Because we’re never sure when that happens – blue lines on pregnancy test only kick in when BHCG levels rise to a sufficiently detectable amount.  
Ages ago, back when “the abortion debate” was happening in the boggersphere – I posted about when I thought life began. In one of the posts below, fatmammycat said “the egg I lose with every period has humanity too, but it is not a person” – absolutely true. Fertilise that egg with a sperm, you’ve still got something with humanity, but it is now a human being.
I’ll just paste what I said back then (‘cos I’m a lazy blogger)…
Without going in to a big birds-and-bees discussion, I want to explain the very basics of human reproduction – because believing foetuses are not human beings or are some other species is just mad, Ted, mad.Human sperm and eggs have only 23 chromosomes – they are not human beings, they are human. They’re not bovine or canine. Sperm and eggs go through a very complicated process where they started as primitive germ cells with 46 chromosomes and are cut up in different ways until they’ve 23. (This is not a scientific paper so excuse the generalisations! But remember meiosis from the Leaving Cert!)  They meet up and join and become something else entirely. This new “thing” is a zygote, a brand new human individual that never existed before – with 46 chromosomes. It immediately starts growing (by division) and making all kinds of human proteins etc which make up human cells which then starting migrating up, down and all over the place which over time forms various parts of the body (which is already male/female!) Embryo is the term used after 1 week, a foetus after 8 weeks, an adolescent after 12 years, a pensioner after 65 years – the substance of our humanity has not changed since we began our existence – at the end of the process of fertilisation.
What goes for foetuses, goes for embryos too.

Cathy Young has an interesting post (that I don't really agree with) about this.



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