When did you start being you? You began as a fertilised egg, but would you identify yourself with that single cell? That was the question being asked in Mississippi on 8 November, as voters expressed their views on the bare minimum it takes to be a human being.
The smart money was on Mississippi ushering in legislation that would have granted human rights to every fertilised egg. The likely impact on abortion law was obvious but it would also have been bad news for anyone in the state who wanted to use post-fertilisation means of birth control, such as intrauterine devices and the morning-after pill. Doctors would also have felt an impact: in vitro fertilisation, in which not every developing embryo is given an equal chance of developing into a fully grown human being, would have become problematic.
Personhood USA, a group that rallied support for the bill, quoted science in support of its campaign: "[The zygote], formed by the union of an oocyte and a sperm, is the beginning of a new human being." The quotation was from an embryology textbook. Science, Personhood USA said, had proved "that a living, fully human and unique individual exists at the moment of fertilisation".
This is simply untrue. Whatever a textbook might say, science has never managed to make definitive statements, even about what is alive and what isn't. Scientists can't say when chemistry becomes biology, when biological cells form into something that can be seen as an independently operating organism, or when that organism, given the right DNA in each of its cells, might reasonably be termed a functioning human being.
And science can't say what makes human beings a special case among animals. There is little distinction between us and the primates; a paltry 0.1 per cent of our genes is unique to our species. That is why, in the early 1990s, a group of eminent scientists, including Richard Dawkins, tried to persuade the UN that higher primates should have what Personhood USA calls the "God-given rights" accorded to humans, such as protection from torture.
It's not as if science has shied away from the personhood question: it started the ball rolling. After examining miscarried foetuses and talking to pregnant women about when they began to feel foetal movement, Aristotle announced that true humanity begins at 40 days after conception for male babies (and, for some reason, 90 days for females). The Talmud and the Catholic Church subsequently set 40 days as the limit for abortion.
After scientists invented the microscope, our new view of the developing embryo made it clear that there was no clear distinction at 40 days. That is why the Church, in a precautionary move, banned abortion altogether.
Sting in the tail
The proposal, thankfully, was defeated but there are two reasons why votes such as this matter. First, if Mississippi had voted to make personhood begin at conception, other states may have followed suit. That would have affected on stem-cell research, with all its promise of treatments for spinal injury, blindness and a host of other conditions. How ironic that a future in which the blind see and the lame walk might have been stymied by those who have excitedly read stories about it for centuries.
Second, if the movement, still growing, gets big enough to gain traction in the US, it could take root in Europe. You might doubt that, but learn a lesson from Disneyland Paris: everyone said that the Magic Kingdom would fail on this side of the Atlantic. Now, it is Europe's most popular tourist attraction.Personhood USA's claims may be Mickey Mouse science but its campaign could have a long and troubling tail.
Michael Brooks's "Free Radicals: the Secret Anarchy of Science" is published by Profile Books (£12.99)