Women aren't planets
In August 2006, in a conference centre in Prague, astronomers voted on a new definition of planet, and Pluto was demoted. But Pluto didn't change; the criteria did. Now imagine the definition of "woman" shifted the way Pluto's status shifted. Imagine that a person who had been a woman all her life woke up one morning, after a working session of biologists, to find herself on the wrong side of a new line. What would that mean for her?
The analogy is uncomfortable, because Pluto is just a piece of rock and ice, and we are not. But there is something quietly strange about deciding what something is by counting votes. Truth, we usually think, isn't democratic. The procedure was awkward enough when it was scientists doing the voting, in a domain where they at least knew what they were talking about. New Zealand's Parliament is now preparing to do something similar with the definition of "woman", except the people doing the voting aren't experts in anything relevant. They're politicians.
The Legislation (Definitions of Woman and Man) Amendment Bill], introduced by New Zealand First MP Jenny Marcroft and passed at first reading on 20 May, asks Parliament to define "woman" in law as "an adult human biological female", and "man" as "an adult human biological male". Marcroft frames the change as restoring "biological reality" to the law. But biology cannot supply the reality she wants. It can supply something messier, more qualified, and less politically useful.
The bill assumes there is a settled biological test for whether a person is female or male, one that the law can simply borrow and apply. There isn't. The leading candidates each fail in their own way.
Visual inspection of newborn genitals, the test that determines what gets written on a birth certificate, works for most births but not all. It misses intersex variations, which occur often enough that birth assignment cannot serve as a clean legal category, and it tells us nothing reliable about chromosomes, hormones, or reproductive function. Chromosomes look more rigorous on paper, but in practice they admit so many exceptions (XXY, XYY, XX males, XY females with androgen insensitivity, and others) that no working biologist treats them as a clean binary. They also vary widely across species, which matters for a discipline that does not get to redefine sex one species at a time. Gametes, often offered as the most stable criterion, are stable only if you ignore that children, women past menopause, and many people with medical conditions do not produce them.
Take gametes seriously for a moment. Does "biological female" mean producing ova? If it does, then women past menopause are not female under the definition. They are also a large part of the constituency the bill claims to defend. The bill either excludes them, which is absurd, or it relies on a looser notion, something like a developmental pathway toward ova production or a phenotype historically associated with female reproductive function. At that point the word "biological" is no longer doing the crisp, settling work the bill needs it to do. The category works for the majority. It is in the minority that it does its real work, and there it works badly.
The age clause produces a parallel problem at the other end of life. A girl, on the bill's definition, is not a woman. Existing legislation that uses "women" to cover both adults and children breaks, or has to be patched with a new vocabulary of "girls", "female children", and whatever else. Attorney-General Chris Bishop's report on the bill flagged exactly this, warning of "discrimination on the basis of age". Labour's Camila Belich gave the clearest example in the House. New Zealand's Abortion Legislation Act refers to "women", and where a statute does not specify an age of maturity, the default is 20. Under the bill as drafted, women under 20 may lose access to abortion. Remove "adult" and the bill defines children as women. Keep it and you create the age discrimination the Attorney-General has already flagged. The bill that promises clarity generates, on its first contact with the rest of the statute book, exactly the kind of definitional mess it claims to be cleaning up.
So why pass it? ACT's Karen Chhour answered the question in the debate. The bill, she said, was "not about science", but about whether ordinary people are "allowed to trust their own eyes, speak honestly". Take her at her word. The bill isn't really resting on biology. It is resting on the social intuition that everyone already knows what a woman is, and on the wish to have that intuition ratified somewhere durable. Biology was meant to do the ratifying. When it wouldn't, statute was asked to step in.
That is the move worth naming. For a long time, the binary between male and female was treated as a fact of nature that science could be relied on to underwrite. Science, when looked at closely, underwrites it only in a loose and qualified way. The bill's response is not to revise the social category in light of what biology can actually deliver. It is a piece of legislation that treats a contested cluster of biological features as if it were one settled thing, and ties legal consequences to the pretence.
Which brings us back to Pluto. Its reclassification was painless because Pluto doesn't care. It went on orbiting whatever it orbits. The bill's reclassification is not painless. It tells people whose lives depend on the category that the question has been resolved. The question hasn't been resolved. It cannot be resolved by a vote in Parliament any more than the nature of Pluto could be resolved by a vote in Prague. And the astronomers at least had the relevant training. Our MPs don't. If it is uncomfortable to settle a scientific question by counting hands among experts, settling it by counting hands among legislators is worse.
If you have to legislate the meaning of woman, you have already admitted the word was doing more than describing biology.
Source for the parliamentary debate: https://www.rnz.co.nz/news/political/595833/bill-seeking-to-legally-define-the-terms-man-and-woman-passes-first-reading
Note: I used Claude (Anthropic) in the drafting of this piece. The ideas and argument are mine; AI helped with structure and prose.
