Reflexions XXVII Child Tax

A Discussion of Dr Robin Baker’s Child Tax System

In his book Sex in the Future (1999), evolutionary biologist Dr Robin Baker (University of Manchester, UK) advocates a ‘child tax system’ in which each male genitor, as determined by now available and satisfactorily reliable paternity tests, would be required on a systematic basis to provide financial support for each of his genetic children. Associated with the paternity test technology, which, if generalized, will in the future abolish paternity uncertainty for ever and allow every man to be certain that a child is his, such a tax system would put an end to the injustice incurred by single mothers abandoned by their mates. The system, in fact, is presented by Dr Baker as an improvement on the child support legislations currently in vigor in the US and United Kingdom, which have such fairness for single mothers as their aim.

Dr Baker presents his idea as follows: ‘The production of a fair formula will need a great deal of discussion and analysis. One principle, though, should be paramount: each of a person’s genetic children should be entitled to an equal share of that person’s income and resources. A proportion of the person’s income should be deducted for child support, then divided equally among his or her genetic children.’ As appears from this quote, Dr Baker is concerned about the finding of a fair formula. However, his system is hardly workable, due to its being fundamentally unfair.

At first sight, it seems reasonable and fair to ask a male genitor to contribute financially to the upbringing of his genetic children, whether they live under his roof or not, because it would release from an unfair burden abandoned mothers left to cope for themselves; but in fact it is not.

If, for instance, the child has been conceived during an orgy, in the course of which the female was inseminated by several men, is the biological father any more responsible for her pregnancy than any of the other male participants? I contend he is not, because his being the father, in this case, only results from his semen ‘beating’ the other participants’ semen inside the ovary tract, a result for which he cannot be held responsible, inasmuch as that depends on physiological mechanisms over which (we shall assume presently, before presenting a few qualifications) he has no control.

The reasoning can be extended to any situation in which a woman has multiple sex partners (though not at the same time) during any period that leads to a pregnancy.

As a consequence, in order to be fair, a child tax system should require that each and every male mate of that woman contribute to the child’s support, since each of them is, in the normal course of events, equally responsible for mating with the woman, and at the same time each of them is equally irresponsible as moral agents (leaving aside notions such as free agent and free will: we consider the man as an agent here when his behavior is concerned – although we agree that this behavior may be entirely determined by previous causes – as opposed to the behavior or performance of his semen inside the tract being concerned) with respect to the outcome, because as far as their moral and legal character is concerned what occurs inside the ovary tract between competing semen is out of their reach. None of them as agents can decide the result.

We will know qualify this statement. In fact, according to Dr Baker, a male has some control over what happens in the female’s ovary tract. This control usually amounts to making sure to have routine sex with his partner, so that he keeps ‘topping up’ the tract with his semen, making it more difficult for a potential lover’s sperm to fertilize an egg inside the tract. Some more technicalities, such as the position adopted during intercourse, would also make a difference, but none of them is seemingly efficacious enough to be likely to thwart natural endowment in that respect, i.e. testes’ size and functioning. Biological species in which promiscuity, and thus sperm competition, are common, such as chimpanzees and humans, develop bigger testes than species in which male dominance and harems are the norm, like gorillas, and than solitary species like orangutans. In the context of promiscuity, penis shape and size would also contribute to remove from the tract the semen already present, and thus weaken this semen’s chances to fertilize an egg, increasing one’s own chances (in case the present semen is that of a third person).

So it seems that all this would have to be taken into account with a view to designing a child tax system. Such a system, then, would have to inquire whether such or such has utilized some technique or other in order to increase the success of his sperm inside the tract and has in this manner slanted the physiological process in his favor, thus arranging for greater chances than his competitors to sire a child during intercourse. Furthermore, natural endowment should be considered as well, in order to determine whether one male did initiate intercourse with chances of fertilization that were objectively greater than his competitors, in which case also the tax burden should lie on him more heavily.

It gets even more complicated when one adds that the woman too can slant the physiological events occurring inside her tract. Female orgasm is described by Dr Baker as a strategy used by the woman to favor the semen of one man, because it would function as a pump sucking up the semen deeper inside the tract, closer to the fertilization zone. A child tax system, in order to be fair, would have to take this into account and determine whose man, if any, was thus favored by the woman, altough I am not quite clear about whether this particular finding should induce the tax burden on that man to be increased or lessened. On the one hand, the woman’s orgasm or any other of her slanting operations increases the man’s probabilities to sire the child, and so to be consistent the burden should be made heavier, but on the other hand the man is not to pay for another agent’s behavior relating to him, and on the contrary as this behavior is to result in loading him with a burden he should be compensated and his burden lessened.

So, leaving the last point aside, it is of two scenarios one or the other. In the simple one, competing males are not responsible for what happens in the ovary tract, the genetic father no more than the other mates, and they are all due to pay the same amount of tax for the child. In the more complex one, each man’s financial burden should be determined according to the initial probabilities that each of them would sire the child (if child there must be), given either the techniques they used (position, timing, frequency, etc) or their natural endowments (men with greater endowments would pay more, in that scenario), and also given the slant of the woman’s intervention. It is important to note that the result itself, i.e. the identity of the biologial father, is not as important as these initial probabilities, because the former is contingent on the latter, and what provides for the rest – that is, what makes sometimes the greater probability and sometimes the lesser occur – here is beyond anyone’s knowledge and handling.

In none of these two scenarios, the father alone, excluding other mates, should pay the tax. A man should be required to pay the whole tax if he has been the only mate, or the tax system is unfair to that man. How the tax administration is to know the woman’s number of mates must be further investigated.

References: The three books by Dr Robin Baker, Sperm Wars, Baby Wars, and Sex in the Future, plus Sperm Competition in Humans by Todd K. Shackelford and Nicholas Pound (ed.). As a rather original way of scientific vulgarization, Dr Baker’s books are interspersed with fictional stories aimed at illustrate the cases in point.

November 2015


  1. florentboucharel

    After I sent Dr Baker the above reflexions through his Website (, he kindly wrote me the following lines, for which I am very grateful to him. I will write more on his research and thoughts in a next post. Here is Dr Baker’s reply:

    Dear Florent Boucharel

    Thank you for sending me this link.

    I thoroughly enjoyed reading your thoughts on the matter and seeing you wrestling with all the same ifs-and-buts that I did over 15 years ago now. Your thoughts are intriguing and interesting – but I still think my system is fairer and certainly more workable than yours. After all, paternity (and maternity) can be proved – the number of sexual partners men and women have cannot.

    Re: your ‘references’ section, I am well aware that some people hate the fictional parts of those three books, and many have said so, often aggressively. Equally, others have been glowing in their praise, the Sunday Times newspaper even saying “The best fiction I’ve read this year is the imaginary sex scenes in Robin Baker’s Sperm Wars … the most entertaining science book of the year.”

    Similarly, you are right that some of my academic colleagues do not think my ideas/work are factually correct. But it is also true that many others do think they are correct, and are probably in the majority (did you read my summary of the matter: It would have been more even-handed of you simply to say the matter is controversial – but it is your blog, so of course you can slant it whichever way you prefer.

    Life would be very boring if everybody agreed.

    Once again, thank you for contacting me.

    Best wishes

    Robin Baker

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  3. florentboucharel

    My own view on the issue is in fact resting on an old legal notion expressed in the Latin phrase “exceptio plurium (concubentium).” The exceptio plurium, namely the objection that the mother had several lovers at the time of a child conception, is a legal impediment to paternity claims. Robin Baker’s proposal amounts to dismissing this notion with the advent of genetic testing.

    In a 1972 French law creating the possibility for a fatherless child to sue a man for maintenance if the child could convince a court of law that that man was a lover of his mother at the time of his conception, the possibility was still made void by the defendant invoking the exceptio plurium. A child could even sue and get maintenance money from several men in cases like gang rape, in which case the exceptio plurium is no defense. (Even allowing for such exceptions a paternity claim could always be rebuked through invoking the woman’s debauchery, which is not the same as the exceptio plurium).

    All right. Now Dr Baker says each genetic father should be made to pay. To rephrase it along the line of legal studies, the exceptio plurium would be a case of “old law is cheap law”: Back then we could not ascertain genetic paternity but now we can, so what the legislation and especially courts of law have to do is integrate genetic testing as proof in judicial proceedings and draw the consequences, rather than rely on intricate constructions all based on ballpark estimates.

    I still believe this is not so simple, for two reasons.

    First, there is abortion. A woman who does not want a child can terminate her pregnancy, that’s her right, but in Dr Baker’s system a man who does not want a child would, if known as the genetic father, still have to pay for the child. Men have less room than women in his system. How is this fair?

    Second, Dr Baker’s system pampers women’s feelings and hurts men’s in yet another way. According to evolutionary psychology, men cheat on their legitimate spouses in order to replicate their genes without incurring the expenses of raising the offspring, whereas women cheat in order to carry babies with better genes than their men’s. Therefore, irrespective of their sexual activity being legitimate or not, women’s psyche is geared toward raising babies, whereas that of men is so geared only with their legitimate partners (in fact, with anyone the man himself finds legitimate, as he may legitimize natural children, which by the way is disguised legal polygyny as the man can thus have legitimate children from several simultaneous women). Dr Baker’s system is vexatious to men’s psyche. Again, how is this fair if each gender’s psyche being the result of natural evolution is per se neither fair nor unfair?

    If we examine the rationale behind the legislator’s making an exception to the exception (to the exceptio plurium), we will reach the conclusion that it is not a case of “because genetic paternity could not be ascertained.” It is the exceptio plurium itself that is a result of this lack of certainty in the past and not the exception to it, which derives from an altogether different reason.

    The reason is that, in the case of gang rapes for instance, it doesn’t matter who the genetic father is, all men involved owe maintenance money to the child. I guess this is because one may argue they had to form a gang to reach their end, the gang was the means to the end.

    So, with all due respect, in such cases I perceive it is Dr Baker’s proposal that would be “cheap law,” because it would subsume the exception under the same head again from which the legislator had wanted to distinguish it in order to take specific circumstances into account.

    • florentboucharel

      I took the man and woman who cheat as example but Dr Baker have single mothers in mind. The successfully cheating wife keeps pouring her man’s wealth on her children anyway, so she doesn’t even need a child tax. But I took this example to show that when both parties do what they shouldn’t the law should do nothing.

      In the West criminal penalties for adultery have been canceled but adverse legal consequences remain in civil, namely divorce procedures, so we may keep saying that people shouldn’t cheat their spouses legally speaking.

      (Consideration of the civil negative effects of adultery –namely, that the adulterous spouse may be the loser in a divorce– should have precluded legalizing the legitimization of natural children, because this is legal polygamy by means of adultery, which is absurd.)

      This leads me to the conclusion that intercourse shouldn’t be had by unmarried people either, if the woman wants the man to invest in the child, that is, because outside a binding contract the law is not bound to see her as committed to one man, only marriage can have the law presume her bound to one man, can clear her presumptively from exceptio plurium concubentium.

      • florentboucharel

        In a recent exchange Robin Baker has reiterated that his proposal is simple, that it could be passed, if not for the floating notion of fairness, in any case for the sake of simplicity. I confess I had the faint notion that he was moved by a will of more fairness for single mothers, but ok let’s examine the argument of simplicity.

        To be sure, filiation law is a mess. As I said, it’s “intricate constructions all based on ballpark estimates.” This describes among other things the guesses judges and legislators have to make about the “moment of conception.” They have had to refine presumptions about said moment in line with developments of biology, but refining here has actually meant to make their guesses more ballpark because they would take into account more and more exceptions to a basic 9 months computation! A serious taking of science into account seems to make things more intricate and this is consistent with the phrase I used, “old law is cheap law” – cheap because old law used to make gross assumptions about biological phenomena for instance, rigidly excluding possible deviations which we know can occur and therefore must make room for. Will genetic testing make things easier rather than the contrary? I wonder.

        Exceptio plurium is an impediment to paternity claims, that is, it will prevent the court from looking further into the merits of the claim; it stops there. This is pretty convenient and simple for courts, isn’t it?

        Then there is the U.S. Supreme Court’s decision Michael H. v. Gerald D. (1989).

        Primary Holding: A state can create an irrebuttable presumption that a husband is the father of a child born into his family.

        The California law that prevailed against a DNA test is one of the oldest and simplest systems, encapsulated in the Latin phrase Pater is est quem nuptiae demonstrant (He is the father whom marriage indicates). I think Dr Baker’s system wouldn’t be as simple as this rule.

        1/ Gerald and Carole do not want Michael’s money (child tax) if that means paternity rights for Michael. Therefore, in Baker’s system, the law would have to dissociate paternity rights and paternity duties, which entails a host of legal intricacies.

        2/ Otherwise the right to child tax money would be actionable by single mothers only. The mother would name a man, whom the court and police would then compel to take a DNA test and if the test found a 98 per cent likelihood of paternity the man would be liable to pay the tax. Beside the fact that a 98% figure is not satisfactory because it means that 2% of such decisions will be miscarriages of justice (however, the figure has probably improved since 1989), the law would likely have to set limits on such name-dropping because we would find out a few of these single mothers have no clue who the father is and they name the man with the deepest pockets, hoping he’s the father, then the second best, and so on.

        3/ If, then, Big Brother has the DNA signature of everybody and allocate individuals’ resources according to a grand child tax scheme whether common-law parents agree or not, then this is likely to impact family, entailing there again a host of new legal questions, all fascinating but not quite simple.

        And what if the single mother names a foreigner, upon whom Big Brother has no jurisdiction? Even in the grand scheme there would be fatherless children unless the grand-scheme country cuts itself from the world.

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