The More You Know …

The previous chapter discussed changes in what we can do to ourselves and our descendants, and possible consequences. This chapter discusses changes in what we know – and possible consequences. More knowledge is, on the whole, a good thing – but there may be exceptions.


Human mating patterns have varied a good deal across time and space, but long-term monogamy is far and away the most common. This pattern – male and female forming a mated pair and remaining together for an extended period of time – is uncommon in other mammalian species. It is, oddly enough, very common among birds, possibly because their offspring, like ours, require extended parental care.1 Swans and geese, for example, have long been known to mate for life.

Modern research has shown that the behavior of most varieties of mated birds is even closer to that of humans than we once supposed. As with humans, the norm is monogamy tempered by adultery. While a mated pair will raise successive families of chicks together, a significant fraction of those chicks – genetic testing suggests figures from 10 to 40% – are not the offspring of the male member of the pair. Similar experiments are harder to arrange with humans, but such work as has been done suggests that some significant percentage – estimates range from about 1 in 100 to 1 in 3 – of the children of married women cohabiting with their husbands are fathered by someone else.2

From an evolutionary standpoint, the logic of the situation is clear. Males play two different roles in human (and avian) reproduction. They contribute genes to help produce children and resources to help rear them. The latter contribution is costly; the former is not. A male who can successfully impregnate another male’s mate gets reproductive success – more copies of his genes in the next generation – at negligible cost. So it is not surprising that males, whether men or ganders, invest substantial effort both in attempting to impregnate females they are not mated to and in attempting to keep the females they are mated to from being impregnated by other males.

A faithful female gets both genes and support from her mate, trading her contribution to producing offspring for his. But an unfaithful female can do even better. She pairs up with the best provider who will have her and then, given the opportunity, becomes pregnant by the highest quality male available, where “quality” is defined by whatever observable characteristics signal heritable characteristics that can be expected to result in reproductive success for her offspring – tail length in swallows, income and status in humans. As Henry Kissinger is supposed to have said, “Power is the ultimate aphrodisiac.”3

This strategy works, for geese and women, because of a curious feature of our biology: the inability of males to reliably identify their offspring. If that were not the case, if males were equipped with some built-in system of biometric identification based on scent, appearance, or the like, they could and would refuse to provide support for the offspring of other males.4


This feature of human biology has just vanished. Paternity testing now does what evolution failed to do; it provides men a reliable way of determining which children are theirs. What are the likely consequences? I started thinking about this question in response to a hypothetical by a colleague: Suppose it became customary to check the paternity of every child at birth. What would happen?

The obvious consequence is that some men would discover that their wives had been unfaithful and some marriages would break up as a result. The slightly less obvious consequence is that married women conducting affairs would take more care with contraception. The still less obvious consequence – except to economists and evolutionary biologists – is that men would take better care of their children.

From the economist’s standpoint, the reason is that people value the welfare of their own offspring above the welfare of other people’s offspring. From the biologist’s standpoint, the reason is that human beings, like other living creatures, have been designed by evolution to act in ways that maximize their reproductive success, and one way of doing so is to concentrate your limited resources on your own children. Either way, the conclusion is the same. Routine paternity testing would mean that men knew that their children were really theirs and so would be willing to invest more resources in them. They would invest less in children that turned out not to be theirs, but there would be fewer of those than before, due to the desire of wives to have children that their husbands will help support. And those children that did have a father who was not their mother’s husband could prove it, and so have at least a hope of support from him.

Readers who question the assumption that parents are biased in favor of their own children might want to look at the literary evidence. Across a very wide variety of cultures, it is taken for granted that stepparents cannot be trusted to care for their stepchildren.5 Across a variety of cultures there is evidence from statistics on child abuse and child murder that the literature is right – judging by one study, stepparents are about forty times as likely to kill children as real parents.6 And, going beyond our species, there is evidence that male birds adjust the amount of parental care they give chicks to take account of the probability that the chicks are not theirs.7

So far I have been considering a straightforward consequence of the combination of a new technology and a new social practice. The technology has already happened; the practice, so far, has not changed in response.

The law, however, has. Under Lord Mansfield’s rule, a common-law doctrine going back to the eighteenth century, a married man cohabiting with his spouse was legally forbidden from challenging the legitimacy of her offspring. This appears in modern statutes as the rule that the mother of a child is the woman from whose body the child is born and, if that woman was married and cohabiting with her husband when the child was conceived, he is conclusively presumed to be the father.

That was a reasonable legal rule as long as there was no practical way of demonstrating paternity. Most of the time it gave the right answers. When it did not, there was usually no good way of doing better and no point in using up time, effort, and marital goodwill trying.

It is no longer a reasonable legal rule and, increasingly, it is no longer the rule embodied in modern statutes. In California, for example, a state whose family law we shall be returning to at the end of this chapter, the current statute provides that the presumption may be rebutted by scientific evidence that the husband is not the father.


So much for the present and the immediate future. A more interesting question is the long-term effect of the technology. One function of the marriage institutions of most human societies we know of, past and present, is to give males a reasonable confidence of paternity by providing that under most circumstances no more than one male has sexual access to each female. With modern paternity testing, that is no longer necessary.

This raises some interesting possibilities. We could, at one extreme, have a society of casual promiscuity – Samoa, at least as imagined by Margaret Mead.8 When a child was born, the biological father, as demonstrated by paternity testing, would have the relevant parental rights and responsibilities. There are problems with that system. It is easier for two parents to raise a child jointly if they are living together, and the fact that two people enjoy sex together is very weak evidence that they will enjoy living together. An alternative that is both more attractive and more interesting is some form of group marriage – three or more people living together and rearing children together. Such arrangements have been attempted in the past and no doubt some currently exist. The only form that has ever been common – polygyny, one husband with several wives – is the one that does not require paternity testing to determine paternity. The question is whether other forms will now become more common.

That in turn comes down to a simple question to which I do not know the answer: Is male sexual jealousy hardwired?9 Do men object to other men sleeping with their mates because evolution has built into them a strong desire for sexual exclusivity or because they have chosen, or been taught, that strategy as a way of achieving the (evolutionarily determined) objective of not spending their resources rearing another man’s children? Weak evidence for the latter explanation is provided by an anthropologist’s observation that men spent less time monitoring their wives when the wives were pregnant, hence could not conceive.10

One person I have discussed the question with reported that he and people he knew did not experience sexual jealousy; readers interested in joining that discussion should be able to find him and some of his friends on the Usenet newsgroup alt.polyamory, which means what it sounds like. But what he was observing may have been only the tail of the distribution – the small fraction of men who, because they have abnormally low levels of sexual jealousy, are willing to experiment with unconventional mating patterns.

Suppose that male sexual jealousy is hardwired. There still remains an interesting possibility: the professional mother. Consider a woman who likes children, is good at bearing and rearing them, and herself has characteristics that men would like in the mother of their child – healthy, intelligent, good looking. Match her up with men who would like to have children but have not been successful in finding a willing mate with whom they would like to have them. The man fathers the child, whether by artificial insemination or more traditional means. The woman bears and rears the child. The man provides financial support and perhaps a paternal role.

One problem with this is that the ideal mother for your children is beautiful, brilliant, and healthy­ – and a woman like that may be able to find a more attractive career than being a surrogate mother. Modern reproductive technology has a solution. There is already a thriving market in human eggs, with the price dependent on the characteristics of the woman who donated them; good genes are for sale. The professional mother could be only a host mother, bearing the better baby constructed by combining your sperm with the best egg money can buy.

What if we reverse the roles? Suppose it is the mother who wishes to build her own baby, combining her egg with the best genes she can find? Being provided with her own womb, she doesn’t have to rent one from someone else, assuming she is willing to accept the costs of bearing the child herself. She has a second advantage as well. Eggs are relatively scarce, since harvesting them from a woman’s ovary is an unpleasant and uncomfortable process. Sperm is, for most practical purposes, a free good. Given a well-developed market for sperm, properly labeled with the characteristics of the donor or perhaps his gene map, the intentional single mother should have a wider range of choice, at a lower cost, than the intentional single father.

There are two trends in modern society that might make such a pattern of increasing importance. One is rising real incomes; it is easier for a single parent to raise a child the richer he or she is. The other is the improvement in our knowledge of genetics. Eventually it should be possible for a couple to build better babies mostly from their own genes, as described later in this chapter. But it requires much less progress – genetic knowledge, not genetic engineering – to do it using someone else’s.

Will it happen? We will have to wait and see.11


Whether or not new reproductive technologies are going to generate new problems for people in the future, they are already producing problems for the legal system and the social institutions in which it is embedded.

The first, and currently the biggest, is the paternity problem. State welfare agencies and unmarried or no-longer-married mothers would like to find a man who can be made responsible for supporting the mothers’ children. If their genetic father can be identified, he is the obvious candidate. But what if he cannot?

The view of some states is that the man who was the mother’s mate ought to be responsible whether or not he is the actual father – a reversion to Lord Mansfield’s rule, extended to cover unmarried couples. It was workable before modern paternity testing because the state could argue that the man she had been living with, perhaps married to, was likely to be the genetic father of her children even if he denied it. That argument no longer works now that he can prove he isn’t.

The obvious argument on the other side is that a man who has been cuckolded by his wife is already a victim of her betrayal; to make him responsible for supporting someone else’s child only adds injury to insult. The counterargument is that even if the mother is at fault her child is not – and requires support from someone. That argument becomes more convincing if the man has functioned as father to the child for long enough to establish an emotional bond between the two.

One possibility a little farther down the road is a genetic database that could be used to identify the genetic father and make him liable, bringing us back to the idea of paternity testing at birth. A less ambitious alternative is to require the mother to identify the father or possible fathers and have the state compel him to permit testing. But if the mother is unwilling or unable to identify the father, we are back with the problem of who, other than the state, can be made responsible.

Paternity testing could also create problems for men who, under current law, are not responsible for supporting children who, genetically speaking, really are theirs. In many states, if a woman conceives by artificial insemination using sperm from a sperm bank, she has no claims for support from the donor.12 Prior to paternity testing, that legal rule could be enforced by simply not keeping the relevant records. Today the records establishing paternity are stamped into every cell of father and child. If law and custom change, as they have changed in the past in the direction of making it easier for adopted children to locate birth parents, including ones who do not want to be located, some men may be in for a surprise.

Two, Four, Many

Paternity testing can establish the fact of paternity. But it does not tell us what paternity, or maternity, or parenthood, means. We can do a better job than in the past of determining who has what relation to a child. But we can also produce a more complicated set of relations, making it harder to fit the new reality into the old law.

With current technology and practice, the term “mother” has at least three different meanings. One is intentional mother: the woman who intended to play the social role of mother when the arrangements for producing the child were made. One is womb mother: the mother in whose womb the fetus grew. A third is egg mother: the mother who provided the egg. Once we start cloning humans a fourth category will be mitochondrial mother: the woman who provides the egg whose nucleus is replaced by the nucleus of a cell from the clone donor, retaining the woman’s extranuclear DNA.

Fathers still come in only two varieties. The intentional father is the man who intended to play the social role of father; the biological father is the man who provided the sperm. The one change associated with the newer technology is that it is more common than it used to be for the intentional father to know he is not the biological father.13 With three or four varieties of mother and two of father, the definition of “parents” becomes seriously ambiguous.

That problem was mentioned back in Chapter 2, where I described the (real, California) case of the child with five parents. All five were different people – and the intentional parents, John and Luanne, separated a month before the baby was born. The court decided that the intentional parents were the ones that counted. Although neither had any biological connection to the child, Luanne ended up with the baby, John liable for supporting it.

The same legal approach could be used to resolve the issues of parenthood raised by cloning. The human clone gets all of his or her nuclear DNA from one donor. Genetically speaking, one might describe that donor as both parents. If we actually did the usual genetic tests, they would show the clone as a child of the donor’s parents. Further complications arise from extranuclear DNA, which comes from the woman who donated the egg used in the procedure and might or might not be the donor of the nuclear DNA. And, since cells can be obtained from a donor without his consent, we have the possibility that a woman could bear the clone of a rich and prominent man and then sue him for child support on a scale appropriate to his income. The nearest real-world case I know of under current technology is one in which a woman apparently impregnated herself with sperm fraudulently obtained and succeeded in establishing a claim for child support against the father.14

The definition established by the California court – parenthood determined by intention – provides a single rule to cover nearly all circumstances, whatever the reproductive technology; in order for the child to come into existence, at least one person had to intend it, or at least choose to take actions that could lead to it, and that person counts as a parent. It still leaves some problems.

Conventional reproduction involves one male and one female. Once the biology can be subcontracted, intentional reproduction could involve one male and one female, two males, two females, a partnership of four of each, or a corporation – say Microsoft, looking to breed a successor for Bill Gates. Only the conventional pattern fits legal rules designed for that pattern. Once we accept intentional parenthood, the law must either restrict who can be an intentional parent – require, for example, that before any form of assisted reproduction can legally take place, one man and one woman (in the most conservative version) must identify themselves as intentional parents – or specify parental rights and obligations broadly enough so that any of the permitted arrangements can fit them.

A similar problem has existed, and been dealt with by the law, for a long time: the firm. For many purposes, we treat firms as if they were persons; we make contracts with them, sell them things, buy things from them, sue them for damages. To do so, we have had to map the rights and responsibilities of a single individual onto organizations of a wide variety of sorts. We have to decide what it means for a firm to agree to something, to be responsible for doing something, to be liable for something, what actual acts by living and breathing human beings count as acts by the fictional person in whose name they are acting. Defining parenthood, in the world being created by modern reproductive technology, presents a closely analogous problem.


When Monsanto, the leading agricultural biotech company, creates a transgenic soybean, it gets to patent it; if other people make copies without permission by using this year’s crop for next year’s seed without paying Monsanto for the right to do so, they are infringing Monsanto’s patent. Some of the problems raised by that situation will be discussed in the next chapter.

What if Monsanto applies its new technologies not to soybeans but to people, producing an improved version with some novel genes, transplanted from another species or created in the lab? On the face of it, the same law would appear to apply. You now have human beings who partly belong to someone else; one or more of the genes in every cell are Monsanto’s intellectual property.

Living creatures, including humans, are continually creating new cells to replace old ones, so it looks as though the patented baby infringes the patent with every breath he draws. The obvious solution is for the contract by which the baby is produced to include a lifetime license to use the patent within that child’s body, just as the contract by which a farmer buys genetically engineered soybeans includes the right to have the resulting plants reproduce their patented genes in the process of growing.

What about making copies that end up outside the child’s body? If I am the child, do I require Monsanto’s permission to reproduce? To engage in any activity that might lead to reproduction? Perhaps the original license ought to include some additional terms, with prices set in advance.

Considering the attitude our legal system takes to private ownership of human beings by anyone other than themselves, I doubt that Monsanto could get very far enforcing its intellectual property rights in this novel context, but one never knows. The issue is unlikely to come up. Human beings mature slowly. By the time I become seriously interested in infringing the patent on me it will probably have expired.

Soybeans, on the other hand, do not have individual rights to self-ownership and their generations are only a year long. For soybeans, the issue of intellectual property rights in things that live and reproduce is a real one, currently faced by courts in a variety of countries.


and a thousand natural ills/That flesh is heir to…


Of the ills that human flesh is heir to, some are entirely due to having the wrong genes – sickle cell anemia, for example. Many others, such as heart disease and Alzheimer’s,15 appear to have a substantial genetic component.16 As knowledge and technology improve, we will increasingly be able to identify individuals who do or do not have the genes that make them more likely to die young of a heart attack, become alcoholics, or suffer other undesirable consequences. It is already possible to do a complete gene map of an individual for less than $1,000,000 and the cost is predicted to get below $1,000 in the not very distant future.17 Combine that with adequate knowledge linking genes to outcomes and it becomes possible to know a great deal about your future prospects.

Someone who knows he is genetically predisposed to heart disease has good reasons to take greater precautions against it – exercise, diet, testing, and the like. That my grandfather died of a heart attack and my father has twice had bypass surgery are good reasons for me to take cholesterol-lowering medication and try to maintain regular exercise. But I would have better grounds for such decisions if I knew whether or not I carried the genes that caused those problems for my father and grandfather; while we do not yet have a complete account of the genetics of heart disease, we do know that carrying certain variants of certain genes substantially increases your chances of dying of a heart attack. And someone who knew he was, for genetic reasons, particularly vulnerable to alcoholism might choose to avoid the problem by never taking the first drink.

What if I have a genetic problem for which there is no solution, such as a gene that results in abnormally rapid aging? Knowing I have it at least lets me do a better job of planning my life – have children early or not at all, for example. But knowledge is not inevitably desirable. If I carry a death sentence in my genes, I might prefer not to know about it. Sometimes ignorance is bliss, at least for a while.

So far I have been considering the effect of my knowledge of my genes. Rather different problems might arise from what other people know about them. Consider an insurance company offering insurance against a disease that is entirely genetic in a future where reliable genetic testing is readily available. Once testing is available, the risk of the disease becomes uninsurable. Only people who know they have the relevant genes will buy the insurance, and the sellers, knowing that, will price it accordingly.

What about the more realistic situation where a problem is in part genetic? The expected cost of insuring me against that problem then depends on what genes I have. If insurance companies are permitted to insist on testing clients before selling them insurance, both those with and without bad genes will be able to buy insurance but at different prices. The part of the risk due to having bad genes becomes uninsurable, leaving insurance only for the residual risk, the uncertainty of the disease for someone with a known genetic propensity. In the more realistic case where what you are insuring against is not a particular risk but the combined effect of lots of risks – the case of life or health insurance – the result is the same. Your life expectancy depends in part on your genetic makeup and in part on other things. Uncertainty due to the former becomes uninsurable; uncertainty due to the latter does not.

The solution some have recommended is to make it illegal for insurance companies to require testing. Individuals still can and will get themselves tested. If I discover that I am, genetically speaking, extraordinarily lucky, I also know that both life insurance and health insurance, priced on the assumption that I am average, are bad gambles. If, on the other hand, I know that I am likely to drop dead at age forty, then lots of life insurance – provided I expect to have survivors I care about – is obviously a good deal.

This effect is known in the insurance literature as adverse selection; it occurs when one party to a transaction has information about the quality of what is being sold that the other party does not have and cannot get. A standard example is the used car market. The ignorant buyers pay the same price for good cars (cream puffs) and bad cars (lemons), making the sale of your car a good deal if you have a lemon and a poor deal if you have a cream puff. Lemons sell and cream puffs, for the most part, do not. Buyers, anticipating that, make their offer on the assumption that if the offer is accepted the car is probably a lemon – and at lemon prices, few cream puffs are offered for sale.

The logic is the same here. Imagine that insurance companies start out by charging a rate that just covers their costs for an average customer. Insurance is a much better deal for customers with genes that make them likely to collect than for customers with genes that make them unlikely to collect, so the purchasers of insurance include a more than average number of bad risks. Insurance companies discover that and raise their rates, driving out still more of the good risks. In the limiting case, where all good risks are driven out, the result is even worse than it would be with testing by the insurance companies. Nobody can insure against genetic risk, because the decision to buy insurance tells the seller that the buyer knows he has bad genes. Those who have bad genes can still insure against risk from other causes; those who have good genes cannot.

One solution would be to somehow make it possible to prove that you have never been tested. Now people can get insured first, then arrange to be tested and modify their life plans accordingly. Unfortunately, such a system provides a large incentive to cheat, to get tested on the black market or in a foreign country so as not to leave any record and then decide what insurance to buy after seeing the results.

An alternative solution would be for parents to buy insurance for their children before the children are conceived. The price might still depend on the parents’ genes, but it cannot depend on the children’s, since that is information that nobody has. Not, at least, until we have worked our way through the developments described in the previous chapter, at which point there should no longer be any bad genes left to worry about.

Insurance companies are not, of course, the only people who might be interested in your genes. There is now some evidence that a tendency toward sexual fidelity – or infidelity – is in part genetic. Requesting genetic testing of your intended just before the marriage seems a bit crass but perhaps, in a future where the relevant technologies are well developed and fully exploited, the questions will be asked – of the online matchmaker – prior to the first date.


We are used to taking it for granted that each of us is either male or female. For a long time that was quite a good approximation.18 But not for much longer. One reason is the knowledge provided by modern biology. Almost all men have an X and a Y chromosome and a male body; almost all women have two X chromosomes and a female body. But there are exceptions. Some humans are XY but have female bodies: genetically male but morphologically female. Some are the reverse – XX with male bodies. And some humans are genetically XYY, with male bodies and a mild tendency toward aggressive personalities, or XXY, or ….

So far we are dealing with genetics and morphology, both fairly unambiguous even if the combinations are wilder than we thought. The situation gets more confused if you add in psychology. Some people who are genetically and morphologically male claim to be psychologically female, to think of themselves as women. Others have the reverse pattern. There is some evidence that this is more than a delusion – that in a way not yet clearly understood, such people have brains designed for the wrong gender. Modern surgical techniques make it possible to at least partly correct the error – for someone who self-identifies as a woman in a man’s body to have the body altered to at least a reasonable facsimile of a woman’s body, although an infertile one. Similarly the other way around.

All of this raises interesting problems for both individuals and the law. Am I to think of Deirdre, a professional colleague who used to be Donald, as a woman, a man surgically altered to look like a woman, or something neither man nor woman? If I had discussed these issues with Donald back when he/she/it possessed, in his/her/its view, the body of a man but the mind of a woman – as it happens I didn’t – how should I have thought of the person I was discussing them with? If Deirdre marries a wealthy man and he later dies intestate, can his heirs successfully challenge her claim to part of his estate on the grounds that she was a he, hence could not contract a legal marriage with a man? That particular case – with a different transsexual – was recently litigated in Kansas. The wife lost.

It’s going to be an interesting century.


1 About 90% of avian species are monogamous, but a smaller fraction is long-term monogamous. The explanation is that both human and avian infants require biparental childcare. For a discussion of the link between that and mating patterns see, among others, Wright, 1994.

2 Baker and Bellis, 1992, cited in Ridley, 1995: “In a block of flats in Liverpool, they found by genetic tests that fewer than four in every five people were the sons of their ostensible fathers. …. They did the same tests in southern England and got the same results.” Numerous studies making estimates of cuckoldry rates among humans are summarized in Baker and Bellis, 2007. See also the meangenes site, – in particular. One Swiss study, in contrast to the English, finds rates of “misidentified paternity” slightly below 1%. A similar figure comes out of the very large-scale Icelandic genetic study. Judging by an extensive survey of the literature, the actual rate of misattributed paternity probably varies, across a large range of human societies, from about 1% to about 30%.

3 Quoted in The New York Times, October 28, 1973.

4 There is some evidence that infants resemble their fathers more than their mothers, which would provide an imperfect system of built-in paternity testing (Christenfeld and Hill, 1995). But see also Bredart and French 1995, which failed to replicate the result.

5 Pinker, 2002.

6 Buss, 2004, pp. 199–202. The figure he cites is from Daly and Wilson, 1988.

7 Daly and Wilson, 1995, discusses behavior in birds related to male sexual jealousy; p. 294 gives the specific case of varying parental investment. The human evidence is on pp. 306–308.

8 For the classic (and convincing) debunking of Mead's description of Samoa, see Freeman (1999).
A somewhat odd set of reflections on Mead's Samoan fantasy and its implications for Anthropology.

9 See Buss, David M., 2000, for a discussion of the evolutionary psychology of male jealousy.

10 Flinn, 1988a, cited in Wilson and Daly, p. 302.

11 One could argue that it has already happened. Using old-fashioned reproductive technology, many women choose to bear children despite the lack of a father willing to help rear them. Evolutionary biology suggests that the father is probably selected, at least in part, for heritable characteristics he can pass on to her children. (Wright, 1994, chapter 3; Buss, 2004, chapter 6, especially pp. 175–186).

12 Summaries of New York and New Jersey  law on surrogacy/IVF, and a brief on artifical insemination and inheritance.

13 Casanova, in his Memoirs, describes an affair with a married woman whose husband was impotent, undertaken with the husband’s support in order to provide him with a legal heir. (Casanova, 1971, volume XI, chapter 10).

14 State v. Frisard, 694 So. 2d 1032 (La. Ct. App. 1997).

15 Ridley, 1999, pp. 258–264.

16 Behavioral characteristics also appear also to be in part genetic, including some that might be viewed as ills of a different sort. For instance, twin studies by Professor Tim Spector, director of the Twin Research Unit at St Thomas’ Hospital in London, show a large genetic element to female infidelity. See http://www.futurepundit.com/archives/002484.html.

17 $5000 sequencing by 2009, $1000 a little later, and the relevance to the connection between biotech, information technology and predictive medicine.

18 The obvious exceptions were hermaphrodites and eunuchs.