In 1969, when Zager and Evans’s song In the Year 2525 became a hit, the prospect of choosing our sons and daughters from the bottom of a long glass tube looked a long way off. Today, that sci-fi vision is reality?complete with complex debates about ethics versus experimentation.

Yet for all the exciting breakthroughs and forays into new territory, it seems that a very fundamental problem has been overlooked: how will the adult children of thousands of anonymous sperm donors know who to kiss and who is kin?

The process is straightforward (even if the science isn’t). A man donates sperm to a clinic and the clinic uses that sperm to impregnate their female client. In some cases, the donor agrees to have his identity revealed to the woman. In others, the donor is guaranteed anonymity. No one besides the clinic staff, including his own child, will ever know his name. (Even if the woman knows the donor’s identity, there’s no guarantee she’ll ever disclose it to their child.)

So what does that mean for the children born of donor insemination (DI)? Quite simply, that unless they are aware of the details of their conception, know the name of their biological father, and know all the other children that donor has fathered, the consequences may be disastrous.

It isn’t hard to imagine the scenario: a young couple meet, are attracted, and start dating. Human nature being what it is, sex inevitably follows. Perhaps they marry, or there is an unplanned pregnancy, or they simply go their separate ways. Perhaps they’ll never discover that they’ve been sleeping with (or even gotten married to) a half brother or sister. But with the rising popularity of DI, the growing number of offspring, and society’s increased mobility, It’s inevitable that, more and more, we’ll be reading about the emotional fallout of unexpected discoveries.

In Canada, there are no limits on how many offspring a single donor can produce. A man who is popular with clinic customers could potentially end up having 50 or even 100 children, none of whom know they’re related. There are some limits; for instance, only a certain amount of a donor’s sperm can be shipped to a particular geographic area. According to a 2005 Vancouver Sun article, the American Society of Reproductive Medicine recommends 25 pregnancies in a population of 800,000.

That’s still a lot of uninformed siblings; except in a few cases, ?the approximately 14,000 Canadians born by DI in the past two decades are locked into a system that protects donor anonymity.?

Even in the U.S., where donors are limited to 40 offspring, there’s no sure way of enforcing the numbers: clients are not obligated to report pregnancies to the clinic.

Even though the technology is relatively new, the shift it will cause in society can already be seen. Starting from a single post on Yahoo several years ago, an online community has grown as people search for unknown relatives. Donors (identified by their clinic-assigned number) are searching for children; children are trying to find fathers; and half-siblings and parents are seeking others who may have used the same donor.

As with any scientific development, it would have been impossible to envision the unintended results of DI (including some we probably haven’t even dreamed of yet.) But in this brave new world, a DNA test may soon go along with that first kiss.