In Brief

Procreation by mail.  In another right to procreate case, prisoner William Gerber sought to have his wife artificially inseminated with his own sperm.  After being given a life-term under California’s three-strike law – for discharging a firearm, making terrorist threats, and using narcotics – Gerber requested prison authorities to permit him to provide a semen sample to a laboratory for his wife to inseminate herself.  He intended to collect the sample, and mail it to a medical center sperm bank, where his wife would go to complete the procedure.  The prison warden refused, alleging that the right to procreate was extinguished, at least temporarily, by incarceration.  The district court found in the warden’s favor, but on appeal, the Court of Appeals for the Second Circuit reversed.  They held that prisoners are not deprived of the fundamental right to procreate when serving jail time.  While acknowledging that prisoners do not have a constitutional right to conjugal visits, nevertheless the court said, this does not bar them from fathering children during incarceration.  Sending sperm through the mail was a legitimate exercise of their procreative rights. The decision, however, did not apply to female prisoners.  Recognizing the biological differences between men and women, the court said that a woman did not have the right to be artificially inseminated with her husband’s sperm while being held prisoner.  A dissenting justice wrote that, while prisoners do not lose all fundamental rights when jailed, it was “a far cry from holding that inmates retain a constitutional right to procreate from prison via FedEx.”  Gerber v. Hickman, 264 F.3d 882 (2nd Cir. 2001).

Conflicts between parents and their offspring.  Birds are sometimes willing to sacrifice their own children to have the chance to breed again. Reproduction is a costly proposal.  Parents must put a lot of energy into finding a mate, producing gametes, the reproductive process, itself, and then raising their offspring.  When predation is a threat, should parents place themselves or their offspring at a greater risk of dying?  Parental feeding visits to the nest can increase the risk of predation to both parent and offspring by attracting the attention of predators.  Birds, faced with the threat of predation, reduce feeding visits to the nest, promoting both their own and their offspring’s survival.  The reduction in the number of feeding visits has a trade-off.  Too few visits can increase offspring mortality when the offspring suffer from the lack of food.  Birds who have a smaller clutch size put more of the predation risk on their offspring, then birds who have larger clutch sizes.  Parents tolerate greater risk to themselves, but not their young, in species with many offspring because the offspring in larger clutches are more likely to survive to a reproductive age.  Parents with few offspring, in contrast, tolerate less risk to themselves because, with the lower numbers of young, there is less a chance that any one nestling will survive to reproductive age.  Ghalambor and Martin, Science, 292: 494-497, 20 April 2001; Pennisi, Science, 292: 414, 20 April 2001. 

The Big-Bang.  Some organisms exercise the right to procreate only once in a lifetime. “Semelparity is the so-called big-bang reproductive strategy, in which an animal invests all in a single mating season, dying soon afterwards.  This is not a strategy one immediately associates with mammals. Nonetheless, semelparity does occur in terrestrial mammals … [M]ale northern quolls (Dasyurus hallucatus) — relatively large marsupials that weigh more than a kilogram — all die after their first mating season.  … Females of studied … Dasyuridae species have a highly synchronized, single oestrus (during which ovulation occurs) in the winter, and males commit themselves totally to obtaining mates at this time, at the expense of future mating attempts.”  The evolutionary significance is not understood, but it has been proposed that “[s]exual selection might be the driving force: females might be biased towards young, vigorous males, meaning that there would be little reproductive benefit to the survival of older males. Alternatively, circumstances might be such that the intensity of fighting between males during the rut means that only the youngest and fittest can win and survive to mate. The cost of such fighting might be reduced lifespan. These ideas, although speculative, illustrate the need for further studies to determine which ecological or evolutionary circumstances promote this extreme, and extraordinary, reproductive tactic in a relatively large mammal.”  Humphries and Stevens, Nature, 410, 758-759, 12 April 2001. Originally described by Oakwood, M., Bradley, A. J. & Cockburn, A. Proc. R. Soc. Lond. B, 268, 407-411, 2001.

Does sex matter?  Many organisms reproduce themselves without the benefit of sex.  Bacteria, for instance, reproduce by simply splitting into two by a process called “binary fission.”  Plants can reproduce asexually (“vegetatively”) by forming new plants from portions of their roots, stems, or leaves.  These vegetatively-produced progeny are clones of the parent plant.  Even more intriguing are organisms which have both male and female parts that can self-fertilize.  Many land snails and slugs are self-reproducers – capable of producing progeny completely on their own, using self-made sperm and self-made eggs.  Self-reproduction is less costly than sexual reproduction.  Self-reproducers do not have to waste resources on elaborate courtship behaviors to find a mate.  As a consequence, they have more resources to invest in their progeny, and, at least theoretically, should surpass sexual reproducers in the quantity and presumably quality of their offspring.  Surprisingly, self-reproducers have not taken over the world.  Although non-sexual reproduction is observed in almost every family of organisms, sexual reproduction predominates.  There must be something wrong with self-reproduction that explains why it has not become the predominant procreative mode, despite its economic efficiency.  The explanation most often proffered is that sexual reproduction is more advantageous because it generates greater diversity in offspring by combining the genomes of two unrelated organisms having different sets of genes.  Greater diversity means more variation to cope with a changing world – disease, parasites, environmental upheavals, etc.  Variation, after all, is the substrate of natural selection.

Contract and consideration genes.  Say A has “sucker” genes and B has “rip-off” genes.  An individual who has sucker genes is easily cheated and deceived, again and again.  He never learns.  Rip-off genes, on the hand, predispose an individual to exploit others.  He always wins.  A’s sucker genes make him less fit for survival because, by losing to B, he is giving up valuable resources that he needs to survive.  Sucker genes damage his reproductive potential.  As a result, the sucker genes are selected against, and their frequency in the gene pool diminishes.  B, on the other hand, is more robust because of his rip-off genes.

What happens when a B contracts with another B?  Neither party is willing to give anything up until something is given up first by the other party.  There is deadlock.  The effect on fitness is the same as it was for A in the A and B contest.  Neither B gets anything.  Exploitive genes are good only in the short-run when sucker genes are abundant.

Say C arises who has “consideration” genes which promote valuable exchanges between parties.  Between C and A, resource allocation will be maximal because each party is willing to exchange something of value in order to get something of personal value to them.  Cs won’t exchange with Bs unless B is willing to give something up in return.  If Cs win when bargaining with As and Cs, but win only with As, in the long-run Cs will outlast Bs.  The consideration rule is nothing more than an adaptive foraging strategy for maximizing the net energy extracted from the environment.