Evolutionary Arms Race: Competing Interests in Male and Female Genomes
Ekaterina Sedia
Siblicide and deadly sperm — both of these are just two examples of wide-ranging and downright creepy consequences of competing interests of males and females. “Battle of the sexes” is a cliché; however, it is fascinating to see this battle play out on the level of genes. Dawkins wrote about ’selfish genes’ in 1976 — and since then, many examples of genes that behave to the detriment of the organisms that carry them had been discovered. This is especially true of the situations where male and female genomes are at odds.
There is strong evidence that the competing interests lead to a much quicker evolution of reproductive proteins, compared with pretty much any other gene. In nature, there is also a wide range of female resistance to harm from males — as well as ample evidence that males do harm females, often reducing their fitness.
For example, in Drosophila, a common fruit fly and the geneticists’ favorite subject, mating success of males is an important issue — the female flies store sperm, and often use stored sperm for fertilizing all of its eggs; however, future re-matings may change that — i.e., the female might use fresher sperm. If there’s re-mating, then sperm from different males would compete with each other for fertilization. That led to the evolution of more and more potent sperm; it was shown in the laboratory that the increased potency of sperm can be evolved in the lab, and that the female flies evolve corresponding resistance. This ’supersperm’ is potent enough to kill females who have not evolved the corresponding defenses.
In terms of progeny, this conflict becomes complicated — after all, we are the product of two parental genomes, which may be in conflict with each other. And this is where the idea of parental imprinting of genes (perhaps one of the most intriguing areas of genetic research) comes into play. “Imprinting” in this context means that the copies of some genes behave differently depending on which parental source they came from. For example, in female mammals only one X chromosome is active — in early embryonic development, it is the copy from the egg that is active in the embryo. Later on, the inactive paternal X is released, and then X chromosomes are inactivated randomly in different cells — this is how we get tortoiseshell and calico cats, each different color patch corresponding to the original cell in the embryo, indicating either paternal or maternal X chromosome being active. So all female mammals are in effect mosaics of their maternal and paternal X chromosomes.
Some diseases are also associated with parental imprinting — for example, both Prader-Willi and Angelman syndromes are associated with a deletion on chromosome 15. If the deletion originated in the egg, the individual will have Angelman syndrome, and if it originated in the sperm — Prader-Willi syndrome. In the rest of us, both copies are present, indicating that both paternal and maternal imprinting are necessary for normal development.
Besides delaying male obsolescence, imprinting has a number of fascinating genetic consequences — and one of them had recently (in the past ten years or so) has drawn quite a bit of scientific and lay attention, because it seemed to shed some harsh light on the most sacred and frequently romanticized of human relationships — the bond between mother and child.
Evolutionary biologists working with both plants and animals have noticed one interesting issue: a conflict between maternal interests and those of the developing embryo. It is clearly in the maternal interest to limit the nutrients she allocates to any given offspring in favor of her own health and survival as well as the any future offspring she might have. The embryo, on the other hand, would clearly benefit from the increase of maternal allocation.
The genes that increase embryo’s ability to demand and receive more resources are imprinted by the father — especially in species where multiple paternities are likely (a good percentage of mammals). The natural selection is likely to favor the offspring of the males that are able to increase maternal allocation at the expense of both the mother and her future offspring. Thus, it results in many unsightly things happening in the mammalian womb: sib murder, as well as tapping of the maternal resources in the manner most similar to parasitism.
Search for genes responsible is well in progress. Mice, who are fairly similar to humans genetically, have a gene known as Mest. It is imprinted paternally, and it regulates maternal care. Mice who are missing this gene are shockingly bad mothers — they pretty much ignore their helpless progeny, usually resulting in their death.
A Mest gene was located in humans; however, it is unclear (and unlikely) that the gene would have such clear-cut consequences, since in humans parental behavior is the result of learning and socialization; moreover, any effects of such genes are likely to be masked by family and social support systems. Instead, in humans the conflict between the mother and offspring are more likely to play out in the womb.
In placental mammals, the embryo implants in the womb and the exchange of nutrients and chemical signals occurs across the placenta. According to David Haig, one of the world’s leading authorities in the issue, there is quite a bit of evidence that the evolutionary arms race resulted in the embryo secreting a lot of hormones designed to manipulate the mother into increasing a nutrient output, while the mother shows very little response to these demands — such resistance likely to have evolved during the selection process as well. Ultimately, the mother and the embryo are two separate beings, honed by the evolutionary process for maximum self-interest, and mothers’ resistance to the embryonic demands ensure her own survival as well as her ability to have more offspring in the future.
Incidentally, this conflict is likely the reason why pregnancy carries so many hazards for the mother — especially considering how common this process is. Most routine biological processes do not carry such a high risk of complications and mortality; the reason why pregnancy is so hazardous is the competing interests of the embryo who uses the placenta to invade and divert maternal blood supply, and to send chemical messages to manipulate the maternal investment and resource allocation.
Many of the genes that are expressed in placenta are, not surprisingly, also imprinted by the father. From the genetic perspective, the father and his offspring share common genes, while the father and the mother (and whatever other offspring she may have in the future) do not; as the result, the selective process would favor father’s ability to increase the survival of his offspring at the expense of the mother and half-siblings.
But what about mother’s genes? Since the offspring shares half of the genes with the mother, it would stand to reason that there would be some synchronization and common interest between mother’s and offspring’s behavior, increasing the survival of both. There are many such examples — such as offspring begging for food causes a maternal response of feeding (unlike the case of placenta where embryonic demands are pretty much ignored.) Such harmonious coevolved behaviors of offspring and mother are likely to be due to the maternal genes.
Each of us is the product of two parental genomes, which often have conflicting interests. These conflicts can play out in the offspring-mother conflict as seen in the expression of Mest and placental genes, as well as the wider issue of parental imprinting.
References used:
Dawkins, R. (1976) The Selfish Gene, Oxford: Oxford University Press
Genomic Imprinting: A Talk with David Haig (2002). Edge (www.edge.org)
Godfray, H. C. J. (2002) Evolutionary theory of parent — offspring conflict (review article). Nature 376: 133-138
Linder, J.E. and W.R Rice. (2005) Natural selection and genetic variation for female resistance to harm from males. Journal of Evolutionary Biology 18: 568 — 575
Panhuis, T.W., N.L. Clark, and W.J. Swanson (2006) Rapid evolution of reproductive proteins in abalone and Drosophila. Philosophical Transactions of the Royal Society of London: Biological Sciences 361: 261 — 268.
Wade, N. (1998) Good Maternal Behavior Is Linked to the Genes of a Father. New York Times, 29 September. [Onlin
e] http://query.nytimes.com/gst/fullpage.html?sec=health&res=
9E0CE1DA1039F93AA1575AC0A96E958260 Retrieved 15 February 2008.
About the Author
Ekaterina Sedia resides in the Pinelands of New Jersey. Her critically acclaimed novels, The Secret History of Moscow and The Alchemy of Stone, were published by Prime Books. Her next one, The House of Discarded Dreams, is coming out in 2010. Her short stories have sold to Analog, Baen’s Universe, Dark Wisdom and Clarkesworld, as well as Japanese Dreams and Magic in the Mirrorstone anthologies.
An Interview with Kage Baker
Jeff VanderMeer
Kage Baker is one of my favorite writers — wise, clever, funny, shrewd, deep, and sometimes horrifying, her stories and novels display a range and sensibility uniquely her own. She has been a finalist for the Hugo and Nebula Award, in addition to having won the Sturgeon Award. Her novels have been translated into Spanish, French, Italian, Hebrew, and German. Still, to my mind she’s not received nearly the critical attention she deserves. Having made her reputation with her Company novels, about a far future organization dedicated to making sure no one changes the past, Baker is now in the process of moving on to other milieus. We talked about that transition, about her talent for humor, about her relationship with the internet, and several other topics via email in February of this year.
My understanding is that you’ve phased out the Company novels and are focusing more on fantasy. If this is correct, has there been any trauma in this? Has it been tough to wean yourself off of that milieu, or are you just sick of it all by now and ready for new things?
There won’t be any more Company novels; that whole 8-book story arc is finished once and for all. There will undoubtedly be other Company short stories, as I find historical incidents that intrigue me, and I’m blocking out a steampunk novel featuring the Company’s 19th-century predecessor, the Gentleman’s Speculative Society; but the Company story is told. Finito. I wasn’t at all traumatized, considering I’d devoted my life to the damn thing since approximately 1985. There are other stories to tell, for now. Some fantasy, some straightforward historical adventure. The science in my science fiction was never that strong, in any case.
The Company’s often morally ambiguous, to say the least. Do your readers recognize that for the most part? Have you gotten fan mail from readers saying “Man, the Company rocks! I’d totally love to be an operative for them.”?
Nobody ever says the Company rocks — and I’d be incredulous if anyone did, since working for a corporate entity with that kind of power would be nightmarish. But a lot of people love the operatives themselves (primarily Joseph and Lewis) and others would love to be immortal operatives. And every so often I’ll get these distressing little emails saying things like, “You know, you’re almost right about the way time travel works, but you have some details wrong” or “If you reveal any more about the Lizard People, you will regret it”.
What’s your own favorite Company novel, and why?
Probably The Life of the World to Come. It’s the point where the whole saga sort of reboots and moves forward into the future, since Garden of Iden and Mendoza in Hollywood are flashbacks, Mendoza’s story told from her prison, and Sky Coyote and Graveyard Game catch up Joseph’s past history so the reader understands how and why he finally rebels. With all that past grief shed, writing LWTC felt like flying at times. It was a lot of fun to write.
What I’ve always been struck by in the Company novels and stories is how varied they are. For example, in your short story collection Black Projects, White Knights, you’ve got serious, horrific, and very funny stories. I’m curious as to what comes most naturally to you. Did you start out writing funny stuff or more serious? Which is most difficult for you?
I never start out to be funny, it just happens... sometimes the most horrific things are also ludicrously funny. My inclination is generally to write serious stuff, but life is absurd, and the more honestly I try to write about the world, the less its essential ridiculousness can be gotten around. Take — at random — the death of Rasputin. Read about his murderers nervously feeding him poisoned petits-fours, and poisoned vodka, and watching in disbelief as he just keeps shoveling it in and demanding their guitarist play his favorite songs. And when they finally can’t stand it any more and unleash this horrifying catalogue of assaults on him — shooting him, beating him with chains, throwing him into the damn frozen river — and he’s still trying to climb out, right up to the moment he freezes to death — you’re wondering, what must they have been thinking? “Christ, can’t we get anything right?”
You’re one of the only writers I know who can pull off slapstick in fiction. Do you have a background in theater or film? Is there any influence that informs this element in some of your fiction? This kind of approach requires a consummate sense of timing.
I do have a background in theater, yes. I’ve been a character actress, stage manager and director with a number of little troupes orbiting mostly around the historical fairs — the Great Dickens show in San Francisco, the old original Renaissance Faire, the Old California Celebration. A lot of what you’d call Vaudeville Nouveau was generated out of those events. Both the Flying Karamazov Brothers and the Reduced Shakespeare Company, for example, got their start there. If my comedic timing is any good, it’s because I learned from some frickin’ geniuses like Marque Siebenthal, David Springhorn, Judy Cory and Billy Scudder — whose names you will not recognize but who are hallowed in comedy heaven.
Let’s talk about your pirate novel. It’s coming up later this year, titled Or Else My Lady Keeps the Key, and I’m very much looking forward to it. There’s a lot of pirate material out there. Is there a particular model you’re riffing off of?
I did a historical novella for the Night Shade collection Dark Mondays which was about Sir Henry Morgan’s sack of Panama in 1670. “The Maid on the Shore”, it was titled. I told it primarily from the point of view of this spear-carrier, a fairly dense but good-hearted young man named John. He grew as a character — as they will — and the end of the story left some interesting possibilities for him. So I wrote Or Else My Lady Keeps the Key which picks up with John returning from Panama, swearing to give up piracy because it doesn’t pay. First, though, he has to fulfill a promise made to a dying friend and deliver a letter to the friend’s mistress. Things get complicated. The title comes from a popular song of that era, The World Turn’d Upside Down.
At some point in the writing of the first story, I had one of those revelatory moments when I could see John’s entire life stretched out — sort of a Pirate’s Progress. So there will be other pirate stories about him, I guess. I did one for the forthcoming antho Fast Ships, Black Sails (forthcoming in the next year) called “I Begyn as I Meane to Go On” which would be the opening illustration, as it were, in the series. My own particular pirate continuum is set about a generation and a half before all the Good Pirate Stuff — could have kicked myself when I realized I’d have no chance to incorporate Blackbeard or the hilarious Stede Bonnet into the stories, because they hadn’t even been born yet. So I can’t really riff off any of the modern takes on pirate adventure, which are all set around 1720. It crimps one’s style a little — no cocked hats yet, and ships have tillers, not wheels — but one has the consolation of being original.
What are some of your favorite pirate novels or stories?
Robert Louis Stevenson’s Treasure Island of course. And I still have my dog-eared copy of Tim Powers’ On Stranger Tides.
You rarely enter into online discussions, as far as I know, and even had your message board deleted at one point. What is your relationship to the internet, and do you think this online element to our lives has helped the genre community as a whole or hurt it?
The internet... nice place to visit, but I wouldn’t want to live there. My relationship to it these days is primarily as a reference source — Google Earth is great, Wikipedia OK if used with a big grain of salt and other sources used to fact-check. I d
id use to take part in online discussions, in the days when Asimov’s scheduled them, but... message boards and online discussions are a lot like study hall or detention, where mostly people are shoving each other and giggling and passing notes with dirty limericks. And one kid in the room is a psycho, and one is a bully, and one is a pompous twit, and you’re at the back of the room dodging spitballs and thinking “Jesus fucking Christ, I’m fifty-five! I could be somewhere else. Why aren’t I?”
I think it has harmed the genre community, personally. People are talking about writing, instead of writing. That’s a bad sign...
What do you read for pleasure? And what recently have you really enjoyed?
When I get the time to read, I’ll read anything Terry Pratchett writes. Ditto Peter S. Beagle and Ian McEwan. I like all the Dead White Males like Somerset Maugham, O. Henry, Kipling, Hammett, Chandler. The late George MacDonald Fraser and Patrick O’Brien. And I absolutely adored “The New Moon’s Arms” by Nalo Hopkinson.
What else do you have coming out in 2008 and what are you working on?
I have a fantasy novel called The House of the Stag coming from Tor. I have the aforementioned Or Else My Lady Keeps the Key coming from Subterranean. I just finished a steampunk story for an anthology Nick Gevers is editing. And I’m working on a novelization of the novella “The Empress of Mars”, because there was a lot more story there than got told.
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