In her new book The Science of Game of Thrones Helen sifts the fact from fantasy and shows us the Seven Kingdoms as we’ve never seen them before. In this extract, she delves into the secret lives of dragons. Word of warning: things are about to get steamy…
When George RR Martin and Parris McBride married in 2011 their wedding gifts from the Game of Thrones producers included one of the three dragon eggs used in the show. Unfortunately, we have no record of how Mr & Mrs GRRM reacted to the egg (‘No, it’s lovely, really, but we did specifically ask for a non-stick wok …’). They may have barely noticed it while they were delighting in the afterglow of their by-all-accounts very lovely nuptials – at which no-one died or anything. But in order to push our narrative forward, let’s imagine that a single question drifted gently through their minds, like smoke from the charred remains of someone Drogon has just taken against: ‘Could we ever ride a dragon of our very own?’
In short, could life imitate art?
We begin the Game of Thrones when dragons (and magic) have long been absent from the Seven Kingdoms. According to ancient lore, they gradually declined and finally died out, with Maester Pycelle helpfully informing us that their skulls line the throne room of the Red Keep in order of birth. The oldest, Balerion, could swallow an ox whole, whereas the last skull of the last dragon was barely the size of a dog’s.
The 150-year-old dragon eggs that Daenerys is given to celebrate her marriage are a valuable curiosity, pieces of portable wealth that she is expected to sell at some point to further the cause of her House Targaryen. Nothing more. However, as is often the case in the Seven Kingdoms, all is not quite as it seems. After her husband’s death, Daenerys orders a huge bonfire to burn several objects and people, including a magical ‘wise woman’ (who Daenerys holds responsible for her husband’s demise), herself and her dragon eggs. Remarkably, from this fiery destruction Dany wanders out, singed but very much alive, and we discover that the eggs have hatched into three adorable baby dragons.
Now, intriguingly, eggs that hatch after a long delay are not entirely unheard of in our world. Reptiles in their eggs can experience what is known as ‘arrested embryonic development’. This may suggest a sitcom about an interrelated bunch of socially dysfunctional fetuses, but the term actually refers to an unhatched reptile that essentially presses the ‘pause’ button on its own development and waits until more favourable environmental conditions arrive (e.g. burny-burny-magic-y-fire, in our particular Game of Thrones case). Researchers believe that two main factors have contributed to the evolution of this remarkable process, and both of these might particularly apply to the eggs of fictional dragons. First, it’s something that happens particularly to eggs with very thick shells, and second, to offspring who don’t receive much in the way of parental care (we can’t imagine Drogon, for example, being super-nuturing). However, typically this developmental ‘pause’ only lasts up to about a year in reptiles, compared to the 150 year stretching out of the spark of life by our Game of Thrones young dragons, so perhaps not.
Sex and the Single Dragon: A Beginner’s Guide
Once you actually have some dragons it might be relatively easy to get more. Obvious sex differences don’t seem to be a big deal in the dragon world as we know it: males generally grow a bit bigger but it’s hard for the human eye to tell dragon-ladies from dragon-gentlemen. Nevertheless, observations of dragon mating have been made by singularly determined biologists, who testify that in the wild, Komodo dragons – the non-flying, non-fire-breathing kind of dragons we have in our world – will seek out chances for sexual reproduction, given the right conditions, and despite their solitary nature.
When an opportunity for socialising with the other sex comes up – for example, while gathered around the messily slaughtered carcasses of their prey – Komodo courtship can occur. It just isn’t going to make for a cute viral YouTube hit anytime soon. The male dragons often kick things off with some bipedal wrestling. This isn’t a euphemism; they really go at each other. The bout of wrestling can go on for several days and the females are expected to watch and look interested.
All good things must come to an end, however, and eventually a male will win over a female’s favour. After licking her scales attentively for some time, he reveals his hemipene. Which – if you wish to imagine it – is a sort of double-headed penis, for presumably half (hemi) the fun? He produces it/them from a sort of pouch called a ‘cloaca’, like a magician producing a bunch of flowers from up his sleeve. Ta-da! Or, if you must have the scientific and appropriately serious description, he ‘everts his hemipene’, and impregnates the, by-now, well-licked and possibly ever-so-slightly bored and wrestled-out female dragon. If all goes to plan, she lays some fertilised eggs, at which point Monsieur Dragon seems quite eager to forget the whole sorry business ever happened and pays no attention whatsoever to the resulting offspring.
Alone, the female dragon will repel potential predators and guard her nest containing the vulnerable eggs as they develop – a task so stressful biologists have speculated it accounts for why female Komodos don’t grow as large as males, and also why they die much younger. In a recent Komodo study, life expectancy of males averaged around 60 years, females managed half that, averaging 32 years.
Once the eggs have hatched, Ms Komodo leaves them to it and gets back to what’s left of her life. The young dragons must toughen up from day one and fend for themselves, usually by hiding up a tree until they’re big enough to avoid being eaten by the other dragons – including their forgetful, hungry Ma and Pa. Ah, family life!
Virgin Births and Flaming Hot Eggs
But what about Dany’s dragons? Given that they are, as far as we know, the only three dragons in the Known World, can they reproduce and if so how? George RR Martin penning a dragon sex scene? I think we’d all be curious to see that …
Like their distant cousins, the Komodos in our world, might Dany’s dragons be able to reproduce sexually (with each other) and asexually (alone)? As Chester Zoo keepers discovered in 2006, their real-world counterparts, Komodo dragons are not at all like picky and hard-to-please pandas when it comes to reproduction. Originally native to Indonesia, the world’s largest living lizards are endangered and down to their last few thousand in the wild. As a result, an expectant Komodo in the family way is a particularly welcome and happy sight. But Flora – Chester Zoo’s pregnant Komodo dragon – was unusual in that she hadn’t had any contact at all with a male dragon, ever, at any point in her life.
When her eggs hatched as all-male baby dragons, it was discovered that the young lizards’ genes were entirely derived from their mother’s own biological makeup, although they were not exact clones of Flora’s. This is known as virgin birth or, as biologists call it, ‘parthenogenesis’ (from the Greek, parthen meaning ‘virgin’ and genesis, meaning ‘well-known progressive rock band whose songs, let’s be honest, can go on a bit’). Flora’s babies caused no end of excitement in the world of sexy dragon studies and beyond, with Scientific American proclaiming that this curious phenomenon may even provide ‘one explanation why Jesus was not a clone of Mary’.
From the get-go, dragons (in fact, many reptiles) are not quite like us when it comes to reproduction. In humans and most other mammals, the X and Y chromosomes determine biological sex at conception, or even before. Females have two of the same kind of sex chromosomes (XX), and males have two distinct sex chromosomes (XY). However, as Jennifer Harrison, Lizard Aficionado Extraordinaire, explains to me, Komodo dragons work with a ZW chromosomal system and it’s the females that have the mix (ZW) and the males that have two of the same (Z) chromosomes.
An unfertilised Komodo egg gets a Z or a W chromosome from the mother. Usually the father will supply a Z, making some children ZZ and some ZW: males and females. Perfect. What the virginal zoo Komodos are doing, lizard expert Jennifer Harrison points out, is doubling the chromosome in their unfertilised egg. So the unfertilised Z becomes ZZ (male) and the W becomes WW (fails to develop). Parthenogenesis in Komodo dragons always results in male offspring; you never get a mix of ZW asexually as it would result in an exact clone of the mother, which isn’t useful in evolutionary terms. Also, if you’re a lonely female looking to occupy a new ecological niche, producing males is the best strategy ever. You can create males to reproduce with and keep the line going. If that’s an adaptive evolutionary strategy, it’s a brilliant one!
The Maesters of Westeros in their wisdom tell us that dragons are as ‘changeable as flame’ – gender fluid even – meaning they can magically choose to become male or female at the drop of a (probably burning) hat. As it turns out, reptiles and dragons in our own world don’t quite have that power, but some do have rather a neat system for deciding on male or female offspring, and Mother of Dragons Daenerys, with her flaming egg-hatching technique, should probably take note.
Even though they are eager to tell you many details about their pregnancy and upcoming childbirth that you haven’t necessarily asked for, many human parents willingly remain in the dark about the sex of their unborn child. ‘We don’t want to know!’ they’ll declare. ‘We want it to be a surprise!’ Of course it’s best to respect this and change tack to something more neutral. (For example, say, ‘What if it turned out you could give birth to, say, a litter of puppies or something, that would be wonderful, wouldn’t it?’ and then speculate about the pros and cons of bringing various breeds and sizes of dog into the world, whether they join in or not. Probably don’t say, ‘ Yes! A surprise! Have you seen Rosemary’s Baby?’)
But even if dragons could have those kind of pre-birth sex conversations, they almost certainly wouldn’t, because there’s an intriguing temperature scale which determines whether, for instance, a young Australian bearded dragon, native to south-eastern Australia, is male or female.
Scientists have found that some Jacky dragons with ZZ chromosomes (genetically male) come out female (whether the chromosomal signature ZZ is also directly responsible for a super-long beard, astonishing musical longevity and technical prowess with a guitar, is yet to be determined)
What’s going on? Well, some species of dragon can bypass chromosomes as sex-determiners altogether and instead respond to temperature while still unhatched. With Jacky dragon eggs, when incubated hot hot hot (well, 30–33°C) they hatch as females, and also when the eggs are chilled to 23–26°C female dragons will appear. In the middle, er, lukewarm temperate band, that’s when you hatch male dragons.
But in the curious world of temperature-dependent sex determination, even these rules aren’t fixed. When it comes to the eggs of crocodiles and alligators, males will hatch in hot conditions, while females will emerge from cooler eggs.
Why does this happen? Well, like so much in the world of reptiles and dragons, it’s still deeply mysterious – no-one’s entirely sure. It would be neat if a parent dragon (or even Daenerys Targaryen) could decide the sex of their offspring by incubating the eggs at different temperatures, but we don’t have much evidence this happens. Forty years ago in the journal Nature, Eric Charnov and James Bull put forward the theory that parents will adapt to local environmental conditions depending on how males or females of their species fare. So if you’re a dragon, the chances of having plenty of choice in meeting and reproducing with your scaly soulmate are informed by climate and temperature.
The Science of Game of Thrones publishes September 22nd and is available to pre-order now.