Why did the dragons die out? Watch this video series on the genetics of dragons

Have you ever wondered why Daenerys Targaryen was able to hatch the first living dragons in over a century? Or why some Targaryens are dragonriders and others aren’t? If the answer is yes, then you may want to check out the YouTube series A Song of Ice and Fire: The Genetics of Dragons and War by Preston Jacobs. Jacobs theorizes that the answers to those questions lie in Mendelian genetics, which explains that genes are responsible for the inherited traits passed from generation to generation. Think Punnett squares from high school biology.

We know that genetics mattered to the Targaryens to some extent since they mostly intermarried. One of the reasons was to keep bloodlines pure. Another probable reason was that intermarriage meant a greater likelihood of producing dragonriders and dragon-hatchers. Using the Mendelian genetics model and known information on certain Targaryens and their dragons, the videos work through the family tree and explore who may have the dragon-riding and dragon-hatching genes.

Jacobs’ dragon genetics theory assumes the following:

• Dragon-related abilities are an X chromosome-linked gene called the dragon X gene;
• The ability to ride a dragon requires at least one dragon X gene;
• The ability to hatch a dragon requires two dragon X genes. This means that women are the only ones able to hatch a dragon because only they carry two X chromosomes.

This theory may also explain the dragon boom and bust around the time of the Dance of the Dragons, the civil war that tore the kingdom apart generations before the events of Game of Thrones. Prior to the birth of Rhaenyra Targaryen, the number of ridable dragons had fallen to six. After her sustained presence around several dragon eggs, many of them hatched and the number of dragons rose to 18. This indicates she was a carrier of two dragon X genes. So in theory, if a dragon hatcher like Rhaenyra married a male dragonrider, all of their daughters would be both dragonriders and dragon-hatchers, and all of their sons would be dragonriders. Under this theory, it’s no wonder the Targaryens wanted to keep things in the family—more dragon-hatches/riders meant more dragons, which was how the family maintained its hold over Westeros.

The videos also delve into other interesting topics such as the ongoing chess match between Bloodraven and the Faith to either keep the dragon X genes alive or snuff them out. Jacobs suggests that Bloodraven was responsible for manipulating Targaryen succession to put Aegon the Unlikely (aka “Egg”) on the throne in an attempt to produce a dragon-hatcher. Conversely, we know that the Faith and most maesters are vehemently opposed to magic. Jacobs points out several instances when the Faith attempted to prevent marriages between Targaryens capable of producing a daughter with the double X dragon gene. Since dragons are obviously the most powerful weapon around, the stakes are quite high for both sides.

Moving ahead to present day, besides Dany there are a number of other potential dragonriders and hatchers floating around Westeros and Essos. This is due to the fact that there are several families with mixed Targaryen heritage, including Houses Blackfyre, Dayne, Baratheon, Martell, and maybe even the Starks and Lannisters.

In addition to those unknowns who possess dragon abilities, there are also rumors of numerous unaccounted dragon eggs. If the eggs are found by one of the aforementioned houses, could they hatch dragons to rival Dany’s? Or if Dany herself stumbles onto the eggs and adds to her brood, could she usher in the next great dragon age?

If you’re interested in learning more about how the genetics of dragon abilities, check out the full video series below.