Whenever I give book talks at schools or colleges, one of the most common questions I get is this.

Were there any stories you left out of the book? Stories you wanted to include but did not.

And the answer is, yes. One story especially leaps to mind from my book on genetics, the violinists' thumb.

This story didn't make the cut for a simple, if aggravating reason. I came across it too late in the

process to include. So today I thought I would write this cosmic wrong and share this story with you all.

This story starts with a great fire of London in 1666. The fire was an absolutely apocalyptic event.

On September 2nd, a baker on pudding lane in London failed to completely put out a fire in his oven.

About one o'clock in the morning, his house went up in flames.

Most houses then were made of wood and had fatched straw roofs.

And they were crowded so close together that the fire easily jumped from building to building.

London did not have an organized fire brigade then, and a strong wind quickly pushed the flames down the street.

The flames eventually reached some warehouses along the Thames River that stored oil and talent.

And after those caught fire on, the inferno was unstoppable.

Over the next few days, the fire consumed 13,000 homes and caused the modern equivalent of

$1.3 billion in damage. Given that London also suffered from an outbreak of plague that year,

and the fact that both events took place in a year ending in 666, well you can see why many people

believe the world was coming to an end. And for some people that actually was the case,

namely the iconic London chimney sweepers. It took a while, but the fire really did destroy

their lives via a genetic disease. When most people think of genetic diseases, they probably

think of something like cystic fibrosis, or hemophilia, or sickle selenemia.

In those cases, a mutation shuts down someone's DNA and the person's cells can't function properly

afterward. But there are other subtler types of genetic diseases as well, including the biggest

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