DNA keeps spreading, just like a plague

I’ve written down the number 524,288 just to remind me how fortunate the four Bradford brothers are.

For the past three decades, I’ve been putting together the most comprehensive family tree that I can. It’s a task I’m not likely to complete because each trip into the tunnel takes me deeper to a different time and place.

It was this number — 524,288 — that told me it was time to take a breather.

I had been working on the Cooke branch of the Bradford tree, and it led me to medieval Scotland and the home of Thomas Crosbye. I knew next to nothing about Mr. Crosbye except that he was born in 1410 in Dumfriesshire, Scotland, and had a wife named Mary Margaret Boyl. 

I looked at a map and an encyclopedia listing, and I found out that Dumfriesshire is where Robert the Bruce launched his campaign for Scottish independence in 1306. 

Somehow, the next thing I knew, I was researching a germ called Yersinia pestis. You may have heard of its common names, the Black Death or the Plague.

This germ likely was spread from a rat-like mammal called a tarabagan to a human being, probably a Muslim, in Mongolia in 1346. The infection caused pus-filled boils, hemorrhages, vomiting and delirium – and millions of deaths.

The plague circulated quickly among the Mongols, who were having a war with some Italians, who fled back to Genoa to escape this terrible disease. The germs went with them to Italy and the rest of Europe.

Wherever the plague hit, residents fled, taking germs to their new hideouts deeper into Europe. Somehow, communities throughout Europe blamed the Jews for this and began murdering them by the dozens. 

On Valentine’s Day 1349, in Strasbourg, France, some 2,000 Jews were burned alive. A couple months later, 3,000 more Jews were massacred in Mainz, Germany. It turned out that the Jews really weren’t the problem. Whether you were a Muslim, Jew or Christian, the germs didn’t care. You would die in the same horrible manner.

England was hit hard in 1350. Knowing that English troops were falling ill, Scottish military leaders decided this would be the perfect time to attack their sworn enemies. The plan might have worked, but Scottish troops were exposed to the germ while waiting to invade. 

These brave Scots, too weak to fight, went home, taking their disease with them to what had been their quiet, safe villages.

The estimate is that half of all Europeans died – maybe 40 million people — because of this Yersinia pestis, the tarabagan and the spread of disease among people intent on killing each other for various reasons.

Somehow, maybe because Dumfriesshire was a fairly remote spot, Thomas Crosbye’s grandparents were among those to survive. And 19 generations later, here I am.

It’s time now for a math lesson. Any baby that is born has two genetic parents, four grandparents, eight great-grandparents, 16 great-great-grandparents and 32 great-great-great grandparents. For each additional generation you explore, you multiply by another two.

Eventually, the numbers go out of control. For 19 generations, the formula is two to the 19th power, for a total of 524,288. 

That is the number of people who needed to be born and to survive to procreate in those years of Yersinia pestis so that my brothers and I might be able to talk about this today. It’s nice that Thomas Crosbye’s grandfather lived through it, but we needed the other 524,287 as well to feed other branches of this tree.

There is an opposite aspect as well with numbers moving in the other direction. If the Crosbye line had a modest family size of four children apiece, 19 generations later Thomas’ grandfather would have 524,288 descendants.

I could draw you a graph to show how that works but, if I wrote each name a half-inch tall, I would need a sheet measuring 4 miles from top to bottom.

So, that’s why I stopped for my breather.

While I rest, I’ll leave you with this thought: Like everyone else who has ever lived, we roam this earth because of our ancestors.

We each are the result of a series of improbabilities. I am not special because I have a Thomas Crosbye or Mary Margaret Boyl somewhere in my family tree. Every person who has ever lived had an ancestor in that generation and the dozens of generations before. 

If you’re of European descent, your kinfolk escaped the plague, an occasional famine and a dozen or so wars. There was no avoiding it.

It can be overwhelming to think about this when I’m sitting around today, doing virtually nothing with this miraculous life I’ve been given. But at least I’m staying indoors, keeping my germs to myself.

I’m just a name on a very big page. I’m lucky to have 524.287 long-lost cousins who can get the important work done.