The search for answers has led to some rather startling results. Separated-twin studies -- involving locating sets of identical twins who were separated at birth and raised in different homes -- resulted in some correspondences that were astonishing. The weirdest one, done back in 1979, found a pair of identical twin brothers who were separated at age four weeks and didn't even know of each other's existence -- and they were both named Jim, drove the same type of car, both had tension headaches and were chronic nail-biters, were both firefighters, and chain-smoked the same brand of cigarettes.
Now, even the most die-hard proponent of the personality-is-inborn explanation wouldn't claim that the kind of car you drive is genetic. Some of these similarities are clearly due to the Law of Large Numbers -- in a big enough sample size, you'll find strange coincidences that don't really mean anything profound. Add to that Dart-Thrower's Bias -- our tendency to notice and remember outliers -- and the Two Jims aren't really that hard to explain. (And, of course, out of the thousands of pairs of twins studied, the media is going to point out the one that is the oddest.)
But still. Consider some of the other similarities. While cigarette brand choice is certainly not genetic, addictive behaviors have an inheritable component. So does anxiety, which accounts for the headaches and the nail-biting. And to be a firefighter, you have to have physical strength, courage, and an ability to take risks -- all features of personality that could well have an origin in our DNA.
Last week, a paper appeared in Scientific Reports that supports a strange conjecture -- that dog ownership is partly genetic. The research, which came out of Uppsala University (Sweden), looked at the concordance rates of dog ownership between identical twins (which share 100% of their DNA) and fraternal twins (which share, on average, half of their DNA). And the data were clear; the concordance between identical twins is far higher, supporting a large degree of heritability for dog ownership.
"We were surprised to see that a person's genetic make-up appears to be a significant influence in whether they own a dog," said Tove Fall, professor of medical epidemiology and lead author of the study. "As such, these findings have major implications in several different fields related to understanding dog-human interaction throughout history and in modern times. Although dogs and other pets are common household members across the globe, little is known how they impact our daily life and health. Perhaps some people have a higher innate propensity to care for a pet than others."
My sense of why I have dogs is that I've somehow become convinced that my house just isn't filthy enough. The entryway from our back yard was once off-white linoleum, but years of tracking by various dogs we've owned has left it way more off than white. And I'm assuming the indoor-outdoor carpeting in our basement has been tan all along, but who knows?
Of course, we own dogs for more than just the random carpet stains and pieces of dismembered squirrel. They're sweet, cuddly, love to play, and have a boundless enthusiasm for enjoying life that I can only aspire to. Every time we lose one -- inevitable, given their shorter life span -- it leaves me grieving for months. And while I've sometimes contemplated not replacing them when they're gone, within the year I'm already perusing PetFinder looking for another rescue puppy to give a home.
Unsurprisingly, given the Fall et al. study, my parents were also major dog lovers. My dad had a little terrier named Max whom he adopted while working for the post office as a letter carrier. He had a walking route, and Max would meet him every morning and follow him the entire way. My dad started bringing snacks for him, and eventually Max's owners said, "You know, we don't have time for him anyway, would you like to take Max home?" My dad agreed -- and his canine pal spent the rest of his life following him around, even after Max had gone complete blind from cataracts. In fact, Max would walk behind my dad, keeping track of where he was by sound and smell, and when my dad stopped Max would keep going till he bumped into my dad's leg, then stand there, nose pressed against him, until he started walking again.
Old habits die hard.
Anyhow, this gives us a new perspective on dog ownership, and the strange relationship between our genes and our behavior. But I need to wind this up, because Guinness wants to play ball, and track more mud around the basement. You know how it goes.
Back in 1989, the United States dodged a serious bullet.
One hundred wild monkeys were imported for experimental purposes, and housed in a laboratory facility in Reston, Virginia, outside of Washington DC. Soon afterwards, the monkeys started showing some odd and frightening symptoms. They'd spike a fever, become listless and glassy-eyed, and at the end would "bleed out" -- capillaries would start rupturing all over their body, and they'd bleed from every orifice including the pores of the skin.
Precautions were taken, but at first the researchers weren't overly concerned. Most viruses have a feature called host specificity, which means that they tend to be infectious only in one species of host. (This is why you don't need to worry about catching canine distemper, and your dog doesn't need to worry about catching your cold.)
It wasn't until someone realized the parallels with a (then) obscure viral outbreak in 1976 in Zaire (now the Republic of Congo) that the researchers realized things might be much more serious. To see why, let me just say that the 1976 epidemic, which completely wiped out three villages, occurred on...
... the Ebola River.
Of course, you know that the feared introduction of this deadly virus into the United States didn't happen. But to find out why -- and to find out just how lucky we were -- you should read Richard Preston's book The Hot Zone. It's a brilliantly-written book detailing the closest we've come in recent years to a pandemic, and that from a virus that carries with it a 95% mortality rate. (One comment: the first two chapters of this book require a bit of a strong stomach. While Preston doesn't go out of his way to be graphic, the horrifying nature of this disease makes some nauseating descriptions inevitable.)
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