In the mid-2000s, David Markovitz, a scientist at the University of Michigan, and his colleagues took a look at the blood of people infected with HIV. Human immunodeficiency viruses kill their hosts by exhausting the immune system, allowing all sorts of pathogens to sweep into their host’s body. So it wasn’t a huge surprise for Markovitz and his colleagues to find other viruses in the blood of the HIV patients. What was surprising was where those other viruses had come from: from within the patients’ own DNA.

HIV belongs to a class of viruses called retroviruses. They all share three genes in common. One, called gag, gives rise to the inner shell where the virus’s genes are stored. Another, called env, makes knobs on the outer surface of the virus, that allow it to latch onto cells and invade them. And a third, called pol, makes an enzyme that inserts the virus’s genes into its host cell’s DNA.

Continue reading “The Lurker: How A Virus Hid In Our Genome For Six Million Years” →

I’ve been writing about science for the New York Times for over eight years now, but today I’m starting something new there. I’ll be writing a column (called “Matter”) every week. The first column is just out. I take a look at the cicada invasion we’re facing here in the eastern United States, and step back to consider the fact that these creatures have the longest lifespan of any insect–seventeen years, almost all of which they spend underground. It’s a bizarre life cycle that’s been millions of years in the making.

My columns will appear each Thursday on the Science Times page online, and some will also appear the following Tuesday in the print edition of the Science Times. Check it out! And do NOT miss Jonathan Corum’s fascinating timeline graphic of the past century of cicada broods.

Originally published May 9, 2013. Copyright 2013 Carl Zimmer.

The nervous system that sprouts from the brain may seem like an incomprehensible tangle. But anatomists can divide it pretty cleanly into two parts. One part is directed to the outside world, while the other is turned inward.

The somatic nerves take in sensory information from the outside world from our eyes, nose, ears, and skin. They also relay commands to move muscles. They are essential for our responding to the external world. Visceral nerves, on the other hand, detect information about our internal state. They sense blood pressure, the queasiness in our guts, even the level of oxygen in our bodies. And they also send signals to those organs, causing racing hearts, gasping lungs, and puking stomachs.

Continue reading “How Our Outside World Turned Inward” →

Nobody in my past was hugely famous, at least that I know of. I vaguely recall that an ancestor of mine who shipped over on the Mayflower distinguished himself by falling out of the ship and having to get fished out of the water. He might be notable, I guess, but hardly famous. It is much more fun to think that I am a bloodline descendant of Charlemagne. And in 1999, Joseph Chang gave me permission to think that way.

Chang was not a genealogist who had decided to make me his personal project. Instead, he is a statistician at Yale who likes to think of genealogy as a mathematical problem. When you draw your genealogy, you make two lines from yourself back to each of your parents. Then you have to draw two lines for each of them, back to your four grandparents. And then eight great-grandparents, sixteen great-great-grandparents, and so on. But not so on for very long. If you go back to the time of Charlemagne, forty generations or so, you should get to a generation of a trillion ancestors. That’s about two thousand times more people than existed on Earth when Charlemagne was alive.

Continue reading “Charlemagne’s DNA and Our Universal Royalty” →