Last week I wrote in my “Matter” column at the New York Times about how wolves became dogs. I described two new studies on the genetic transformation that produced our canine pets, starting about 32,000 years ago. The scientists who did the research discovered that certain genes in the dog genome have experienced strong natural selection.

Some of those evolving genes are especially intriguing, because they’re known to be important in the brain. One of these genes, for example, makes a protein that’s involved in controlling the level of a neurotransmitter called serotonin. Serotonin influences behaviors like aggression–not just in dogs, but in humans. And in humans, that same gene has experienced strong natural selection, too. For humans and dogs, alike, a key step in our recent evolution may have involved becoming more sociable.

Continue reading “Another Link Between Dog Brains And Our Brains” →

Leave a bagel on the counter for a few days, and you’ll probably notice purple splotches growing over it. At some point a mold spore wafted across the kitchen, landed on the bagel, and started to eat your food. Molds are a kind of fungus–just like toadstools, brewer’s yeast, and death cap mushrooms. They don’t just nosh on bagels. Fungi exist on all continents, and have been thriving for many hundreds of millions of years. Some break down the remains of animals and plants in the soil. Some provide nutrients to trees and crops through their roots, in exchange for a supply of carbon the plants make with sunlight. While fungi have evolved different shapes and sizes, they are all alike in some fundamental ways. When it comes to eating, for example, they are like inside-out animals. We animals swallow food and then break it down with enzymes. Fungi break their food down first by releasing enzymes, and then they absorb it.

Continue reading “Getting To Know Your Inner Mushroom” →

With deadly new viruses emerging these days in Saudi Arabia and China, it can be hard to imagine that viruses can be good for anything. It’s easy to forget that we are home to trillions–perhaps quadrillions–of viruses on our healthiest days. And, according to a team of California scientists, those viruses are our symbiotic partners, creating a second immune system. These viruses serve as a defensive front-line, keeping bacteria from invading our gut lining and causing deadly infections.

The viruses in question are far less familiar than, say, influenza viruses or Ebola viruses. They are known as bacteriophages, which means “eater of bacteria.” And yet bacteriophages (or phages for short) are vastly more common than viruses that infect humans. They’re more common than all the viruses that infect every animal on Earth. The reason is simple arithmetic: there are far more hosts for phages to multiply in than there are for viruses that infect our own cells. They’re in the ground, in the oceans, under ice, and in the air. By some estimates, there are 10³¹ phages on Earth. That makes phages the most abundant life form, period.

Continue reading “Meet Your New Symbionts: Trillions of Viruses” →

Matt Zielinski writes, “I recently learned that you collect images of science tattoos. Attached is a photo of a tattoo I recently had done. I wanted a biomechanical theme to the piece with a special focus on the material chemistry that could potentially be used if this piece of sci-fi comes to life. The tattoo starts on the left with simple atoms and molecules (water, NO3) and evolves into the organic chains. Those macromolecules are PEEK, PEI, and polysulfone, all of which are engineered polymers commonly used in the medical device industry today. They can also withstand incredibly high temperatures and are very strong materials. The ball-and-stick macromolecule is intended to be ADP to demonstrate a synthesis of engineered and natural chemistry in the final product, the half-machine, half-woman face at the top right.

“I am a chemical engineer by education who works in the specialty polymer industry. A lot of the projects I work on were the inspiration for this tattoo and I believe that the technology to produce the biomechanical woman is not so far fetched as many would think.”

You can see the rest of the Science Tattoo Emporium here or in my book, Science Ink: Tattoos of the Science Obsessed.

Originally published May 19, 2013. Copyright 2013 Carl Zimmer.

It’s easy to forget sometimes that evolution is always a work in progress. We contemplate the eye or look upon an oak tree, and ask, how could they be any better? Somehow, in those moments of awe, we forget about detached retinas and sudden oak death. The evolutionary race is not in fact won by the perfect, but by the good-enough. And it just so happens that one of the best illustrations of evolution’s mediocrity is unfolding in front of us right now.

This episode of evolution is entirely of our own doing. In 1936, a chemical called pentachlorophenol went on the market. It was hugely popular as a way to preserve telephone poles and lumber against fungi and termites. Unfortunately, it also turned out to be toxic to humans, and once it got into the soil it could contaminate the ground for years. That’s because the molecule–five chlorine atoms decorating a ring of carbon atoms–had not previously existed in nature. Microbes had not evolved to feed on it before. It was as toxic to them as it was to us.

Continue reading “Mediocre Poison Eaters And The Imperfection of Evolution” →