If you explore our genealogy back beyond about 370 million years ago, it gets fishy. Our ancestors back then were aquatic vertebrates that breathed through gills and swam with fins. Over the next twenty million years or so, our fishy ancestors were transformed into land-walking animals known as tetrapods (Latin for “four feet”).

The hardest evidence–both literally and figuratively–that we have for this transition comes from the fossil record. Over the past century, paleontologists have slowly but steadily unearthed species belong to our lineage, splitting off early in the evolution of the tetrapod body. As a result, we can see the skeletons of fish with some–but not all–of the traits that let tetrapods move around on land. (I wrote about the history of this search in my book At the Water’s Edge; for more information, I’d suggest Your Inner Fish, by Neil Shubin, who discovered Tiktaalik, one of the most important fossils on the tetrapod lineage.)

Continue reading “Evolution’s Baby Steps” →

I’ve been on something of a microbial jag recently. For my past two columns for the New York Times I’ve explored the creepy biochemical sophistication of bacteria.

First, I took a look at the outbreak of toxic bacteria that shut down Toledo’s water supply a couple weeks ago. A lot of people don’t realize it, but those microbes have been spewing out these toxins for about three billion years–for reasons that scientists are still trying to figure out.

Then I wrote about the chemicals that our own microbiome releases, and the ways they can affect our behavior. Some scientists don’t think those changes are just random side effects. Instead, our microbes may be trying to manipulate us for their own benefit, eating certain foods or getting close to other people (also known as hosts).

Check them out!

Continue reading “Microbes as Poisoners and Puppet Masters” →