What if animals came with bar codes? Biologist George Johnson say they come with something just as good, meaning that telling tilapia from tuna may soon be within the power of everyman. (Photo from Sxc.hu)

Up to three centuries ago, at the time of Galileo, there was no clock worthy of the name. The most technically sophisticated instruments used to measure time were sundials.

Sundials date back to about 1500 BC. And today, most are out of sight and out of mind.

Performance-enhancing drugs such as anabolic steriods must be banned: Athletes who use them are cheating and harming the body in several ways. Biologist George Johnson explains how they work and why athletes think they can beat the testing regimes. 

You're driving down I-44 about an hour south of St. Louis. You glance at another dead opossum by the side of the road.

Look again. These days, that possum is very likely to be an armadillo. (Photo from www.birdphotos.com)

As biology professor George Johnson prepares to try out for a production of War of the Worlds, his thought soar to toward those other worlds and the possibility of life on other planets.

The good news is that the AIDS epidemic has peaked. The bad news is that we have had very little luck in developing an effective AIDS vaccine. Many promising approaches have been tried, but none has worked.

Not believe in UFOs? You might as well not believe in fairies. Or, as Francis P. Church also wrote to young Virginia O'Hanlon, "In this great universe of ours, man is a mere insect, an ant, in his intellect as compared with the boundless world about him, as measured by the intelligence capable of grasping the whole of truth and knowledge." (Photo from "Close Encounters of the Third Kind")

A plague is stalking bats and needs to be countered. As biologist George Johnson explains, the bad reputation of the winged mammals is entirely unwarranted. They help control insect pests, pollinate plants and and can be important to people medically.