If you’ve ever been to a Central American forest, you’ve probably heard the hoots and wails of a howler monkey. But these creatures deserve our attention for more than their howls. They turn out to tell us a lot about the evolution of our own senses. We and some of our close primate relatives are remarkable for having powerful color vision. What triggered the evolution of this adaptation some 25 million years ago? Some researchers have proposed that as the global climate cooled, our ancestors were forced to shift from a diet of fruit to leaves. An ability to detect red and green colors would have helped these early primates detect the best leaves to munch on. The descendants of these leaf-munching primates shifted to other foods in later years, but they held onto their color vision.
The emotions that other species summon up in the human brain are perplexing. A lion inspires awe and respect. It is the king of the jungle, a great name for a football team, a noble guardian of the entrance to the New York Public Library. A tapeworm, on the other hand, summons disgust mixed with a little contempt. You will never find yourself cheering for the Kansas City Tapeworms. But are these species really so different? Both animals get their nutrition from the bodies of other animals, and tapeworms are arguably more sophisticated in the way they get their food than a lion. Tapeworms escape our immune systems with ingenious biochemistry, and may even be able to eat our antibodies as food. Some species that live in fish make the fish leap around at the surface of the water so they are easier prey for birds, the final hosts of the tapeworm. And is it any less gruesome to be torn apart by a lion than to be host to a tapeworm? The best that a parasite can hope for, if a parasite could ever hope, would be to inspire fear. That’s the fate of parasitoid wasps, which, as I mentioned in a previous post, are the inspiration for the monsters of the Alien series. The precision of their cruelty, the intimate ways in which they can use up their hosts, give us chills. Yet they remain truly alien–a malevolence that is separate from the rest of the natural world.
Based on some feedback from subscribers and my own nosing around, I’ve decided to switch the subscription system to Bloglet. While this requires you to create a user name over at bloglet.com, the result of this minor chore seems better to me. The main attraction is that links and such don’t turn into ugly, unreadable HTML. I will continue to send out the pre-bloglet notifications to those who have it, but you may want to switch over to the new system. Please drop me a note to let me know if you want to be taken off the old notification list.
Last week I briefly mentioned some stark estimates about the potential extinctions that could be triggered by global warming. Since then, some global warming skeptics have tried to pour cold water on these results by making some dubious claims about natural selection and extinctions. While I have reported about global warming from time to time, I leave blogging on the subject to others (particularly David Appell over at Quark Soup). But in this case, evolution is drawn into the mix.
Today I’ll be talking for an hour about Soul Made Flesh on Minnesota public radio. You can listen to the broadcast live online at 11 am EST (the show will be archived). At 2 pm EST, you can listen online again when I talk on the Glen Mitchell show on Dallas public radio.