Writing about paleontology without illustrations is like directing a movie without a camera. When I wrote my first book, At the Water’s Edge, I had the good fortune to join forces with Carl Buell, who brought walking whales and fish with fingers to life. Now he has come to the other side, with a blog of his own, complete with pictures. Check it out.
I’ve got a short piece in tomorrow’s New York Times about the 400-million year history of insects. Some beautiful pictures of the creepers included.
Getting back home from a Thanksgiving journey full of turkey and queasy toddlers on airplanes, I just noticed that my visit-counter has rolled past the 500,000 mark. I never would have dreamed of such figures when I started this blog, and I just want to take a second to thank everyone who has ever clicked their way to the Loom.
Natural selection is not natural perfection. Time and again, biologists have discovered traits that are both beneficial and harmful. Perhaps the most famous example is the devastating disorder known as sickle-cell anemia. To get sickle-cell anemia, you have to inherit two faulty copies of a gene that helps build hemoglobin, the molecule that traps oxygen in red blood cells. In this condition, hemoglobin can’t hold its shape if it’s not clamped around oxygen. Without it, the defective hemoglobin collapses into needle-shaped clumps, which then turn the cell itself into a sickle shape. The sickle cells snag in small capillaries, and the blood can no longer supply as much oxygen to the body. People who inherit only one copy of this defective gene can get by on the hemoglobin made by the remaining normal copy. But people who get two copies of the bad gene make nothing but defective hemoglobin, and they’re usually dead by the time they’re thirty. A person who dies of sickle cell anemia is less likely to pass on the defective gene, and that means that the disease should be exceedingly rare. But it’s not–one in 400 American blacks has sickle cell anemia, and one in ten carries a single copy of the defective gene.
The New York Times, November 22, 2005
Islands hold a special place in the hearts of evolutionary biologists. When Charles Darwin visited the Galápagos Islands in 1835, he was stunned by the diversity of birds, which helped guide him to his theory of evolution by natural selection.
Beginning in the middle of the last century, the ornithologist Ernst Mayr laid the foundation for the modern understanding of the way new species evolve, arguing that they mainly emerged when populations became geographically isolated. Mayr based his theory on his studies of birds from Pacific islands.
Continue reading “In Give and Take of Evolution, a Surprising Contribution From Islands”