It’s been twenty months now since scientists reported discovering fossils on the Indonesian island of Flores belonging to a three-foot-tall hominid with a brain the size of a chimp that lived recently as 12,000 years ago. Homo floresiensis, as this hominid was dubbed, has inspired two clashing interpretations. Its discoverers declared it a separate species descended from another branch of hominids. In others words, the most recent common ancestor we share with Homo floresiensis lived two or even three million years ago. Skeptics argued that the fossils belonged to human pygmies. The one fossil of a Homo floresiensis brain-case belonged to a female with a rare genetic defect. In brief: healthy hominid versus deformed human.
Author: Lori Jia
The New York Times, June 20, 2006
On paper, Toxoplasma gondii looks as if it ought to be the most famous parasite on earth. This single-celled pathogen infects over half the world’s population, including an estimated 50 million Americans. Each of Toxoplasma’s victims carries thousands of the parasites, many residing in the brain. As if that were not enough of an accomplishment, Toxoplasma is equally adept at infecting all other warm-blooded animals, as disparate as chickens and kangaroos.
Scientists are now discovering some of the secrets of Toxoplasma’s success. Researchers in Sweden report that the parasite fans out through the body by manipulating mobile cells that are part of the immune system.
Continue reading “A Common Parasite Reveals Its Strongest Asset: Stealth”
Next time I go to the doctor, I think I’ll get him to give me a test for Toxoplasma. Fifty million Americans have the parasite, so I wouldn’t be the first. And if I was carrying it around in my head, that might explain why it’s so fascinating to me.
I first encountered the strange ways of this single-celled creature while working on my book Parasite Rex, and since then I’ve tried to keep up with new research on what makes it so successful. In January I wrote on the Loom about a potential link between Toxoplasma and schizophrenia.
Two hundred thousand years ago or thereabouts, an African lion killed someone. Along with a meal, the big cat got a wicked stomachache. Today a record of that unfortunate death still survives, in the bacteria that make big cats sick.
The trail of this strange story starts in the 1980s, when scientists discovered that ulcers are caused by bacteria known as known as Helicobacter pylori. H. pylori is found in people around the world, and scientists learned how to recognize the different strains they carried.
A bunch of good reviews on natural selection in humans are coming out, reflecting the explosion of research on how evolution has shaped our genome. See here and here. Today in Science another good one is out. What sets this one apart from the others is that it comes with a slide show with audio from the authors. As far as I can tell, the show is free. And it’s a pretty clear summary. Check it out.
Originally published June 15, 2006. Copyright 2006 Carl Zimmer.