As the autumn leaves turn handsomely, I’ve been wondering, why do trees bother? It’s a question scientists have been asking for the past few years, and for the first time, they’ve carried out an experiment to find out.

The color of an autumn leaf can actually take a lot of work. In the fall, the green chlorophyll in a tree fades away, while the tree actively builds new pigments to turn it red or yellow. It’s generally agreed that these colors must serve some function for trees. Otherwise, natural selection would favor drab trees that dropped their leaves without such bother. They could use the energy they didn’t waste on autumn colors to fight diseases, capture more sunlight, or some other essential task.

Continue reading “Autumn Leaves: The Search for Purpose” →

Galileo discovered Saturn’s rings, but called them ears. If only he could see what Cassini sees.

Cue kettledrums… 

Originally published October 13, 2006. Copyright 2006 Carl Zimmer.

Toxoplasma, that mind-altering, cell-manipulating, all-around awesome parasite that sits in the brains of billions of us, is back in the news. Infection with the parasite raises the chances a woman will have a boy from 51% to 72%. The average ratio of boys to girls at birth is 51%. Women with high levels of antibodies to Toxoplasma, scientists found, have a 72% chance of having a boy. While many effects of Toxoplasma probably have something to do with adaptations that allow the parasite to thrive and spread successfully, this one seems more like a side-effect, albeit a dramatic one.

Continue reading “Toxoplasma: Bet On Boys” →

The Seed in-house blog, Page 3.14 has been running Q & A’s with some of its bloggers. Mine’s up now. 

Originally published October 10, 2006. Copyright 2006 Carl Zimmer.

Two years ago this month, I was taken aback by some explosive news. A team of Indonesian and Australian scientists reported that they had discovered fossils of what they claimed was a new species of hominid. It lived on the island of Flores in Indonesia, it stood three feet tall, and it had a brain about the size of a chimp’s. Making the report particularly remarkable was the fact that this hominid, which the scientists dubbed Homo floresiensis, lived as recently as 18,000 years ago. I wrote up a post on the paper, and took note of some strong skepticism from some quarters. And since then, I’ve found myself devoting a number of posts to the new papers from the discoverers of Homo floresiensis, and the emerging responses from the skeptics–so many that I gave them their own category.

Continue reading “Homo floresiensis: Two Years Out” →