Like many parasites, a species of bacteria called Wolbachia takes charge of its own fate. Wolbachia can only survive inside the cells of its hosts–invertebrates such as this lovely common eggfly. This way of life limits Wolbachia’s opportunities for long-term survival. If Wolbachia lives inside a female insect, it can infect her eggs. When those eggs hatch and mature into adult insects, they will be infected by Wolbachia as well. But if Wolbachia should find itself in a male, it has reached a dead end. It cannot infect sperm cells, and thus it has no escape from a male host. When a male host dies, Wolbachia dies as well.

Continue reading “Down with the Male-Killers: A Tale of Evolution in Our Time” →

The Sunday Times in the UK reported yesterday on an upcoming paper that claims that the ever-fascinating Homo floresiensis (a k a the Hobbit) is not a new species, as previously reported. Instead, it was a human with a genetic defect called microcephaly that gave it a small head.

This is a long-standing criticism, but only a couple papers based on it have been published since the Hobbit fossils were discovered almost two years ago. The article doesn’t have a lot of details. When the new paper comes out (in the Proceedings of the National Academy of Sciences) I guess we’ll get more.

Continue reading “Return of the Microcephalic Hobbit” →

I was happy to see that my post on Tuesday about the evolution of whales attracted a lot of readers. One commenter asked about seals and manatees. As other commenters kindly explained, those mammals descend from other ancestors (relatives of bears and elephants, respectively) that independently moved into the water. This transition has occurred many times since vertebrates moved on land. In some cases, the animals have adapted completely to the water (such as marine reptiles). In other cases, the transition has not been so complete. Other relatives of elephants evolved into desmostylians, sometimes called “sea-bears.” They looked like polar bears but fed on aquatic plants. (pdfs here and here) The picture here is of Paleoparadoxia, from Siberia.

Continue reading “More Ridiculous Fossils” →

The textbook explanation of DNA goes something like this: enzymes in our cells read a stretch of DNA and convert its code into a single-stranded RNA molecule, which is then used by ribosomes as a template for building a protein. That stretch of DNA biologists call a gene. The protein it encodes drifts off to do some job–building cell membranes, maybe, or switching off other genes, and so on.

Continue reading “And the award for the fastest-evolving piece of human DNA goes to…” →

Whales are beautifully ridiculous. They are majestic divers, in some cases plunging nearly two miles underwater. And yet sooner or later they must rise back to the surface to breathe air. They breathe through a rather ridiculous-looking hole on top of their head. Unlike fish, which often reproduce by spraying millions of eggs and swimming away, whales give birth to one calf at a time, which they proceed to nurse for months. Some whales are like underwater bats, shrieking through their blowholes and listening to the echoes. And perhaps most ridiculous of all are whales that turn themselves into giant filters, thanks to a ridiculous tissue called baleen.

Continue reading “The Origin of the Ridiculous” →