In the early 1900s, scientists discovered that each person belonged to one of four blood types. Now they have discovered a new way to classify humanity: by bacteria. Each human being is host to thousands of different species of microbes. Yet a group of scientists now report just three distinct ecosystems in the guts of people they have studied.

Blood type, meet bug type.

“It’s an important advance,” said Rob Knight, a biologist at the University of Colorado, who was not involved in the research. “It’s the first indication that human gut ecosystems may fall into distinct types.”

Continue reading “Bacterial Ecosystems Divide People Into 3 Groups, Scientists Say” →

Over the past 540 million years, life on Earth has passed through five great mass extinctions. In each of those catastrophes, an estimated 75 percent or more of all species disappeared in a few million years or less.

For decades, scientists have warned that humans may be ushering in a sixth mass extinction, and recently a group of scientists at the University of California, Berkeley, tested the hypothesis. They applied new statistical methods to a new generation of fossil databases. As they reported last month in the journal Nature, the current rate of extinctions is far above normal. If endangered species continue to disappear, we will indeed experience a sixth extinction, over just the next few centuries or millennia.

Continue reading “Multitude of Species Face Climate Threat” →

Ever since Darwin, biologists have recognized that life evolves. But in the past 25 years, some researchers have argued that certain organisms are better at evolving than others. Their genomes have a flexibility that lets them adapt effectively. The less evolvable species, by contrast, are too rigid to take advantage of new mutations or to find new solutions for survival.

Many biologists agree that evolvability makes sense in theory. But finding evidence of it in the natural world has proved difficult.

Continue reading “Tortoise and Hare, in a Laboratory Flask” →

Lurking in the blood of tropical snails is a single-celled creature called Capsaspora owczarzaki. This tentacled, amoebalike species is so obscure that no one even noticed it until 2002. And yet, in just a few years it has moved from anonymity to the scientific spotlight. It turns out to be one of the closest relatives to animals. As improbable as it might seem, our ancestors a billion years ago probably were a lot like Capsaspora.

The origin of animals was one of the most astonishing and important transformations in the history of life. From single-celled ancestors, they evolved into a riot of complexity and diversity.

Continue reading “From Single Cells, a Vast Kingdom Arose” →