Microbiologists contend that instead of increasing complexity, evolution of some systems—like interdependent microbial communities—can occur by losing complexity. How accurate or meaningful is this new idea about "reductive evolution," whereby life evolves by losing genes?¹

Nineteenth-century English poet Alfred Tennyson famously described nature as "red in tooth and claw."¹ But were claws and teeth originally intended to draw blood, or were they used to eat vegetation?

How much time would evolution need in order to make a mouse the size of an elephant?

Since this kind of evolution supposedly occurs too slowly for biologists to observe, one place to look for answers is in the fossil record. But in order to answer this particular research question, a team of evolutionary biologists made some large assumptions.