Scientists Track Ancient DNA
Lice Offer New Clues on Evolution
by Lucy Ji, age 15
Almost everyone considers the common louse a pesky little critter. But now scientists have discovered that they are more useful than first thought.
Lice almost always live on one specific species for their entire lives. If they fall off or are picked off their host, they try to find another host of the same species. Knowing this, scientists can track and use lice to study the evolution of their hosts.
A recent study in the Biology Letters compares lice. It shows that there was an abundance of animals similar to mammals and birds 65 million years ago, just before dinosaurs became extinct. This new finding contradicts long-held beliefs. Until now man scientists assumed lice began to prosper after the dinosaurs were gone.
A team of researchers studied DNA of 69 modern descendants of lice that fed on various types of mammals and birds. From the DNA, scientists were able to figure out when the lice shared a common ancestor. They used fossils of various types of lice to build a “louse family tree”.
In this way researchers were able to keep track of each species and determined when each species evolved. They used a 44 million-year-old bird louse fossil and another 100 million-year-old book louse fossil, which is a type of non-parasitic louse.
By observing the physical features of lice, scientists were able to infer where the lice fit genetically on the family tree. Their placement on the family tree allowed researchers to determine when other lice in that “tree branch” became a separate species. The scientists finally concluded that lice began to thrive 125 million years ago. Therefore, their hosts must also have begun to diversify during that time.
These new findings give scientists who study evolution a great deal of new information about animals that lived at that time. These seemingly useless lice have actually been quite helpful.
[Source: Los Angeles Times]