Newspaper article Pittsburgh Post-Gazette (Pittsburgh, PA)

Scientists Draw Tree to Trace Mammal Evolution Database Helps Answer Questions

Newspaper article Pittsburgh Post-Gazette (Pittsburgh, PA)

Scientists Draw Tree to Trace Mammal Evolution Database Helps Answer Questions

Article excerpt

Where each placental mammal exists on the evolutionary tree and what common ancestor they share are questions that have puzzled evolutionary biologists ever since Darwin.

But a study and database, funded through the National Science Foundation's Assembling the Tree of Life Program, already are offering answers about the evolution of placental mammals, humans included. The research not only describes the hypothetical common ancestor of all placental mammals, but provides a method of placing each species at its most appropriate place on the tree.

The online database at is a matrix of information that could bring advances in the science of mammal evolution much the way the decoded human genome helped to explain human biology. One scientist compared its importance to evolutionary science to the Large Hadron Collider's impact on particle physics.

Twenty-three scientists, including two from the Carnegie Museum of Natural History, worked for six years on the study and tree of life published today in the journal Science. The most comprehensive picture of mammal evolution to date combines 4,500 anatomical characteristics of living and ancient fossil mammals along with DNA from living mammals to produce an information matrix to help researchers untangle mammal evolution over the past 65 million years, and possibly farther back.

"We built an amazing tool to answer questions now, but this represents a building block for the future," said John R. Wible, the study co-author who holds a doctorate in anatomy and is curator of mammals at the Carnegie Museum of Natural History. "We built a framework and will build more and more on that framework as we add more fossils and more DNA."

Michelle Spaulding, a Carnegie Museum postdoctoral fellow with a doctorate in earth and environmental science, also participated in the study.

Placental mammals give birth to live babies, nourish offspring with milk, and have hair (fur). Yes, hippopotami and whales lack hair, but their ancestors once had hair, but it later disappeared, providing the animals the evolutionary advantage of baldness in watery habitats, much as swimmers shave their bodies and wear swimming caps.

There are 5,100 living placental mammals, only five species of egg-laying mammals and 310 marsupial species, including such pouched mammals as opossum and kangaroo. The placenta has the same membranes that surround embryos in reptile and bird eggs.

In the field of mammal biology, disagreements arose between the molecular group that uses DNA analysis to track evolution, and the morphology group that traces evolution through gradual anatomical changes through time. …

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