New Knowledge Changes How We Classify

Classification systems change with expanding knowledge about new and well-known organisms.

Early skeleton sheds light on primate evolution

Published: Tuesday, May 19, 2009

• NEW YORK (AP) — The nearly complete skeleton of a small 47 million-year-old creature found in Germany was displayed Tuesday by scientists who said it would help illuminate the early evolution of monkeys, apes and humans.

• About the size of a small cat, the animal has four legs and a long tail. It's not a direct ancestor of monkeys and humans, but it provides a good indication of what such an ancestor may have looked like, researchers said at a news conference.

• Because the skeleton is so remarkably complete, scientists believe it will provide a window into primate evolution. The animal was a juvenile female that scientists believe died at about 9 or 10 months.

• "She tells so many stories. We have just started the research on this fabulous specimen," said Jorn Hurum, of the University of Oslo Natural History Museum, one of the scientists reporting the find.

• The creature is nicknamed Ida after Hurum's 6-year-old daughter.

• The unveiling, at New York's Museum of Natural History, was promoted by a press release for the cable TV show History, which called it a "revolutionary scientific find that will change everything."

• Mayor Michael Bloomberg, among the speakers at the news conference, called it an "astonishing breakthrough.“

Problems: Organisms that move alike may not be related Organisms that don’t move alike may be related Some organisms go in no categories Some organisms go in several categories

Scientist

Aristotle

Observed

appearancebehaviormovement

Classified

flySwimcrawl-walk -run

4 B.C.

Classified“Phylogenetic Cladistics

1750’s

Scientist

Carolus Linneaus

Observed

Structural descriptions

Classified

Observable features

“Oak with deeply divided leaves...”

Today’s Classification

Scientist

Us

Observed

Theoretically share common ancestor

Classified

Similar evolutionary history

Tomorrow

Scientist

You in college

Observed

Diversity of organisms and the way they relate to each other

Classified

Phylogenetic Cladistics/Systematics

Examples of Current Classification:

• Fossil Record-

• Comparative Homologies

• Embryonic Development

• Cladograms

• DNA sequencing

• Taxonomic Diagrams

• Molecular Clocks

Systematics… is the study of the evolution of biological diversity, and combines data from the following areas.

Fossil record

Comparative homologies

Embryonic DevelopmentWhich column is the human?

#1 #2 #3 #4 #5 #6 #7 #8

Pig? Tortoise? Cow? Rabbit? Human?

Salamander? Chicken? Rabbit?

Cladograms Although cladistics provides us with the best current method of determining evolutionary relationships, it is not perfect. Contradictions among advanced features often suggest alternative evolutionary trees. In such cases, the cladogram consistent with the most features is chosen for the time being. True evolutionary relationships can never be definitively established, either by examining fossils or studying DNA. But we can get closer and closer to the actual sequence of evolution by testing hypotheses about relationships with as many features as possible.

Why use cladistics? Although cladistics provides us with the best current method of determining evolutionary relationships, it is not perfect. Contradictions among advanced features often suggest alternative evolutionary trees. In such cases, the cladogram consistent with the most features is chosen for the time being. True evolutionary relationships can never be definitively established, either by examining fossils or studying DNA. But we can get closer and closer to the actual sequence of evolution by testing hypotheses about relationships with as many features as possible.

Why use cladistics? Although cladistics provides us with the best current method of determining evolutionary relationships, it is not perfect. Contradictions among advanced features often suggest alternative evolutionary trees. In such cases, the cladogram consistent with the most features is chosen for the time being. True evolutionary relationships can never be definitively established, either by examining fossils or studying DNA. But we can get closer and closer to the actual sequence of evolution by testing hypotheses about relationships with as many features as possible.

Comparative sequencing of DNA/RNA among organisms

Taxonomic Diagrams

Mammals Turtles Lizards and Snakes

Crocodiles Birds Mammals Turtles Lizards and Snakes

Crocodiles Birds

CladogramPhylogeneticTree

BioEd Online

Molecular clocks

Molecular clocks allow scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates.