• “To knock a limpet from the rock does not even require cunning.” – Charles Darwin

This quote gently mocks the scientific interests of researchers such as Dr. David Lindberg, of UC Berkeley’s Center for Computational Biology. And his mid-February talk at Chabot, on evolutionary biology, meteorites, and extinction patterns, included several of these snippets of humor.

As he first explained, meteorites are fairly common, and provide some clues to the composition of the world beyond Earth. asteroids the size of the one which recently approached the Earth come that close to us roughly every 40 years. And parts of them break off and crash on our planet as meteorites about every 1, 200 years.

The famous Murchison meteorite, which fell in 1969, contains amino acids, purines, and pyrimidines, the building blocks of DNA. And a Science Daily article published in 2011 points out that organic carbon-containing compounds likely exist throughout the universe. So meteorite impacts may not be purely destructive, and may actually have assisted in the formation of life on our planet.

Next, Dr. Lindberg described the patterns of biodiversity and species development over our planet’s history. Extinction has actually proved more common than survival for new species and genera, with five major mass extinction periods since the evolution of life. The largest mass extinction occurred during the Permian era, when ocean acidity increased, eliminating 95 percent of the species on Earth, including the trilobites.

Were meteorite impacts and the accompanying disruption factors in bringing about these extinctions? The Center for Computational Biology’s work helps to address that question.

According to the Earth Impact Database, our planet contains 183 confirmed impact structures, where meteorites once landed. Researchers identify these by seeking out certain types of geological features that form upon impact, such as shatter cones, deformation features, impact meltsheets and breccias, and high-pressure polymorphs. So we’ve certainly collided with enough extraterrestrial material for it to have affected the evolution of life.

Dr. Lindberg said he envied astronomers for being able to look back in time, because of the delay in light’s reaching Earth. He has no way to go back to see what happened to the dinosaurs, for example, so must rely upon theories and relics.

Scientists would like to find out whether the mass extinctions occurred slowly, as suggested by the gradual model, or whether living beings suddenly disappeared, as in the catastrophic model. Current evidence and thought leans towards the gradual model, as we see slow declines in plant and animal diversity throughout the Cretaceous period, when the dinosaurs died out. Also, the destructive events accompanying a major meteorite impact – heavy metal poisoning, cooling and photosynthesis interruption due to atmospheric dust blocking the sun, acid rain, disruption of the ozone layer – all take months, years, or decades to destroy life forms. So even a serious impact would likely have contributed to a slower decline in biodiversity.

Geologists and biologists speculate that the meteorite which killed off the dinosaurs was roughly six miles across. Its impact would have been close to that of 100 million megatons of TNT, burning up most organisms not sheltered in water or burrows. Mammals, crocodiles, lizards, turtles, fish, frogs, and birds all survived, however, and helped repopulate the planet.

In this evolutionary instance, the beneficiaries were not necessarily the best adapted to long-term planetary conditions, but simply those who avoided dying from a sudden event. Hence, Dr. Lindberg and others joked that God was not playing dice, but rather pinball, with the universe.

For more information on the subjects he discussed, Dr. Lindberg suggests people read Neil Shubin’s The Universe Within, which provides a well-written common history of matter in the universe, from rocks to planets to people.

Article by staff editor Cristina Deptula, who may be reached at cedeptula@sbcglobal.net