This site is not maintained. Click here for the new website of Richard Dawkins.

Case Closed for Dino Killer?


Mind the gap! Yale University graduate student Stephen Chester admires a dinosaur bone he helped find just below fallout from an asteroid impact (dark layers).
Credit: Tim Webster

What happened to the dinosaurs? For more than 100 million years, they ruled the world. Then, suddenly—poof—about 65 million years ago, they were gone. At least that's the way it looks to most scientists, who blame an asteroid hitting Earth for the ancient beasts' dramatic demise. Some researchers are still skeptical about the asteroid hypothesis, but a new fossil discovery in Montana may lend it new impact.

Back in 1980, when the late Nobel laureate physicist Luis Alvarez and his son, geologist Walter Alvarez, first tried to pin dinosaur extinction on an errant asteroid, they faced a major credibility gap. At the time, there was little firm evidence for such a catastrophic event. But then they and other researchers found an overabundance of iridium in geological formations at the 65-million-year transition line between the Cretaceous and Tertiary periods, known as the K-T boundary. Iridium is common in asteroids but rare in Earth's crust.

Still, the Alvarezes' hypothesis faced another hurdle: No dinosaur fossils had been found any higher than 3 meters below the K-T boundary, a gap which equates to about 100,000 years. Most researchers concluded that the dinosaurs went extinct before the asteroid impact and that they died off gradually. Alternative hypotheses for their demise included an increase in Earth's volcanic activity around the same time which threw ash into the atmosphere, diminished available sunlight, and affected the growth of plants that herbivorous dinosaurs ate, or a draining away of the shallow inland seas that dinosaurs relied upon for their vegetation-rich habitats.
Read more

TAGGED: EVOLUTION, PALEONTOLOGY


RELATED CONTENT

Planet of the apes

Stephen Cave - Financial Times Comments

What we really know about our evolutionary past – and what we don’t

WALK DARWIN’S TREE OF LIFE ~ 25 - 26...

- - Ancestors Trail Walk Comments

WALK DARWIN’S TREE OF LIFE ~ 26 AUGUST 2012 - event begins on Saturday 25 August

Astrophysicists simulate 14 billion...

Liat Clark - Wired.co.uk Comments

Astrophysicists simulate 14 billion years of cosmic evolution in high resolution

Study casts doubt on human-Neanderthal...

Alok Jha - The Guardian Comments

Cambridge scientists claim DNA overlap between Neanderthals and modern humans is a remnant of a common ancestor

Why do organisms build tissues they...

- - Science Blog Comments

Why, after millions of years of evolution, do organisms build structures that seemingly serve no purpose?

New flat-faced human species possibly...

Charles Choi - CBS News Comments

Four decades ago, in 1972, the Koobi Fora Research Project discovered the enigmatic fossilized skull known as KNM-ER 1470 which ignited a now long-standing debate about how many different species of early Homos existed.

MORE

MORE BY MICHAEL BALTER

The Wisdom of Not Being Too Rational

Michael Balter - Science Comments

Studies to examine how children learn tasks that are not obvious and can even be counterintuitive.

Modern Humans Blamed for Neanderthal...

Michael Balter - Wired Science Comments

New studies on volcanic glass show that a volcanic eruption once thought to be blamed for the demise of Neanderthals occurred after they were already gone.

Mass Killings of Gazelles Marked Rise...

Michael Balter - Scientific American 5 Comments

Language May Have Helped Early Humans...

Michael Balter - AAAS 11 Comments

Ancient Britons Used Skulls as Cups

Michael Balter - news.sciencemag.org 17 Comments

MORE

Comments

Comment RSS Feed

Please sign in or register to comment