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Science Friday > Archives > 1997 > May > May 30, 1997

Hour One: Early Hominids / Early Faint Young Sun Paradox

Our species, Homo sapiens, is the last surviving member of a family of two-legged primates called Hominidae -- the hominids. Now, a research team digging in a Pleistocene cave site in Atapuerca, Spain has identified a new species of hominid -- one that they believe may be the common ancestor of both modern humans and our extinct cousins, the Neanderthals. The new species, named Homo antecessor, is thought to have lived some 800,000 years ago, yet has a face that looks strikingly similar to modern humans. These new discoveries are changing our understanding of the relationships between members of our primate family. We'll look at those findings, and talk about what they mean.

Then, we'll take a look out into space... The Earth once was a cold world -- too cold, it is thought, to support life. However, at a time when the sun was still too faint to warm the Earth's surface above freezing, some 3.5 billion years ago, the oceans teemed with photosynthetic bacteria. The greenhouse effect, driven by ammonia and methane, had been offered as a solution, but a mystery still remained. Without life, it was thought, there would not be enough of these gases to warm the world. But without a warm world, there could be no life. Now, in a paper accepted for publication just before Sagan's death last year, Drs. Carl Sagan and Christopher Chyba present a theory to explain this "Early Faint Sun Paradox."

Sagan, who taught at Cornell University, was well-known for his work as an astronomer and for his ability to explain complex scientific topics to the public. Christopher Chyba, who earned his Ph.D. from Cornell in 1991, has been cited by Time Magazine in 1994 as one of its "50 for the Future." He is now a faculty member at the University of Arizona, where he researches the role comets played in shaping the environment in ways relevant to the origins of life.

 

Listen to this program in RealAudio!

Guest:
Dr. Christopher Chyba
Planetary Scientist
University of Arizona

Antonio Rosas
Biologist
Museo Nacional de Ciencias Naturales
Madrid, Spain

Ann Gibbons
Correspondent
Science

http://smallcomets.physics.uiowa.edu

Guest to be announced

Books/Articles Discussed:

"A Hominid from the Lower Pleistocene of Atapuerca, Spain - Possible Ancestor to Neandertals and Modern Humans," by J.M. Bermudez de Castro and A. Rosas at Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Cientificas (CSIC) in Madrid, Spain; J.L. Arsuaga and I. Martinez at Universidade Complutense de Madrid, CSIC in Madrid, Spain; E. Carbonell and M. Mosquera at U. Rovira I Virgili, CSIC in Tarragona, Spain. Science , May 30, 1997.

"The Early Faint Sun Paradox: Organic Shielding of Ultraviolet-Labile Greenhouse Gases." C. Sagan and C. Chyba.   Science, May 23, 1997.

Related links:

A tour of the family Hominidae: http://govan.cent.gla.ac.uk/Museum/guided/Hominid/

Sagan:   http://www.geocities.com/CapeCanaveral/Lab/1672/index.html
Chyba:   http://www.lpl.arizona.edu/faculty/chyba.html
Science :   http://www.sciencemag.org
Faint Early Sun Paradox:   http://www.astro.virginia.edu/~eww6n/astro/FaintEarlySunParadox.html