"Cradle of Life" recounts the discovery over the last three decades of a vast, ancient fossil record, unknown and thought to be unknowable. This immense fossil record fills in gaping holes in our knowledge of the earliest 85 percent of the history of life on Earth, and changes our understanding of how evolution works. In addition to writing about this remarkable success story, however, Schopf also details two of science's stunning failures.

Schopf, director of UCLA's Center for the Study of Evolution and the Origin of Life, cites the "discovery" in the early 1700s of a skeleton of a human said to have drowned in Noah's flood -- taken for many decades as proof of Biblical truth. The claim was made by Dr. Johann Jacob Scheuchzer, a highly respected Swiss physician and naturalist. In 1725, Scheuchzer uncovered the partial skeleton of a large vertebrate animal in limestone, and dubbed the specimen Homo diluvii testis -- "Man, a witness of the Deluge."

Hailed as irrefutable evidence of Noah's flood, it was shown -- almost a century later -- to be a misidentified huge fossil salamander.

Another distinguished scientist from the early 1700s, Johann Bartholomew Adam Beringer, reported the discovery of "perfect" fossils of many animals, Including butterflies, birds with freshly laid eggs, spiders with webs, and "fossilized imprints" of the moon, sun and stars. However, Beringer was duped into falling for a hoax; the stones had been carved, hidden, and dug up -- a plot to disgrace Beringer by scholars who despised him.

"Beringer thought he had discovered a Rosetta stone, and Scheuchzer was certain he had unearthed a Rosetta stone," Schopf says. "Yet who are we to smugly sit in judgment? Though it is now harder to be fooled since so much more is known, it's a sure bet that some of what passes as 'known' today will eventually turn to dust. Like Beringer's and Scheuchzer's, our most glaring errors will also be cast aside."

Following his account of Scheuchzer and Beringer, Schopf concludes with a chapter on the NASA scientists who claimed in 1996 that they had found evidence of life on Mars in a meteorite (ALH84001) that landed in Antarctica 13,000 years ago. His implication is that these respected scientists may be modern successors to Scheuchzer and Beringer.

Evidence for life on Mars is "inconclusive, overblown"

Schopf, who first assessed the evidence for life on Mars a year and a half before the 1996 press conference produced worldwide headlines, offers this judgment: "The evidence was (and still is) inconclusive." Analyzing the three kinds of evidence presented, he says, "The minerals can't prove it. The PAHs (organic compounds known as polycyclic aromatic hydrocarbons) can't, either. The 'fossils' could -- but they don't, and there are good reasons to question whether they are in any way related to life.

"I want there to be life on Mars more than anyone else -- but it doesn't matter what I want!" Schopf says. "The evidence isn't there. Possibly, perhaps, maybe are not good enough."

In "Cradle of Life," Schopf recounts his involvement in evaluating the evidence for life on Mars, and the events that led to the life on Mars NASA press conference. NASA administrators asked him in January 1995 to assess what geologists at the Johnson Spacecraft Center (JSC) in Houston believed might be microfossils in a chunk of a meteorite thought to have come from Mars. The focus was on tiny, orange pancake-shaped globules of carbonate material. The scientists thought these globules might be Martian "protozoans," but Schopf's analysis showed that their guess was wrong.

"Many of the objects merged one into another in a totally nonbiologic way," Schopf says. "Their overall size range also did not fit biology, and they lacked any of the telltale features -- pores, tubules, wall layers, spines, chambers, internal structures -- that earmark tiny protozoan shells. In addition, the 'lifelike' traits they did possess could be explained by ordinary inorganic processes.

"I raised these points with the JSC scientists. They seemed to agree. I thought the matter was closed. But more than a year later, at the August 1996 news conference, the same little pancakes were again proffered as evidence of Martian life, this time of bacteria rather than protozoans. Evidently the scientists' minds were set -- the facts hadn't changed, only the meaning attached to them."

Several weeks before the press conference, NASA again asked Schopf to evaluate the findings. He studied the evidence three times, and was not impressed.

"Crucial questions had not been asked," he writes. "Articles published earlier and critically relevant to the authors' contentions had been ignored. More plausible ways to explain the findings were given short shrift. The claim of 'evidence for primitive life on early Mars' seemed overblown, ill-conceived."

At the press conference, the JSC scientists presented their findings with the aid of "high-tech cartoon videos," says Schopf, who spoke after them.

"I was wearing my best suit -- the one I got married in -- looking at hundreds of reporters who wanted me to say there was life on Mars," he says. "I had no doubt my words would prove unwelcome. On a scale of one to 10, I gave each piece of their evidence a score. Some, such as the suggested Mars source of the meteorite, I ranked high. But the evidence for life was weak; I gave it a two. A number of scientists later called me to task for being too generous. One Nobel laureate said I should have ranked the evidence zero!

"This attempt failed to find life at Mars. That does not mean Mars contained no life -- just that these scientists didn't find any."

How do respected scientists, from Scheuchzer and Beringer to the JSC team, Make such blunders? One answer, Schopf says, is that scientists have the same "strengths, fears and foibles as everyone" and are not so different from our neighbors. They have great successes and, sometimes, great failures. Mostly, "Cradle of Life" addresses one of science's great successes.

Immense fossil record fills in 85 percent of our history

As an honors student at Oberlin College in Ohio in the 1960s, Schopf learned in great detail about the most recent 500 million years of the planet's history. But geologic time covers more than 4.5 billion years, and Schopf's textbooks and professors taught virtually nothing about the Earth's first four billion years. The reason this period was neglected, Schopf learned, was that nobody knew much about it. He vowed to fill that black hole of knowledge, and he explains in "Cradle of Life" how he and other scientists succeeded in doing so.

What significant events occurred in that first 85 percent of the Earth's history? Among other things, the first living organisms, the modern food chain, photosynthesis, the ability to breathe oxygen, the development of the atmosphere and oceans, various types of cell division, and sexual reproduction all date from this enormously long period of time, Schopf says.

What if U.S. history began in 1963?

"Think how extraordinary it is that the earliest 85 percent of life's history has until now remained a mystery," Schopf says. "What would it be like if more than four-fifths of America's past were unknown? Imagine if history professors said that 'a pre-1963 historical record ought to exist, but there are no facts to go on. No one knows what happened, or why the record's been wiped out.' And then imagine if researchers discovered conclusive evidence of the earliest 85 percent of U.S. history: a Declaration of Independence, a Constitution, Washington, Franklin, Jefferson, Lincoln, a Civil War, electricity, telephones, radio, television, a Great Depression, World War I, World War II, the nuclear age. Astounding!"

In "Cradle of Life," Schopf tells an "even more mind-boggling tale," scaled in millions and billions of years, dealing with "all of life, over all of time, over the entire globe" -- a tale that reveals "where we have come from and who we are."

The tracing of life's earliest history is an acrimonious story of false starts, embarrassing mistakes, and ultimately, dogged persistence and remarkable success. Schopf shows why it took so long for the hidden record to emerge.

The early fossil record is richly complex and full of surprises. One such surprise: Evolution itself evolved.

"Everyone had expected early organisms would be smaller, simpler, perhaps less varied, but they were universally thought to have evolved in the same way and at the same pace as later life," Schopf writes. "This turned out not to be true. That evolution itself evolved is a new insight."

The pivotal point in evolution's own evolution turned out to be the advent of sex about 1.1 billion years ago. The origin of sex caused monumental change. Sex increased variation within species, diversity among species, and the speed of evolution and genesis of new species -- and brought not only the rise of organisms specially honed to particular settings, but because of this specialization, the first appearance of life-destroying mass extinctions.

The first organisms to engage in sexual activity were single-cell floating plankton. They started to appear about 1.1 billion years ago with a porelike mechanism that permits the release of sex cells into the environment. Before this time, organisms reproduced by asexual division, as do human body cells. Data from the fossil record clearly show that there appeared many new types of species at about 1.1 billion years ago, evidently when sexual activity first began.

"The start of sexuality," Schopf says, "had an enormous effect on the world's biodiversity. The pre-sex world was monotonous, dull, more or less static, but every organism born from sexual reproduction contains a genetic mix that never existed before."

Among the lessons Schopf draws is one that might surprise many high school students: "Science is enormous fun, and the greatest adventure ever devised. The past, present, even the future of life, Earth and all beyond are within its scope. There's hardly anything better than having a novel idea and finding that it makes sense."

Martian Life at SpaceDaily