Science + Technology

Evidence for Life on Mars Remains Weak, Likely to Join Scientific "Discoveries" That Fizzled List, Says UCLA Scientist


For all its achievements, science has also been spectacularly wrong,UCLA paleobiologist J. William Schopf shows in his new book, "Cradleof Life: The Discovery of Earth's Earliest Fossils" (Princeton UniversityPress). Facts always prevail eventually - but sometimes they don't emergefor decades.

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

Schopf, director of UCLA's Center for the Study of Evolution and theOrigin of Life, cites the "discovery" in the early 1700s of askeleton of a human said to have drowned in Noah's flood - taken for manydecades as proof of Biblical truth. The claim was made by Dr. Johann JacobScheuchzer, a highly respected Swiss physician and naturalist. In 1725,Scheuchzer uncovered the partial skeleton of a large vertebrate animalin 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 - almosta century later - to be a misidentified huge fossil salamander.

Another distinguished scientist from the early 1700s, Johann BartholomewAdam Beringer, reported the discovery of "perfect" fossils ofmany animals, including butterflies, birds with freshly laid eggs, spiderswith webs, and "fossilized imprints" of the moon, sun and stars.However, Beringer was duped into falling for a hoax; the stones had beencarved, hidden, and dug up - a plot to disgrace Beringer by scholars whodespised him.

"Beringer thought he had discovered a Rosetta stone, and Scheuchzerwas certain he had unearthed a Rosetta stone," Schopf says. "Yetwho are we to smugly sit in judgment? Though it is now harder to be fooledsince 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 accountof Scheuchzer and Beringer, Schopf concludes with a chapter on the NASAscientists who claimed in 1996 that they had found evidence of life onMars in a meteorite (ALH84001) that landed in Antarctica 13,000 years ago.His implication is that these respected scientists may be modern successorsto Scheuchzer and Beringer.

Evidence for life on Mars is "inconclusive, overblown"

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

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

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

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

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

Several weeks before the press conference, NASA again asked Schopf toevaluate the findings. He studied the evidence three times, and was notimpressed.

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

At the press conference, the JSC scientists presented their findingswith the aid of "high-tech cartoon videos," says Schopf, whospoke after them.

"I was wearing my best suit - the one I got married in - lookingat 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 scaleof one to 10, I gave each piece of their evidence a score. Some, such asthe suggested Mars source of the meteorite, I ranked high. But the evidencefor life was weak; I gave it a two. A number of scientists later calledme to task for being too generous. One Nobel laureate said I should haveranked the evidence zero!

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

How do respected scientists, from Scheuchzer and Beringer to the JSCteam, make such blunders? One answer, Schopf says, is that scientists havethe same "strengths, fears and foibles as everyone" and are notso different from our neighbors. They have great successes and, sometimes,great failures. Mostly, "Cradle of Life" addresses one of science'sgreat successes.

Immense fossil record fills in 85 percent of our history

As an honors student at Oberlin College in Ohio in the 1960s, Schopflearned in great detail about the most recent 500 million years of theplanet's history. But geologic time covers more than 4.5 billion years,and Schopf's textbooks and professors taught virtually nothing about theEarth's first four billion years. The reason this period was neglected,Schopf learned, was that nobody knew much about it. He vowed to fill thatblack 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'shistory? Among other things, the first living organisms, the modern foodchain, photosynthesis, the ability to breathe oxygen, the development ofthe atmosphere and oceans, various types of cell division, and sexual reproductionall 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 oflife's history has until now remained a mystery," Schopf says. "Whatwould 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 oughtto 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 discoveredconclusive evidence of the earliest 85 percent of U.S. history: a Declarationof 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-bogglingtale," scaled in millions and billions of years, dealing with "allof 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 falsestarts, embarrassing mistakes, and ultimately, dogged persistence and remarkablesuccess. Schopf shows why it took so long for the hidden record to emerge.

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

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

The pivotal point in evolution's own evolution turned out to be theadvent of sex about 1.1 billion years ago. The origin of sex caused monumentalchange. Sex increased variation within species, diversity among species,and the speed of evolution and genesis of new species - and brought notonly the rise of organisms specially honed to particular settings, butbecause of this specialization, the first appearance of life-destroyingmass extinctions.

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

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

Among the lessons Schopf draws is one that might surprise many highschool students: "Science is enormous fun, and the greatest adventureever devised. The past, present, even the future of life, Earth and allbeyond are within its scope. There's hardly anything better than havinga novel idea and finding that it makes sense."



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