by Charles Baum
their white surface. Scientists in helicopters or on snowmobiles can collect
dozens of pristine specimens in a short field season. These areas are also
valuable because they provide a relatively unbiased inventory of meteorite
types. In more temperate regions, stony meteorites often blend into the sur-
rounding rocky landscape, where they just weather away; only the resistant
iron meteorites stand out, so they have always constituted the majority of
meteorite finds. Antarctic collecting areas reveal that stony meteorites are
much more common. For an informative visual overview, see the Web site of
ANSMET, the Antarctic Search for Meteorites program, cosponsored by
NASA and the Smithsonian Institution: http://geology.cwru.edu/~ansmet/.
p. 34
A team of biologists: D. S. McKay et al. (1996).
p. 34
On August 7, 1996: Dick and Strick (2004, pp. 179-201) provide
a detailed history of this incident. The timing of the prepublication press
conference was unusual because Science nearly always holds up press an-
nouncements until the afternoon before an article’s publication date (in this
case, Friday, August 16). However, the important story leaked more than a
week before publication because, according to Goldsmith (1997), a top offi-
cial in the Clinton administration told a prostitute, who, in turn, sold the
information to a tabloid. Science, in agreement with the authors and NASA, therefore made the article available on their Web site eight days before print
publication. [R. Brooks Hanson to RMH, 15 April 2004]
p. 35
“Although there are alternative . . . ”: In subsequent years, team
leader David McKay elaborated on this argument by attempting to calculate
the degree to which several weak lines of evidence coalesce to produce a
strong probability when taken together. See, for example, D. S. McKay et al.
(2002).
p. 36
aggressively challenged: Science received dozens of letters to the
editor and technical comments challenging aspects of the D. S. McKay et al.
NOTES
255
(1996) paper. Of these submissions, three letters were published in the Sep-
tember 20, 1996, issue and a technical comment appeared in the December
20, 1996, issue.
p. 36
Point number one: The most abundant organic molecules in
the Allan Hills meteorite are polycyclic aromatic hydrocarbons, or PAHs,
which are a ubiquitous component of carbon-rich meteorites as well as of
soot, diesel exhaust, and myriad industrial processes. See, for example,
Allamandola et al. (1985, 1989).
p. 36
Point two: An extensive and often contradictory literature has
arisen around the question of Allan Hills’ carbonate origins, particularly the
temperature of their formation. See, for example, Harvey and McSween
(1996) and Scott et al. (1997).
p. 36
Skeptical experts: The distinctive magnetite crystals, which pos-
sess a purity, crystal form, magnetic structure, and chainlike distribution
characteristic of Earth microbes, provide the greatest remaining hope for
proponents of the Martian life hypothesis. No plausible nonbiological ex-
planation for these features has yet been proposed.
p. 36
purported fossil microbes are too small: Morowitz (1996). See
also Schopf (1999, pp. 317-320).
p. 36
The story became even more confused: Steele et al. (2000a,
2000b).
p. 37
J. William Schopf: Schopf (1999, pp. 304-325).
p. 37
“I was like Daniel . . .”: Schopf (1999, p. 309).
p. 37
“The minerals can’t prove it . . .”: Schopf (1999, p. 316).
p. 37
“There are fine lines . . .”: Schopf (1999, p. 325).
p. 38
Such catastrophic events: Maher and Stevenson (1988), Sleep et
al. (1989). Estimates of the rate and magnitude of large impacts come largely
from statistical studies of the sizes and ages of lunar craters.
p. 38
We don’t know: Jack Szostak notes that “some people now think
that a Hadean origin is likely, and that totally sterilizing impacts may have
ended earlier than previously thought. And even following a sterilizing event,
cells blasted into space might have reseeded the Earth.” [Jack Szostak to
RMH, 21 August 2004]
p. 38
oldest known fossilized penis: The original report was Siveter
et al. (2003). The story appeared in USA Today on December 12, 2003. There was much scientific interest in this discovery because highly varied penile
appendages constitute the basis for classifying the group of crustaceans called
copepods.
p. 39
Apex Chert: Schopf (1993). Apex Chert fossils had been reported
earlier, for example in Awramik et al. (1983) and in Schopf and Packer
(1987). The 1993 paper was the first to enumerate 11 species of ancient Apex
microbes.
256
GENESIS
Bruce Runnegar writes, “Although it is more dramatic to highlight the
1993 announcement of Schopf ’s discovery of Earth’s oldest fossils, one
should be aware that the same kind of announcement came out of the Schopf
lab in the late 1970s from rocks of about the same age in the North Pole area
of Western Australia. These were discovered by Stan Awramik at UC Santa
Barbara and some people still believe these are the ‘best of the oldest.’ How-
ever, there are problems with these as well.” [B. Runnegar to RMH, 4 March
2005]
p. 39
world’s leading experts: Among Schopf ’s most noted works is
the volume he edited on Precambrian paleontology, Earth’s Earliest Bio-
sphere: Its Origin and Evolution (Schopf 1983). In that work he presents his own review of the earliest known microbes (Schopf and Walter 1983).
p. 39
UCLA protocol: Schopf (1999, pp. 71-100).
p. 40
Bonnie Packer: [James Strick to RMH, 1 September 2004] The
initial publication was Schopf and Packer (1987). Packer was the first person
to observe unusual microstructures in Apex Chert samples.
p. 40
Controversy erupted: Brasier et al. (2002). An account of the
controversy is presented by Knoll (2003, pp. 60-65).
p. 41
Further study: The geology of the Apex Chert site is still a mat-
ter of considerable debate. Brasier and Australian geologist John Lindsey
highlighted these concerns at subsequent seminars, including a joint presen-
tation at the Carnegie Institution’s Geophysical Laboratory on July 1, 2002.
For opposing viewpoints see Lindsay et al. (2003a, 2003b), Brasier et al.
(2004), and Schopf et al. (2002).
p. 41
“We reinterpret . . . ”: Brasier et al. (2002, p. 77).
p. 41
a rebuttal: Schopf et al. (2002).
p. 42
“News and Views”: Gee (2002). See also Dalton (2002).
p. 42
This debate: The Astrobiology Science Conference 2002 (the sec-
ond such meeting) took place from April 7 to April 11 at NASA Ames Re-
search Center. Abstracts of the meeting are available at http://
&
nbsp; web99.arc.nasa.gov/abscon2.
p. 42
Schopf spoke: The original NASA videotape of this debate was
provided by Lynn Rothschild of the NASA Ames Research Center. A descrip-
tion of the session, including a photograph of Schopf peering at Brasier,
appears in Dalton (2002).
p. 42
soften his assertion: While Schopf did back off his claim of fos-
sil cyanobacteria in the lecture, he repeated the arguments in a later article,
claiming that “Several of the Apex species seem almost indistinguishable
from living cyanobacteria.” (Schopf 2002, p. 173).
p. 43
Raman spectroscopic data: see also Pasteris and Wopenka
(2003).
p. 44
equally difficult to disprove: Scientists are taught to evaluate
NOTES
257
alternative hypotheses based on Occam’s razor: Accept the hypothesis that
requires the fewest assumptions. But how does one choose between evidence
for and against the existence of ancient microbial life, or life in a Martian
meteorite, for that matter? If your philosophical bias is that life emerges
rapidly and is thus ubiquitous in the universe, then any tantalizing sign of
life—carbon smudges or scrappy fossils—will provide encouraging support-
ing evidence. If you think life rare or unique, then the tenuous character of
the same data will prevail. Consequently, to prove either case—that an an-
cient rock does or does not hold evidence for life—is extraordinarily diffi-
cult. Brasier et al. were successful in casting doubt on Schopf ’s claims of
microbial fossils, but they came nowhere close to disproving that the carbon
residues were biogenic in origin.
p. 44
Meanwhile, paleontologists: Claims of 3.5-billion-year-old mi-
crofossils from South Africa were published by Furnes et al. (2004).
4
EARTH’S SMALLEST FOSSILS
p. 47
“Millions of brutal years . . .”: Simpson (2003, p. 72).
p. 48
Andrew Knoll: The “Origin of Life” Gordon Research Confer-
ence took place from July 27 to 31, 1997. Two of Knoll’s reviews (Knoll 1996,
2003) provide accessible overviews of Earth’s earliest fossil cells.
p. 50
severe analytical challenge: Simultaneously with our efforts,
Derek Briggs and co-workers at the University of Bristol produced similar
electron microprobe maps of fossils (Orr et al. 1998).
p. 51
Rhynie, Scotland: The fossils of the Rhynie Chert are docu-
mented in the classic studies of Kidston and Lang (1917-1921).
p. 51
Kevin Boyce: Boyce’s analytical work on Devonian plant fossils
is described in Boyce et al. (2001, 2003).
p. 54
Analytical studies: Schidlowski et al. (1983), Schidlowski (1988).
p. 54
mammoth bones: Koch (1998).
p. 54
fossil coal: McRae et al. (1999).
p. 54
Burgess Shale: Butterfield (1990) reports bulk isotopic values of
approximately –27 for the Burgess Shale. The classic 525-million-year-old
Burgess Shale deposits of British Columbia preserve a diverse soft-bodied
fauna in exquisite detail. These fossil forms are vividly described in Gould
(1989).
p. 55
Values as low as –50: The distribution of ancient carbon isotope
values has been tabulated, for example, by Schidlowski et al. (1983) and H. D.
Holland (1997).
p. 55
Walter’s work: See, for example, Walter et al. (1972), Walter
(1976, 1983).
258
GENESIS
p. 55
“It’s Strelley Pool Chert . . .”: The age and geological setting of
the Strelley Pool Chert has been described by C. P. Marshall et al. (2004) and
Allwood et al. (2004).
p. 59
Earth’s Oldest “Fossils”?: Bruce Runnegar writes, “I would pre-
fer to title this section “Earth’s Oldest Life” . . . . Fossils have been reported, even named ( Isuasphaera), from the Isua rocks by Hans-Dieter Pflug but no
one accepts them as remains of living organisms. What is being discussed
here is only, at best, ‘isotopic fossils.’” [B. Runnegar to RMH, 4 March 2005]
p. 59
oldest known rocks: Moorbath et al. (1986), Nutman et al.
(1996, 1997).
p. 59
Stephen J. Mojzsis: Mojzsis et al. (1994, 1996). See also E. K.
Wilson (1996) and H. D. Holland (1997) for analyses of the report.
Bruce Runnegar writes, “This is a dramatic way to present the discovery,
but light carbon had been reported from the Isua rocks since the 1960s, I
believe. Manfred Schidlowski, in particular, published many articles arguing
that Isua provided evidence for life on Earth prior to the Mojzsis et al. article
in Nature.” [B. Runnegar to RMH, 4 March 2005]
p. 59
Akilia rocks posed problems: Fedo and Whitehouse (2002). See
also Whitehouse (2000), Lepland et al. (2005). Kerr (2002a), Simpson (2003),
and Dick and Strick (2004) provide analyses of the controversy. Aivo Lepland
of the Geological Survey of Norway, who spent five years attempting to du-
plicate Mojzsis’s results without success, has raised additional questions
about the validity of the results. As a consequence, Gustaf Arrhenius, a coau-
thor on the 1996 paper, has distanced himself from the original conclusions
(Lepland et al. 2005). “I think there must have been a mix-up of the samples,”
he says (Dalton 2004, p. 688).
More convincing evidence for ancient biogenic carbon is provided
by Rosing (1999), who reported negative carbon isotope values from
3.7-billion-year-old sediments from the Isua region of Greenland. [Gustaf
Arrhenius to RMH, 8 August 2004]
p. 60
plausible explanations: See, for example, van Zuilen et al.
(2002). Negative carbon isotope fractionation is known to occur inorgani-
cally, for example, at high temperature, when iron carbonate breaks down to
graphite plus iron oxide.
5
IDIOSYNCRASIES
p. 61
“The ability of . . .”: Lahav (1999, p. 64).
p. 62
industrial chemists: The standard industrial process for synthe-
sizing chainlike carbon molecules is called Fisher–Tropsch synthesis.
NOTES
259
p. 62
Life builds hydrocarbons: The biochemical process for synthe-
sizing chainlike molecules is detailed in Lehninger et al. (1993, pp. 642-649).
p. 62
produced abundantly: Allamandola et al. (1985, 1989, 1997),
Allamandola and Hudgins (2003). PAHs are identified by their distinctive
infrared emission spectra.
p. 63
4-ring molecules called sterols: Lehninger et al. (1993, pp. 669-
674).
p. 64
A crucial requirement: For a survey of molecular biomarkers
see K. E. Peters and Moldowan (1993).
p. 65
The Hopane Story: Hopanes were discovered by Guy Ourisson
of the Université Louis Pasteur and co-workers (Rohmer et al. 1979,
Ourisson and Albrecht 1992, Ourisson and Rohmer 1992, Tritz et al. 1999).
The identification of hopane-related compounds in ancient Australian rocks
is reported by Summons et al. (1999), with a commentary by Knoll (1999).
For related work on ancient biomolecules from Australian rocks, see Sum-
mons and Walter (1990), Summons et al. (1996), and Buick et al. (1998).
p. 65
In 1999: Brocks et al. (1999).
p. 67
2-methylhopanoid: Bruce Runnegar writes, “As all extant cyano-
bacteria, so far as is known, make 2α-methylhopanes, the time of origin of
this innovation may significantly predate the origin of the last common
ancestor of living cyanobacteria.” [B. Runnegar to RMH, 4 March 2005]
p. 67
Biosignatures and Abiosignatures: This section is adapted from
Hazen et al. (2002).
p. 70
biomolecular fragment: See the Web site www.biocyc.org for a
database that illustrates many of the hundreds of common small molecules
found in cells.
p. 72
microbial corrosion: Steele et al. (1994).
p. 72
Steelie’s assignment: Steele et al. (2000a, 2000b).
p. 73
the term “astrobiology”: Dick and Strick (2004, p. 205).
p. 73
Enspel, Germany: Toporski et al. (2002).
p. 75
MASSE: For information on the project development visit
http://astrobiology.ciw.edu/main.php. The group proposes to look for mor-
phological as well as chemical evidence (Cady et al. 2003). For an overview
of Andrew Steele’s life-detection experiments, see Whitfield (2004). The dif-
ficulties of detecting life remotely on Mars are underscored by the ambigu-
ous results of the Viking mission in the 1970s (Levin and Straat 1976, 1981).
INTERLUDE—
GOD IN THE GAPS
p. 77
Darwinists rarely mention the whale: This quote comes from
Alan Haywood’s (1985) Creation and Evolution. These sentiments are ech-
260
GENESIS
oed in Duane T. Gish’s (1985) Evolution: The Challenge of the Fossil Record, in which he says: “There are simply no transitional forms in the fossil record
between marine mammals and their supposed land mammal ancestors. . . .
It is quite entertaining, starting with cows, pigs, or buffaloes, to attempt to
visualize what the intermediates may have looked like. Starting with a cow,
one could even imagine one line of descent which prematurely became ex-
tinct, due to what might be called an “udder failure” (pp. 78-79).
p. 78
35-million-year-old Basilosaurus: Gingerich et al. (1990).