by Charles Baum
RMH, 7 June 2004]
266
GENESIS
p. 105
Heaven Versus Hell: A version of this text appeared in Hazen
(1998).
p. 106
ancient Mars or Venus: Speculations on the habitability of vari-
ous bodies in the solar system include Reynolds et al. (1983), Sagan et al.
(1992), Thompson and Sagan (1992), and Boston et al. (1992).
8
UNDER PRESSURE
p. 107
“Where is this . . . ”: Wächtershäuser (1988a, p. 480).
p. 108
Geophysical Laboratory: High-pressure research at the Geo-
physical Laboratory is described in Hazen (1993) and Yoder (2004). For a
general history of the Carnegie Institution, see Trefil and Hazen (2002).
p. 108
well funded by NASA: NASA’s Astrobiology Institute (NAI) was
founded in 1998 with the Carnegie Institution as one of 11 charter research
teams. Additional groups were added in 2001 and 2003. For more informa-
tion, see the NAI Web site: http://nai.arc.nasa.gov.
p. 108
Our first experiments: Cody et al. (2000).
p. 108
In a later set of experiments: Brandes et al. (1998).
p. 108
Carrying on with this line: Brandes et al. (2000).
p. 109
“This proposal is based . . .”: S. L. Miller and Bada (1988, p.
609).
p. 109
“a real loser”: Stanley Miller as quoted in Radetsky (1992, p.
82).
p. 110
again and again: These quotes appear in Wills and Bada (2000,
pp. 98 and 101). “Ventists,” annoyed at this condescending label, have been
known to refer to Bada and colleagues as “Millerites”—or, after a couple of
beers, “Miller lites.” In fact, the name “ventists” was coined by RPI chemist
James Ferris, who also dubbed Miller and his followers “arcists” (as quoted
in Simoneit 1995, p. 133).
p. 111
roles as varied: The possible roles of minerals in life’s origin
are reviewed by Hazen (2001).
p. 111
“Before enzymes . . .”: Wächtershäuser’s ideas initially appeared
in four papers (Wächtershäuser 1988a, 1988b, 1990a, 1990b). The central
tenets were summarized in “Pyrite formation, the first energy source for life:
A hypothesis” (Wächtershäuser 1988b), which emphasizes the role that
Popperian philosophy played in the theoretical effort. That paper was sub-
mitted to Systematic Applied Microbiology in March of 1988 and published
later that year. A more elaborate presentation, “Before enzymes and tem-
plates: Theory of surface metabolism” (Wächtershäuser 1988a) soon fol-
lowed in Microbiology Review. The paper that first brought his ideas to the
NOTES
267
attention of a wide audience appeared two years later in the Proceedings of
the National Academy of Sciences (Wächtershäuser 1990a). Articles submit-
ted to the Proceedings are often communicated by an Academy member;
Wächtershäuser’s paper, “Evolution of the first metabolic cycles,” was spon-
sored by Karl Popper himself. The full-blown theory is articulated in the
massive “Groundworks for an evolutionary biochemistry: The iron–sulfur
world” (Wächtershäuser 1992). Several subsequent papers clarify and elabo-
rate on the model and respond to a growing barrage of comment and criti-
cism (Wächtershäuser 1993, 1994, 1997).
p. 111
Karl Popper: Popper’s key ideas are summarized in three of his
books, The Logic of Scientific Discovery (Popper 1959), Conjectures and Refutations: The Growth of Scientific Knowledge (Popper 1963), and Objective Knowledge: An Evolutionary Approach (Popper 1972). Wächtershäuser’s presentation of his own hypothesis in terms of “Theory Darwinism” (essen-
tially, competition among rival hypotheses and survival of the fittest) is most
clearly presented in Wächtershäuser (1988a).
p. 111
“During breakfast . . . ”: As quoted in Nicholas Wade, “Gunter
Wachtershauser: Amateur Shakes up on Recipe for Life” ( New York Times,
April 22, 1997).
p. 112
patched together a theory: A number of widely cited origin-
of-life hypotheses, including those based on a primordial soup, can be criti-
cized for their poor predictive ability.
p. 113
“You don’t mind . . .”: Günter Wächtershäuser as quoted in
Radetsky (1998, p. 36). Experiments designed to test aspects of
Wächtershäuser’s theory include Blöchl et al. (1992), Keller et al. (1994),
Huber and Wächtershäuser (1997, 1998), and Huber et al. (2003).
p. 113
“It takes maybe two weeks”: Günter Wächtershäuser in re-
sponse to Robert Hazen at his Geophysical Laboratory seminar, March 23,
1998. Other estimates vary widely. De Duve (1995b, p. 428) suggests, “mil-
lennia or centuries, perhaps even less.” See also Lazcano and Miller (1994)
and Fry (2000, pp. 125-126).
p. 113
“not a new idea”: Bada and Lazcano (2002, p. 1983). The paper
they refer to, “A note on the origin of life” (Ycas 1955), introduces the idea of
an autocatalytic cycle of metabolites as the first living system. Dick and Strick
(2004, p. 64) agree that “Ycas had pioneered the ‘metabolism first’ idea.”
However, Noam Lahav notes that Alexander’s (1948) discussion of autoca-
talysis predates that of Ycas. [Noam Lahav to RMH, 27 August 2004]
p. 114
January 1998: “We have not met, but your work of the past
decade on the role of sulfides in organic synthesis and the origin of life is
having a profound effect on our current research,” I wrote. “We would be
delighted if you could schedule a trip to the States, for which we would pay
expenses.” [RMH to Günter Wächtershäuser, 14 January 1998]
268
GENESIS
p. 114
Wächtershäuser delivered his lecture: The Geophysical Labo-
ratory seminar, “Chemoautotrophic Origin of Life in an Iron–Nickel–Sulfur
World,” took place on March 23, 1998.
p. 114
“We would like to explore . . .”: [RMH to Günter
Wächtershäuser, 8 April 1998]
p. 115
I was left: That memorable meeting was the last contact any of
us had with Günter Wächtershäuser until Harold Morowitz received a stern
letter on Wächtershäuser & Hartz legal stationary dated October 11, 2000.
Copies of the letter were also sent to the bosses of everyone involved, includ-
ing Bruce Alberts, president of the National Academy of Sciences; Maxine
Singer, president of the Carnegie Institution; and Alan Merten, president of
George Mason University. Harold Morowitz, with three coauthors (includ-
ing George Cody), had recently published a short article in the Proceedings of the National Academy of Sciences on life’s most primitive metabolic cycle.
Morowitz et al. (2000) proposed that molecules used in the so-called “reduc-
tive citric acid cycle” (what I refer to in the text as the “reverse citric acid cycle”) are highly selected, with a long list of distinctive features. Such selectivity, Harold concluded, suggests that life’s earliest metaboli
sm is determin-
istic and likely to be the same on any planet or moon where life emerges.
Wächtershäuser denounced the article as improperly claiming credit for
ideas that were originally his, and he demanded an immediate retraction.
Harold ignored the veiled threat of legal action, but we were saddened that a
brilliant man with such creativity and vision could so remove himself from
the cooperative spirit of scientific research.
p. 115
His first paper: Brandes et al. (1998).
p. 115
He followed up: Brandes et al. (2000).
p. 115
In spite of these successes: Bada et al. (1995). The hydrother-
mal stability of amino acids is also discussed by Shock (1990b), Hennet et al.
(1992), and W. L. Marshall (1994).
p. 116
a few centuries: Wolfenden and Snider (2001).
p. 116
preserve proteins: Recent studies on the essential bone protein
osteocalcin underscores the ability of minerals to stabilize organic molecules.
Hoang et al. (2003) document the complex structure of osteocalcin and il-
lustrate how it binds strongly to hydroxyapatite, the principal mineral con-
stituent of bone. This binding not only provides strength and flexibility to
bone but also protects osteocalcin from the rapid decay experienced by most
other proteins. Christine Nielsen-Marsh and co-workers at the University of
Newcastle (Nielsen-Marsh et al. 2002) exploit this feature to extract and se-
quence osteocalcin from fossil bison bones more than 50,000 years old. Over
time, osteocalcin undergoes slight mutations in its amino acid sequence.
Comparison of small differences in this sequence among fossils of various
species and ages thus reveals patterns of mammalian evolution.
NOTES
269
Bruce Runnegar writes, “I’m skeptical of the report of collagen in dino-
saur bone. Osteocalcin maybe, but I wait to be convinced about collagen.”
[B. Runnegar to RMH, 4 March 2005]
p. 116
Additional evidence: Lemke et al. (2002) and Ross et al. (2002a,
2002b).
p. 117
molecules might separate out: The idea of the separation from
water of an amino-acid-rich phase first appeared in von Nägeli (1884). This
idea was also a central feature of Oparin’s original hypothesis (Oparin 1924,
1938), as well as several subsequent proposals. See, for example, Fox and
Harada (1958) and Fox (1965, 1988).
p. 117
more work to be done: In spite of these results, David Ross
emphasizes that amino acids cannot survive long enough in a hydrothermal
environment to start life. “The utility of hydrothermal work is that it allows
us to accelerate reactions to convenient times so that we can study them. No
more than that. . . . The key reactions leading to life involved very, very slow
reactions. Half-lives of a million years or more would be the order of the day,
and it would take a graduate student of unusual longevity, durability, and
endurance to get any data on such reactions.” [David Ross to RMH, 14 July
2004]
p. 118
Such reactions occur rapidly: These experiments are detailed
in Cody et al. (2004).
p. 118
Fischer–Tropsch (F–T) synthesis: A number of researchers
have studied F–T synthesis under hydrothermal conditions (McCollom and
Simoneit 1999, McCollom and Seewald 2001, Foustoukos and Seyfried
2004).
p. 118
Recent intriguing analyses: Sherwood-Lollar et al. (1993,
2002).
p. 119
thiols and thioesters: The possible role of these sulfur-con-
taining compounds in life’s origins has been detailed by de Duve (1995a,
1995b).
9
PRODUCTIVE ENVIRONMENTS
p. 121
“The limits of life . . .”: Nealson (1997b, p. 23677). Nealson
notes that the quote appeared “again in slightly different form in 1998 in a
Caltech lecture, and in the final form in Nealson and Conrad (1999).”
p. 121
immense tenuous clouds: Ehrenfreund and Charnley (2000)
enumerate several types of interstellar structures where organic synthesis
occurs. The density of these structures ranges from about one atom per cu-
bic centimeter in “interstellar clouds” to a million atoms per cubic centime-
270
GENESIS
ter in “dense molecular clouds.” Louis Allamandola writes: “A volume
roughly the size of a large auditorium is home to only one tenth-micron-
sized dust grain. It is the dust which absorbs background starlight, making
dark interstellar molecular clouds dark. Thus their sizes are enormous, often
measured in thousands of light-years.” He notes that in these clouds, PAHs, which are produced primarily during earlier star-formation processes, are
more abundant than all other interstellar molecules combined. [Louis
Allamandola to RMH, 16 July 2004]
p. 122
more than 140 different compounds: Infrared spectroscopy of
molecular clouds is reviewed by Pendleton and Chiar (1997) and Rawls
(2002). An up-to-date list of all identified interstellar molecular species is
available at: http://www-691.gsfc.nasa.gov/cosmic.ice.lab/interstellar.htm.
p. 122
Allamandola and co-workers’ experiments: See, for example,
Bernstein et al. (2002). A lively, accessible, and richly illustrated account of
this research appears in Scientific American (Bernstein et al. 1999a). Similar experiments have been performed by Mayo Greenberg and coworkers at the
Leiden Observatory in The Netherlands (Muñoz Caro et al. 2002).
Louis Allamandola write: “Mayo hired me ... because of my expertise in
low temperature chemistry and spectroscopy. He gave me full rein to design
the equipment because he was a theoretical astrophysicist with no labora-
tory experience in this area.” [Louis Allamandola to RMH, 29 November
2005]
p. 123
Evidence from space: Reviews of the rich variety of organic
molecules recovered from meteorites include Cronin and Chang (1993),
Glavin et al. (1999), Becker et al. (1999), Ehrenfreund and Charnley (2000),
and Cody et al. (2001a). Cometary organic molecules, though less well docu-
mented, are described by Chyba et al. (1990) and Ehrenfreund and Charnley
(2000). Kwok (2004) also emphasizes the important role of “proto-planetary
nebulae”—the envelopes of gas and dust around newly forming stars—in
the production of organic molecules. See also Oró (1961b), Urey (1966),
Kvenvolden et al. (1970), Cronin and Pizzarello (1983), Anders (1989),
Cronin (1989), Delsemme (1991), Engel and Macko (1997), Irvine (1998),
and Pizzarello and Cronin (2000).
p. 123
seeded abundantly: Allamandola argues that interstellar ice
particles could have provided much more than simple organic building
blocks. “These could well have been a source of prebiotic/biogenic molecules
which played a specific role in the origin of life. Going even further, I am
beginning to think we should also consider the possibility that the chemistry
in these ices might be even more advanced, perhaps being
a fountainhead of
life” [Louis Allamandola to RMH, 16 July 2004]
p. 123
“that’s garbage . . .”: Stanley Miller as quoted by Radetsky (1992,
p. 80).
NOTES
271
p. 123
“Even if cosmic debris . . .”: Jeffrey Bada as quoted by Radetsky
(1998, p. 37). More recently Bada (2004, p. 7) has softened his objections and
points to a combination of sources: “It is now generally assumed that the
inventory of organic compounds on the early Earth would have been de-
rived from a combination of both direct Earth-based syntheses and inputs
from space.”
p. 123
It’s hard to imagine: In the mid-1990s, when NASA scientists
subjected carbon-rich meteorite fragments to realistic impact velocities of 3
miles per second, about 99.9 percent of the amino acids were obliterated
(Peterson et al. 1997). They concluded that impact velocities of the
Murchison and other amino-acid-bearing meteorites must have been sig-
nificantly less, perhaps owing to aerobraking, thus preserving more of the
delicate organic molecules.
p. 123
impacts don’t destroy all: Other shock experiments to induce
organic synthesis have been reported by C. P. McKay and Borucki (1997),
who used a high-energy infrared YAG laser to shock-heat a gaseous sample
to temperatures greater than 10,000°C. These experiments simulate the ef-
fects of an impact on the atmosphere.
p. 123
giant experimental gas gun: See Blank et al. (2001).
p. 124
idea of Friedemann Freund: Freund et al. (1980, 1999, 2001).
p. 124
“Maybe,” he remarked: Friedemann Freund to Wesley Hunt-
ress, undated note ca. 2000 attached to a copy of Freund et al. (1999).
p. 125
“I am a hundred percent sure . . .”: [Anne M. Hofmeister to
RMH, 21 November 2002]
p. 125
synthetic magnesium oxide: Crystal growth of MgO is de-
scribed by Freund et al. (1999), who also document the identity of extracted
carboxylic acids. Freund’s studies on MgO properties include Kathrein and
Freund (1983), Kötz et al. (1983), and Freund et al. (1983).
p. 126
gem-quality olivine: Freund’s olivine samples come from the
classic San Carlos, New Mexico, locality, which is an active gem-producing
area. The gemmy green olivine crystals (also known as peridot), as much as
an inch across, comprise up to 50 percent of the basaltic rock, which was