Nucleic acid bases in Murchison meteorite?
Have they proved that life came from outer space?
Photo Wikipedia
Fragment of the Murchison meteorite (at right) and isolated individual particles
(shown in the test tube).
by Jonathan Sarfati
Published: 25 June 2008(GMT+10)
Have evolutionists proved that life came from outer space?
Evolutionary papers are buzzing with the reports that nucleobases were found in
a meteorite. In some minds, this is tantamount to discovering life itself. But does
the discovery justify the hype?
Introduction
In 28 September 1969, fragments of a meteorite landed 2 kilometres south of the
small village of Murchison, Victoria, Australia. Local residents collected about
100 kg of material, and the largest fragment was about 7 kg.
Photo Wikipedia
Xanthine
The Murchison fragments came from a class of meteorite called carbonaceous chondrites,
because they contain small nodules called chondrules. Since this class is rich in
carbon and water, right from the beginning the Murchison meteorite has been analysed
for organic molecules. Chemical evolutionists, who have
faith that life evolved from non-living chemicals, were hoping to find evidence
to support their faith. They had hoped that this meteorite would provide evidence
that such processes were widespread in the universe, even if
some of them were pessimistic that life could arise on earth.
One of the first discoveries was amino acids, the components of proteins.1 Later, there were dubious
claims that some of the amino acids had a slight excess of the ‘handedness’
(chirality) required
for life, as we have reported.
Still later, there were claims that sugars and sugar-related compounds were discovered,
which excited many because the backbones of DNA and RNA contain the sugars deoxyribose
and ribose respectively. But see
our report on why this offers no support for chemical evolution.
What was just discovered?
Photo Wikipedia
Pair of grains from the Murchison meteorite.
A team led by Zita Martins of Imperial College, London and Leiden Institute of Chemistry,
Netherlands, reported that they discovered two nucleobases in this meteorite.2
This could be important, because these are the
letters of the genetic code that stores the information of life in DNA and RNA.
In particular, the bases found were uracil, a pyrimidine (single-ringed
base), and xanthine, a purine (double-ringed base). Uracil is found in
RNA, and pairs with adenine, thus it substitutes for DNA’s thymine. Xanthine
is not part of the genetic code, but it is found in living organisms from the breakdown
of guanine, which is a base in DNA and RNA.
These compounds were highly enriched in a heavy isotope of carbon, 13C,
and this was said to be consistent with formation in space, not earth. Surrounding
soil samples had a much lower 13C/12C ratio.3
Worldviews matter
Photo Wikipedia
Uracil
As always, creationists do not necessarily dispute the observations of
evolutionists, but often dispute the interpretations of these observations.
Most of the researchers are not trying to find out whether chemical evolution has
occurred. Rather, they assume that it has occurred, and merely trying to
find out how. So it is small wonder that many are excited by the finding
of the ‘building blocks’ of life anywhere, although they are light years
away from finding proof that they ever could build anything.
Contamination?
Even some evolutionists are not convinced that these nucleobases formed beyond earth,
and believe that contamination has not been ruled out. For example, Sandra Pizzarello,
a chemist at Arizona State University in Tempe, US, who has previously researched
amino acids in this meteorite, is unconvinced. A New Scientist report on
the discovery includes:
‘But it may be too early to conclude these nucleobases formed beyond the Earth,
says Sandra Pizzarello, a chemist at Arizona State University in Tempe, US. The
study “raises a very interesting question that was raised a very long time
ago, but I don't think it solves it”, she told New Scientist. …
‘But Pizzarello says too many other chemicals were present in the samples
to clearly distinguish the carbon ratio. “Analytically, it's not convincing,”
Pizzarello told New Scientist.4
But [astrochemist Sandra] Pizzarello says too many other chemicals were present
in the samples to clearly distinguish the carbon ratio. ‘Analytically, it’s
not convincing,’ Pizzarello told New Scientist.
Contamination is not so implausible. Uracil is not just a nucleobase in its own
right, but also forms from hydrolysis of cytosine. Indeed, this
instability of cytosine is a huge problem for chemical evolution. And cytosine
pairs with guanine, which breaks down to form xanthine.
‘Degradation of nucleobases in the hydrated parent body environment also has
to be considered. For example, cytosine degrades to uracil with a half-life of 17,000
years and guanine decomposes to xanthine with a half-life of 1.3 Ma at 0°C and
pH 7.5 Consequently, meteoritic
nucleobase distributions are the result of both synthetic and subsequent degradation
reactions.’2
However, this would be consistent with degradation from terrestrial sources
as well. In DNA of living organisms, G-C linkages are somewhat more stable than
A-T linkages, because the former have three hydrogen bonds while the latter have
only two.
Small molecules are not life
Creationists have long pointed out that some monomers (the components of
big molecules or polymers) would be expected to be able to form naturalistically.
So it is not surprising that some have been formed in both outer space and in the
Miller–Urey simulation experiments.
However, rather than proof of chemical evolution, the observations are evidence
against it. This is because we never see them progress any further—they are
chemical dead ends.
In particular, to form DNA and RNA, it’s far from enough to find nucleobases.
- They must be purified from other closely related compounds, then concentrated.
- They must combine with ribose to form a nucleoside. But this reaction just
doesn’t occur in water. And even in a dry environment (a primordial soup doesn’t
quite qualify), purine nucleosides have been formed, but even this failed to form
pyrimidine nucleosides.
- They must combine with phosphate to form a nucleotide. Yet phosphate concentrations
in naturally occurring water are far too low. And this phosphate must be activated
otherwise the reaction won’t occur.
- These nucleotides must be activated, purified and concentrated so they
will combine to form polymers. But even then, polymerization must have first occurred
without a template, and pyrimidines won’t polymerize even with a
polypurine template.
- The biological significance of DNA and RNA is in the sequence of the nucleobase
‘letters’. There is nothing in the bases themselves that would make
them join up in predetermined ways that have any biological significance, any more
than forces between ink molecules make them join up into letters and words. Michael
Polanyi (1891–1976), a former chairman of physical chemistry at the University
of Manchester (UK) who turned to philosophy, confirmed this:
Rather than proof of chemical evolution, the observations are evidence against it.
This is because we never see them progress any further—they are chemical dead
ends.
‘As the arrangement of a printed page is extraneous to the chemistry of the
printed page, so is the base sequence in a DNA molecule extraneous to the chemical
forces at work in the DNA molecule. It is this physical indeterminacy of the sequence
that produces the improbability of any particular sequence and thereby enables it
to have a meaning—a meaning that has a mathematically determinate information
content.’6
The
Imperial College press release called the findings ‘an important component
of early genetic material’. But this is true only in the sense that a carburettor
is an important part of an early car, or that a letter of alphabet soup might have
been an important component of an early message.
Conclusion
This is hardly the first time that the
pro-evolution mass media have hyped scientific discoveries as proof of goo-to-you
evolution. When the actual evidence is analysed, even if reported correctly, it
fails to support what it claims. In the case of the origin of life, such discoveries
really show the limits of what real chemistry can achieve without intelligent design.
That is, not only do the observations provide no support for chemical evolution,
they are actually further evidence that chemical evolution is based on blind faith
rather than fact.
Related articles
Further reading
Recommended Resources
References
- Kvenvolden, Keith A. et al.
Evidence for extraterrestrial amino-acids and hydrocarbons in the Murchison meteorite,
Nature 228 (5275): 923–926, 1970 | doi:10.1038/228923a0.
Return to text.
- Martins, Z. et al.,
Extraterrestrial nucleobases in the Murchison meteorite, Earth and Planetary
Science Letters 270:130–136. 15 June 2008 | doi:
10.1016/j.epsl.2008.03.026 Return to text.
- ‘Carbon isotope ratios for uracil and xanthine of δ13C=+44.5‰
and +37.7‰, respectively, indicate a non-terrestrial origin for these compounds
… Soil uracil has a δ13C value of −10.6‰ (±1.8‰)
and xanthine was below the detection limit of GC-CIRMS (~1 ppb). Thus, there should
be no terrestrial contribution from the landing site soil to the value for xanthine
measured in the meteorite.’; Martins, Ref. 2 Return to text.
- Courtland, R.,
Genetic building blocks may have formed in space, NewScientist.com
news service, 13 June 2008 Return to text.
- Levy, M., Miller, S.L., 1998. The stability of the RNA bases:
implications for the origin of life. Proc. Natl. Acad. Sci. 95:7933–7938.
Return to text.
- Polanyi, M., Life’s irreducible structure, Science
160:1308, 1968. Return to text.
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