B8 was introduced after the original Section B FAQ post, and B9
appears here for the first time. Also, B2 is slightly revised in the
light of some experiments reported on by Shapiro.
B. Some Pointed Questions about Directed Panspermia
B1. Doesn't directed panspermia simply "kick the can down the road"
where the origin of life is concerned?
This question is based on a misconception of what the directed
panspermia hypothesis is all about. It has nothing to say about the
ultimate origins of life in our universe; it is about the origin of
life ON EARTH.
B2. Aren't origin-of-life experiments showing that life very likely
began on earth?
The experiments have yet to produce even one of the four basic
nucleotides of RNA under simulation of conditions on the early earth,
after over six decades since the original Urey-Miller experiment. In
fact one website that has been approvingly quoted by "evolutionists"
in talk.origins has gone so far to say that scientists aren't trying
to produce life from scratch in the laboratory, at all.
The experiments that have been done to date only help to shed light
(very feeble light at that, see B7 below) as to how abiogenesis could
take place *somewhere*.
B3. But doesn't Ockham's Razor strongly favor life abiotically
produced on earth rather than by seeding by space aliens?
Ockham's Razor decrees only that the most parsimonious explanation be
given after ALL evidence has been scrutinized, and what little
evidence there is [see the answer to A7], is on the side of directed
panspermia.
By the way, the wording "space aliens" is a bit misleading in that it
suggests that the panspermists engaged in far-ranging space travel,
whereas they might never have even gone as far as the last large
planet in their system. The distances between stars are so great,
that all probes to other systems might have been only carrying much
smaller and hardier organisms than the intelligent species to which
the panspermists belonged.
B4. Why have we not found any evidence of space probes? Doesn't that
count as evidence against directed panspermia?
[The following answer is taken largely
from
http://groups.google.com/group/talk.origins/msg/a984ba163776071f]
This question begs the question. What artifact could possibly have
survived meteor bombardments on the moon or other body, or plate
tectonics and weathering on earth, over close to 4 billion years? What
evidence at all? The best answer takes us far away from the concept of
a probe: a biological organism, able to propagate its characteristics
indefinitely.
For instance, the panspermists might have invented the highly unusual
device called the bacterial flagellum, which is useful enough to have
a good chance of staying in existence all those billions of years
through being handed down from one generation to the next.
I once suggested that it may partly have been designed as a sort of
analogue of "Kilroy was here": intelligent beings eventually evolving
from the microscopic life the panspermists sent might look at it and
begin to suspect that their existence is due to another species having
sent life to earth, and be suitably appreciative of the gift of life
to the unknown beings that sent it.
B5. What about the astronomical expenses of a panspermia project?
The expenses would be spread out over thousands, perhaps millions of
years in the sort of project that Crick and Orgel had in mind. The
project might grow out of a long project of simply exploring the
planets of other stars with instrumental probes, and during that time
the panspermists could be expected to mine a great many asteroids or
moons of their own "solar" system, greatly expanding the resources at
their disposal.
The panspermia project can be expected to start only after hundreds of
very likely candidates for abiogenesis were found, and no life found
on any of them.
B6. What if life is very common in our galaxy? What would that do to
the hypothesis of directed panspermia?
That would entirely depend on the origins of that life. If all
technological societies preceding ours were confronted with life in
the majority of suitable planets, I doubt that there would ever have
been a directed panspermia project.
B7. Didn't Crick and Orgel later repudiate directed panspermia on
somewhat similar grounds?
One talk.origins regular has claimed this, but the claim seems to rest
on a misleading juxtaposition of references [62] (the directed
panspermia paper) and [63] in the Wikipedia entry on Francis Crick,
where the entry addresses the hypothesis of directed panspermia.
[63] is a January 1993 joint paper by Crick and Orgel,
"Anticipating an RNA world. Some past
speculations on the origin of life: where are they today?". The FASEB
Journal 7 (1): 238-9. PMID 7678564
It can be read in scanned form at:
http://www.fasebj.org/content/7/1/238.long
This paper not only does not make any mention of directed panspermia,
it also makes no guesses as to the frequency or rarity of life in our
galaxy. Crick and Orgel merely acknowledge that RNA World hypothesis
had shown that an assumption they had made a number of years back was
obsolete.
At the end of this paper, they showed how they had NOT changed
their minds on one of the chief pieces of evidence they had given
for directed panspermia: the essential universality of the genetic
code:
Perhaps the most interesting
question concerns the nature of the interaction that led to
specific attachment of amino acids to primitive tRNAs. Was
the anticodon involved? If the answer is yes, then certain
codon assignments are predetermined. If the answer is no,
then the genetic code is a frozen accident. We still favor the
frozen accident theory, and we know of no convincing
evidence that argues against it.
http://www.fasebj.org/content/7/1/238.long
As the Wikipedia entry puts it:
"Crick and Orgel noted that they had been overly pessimistic about the
chances of abiogenesis on Earth when they had assumed that some kind
of self-replicating protein system was the molecular origin of life."
This is a reasonable inference from what they actually wrote, but that
is all.
They did NOT claim that this made them think abiogenesis is
commonplace in our galaxy, nor easily attained on the early earth. In
fact, in the same year that [63] was published, Orgel published
another joint article in which pessimism about RNA world was voiced:
Scientists interested in the origins of life seem to
divide neatly into two classes. The first, usually
but not always molecular biologists, believe that
RNA must have been the first replicating molecule
and that chemists are exaggerating the difficulty
of nucleotide synthesis. ... The second group
of scientists is much more pessimistic. They believe
that the de novo appearance of oligonucleotides on
the primitive earth would have been a near miracle.
(The authors subscribe to this latter view). Time
will tell which is correct.
--G. F. Joyce and Leslie E. Orgel, "Prospects
for understanding the origin of the RNA
world," in: _The RNA World_, ed. R. F.
Gesteland and J. F. Atkins, Cold Spring
Harbor Press, 1993, p. 19.
B8: Isn't directed panspermia essentially untestable, thereby removing
it from the category of science?
It is eminently testable *in principle*, and may also become testable
in practice if human beings make serious attempts to find out whether
there is life on other worlds. The following is mostly taken from
http://groups.google.com/group/talk.origins/msg/90027d90c58f7b4c
If we send enough probes, whether manned or unmanned, to
investigate the occurrence of life in many likely planets
in our galaxy, a lot of possibilities will be tested and
of the following four, only one will emerge the winner:
(1) We may find life in many stages of "protein takeover", all with
closely similar genetic codes.
That would be a big argument in favor of what I have called "the
Throomian sub-hypothesis." This has it that the panspermia project was
carried out by intelligent creatures that had ribozymes in place of
protein enzymes, and who carried out experiments in which they
replaced ribozymes incrementally with protein enzymes in organisms
over the course of thousands of years. They might have sent "the
latest models" to the planets they were seeding at that time.
On the other hand, if the takeover is in essentially the same stage as
that of earth, and the genetic code is very similar, that would
strongly support the overall hypothesis of directed panspermia while
all but falsifying the Throomian sub-hypothesis.
A third possible outcome is that we encounter lots of life with
genetic codes all very different from ours. That would all but
falsify all three main sub-hypotheses of directed panspermia,.
And finally, if we find no life after searching a million likely
planets, that would falsify the hypothesis that WE are the result of
evolution from unicellular organisms sent here by directed
panspermists, but would still leave my general hypothesis about the
frequency of directed panspermia largely unscathed.
B9: Is directed panspermia incompatible with Christian faith?
No, why should it be, when the Bible makes no mention of
microorganisms? Even if one takes an absolutely literalist view of
Genesis, the arrival of unicellular life on earth could be fit into
either the second day or the beginning of the third day of creation.
The plants that are mentioned on the third day are eukaryotes, which
function better if there is plenty of oxygen in the air. And, of
course, animals could not live without large amounts of oxygen. There
were only trace amounts of oxygen on earth when it was first formed,
and the oxygen that subsequently became an important component of the
atmosphere is due to photosynthesis, especially by cyanobacteria,
during the billions of years before the plant kingdom arose.
The theory of directed panspermia dovetails scientifically with the
theory of naturalistic evolution, but it is also compatible with God
creating every earth species after the first infusion. As for the
microorganisms sent by the panspermists, they in turn could have been
the product of divine creation, if one insists on going the whole nine
yards with species immutability.
Directed panspermia is even quite in the spirit of Genesis 6 through
8, where Noah is depicted as saving the animals from the great flood
and then (8: 17-19) sends them out from the ark to swarm and multiply
all over the earth. Substitute the spacecraft delivering the microbes
for the ark, and the analogy is very good.
NEXT: C: Connections with abiogenesis and intelligent design