The Debate of Panspermia: Are We the Descendents of Aliens?

Biology 103
2001 First Web Report
On Serendip

The Debate of Panspermia: Are We the Descendents of Aliens?

by A.B.

The type of panspermia most widely accepted is called weak panspermia or pseudo-panspermia. Weak panspermia is the theory that organic compounds arrived from outer space and added to the nutrient broth that spawned the first life. (3) The theory of weak panspermia is widely accepted and has extensive evidence to back it up. In 1969 a meteorite landed in Australia that was 12% water and contained traces of 92 amino acids. (9) This evidence points to not only the presence of organic compounds in outer space, but also the capacity of such compounds to reach earth. Also, millimeter arrays have detected the presence of complex organic molecules in star-forming clouds (9), further adding to the proof of organic molecules in space.

The second type of panspermia is called basic panspermia and can be defined as the presence of microbial life in space or on bodies such as comets or meteors that then reach a planet and start life on that planet. (3) Basic panspermia can then be broken down into three subcategories: radio-panspermia (cells travel by themselves and are propelled by light pressure), directed panspermia (microbial life was sent to earth in a spaceship by intelligent beings from another planet), and litho-, ballistic-, impact-, or meteoritic-panspermia (microbial life escapes from its home planet on fragments after a meteor impact). (3)

Very few scientists subscribe to the theory of radio-panspermia. Naked cells traveling through space would be subject to harmful UV light from stars, cosmic rays, solar X-rays, and zones of charged particles such as the Van Allen Belts around the earth. (2) A light coating of carbon could protect a naked cell floating through space from UV rays, but not cosmic rays. (3) Therefore, scientists have surmised that naked cells traveling through space would never survive. Indeed, research has shown that the longest a cell can survive in outer space is 6 hours (2) —not nearly enough time for a cell to travel from one planet to earth.

Similarly, the theory of directed panspermia is not taken seriously. There is no proof to support such a theory and most evidence is to the contrary. The universe is about 15 billion years old and life on earth began perhaps 5 billion years ago. (2) This window of time leaves a relatively small time frame for a planet to form, develop beings intelligent enough to make a rocket ship capable of carrying small cells to earth, and then for the rocket ship to travel the billions of miles to earth. Not to mention the fact that the cells themselves would have to survive first a trip of perhaps millions of years and then the impact when the rocket ship crashed into the earth. (2)

The theory of litho-panspermia is more plausible than the other two forms of panspermia, but still lacks definitive proof. Several recent discoveries have led to a growing support of litho-panspermia. Living microbes were recently found deep in the Antarctic. (1) Such observations point to the capability of certain organisms to survive in extremely harsh conditions (such as on a comet traveling through space). Critics of panspermia point out that any cells coming from outer space would have to survive the (perhaps) millions of years needed to make the journey from a distant planet to earth. Advocators of panspermia have proposed two theories to counter this criticism. The first being that the cells first brought to earth were dormant during the journey and then were revived once they reached earth. A study published in Nature claimed to have found and revived dormant bacteria that had been trapped in New Mexican salt crystals for 250 million years. (1) The implications of such a study are that some organisms could survive for millions of years. Some scientists even suggest that the planet that donated the first cells was Mars thus making the distance the first cells would have to travel much shorter. Some space rocks have been known to make the trip to Earth from Mars in less than a year. (1) Mars is also believed by some scientists to have once contained life. If Mars did have life, such life probably would have developed before that of Earth in that, Mars is smaller and therefore would have cooled faster. (1) Because Mars has a lower gravity than that of earth, rocks from Mars would travel more easily towards Earth than vice versa. (1)

There have been several cases of scientists discovering fossilized bacteria in meteorites. (3) However, at least one of these samples was found to be contaminated and others were suspected of being contaminated. (1) (3) As a result, such evidence can’t be considered definitive.

Critics of litho-panspermia also raise the argument that any cells on a rock traveling through space must survive being blasted by fast-moving atomic and sub-atomic particles. These attacks would destroy the DNA molecules of the microbial life and would eventually kill the organisms themselves. (1) To counter such arguments, panspermists propose that the cells did not travel on the outside of the rock, but rather on the inside, buried in at least 3 meters of rock where they would be protected from cosmic radiation. (1) This theory, however, raises a whole new problem: how would such a huge rock be coincidentally launched into space? And why wouldn’t whatever caused the rock to be launched kill the cells inside?

Strong panspermia is perhaps the most radical and consequently the most controversial form of panspermia. The prime advocator of strong panspermia is Brig Klyce. According to Klyce’s theory of strong panspermia, microorganisms from space provide the new genes necessary for sustained macroevolutionary progress on Earth”. (5) In strong panspermia, evolution does not rely on random point mutations, but rather on horizontal gene transfer. (3) Microorganisms (possibly bacteria) from space insert a gene into another organism. The new gene may give the organism the capacity to better adapt to its environment and thus evolve. Bacteria on Earth perform horizontal gene transfer in place of reproducing sexually. (6) Bacteria can sometimes carry out a type of horizontal gene transfer called conjugation which can occur between bacteria and eukaryotic cells in which long fragments of DNA are transferred. (6) There have even been cases where a virus will invade a cell and its genetic material will be incorporated into the host cell’s genetic material and benefit the host cell. (6) Klyce believes this phenomenon took place between organisms on Earth and bacteria from a different planet, and resulted in macroevolution. (4)

Klyce uses the faults of the Darwinian Evolution theory to support his theory for strong panspermia. Many scientists agree that the theory of Darwinian Evolution has flaws. Darwinian evolution relies on random point mutations to produce evolved organisms. As mathematician David Belinski points out from a mathematical point of view, Darwinian theories appear far too weak to have brought about the remarkable structures evident in living creatures. (10) If one assumes that all life arose out of random generations of proteins then there’s a problem. First of all, every known example of genetic mutation either produces no noticeable change or causes death (or in rare cases undoes the mistake of a past mutation). (8) Yet, Darwinian evolution relies on random point mutations creating lots of biological advantages. The ratio of useful proteins to possible random proteins is 1:10500. (7) Therefore, barring incredible luck, it would take about 10500 trials to produce one useful protein when a cell needs a minimum of one to two thousand proteins. (7) Hence, life appeared on earth (and evolved) too quickly for the Darwinian theory of evolution to be completely correct.

Klyce’s solution to this problem is strong panspermia. Many eukaryotic genes…seem to come from nowhere, observes scientist W. Ford Doolitle. (5) According to Klyce, these genes didn’t come from nowhere; they came from another planet. The discovery of some genes that appear older than they should be according to the fossil record, leads Kyce to the conclusion that these genes were brought by bacteria (that had probably started evolving much earlier) from another planet. (5) Klyce believes his theory of strong panspermia --since it relies on the replacement of entire genes rather than point mutations-- would match the actual pattern of evolution. (3) Strong panspermia also might be able to account for the sudden bursts of evolution. An influx of bacteria from outer space would cause a rapid replacement of different genes and cause widespread changes in organisms resulting in accelerated evolution.

Though Klyce’s theory of strong panspermia makes sense in many respects, it should by no means completely replace neo-Darwinism. Virtually the only advocate of panspermia is Brig Klyce, which is suspicious in itself. Also, even though Darwinism doesn’t seem to conform to a mathematical model, one still can’t discount the role chance might have played. Just because the odds are very, very low that random point mutations produced the organisms alive today does not mean that such a phenomenon should be completely discounted. Also, disproving neo-Darwinism does not necessarily prove strong panspermia. It’s possible that there is another reason altogether for life’s rapid appearance and evolution.

The main problem with the theory of panspermia (in all its forms save weak panspermia), is that it still fails to address where life came from. If one believes that life on Earth arose from cells from another planet, then where did those cells come from? The same question can be applied to strong panspermia in particular. If bacteria from another planet gave the genes necessary for evolution to organisms on Earth, then we’re still left with the question: how did the alien bacteria develop the genes?

The theories of panspermia (with perhaps the exception of weak panspermia) remain debatable. They are definitely worth pondering, but only with more studies and more observations will we have a better idea of their validity.

WWW Sources

2) Panspermia”, excerpted from History of Evolutionary Theory”, a creationist website

3) Panspermia Asks New Questions”, by Brig Klyce

4) Panspermia and Cosmic Ancestry: An Interview with Brig Klyce”, from the Astrobiology: A Living Universe website

5) Is Sustained Macroevolutionary Progress Possible?, by Brig Klyce

6) Horizontal Gene Transfer , from the University of Illinois Life Sciences’ homepage

7) The RNA World , by Brig Klyce

8) Viruses: Imported Genetic Software , by Brig Klyce

9) Lecture 12: The Origin of Life , by Tim Benton

10) The Limits of Darwinism , by David Berlinski