Purpose/2. Life/Endnotes

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1. J. D. Bernal’s book, The Origin of Life (London: Weidenfeld and Nicolson, 1967) provides a classic account and critical discussion of what was known in the 1960’s about the origin of life.
Many books have been written about life’s origin, more recently including:
David W. Deamer and Gail R. Fleischaker, Origins of Life: The Central Concepts (Sudbury, Massachusetts: Jones and Bartlett, 1994).
John H. Holland, Emergence From Chaos to Order (Helix Books, 1998).
Noam Lahav, Biogenesis: Theories of Life’s Origin (Oxford: Oxford University Press, 1999).

2. Miniscule microbes (about one thousandth of a millimetre in length) that possess membranes and DNA have also been found living in solid rock, at temperatures over 150º Centigrade, five kilometres underground. These probably developed from life forms that existed when the rocks formed. See “It’s a small world after all,” Discover, January 2001, 58.

3. Other theories relating to the origin of life are mentioned in the postscript to this chapter.

4. For more detail on this subject, see Michael Gross, Life on the Edge: Amazing creatures thriving in extreme environments (Perseus Publishing, 2001).

5. Meteorites are fragments of asteroids that did not become part of the solar system’s planets, and they carry information that depicts what existed at the time of their formation. The Murchison meteorite was extensively examined in 1997 and found to contain an excess of left-handed amino acids—the same bias that life on Earth exhibits.

6. Amino acids in space show a slight predominance of left-handedness. (N.B. Miller-type experiments produce equal-handed amino acids.)

7. And may still be forming.

8. See “Life’s Far-Flung Raw Materials” by Max. P. Bernstein, Scott A. Sandford and Louis J. Allamandola, in the July 1999 edition of Scientific American, 42-49.
Also see: David F. Blake and Peter Jenniskens, “The Ice of Life,” Scientific American, August 2001, 44-51; Jason P. Dworkin et al, “Self-assembling amphiphilic molecules: Synthesis in simulated interstellar/precometary ices,” Proceedings of the National Academy of Science, January 30, 2001. The SETI website (www.seti.org) also provides links to other information on this topic.

9. It should be noted that complex (i.e., multicellular) life forms could not have existed anywhere in our universe during the first third or so of its life. It takes several billion years for most stars to burn, then collapse, so producing the novae and supernovae that make and release the heavier chemical elements that partly constitute all planets and life as we know it. It has taken another four billion years for life on this planet to evolve into us. Complex life is a relative late-comer to the universe’s party.

10. See Sarah Simpson, “Questioning the Oldest Signs of Life,” Scientific American, April 2003, 70-77, for a recent review of this topic.

11. Research carried out by some two hundred scientists from a dozen countries led them to recently state that there are at least five major kingdoms: animals, fungi, green plants, red plants, and brown plants. Their classification is based upon cladistics, a method that groups organisms according to evolutionary characteristics that are genetically shared with a common ancestor. (This contrasts with traditional classification methods whereby life forms are grouped according to the postulated relative importance of shared physical characteristics.)
Undeniably genetic tracing is the more accurate method. However, it is likely that the traditional classification system will continue to be used for many years to come—the scientific nomenclature that has developed over the centuries based upon these approaches is too vast to be revised very quickly.
The modern “family network” (rather than “family tree”) is sketched in the article, “Deciphering the Code of Life” by Francis S. Collins and Karin G. Jegalian (Scientific American, December 1999, 90). It looks markedly different from those traditionally shown in school.
Ian Tattersall, in “Once We Were Not Alone,” Scientific American, January 2000, diagrams (on page 60) the latest thinking about our own (the hominid) family tree. The essay is accompanied by two lovely illustrations of early life painted by Jay H. Matternes. The subsequent issue of this journal (February 2000) outlines the relationships between bacteria, Archaea and eukaryotes. (See in particular W. Ford Doolittle’s article, “Uprooting the Tree of Life,” 90-95.)

12. Archaea have now been found to be living in many other environments—animal intestines, compost piles, and marshes, for instance.

13. Hydrothermal vents are likely to exist on any planet having a hot core and water. (Possibly most planets possess these two features during their early years, with some retaining them for most of their lives). If so, primitive Archaea-type life forms may be abundant throughout the universe.

14. Anaerobic: not requiring air or oxygen. Cyanobacteria still exist and can be found in water and soil, on trees and on rocks. Mats of floating cyanobacteria frequently form mound-like structures called stromatolites. Fossil stromatolites date from all ages, including back to 3.5 billion years ago.

15. The transition from prokaryotic to eukaryotic cells is discussed by Christian de Duve in “The Birth of Complex Cells,” Scientific American, April 1996, 50-57.

16. Perhaps those that grew larger became more readily visible and excessively preyed upon.

17. More than 98% of human genes are identical to those possessed by chimpanzees. (Thus we can effectively resuscitate the “missing links” any time we want—by way of the petri dish and molecular genetic techniques. The recipe would be: take one chimp zygote, replace those DNA portions that differ from ours with human DNA, return to the womb and wait. Turning one human race into another should be even easier: humans are over 99.9% genetically identical.)

18. Via Earth’s magnetic field reversal.

19. Long before our species appeared, however, the brain pan size of early Homo ancestors began enlarging. This size change, occurring about two million years ago, could be related to the development of language, but, since complex languages probably did not develop until later (see Chapter One, section four), it is more likely that the increase was a result of the changes introduced by the onset of the ice ages. Having to cope in a frozen environment would have rapidly increased the number of life-threatening problems to be addressed. Larger brain pans in and of themselves do not improve problem solving, but, if the genetic mutation that first brought them into existence also caused an increase in the number of neurons grown, this would. Greater problem-solving ability enhances survival, and the mutated genes that produced a larger brain pan (able to accommodate additional neurons) would have been passed on to subsequent generations.
(Several forces favour smaller heads [not the least being birth canal dimensions] and brain pans stopped enlarging about 200,000 years ago. Possibly word use [and the communal problem solving that third-level thinking and language use encourages] reduced the requirement for further enlargements.)

20. The Vostok ice core from Antarctica contains records that date back to 420,000 years ago.

21. More than a dozen intriguing photographs of insects entombed in fossilized resin are printed in “Captured in Amber,” by David A. Grimaldi (Scientific American, April 1996, 84–91). DNA from plant and insect life preserved in amber for some 125 million years has been sequenced (i.e., the nucleotide order determined), adding to our understanding of evolution’s pathways.

22. See J. William Schopf, Cradle of Life: The Discovery of Earth’s Earliest Fossils (Princeton: Princeton University Press, 1999) for a description of the beginnings and development of the science of precambrian paleobiology.

23. Robert Francoeur, Evolving World, Converging Man (New York: Holt, Rinehart & Winston, 1970) provides a nice summary that, in less than twenty pages, describes life’s gradual changes from its beginnings to the rise of man. By letting one day represent a fourteen million year time period, he compresses the more than 3.5 billion years of life’s history on Earth into a one-year time-line. On this scale the Cambrian Period (when most of the major animal groups first appeared) corresponds to November 16–25, and the Jurassic (dinosaur) Age lasts from December 19–22. Early man does not appear until 6:30 p.m. on December 31 (the equivalent of 3 m.y.a. on this one-year time-line). Many similar accounts are in print.

24. Every copy of Darwin’s book was sold the first day it came out. It has been called “the book that shook the world.”
For a readily accessible series of more recent discussions about Darwin and life’s evolution, visit www.pbs.org and link to “evolution” at www.pbs.org/wgbh/evolution.

25. Eukaryotic organisms (i.e., plants and animals) possess intracellular structures called mitochondria which process chemical molecules obtained from food to release their energy. Mitochondria possess their own DNA (called mitochondrial DNA, or mDNA) which is passed directly from mother to child and does not vary between generations unless some random mutation occurs. The mutations that do occur can be used to trace a species’ history, as well as relationships between different species. By this means, the progression from one original organism to subsequent divergent organisms can be uncovered.

26. Scientists, for instance, have mapped the entire genome of the Archaean microbe known as Methanococcus jannaschii. This information, together with the genomes of representatives of the Prokarya and Eukarya kingdoms, may eventually allow us to find the genes common to all living things—that is, some of the genes possessed by the universal ancestor of life on this planet. It may only be a matter of time before a map can be drawn that will show definitive interconnections between all Earthly life forms. This will concurrently trace the major features of the full evolutionary route to Homo sapiens. (Genetic tracing becomes difficult in bacteria, however, because they are able to transfer genes laterally, i.e., directly from one to another. This suggests that we may have to be content with tracing life’s ancestry back no further than bacteria.)
Scientists have already used mitochondrial DNA taken from five major ethnic groups which make up the current global human population to trace the ancestry of Homo sapiens back to a time between 140,000 and 290,000 years ago. We have all evolved from one or another of about one hundred or so woman, the “original Eves,” who lived in Africa. (And we should really repaint any of our pictures involving Eve that do not show her having very dark skin.)

27. Weiner, Time, Love, Memory, 184. Surprisingly, the human genome contains around 30,000 genes, only about twice the number of genes possessed by a worm or a fruit fly. Several hundred of our genes turn out to be identical to those found in simple bacteria.

28. Weiner, ibid, 206.

29. de Duve, Vital Dust, 112.

30. Human change today is likely to be occurring most rapidly in the mental, rather than the physical, arena. The most “mentally alert” individuals are the most likely to provide the broadest environment for their children to experience. These children will, as a consequence, likely learn more, in depth and variety, than their peers, thus becoming potentially better equipped for success in later life. Whether or not the descendants of the “most mentally alert” will create a sub-division that eventually becomes genetically built into H. sapiens’ future will depend upon the environment—it must continue to provide a niche where this behaviour is rewarded by reproductive success. For instance, if humans eventually move out into space, it is likely to be the most mentally able that are chosen to go. If these space colonizers do succeed and multiply, then this kind of speciation may become a wide-spread, potentially dominant, reality.
(Because social programs support the survival and reproduction of all, the genes of the “most mentally alert” individuals are unlikely to dominate on this planet in the foreseeable future [because individuals possessing such genes currently tend to have fewer children than others]. The fact that rational behaviour acts to eliminate the genes that result in this behaviour suggests that there is something irrational [possibly its sustainability] about the environment our current social programs create.)

31. Natural selection states, essentially, that offspring are never identical, and that those possessing advantageous variations are more likely than their less-advantaged siblings or peers to survive and procreate. These advantages are thereby passed in greater numbers to the next generation, and this causes all species to change over time. There is not much to dispute about any of these postulates.

32. We continue to call Einstein’s masterpiece “The General Theory of Relativity,” but few state that it is just a “theory,” or that atomic bombs cannot exist.
“Laws,” too, including the Conservation Laws of physics, can be overthrown if negating proof is discovered.
(Never knowing if any “fact” or theory is entirely correct is a consequence of living within a [presumably] closed system. See the postscripts to Chapter Seven for elaboration.)

33. A certain amount of knowledge is needed to understand and appreciate what the theory of natural selection tells us about evolution. However, even those without such schooling still require some kind of explanation to account for life’s beginning and the presence of humankind. Creationism was developed to offer an explanation of sorts. It is an ancient idea that attempts to explain the unknown in a simple way. (All religions, if they are to be taken seriously, must explain how and why things are as we find them to be.) Unfortunately, Creationism ignores or attempts to refute too many evolutionary facts to be credible to anyone with an educated and impartial mind. Moreover, a belief in Creationism (like all beliefs) installs the opinion that one knows just as much as (and, often, even more than) is known by those who can call upon mountains of solid evidence that supports a different view.
That a few hold creationist views wouldn’t particularly matter, if it were not for the fact that their belief forces them to influence what is taught to children. Currently, schools in the American states of Alabama, Kansas, Nebraska, New Hampshire, New Mexico, Ohio, Tennessee, Texas, and Washington must teach that evolution is deemed to be no more significant than the belief that Creationists hold to be true (in spite of the mountains of credible evidence that support the former, and none that supports the latter). Still other schools deliberately leave evolution entirely off the curriculum to avoid controversy; they resort to teaching facts alone, and say nothing about the simplifying and edifying explanation that makes the existence of all we see in nature so logical and understandable.
In our world so dependant upon scientific knowledge, Creationism is a capricious belief to support, and it is very likely to limit the future success of its believers. This may not matter to adults, but it hampers children, who have many years to live in a techno-medical society. Of course, in the long run, the fallacy is self-correcting—after all, we live in a universe where survival of the fittest gives preference to those whose actions fit the facts. Unfortunately, as noted in endnote 30 to this chapter, it can only confer preference to those who act rationally when the immediately controlling environment is a rational one. This appears not to be the situation in a number of U.S. school boards.
It may be necessary to articulate that science neither opposes nor supports religion—it simply tries to uncover and understand the facts as they are found to be. To refute the millions upon millions of pieces of evidence that reveal that life evolved (and that humans are just one consequence of this evolution) is foolhardy. Rational individuals might better ask themselves which is most likely to be the truth—that which was originally written by a few wishing to promote a particular belief, or that for which evidence can be found in tangible form, everywhere, by anyone who cares to look.
Read Robert T. Pennock, Tower of Babel: The Evidence against the New Creationism (Boston: MIT Press, 1999) for a scholarly refutation of creationist ideas.

34. A single DNA change in a one-celled life form will have a more profound effect, more often, than a single change in a many-celled life form. Thus, although many mutations may be inconsequential and some may be fatal, the few that are neither can result in the rapid diversification and adaptation of simple life forms. This is a common phenomenon in hospitals, where environments hostile to pathogens are routinely maintained—so this is where strains of bacteria able to resist the latest antibiotics keep cropping up.

35. Darwin was ill at home and Wallace was collecting abroad at the time.

36. See Jonathan Weiner, The Beak of the Finch: A Story of Evolution in Our Time (New York: Alfred A. Knopf, 1994). A lovely book for anyone to read.

37. This chain of events is known as “punctuated equilibrium,” and has been popularized by Stephen Jay Gould, an influential evolutionary biologist and widely read author of many books.

38. The fallen rock perhaps forces a nourishing stream to forge a different channel. The fine dust thrown into the atmosphere from a volcanic eruption or a comet’s impact might block sunlight for several years. Extensive ice sheets can prevent plant growth for centuries.

39. Research suggests that biological recovery following any wide-spread ecological extinction takes an average of ten million years for complex animals, a relatively short period of time on the geological scale used to date fossils. (Recovery can be a matter of days, or even hours, for rapidly reproducing organisms such as bacteria.)

40. Sediments formed around 245 m.y.a. have recently been found to hold carbon “buckyballs” that contain trapped helium and argon gases which are present in a ratio similar to that found in carbon-based meteorites. This adds support to the theory that the effects of a sizable comet or asteroid impact caused the massive extinction that wiped out over 90% of all extant species (and marks the Permian-Triassic Boundary). This extinction eliminated much competition and provided the niches that some lizards exploited during the following twenty million years as they slowly evolved into the earliest forms of dinosaurs.
Other environmental calamities may have occurred several times between 750 and 570 m.y.a. An analysis of carbon-12 to carbon-13 ratios in sedimentary layers formed in ancient oceans shows that life came to a standstill four times during that period (see the August 28, 1998 edition of Science). It is postulated that the Earth was entirely covered with ice during these times, resembling a planetary snowball. What subsequently happened may have been as follows. Life survived (as multicellular algae and seaweeds) in the small pockets that formed where volcanoes and hot springs maintained some warmth. Meanwhile, the same volcanoes continuously pumped carbon dioxide into the atmosphere, and a greenhouse environment slowly developed. After some tens of millions of years (during which time life in the warm pockets diversified as it variously adapted to each pocket’s particular environment), the greenhouse gases triggered periods of planetary warming. About 565 m.y.a. most of the ice covering the Earth melted, and the pockets opened up. The life forms released from different zones would then have been able to cross-fertilize, and in the warm, nutritionally rich environment, with minimal competition, evolution would have run rampant. This could have spawned the broad diversity of ancestral multicellular plants and animals that we find in fossil form from this period, and begun the Cambrian Age.

41. This type of formulation was first proposed in 1961 by Frank Drake, currently Chairman Emeritus of the SETI Institute. (SETI, the Search for Extra-Terrestrial Intelligence, is a project that has been running for over 25 years at University of California-Berkeley using radio telescopes.) Drake wished to guesstimate the possibility of being able to contact extra-terrestrial life, and made a calculation somewhat like the following:

Number of technical civilizations in the Milky Way =

Number of stars in the Milky Way (say 2x10¹¹) x

Fraction of stars with planetary systems (say ½) x

Number of planets per star (say 1) x

Number of planets favourable to life (say 1/10) x

Fraction eventually developing life (say 1/10) x

Fraction with intelligent life (say 1/100) x

Fraction at our technical stage of development (say 1/10,000).

See w:Drake equation.
Multiplying these together we find that the number of planets with life at an “electronically-developed” stage in our galaxy could be around a thousand. Of course, the number likely to be at our stage of development, when communications over distances are carried out by AM, FM, or digitally encoded electro-magnetic waves, the kind of signals SETI’s instruments have been looking for, is quite critical. More advanced beings may well be using a different form of communication—piped-optical for example, or some other method that our current instruments would not detect. SETI has also been conducting optical searches (without success) and has just begun looking for laser beacons (which, if narrowly focused, would only be detected if we happened to pass through their beam).
In our calculation, since we are only estimating the possibility that life exists elsewhere, we are not bothered about its intelligence or stage of development so can ignore the reduction these fractions would contribute. Moreover, we are discussing life’s presence in the entire universe, not just our own galaxy.

42. See Guillermo Gonzalez, Donald Brownlee and Peter D. Ward, “Refuges for Life in a Hostile Universe,” Scientific American, October 2001, 60-67.

43. Common understanding holds that, to be considered living, an entity must meet at least four criteria: consume energy, expel wastes, respond to its environment, and reproduce. But see Chapter Ten for an alternative definition.

44. For a discussion on this topic see “Livable Planets: Calculations raise the odds for finding life in the cosmos,” by Corey S. Powell in Scientific American, February 1993, 18-20.
The Earth may already possess a few samples of life from elsewhere in the cosmos, lying undiscovered on our ocean floors or hidden in rocks or crannies on our continents. Entities resembling a string of cells (and possibly being primitive life forms) have been discovered on a meteorite originating from Europa (one of Jupiter’s moons). However the sample is not large enough to conclude whether any of the entities were once living.
Analyses of magnetic-field intensities along with various other measurements taken by satellites, indicate that Ganymede, Europa and Callisto (all moons of Jupiter) possess water. Some form of life may exist or have existed within this water, but this possibility remains to be explored. Probes, specifically equipped to test for water, may be sent to Europa within the next decade. Future Mars landers will be exploring areas where frozen reservoirs of water have been discovered, specifically looking for the presence of life. However, within our solar system, only our planet provides easy living; conditions on the other planets and moons are such that any life that might be found is bound to be primitive.
Astronomers occasionally search for distant signs of life using satellites and telescopes principally designed for other purposes. This will change in 2007, provided NASA’s scheduled Kepler Mission satellite launches successfully. This mission will carry telescopes designed to locate and check the atmospheres of exoplanets for the presence of ozone. Ozone is a gas formed from free oxygen, and free oxygen can only be produced in lasting quantities by life. This is because methane, produced by bacterial decomposition of organic matter, constantly removes free oxygen by combining with it to form other compounds. If both methane and oxygen are found in exoplanet atmospheres, then life is almost certain to be producing a continuous supply of the oxygen.)

45. This guess may be far too cautious. For reasons to be outlined in the next chapter, it is highly likely that life will always arise when circumstances permit (see also de Duve, Vital Dust, xv and 20).

46. The pyramids, Nazca lines, Stonehenge, crop circles and other occurrences have all been suggested as being possible evidence of alien visitation. However, all can be more credibly explained as being due to human effort.

47. Ian Crawford, “Where are they?” Scientific American, July 2000, 38-43.
See also Peter D. Ward and Donald Brownlee, Rare Earth: Why Complex Life is Uncommon in the Universe (New York: Copernicus, 2000).
For the opposite view, read Amir D. Aczel, Probability 1: Why there must be Intelligent Life in the Universe (New York: Harcourt Brace & Company, 1998).

48. For an excellent review of life’s evolution through its four billion years of development, read Vital Dust (op. cit.) by Christian de Duve, a Nobel Prize-winning biologist. de Duve traces life’s four billion years of development on this planet from its chemical beginnings, through its RNA and DNA encodings, to its current status. His text contributes the kind of understanding that should be possessed by all who make decisions that bear upon life’s future.

49. In particular, the second law of thermodynamics. This law states that the total amount of disorder (also known as entropy or complexity) in a closed system (for example, the universe) can never decrease.
To understand entropy, it may help to consider a handful of black marbles shaken into a box containing a handful of white ones. The two mix, and the marbles become disordered, their arrangement “complex.” It takes energy to separate the black and white marbles and return this “system” to “simplicity.” Thus, the disorder of a complex system can be decreased but energy is required, and this energy must come from some larger system. In the example just given, the energy comes from the food eaten by the person separating the marbles. In turn, the energy in the food came from an even larger system—our sun (via photosynthesis), whose energy in turn came from that introduced at the universe’s beginning (through the singularity that opened into the Big Bang).
But, the universe is the largest system we know. It is a closed system (as far as we can tell) and energy cannot be taken from “outside” (if such a place exists). So the universe becomes more and more disordered each second as innumerable events occur everywhere. It becomes more complex, its entropy is ever increasing, and it must forever continue to become so, because there is nowhere (again, as far as we know) from which can be taken the energy needed to order it again.
Subsystems within the universe can be made more ordered because they are open systems, and energy can therefore be taken from elsewhere in the universe’s stock. Life does this organizing, for example when it changes complex food molecules into simpler ones before recombining them in ways useful to itself. Many other processes also reduce entropy, for example when sunlight or lightning break water into its constituent hydrogen and oxygen molecules. But the net result of any kind of organizing is always an increase in the universe’s complexity, because the energy exchanges that are involved all release electromagnetic radiation (usually in the form of heat—think how hot a person would become were they to quickly sort ten thousand marbles, for instance). This energy release eventually heats (i.e., agitates) atoms somewhere, and adds disorder. In other words, with each exchange the total quality of the energy is irreversibly degraded, increasing the total complexity of the universe.
Life started simple and is becoming more and more complex through the addition of variations and adaptations to what existed earlier. In this manner, its evolution parallels that of the universe.