topics: |  biology | evolution | paleontology | genetics

Sixth volume in the series of essays, 1974-2001, from Natural History in the
column "This View of Life," containing 31 essays from his The book urges
conservation for preserving bio-diversity, pointing to massive extinctions of
species - the land snail Partula from Bali Hai in the South Pacific, and why
the Mount Graham red squirrel of Arizona is worth fighting for.

The title essay discusses why we have five fingers - what an ingenuous
title for such a topic.  The archetype or primal pattern for tetrapod
vertebrates, proposed in the 1800s, all had 5-digits on each limb -
pentadactyl limbs.  Some animals alter it - horses have only one; whales
loose the whole hind limb.  Swedish paleontologist Erik Jarvik:
	The most prominent feature of man is no doubt his large and elaborate
	brain. However, this big brain would certainly never have arisen--and
	what purpose would it have served--if our arm and hand had become
	specialized as strongly as has, for instance, the foreleg of a horse
	or the wing of a bird. It is the remarkable fact that it is the
	primitive condition, inherited from our osteolepiform ancestors
	[fishes immediately ancestral to tetrapods] and retained with
	relatively small changes in our arm and hand, that has paved the way
	for the emergence of man. We can say, with some justification, that
	it was when the basic pattern of our five-fingered hand for some
	unaccountable reason was laid down in the ancestors of the
	osteolepiforms that the prerequisite for the origin of man and the
	human culture arose.
But discoveries since 1984 reveal that early tetrapods had 6 fingers on each
limb.  The three Devonian tetrapods known bear 6, 7 and 8 fingers.  But most
tetrapods today have 5 fingers, and these are formed in a particular sequence
called the Shubin-Alberch.  Animals like the panda which has a false 6th
"thumb", and some moles, differ in the embryogenetic process by which these
fingers develop.  So 5 is the stable pattern.  The answer may be that after
transitioning from fins to limbs, five toes provided optimal support for the
greater weight while meeting locomotion needs.   That this hypothesis may be
correct gains support from the fact that "five digits evolved
twice--separately, that is, in the two great divisions of tetrapods."   But
if this is right, how come one of these two divisions, the amphibians, have
only
	four toes on their front legs, and we have no evidence for an initial
	five--so pentadactyly may not be a universal stage in terrestrial
	vertebrates.  Second, if five (with symmetry about a strong central
	toe) is the source of advantage, then why do [humans] who retain
	five, require great strength in using two limbs against gravity, but
	construct the end-member first toe as the main weight bearer?
	[Also,] the most successful of all large mammals, the "cloven-hoofed"
	artiodactyls, or even-toed ungulates--including cows, deer, giraffes,
	camels, sheep, pigs, [etc.] - bear an even number of toes, with the
	central axis running through a space between the digits...
Finally, after this majestic sweep, Gould argues for mere "historical
contingency" - that five was not meant to be, but just happens to be.

In another essay, we learn the golden rule which may save us yet:
	I have never been much attracted to the Kantian categorical
	imperative in searching for an ethic-to moral laws that are absolute
	and unconditional and do not involve any ulterior motive or end. The
	world is too complex and sloppy for such uncompromising attitudes
	(and God help us if we embrace the wrong principle, and then fight
	wars, kill, and maim in our absolute certainty). I prefer the messier
	"hypothetical imperatives" that invoke desire, negotiation, and
	reciprocity. Of these "lesser", but altogether wiser and deeper,
	principles, one has stood out for its independent derivation, with
	different words but to the same effect, in culture after culture. I
	imagine that our various societies grope toward this principle
	because structural stability, and basic decency necessary for any
	tolerable life, demand such a maxim. Christians call this principle
	the "golden rule"; Plato, Hillel, and Confucius knew the same maxim
	by other names. I cannot think of a better principle based on
	enlightened self-interest. If we all treated others as we wish to be
	treated ourselves, then decency and stability would have to prevail.
	    I suggest that we execute such a pact with our planet. She holds
	all the cards and has immense power over us--so such a compact, which
	we desperately need but she does not at her own time scale, would be
	a blessing for us, and an indulgence for her. We had better sign the
	papers while she is still willing to make a deal. If we treat her
	nicely, she will keep us going for awhile. If we scratch her, she
	will bleed, kick us out, bandage up, and go about her business at her
	planetary scale. p.50
Another question dealt with at some length (ch.28) relates to the vestigial
eye tissue which is generated in completely bind mole rats. However, in these
rats, the genes related to the eye lens protein are changing more rapidly in
other rodents The average tempo of change in alpha-A-crystallin among
vertebrates as a whole is 3 amino acid replacements per 100 positions per 100
million years.  This mole, spalax is changing 4x faster, at about 13 percent
per 100 my.  But other, truly selection-neutral "pseudogenes" are changing at
5x the spalax - so do this vestigial eye still confer some advantage? Maybe
it helps it respond to day and night, by secreting the hormone melatonin?
Like many other questions at the frontiers of research, the answer is not
clear.

Other essays deal with how Darwin based his theory upon the effect of human
breeding on pigeon colouration, or on how Charles Darwin's first published
work was an article called "The moral state of Tahiti" (where he and a
shipmate write saying that stories of licentious women no longer hold), and
his view on women -  "The Descent of Man" he writes:
	It is generally admitted that with woman the powers of intuition, of
	rapid perception, are more strongly marked than in man; but some, at
	least, of these faculties are characteristic of the lower races, and
	therefore of a past and lower state of civilisation.
Contents:
1. THE SCALE OF EXTINCTION
      1. Unenchanted Evening
      2. The Golden Rule: A Proper Scale for Our Environmental Crisis
      3. Losing a Limpet
2. ODD BITS OF VERTEBRATE ANATOMY
      4. Eight Little Piggies
      5. Bent Out of Shape
      6. An Earful of Jaw
      7. Full of Hot Air
3. VOX POPULI
   Evolving Visions
      8. Men of the Thirty-Third Division: An Essay on Integrity
      9. Darwin and Paley meet the Invisible Hand
     10. More Light on Leaves
   Time in Newton's Century
     11. On Rereading Edmund Halley
     12. Fall in the House of Ussher :
		James Ussher was the Anglican Archbishop who computed the
		date of creation as October 23, 4004 BC.
4. MUSINGS
   Clouds of Memory
     13. Muller Bros. Moving and Storage
     14. Shoemaker and Morning Star
   Authenticity
     15. In Touch with Walcott
     16. Counters and Cable Cars
5. HUMAN NATURE
     17. Mozart and Modularity
     18. The Moral State of Tahiti—and of Darwin
     19. Ten Thousand Acts of Kindness
     20. The Declining Empire of Apes
6. GRAND PATTERNS OF EVOLUTION
   Two Steps Towards a General Theory of Life's Complexity
     21. The Wheel of Fortune and the Wedge of Progress
     22. Tires to Sandals
   New Discoveries in the Earliest History of Multicellular Life
     23. Defending the Heretical and the Superfluous
     24. The Reversal of Hallucigenia
7. REVISING AND EXTENDING DARWIN
     25. What the Immaculate Pigeon Teaches the Burdened Mind
     26. The Great Seal Principle
     27. A Dog's Life in Galton's Polyhedron
     28. Betting on Chance—And No Fair Peeking
8. REVERSALS-FRAGMENTS OF A BOOK NOT WRITTEN
     29. Shields of Expectation—And Actuality
     30. A Tale of Three Pictures
     31. A Foot Soldier for Evolution