fossil:  any distinctive object or material dug up from the earth or found lying on the surface
 
• Are fossils simply rocks that look like life forms, or are they remnants of things that were once alive?
• If fossils are the remains of living things, where can we find specimens of these strange animals and plants today?
• How can fossils resembling seafloor creatures become embedded in rock at high elevations?

Georges-Louis Leclerc, le Comte de Buffon (1707-1788)

In general, kindred of species is one of those mysteries of Nature, which man can never unravel, without a long continued and difficult series of experiments....

• Is the ass more allied to the horse than the zebra?

• Does the wolf approach nearer to the dog than the fox or jackal?

• At what distance from man shall we place the large apes, who resemble him so perfectly in conformation of body?

• Are all the species of animals the same now as they were originally?

• Has not their number augmented, instead of being diminished?

• Have not the feeble species been destroyed by the stronger, or by the tyranny of man, the number of whom has become a thousand times greater than that of any other large animal?...

• What relation can be established between kindred species, and ... that of different races in the same species?

• Does not a race, like the mixed species, proceed from an anomalous individual which forms the original stock?

How many facts must be discovered before we can even form probable conjectures?

• in nature there are only individual organisms that differ from one another by very small and continuous gradations
• discontinuities in classification schemes are artificial creations of the human mind
• interfertile individuals do constitute a natural grouping
• animals today might be descended from common, more perfect ancestors
• man --> ape
• horse --> ass

Life science is rigorous and law-bound like physics and chemistry.

• do not speculate!
• collect specimens
• describe individual characteristics
• compare distinctions
• establish natural laws

• structure follows function
• species are not arbitrary designations of the human mind
• species are real and immutable divisions in living things

• each organism exists as a coordinated whole
• function of any one organ depends on that of others
• change one part, kill the whole
• should be able to reconstruct animal by seeing only one part, like a tooth, femur, or claw

• functional parts can be arranged hierarchically
• most essential parts show least variation from one species to another
• least essential parts show most variation

According to Cuvier, laws serve as rational basis for classifying living things.

• nervous system is the most fundamental of animal organs
• based on structure and complexity of nervous system, animals can be divided into four major categories:
• spine and brain--vertebrates (i.e., horse)
• brain--mollusks (i.e., clam)
• small brain--articulates (i.e., fly)
• least specialized--radiates (i.e., starfish)

Laws guide the application of comparative anatomy to fossil remains.

• based on careful analysis of just one skeletal fragment (one tooth, claw, bone), the entire animal can be reconstructed

Comparing skulls of modern sloths (top, middle) with the fossil skull of a Megatherium found in Paraguay (bottom).

Lamarck challenged Cuvier's views and methods:

• species are artificial divisions
• similar-looking animal structures (arms, legs, fins, wings) may be responsible for dissimilar functions (reaching, walking, swimming, flying)
• willing to speculate

[Animals] feel certain needs, and each felt need, stirring their inner consciousness, immediately causes fluids and forces to be directed toward the point of the body where an action capable of satisfying the need can take place.

• surrounds and adheres to rigid particles
• can be stimulated by activity or environmental factors:
• maintains and enhances elasticity of fluid and parts it permeates
• induces change in bodily structure
• responsible for increased complexity in existing beings
• electricity or heat can make living fluid and infuse it into inanimate material
• lack of stimulation causes shrinking and wasting
• acquired characteristics are transferrable to next generation
• breeders can artificially alter the form of an animal
• extinction is impossible

All animal life can be arranged in a line from least to most complex:

Natural force (like gravity) acts via animating fluid to move all living things toward increased complexity:

If all living things were subjected to same environmental factors, then chain of being would be completely linear, but variations in the environment creates branches on the complex/simple line:

Positive consequences to the disagreement between Lamarck and Cuvier on species, extinction, evolution ...:

• sparked public debate
• kept issue in discussion for decades
• generated wide and long-term interest in life science and natural history

• no matter what you do, things will advance and improve
• hierarchical structure of society is not fixed
• individual can generate own self-improvement

• biology is a legitimate science
• life forms of the past, although different, can be analyzed using modern methods

Has the earth developed in abrupt jumps and starts?  Or has it been a slow and gradual metamorphosis?

Are the forces of geologic change the same today as they were millennia ago?  Or, are they drastically different?

What clues do we have?  What methods are legitimate for investigators to use?

• world we see today is different from that of the past

• world we see today as the same as that of the past

• global catastrophes have caused large scale extinction

• small-scale change modified the world over time

• may have been multiple sequential episodes

• continual process

• causes do not have to be natural

• same natural forces of change always at work