We know species can vary over time: humans have been breeding animals for profit and pleasure since the dawn of civilization. We also know that any species, left to its own will, can repopulate at a rate of geometric growth, until they consume all available resources. All species could reproduce faster than their members die off. The only thing keeping them in check is the limited number of resources.
With only a limited number of resources then, it is those variants of a species that are most successfully suited to extracting resources for survival that survive — and are around to breed the most.
This is the idea of Darwin's Natural Selection, as outlined in "The Origin of Species": Geometric increase of species + limited resources + variation = natural selection.
Natural selection takes place not only within species traits, but also across different species competing for the same resources. Those better at obtaining resources through new genetic traits, will, through time, overpower others.
And there is a compound effect: The greater the diversity within the species, the more likely that species will be able to adapt those traits that make it better compete for resources. Species that are most numerous will have the best chance of producing favorable variation. Those less able to compete become rarer, and, over time, go extinct. "Rarity is the precursor to extinction," Darwin wrote.
Natural selection is ruthlessly efficient. "Natural selection is continually trying to economize in every part of the organism," Darwin tells us. Any diminution of a trait that does not hinder the survival of the species will quickly be seized upon and capitalized.
To this day, "Origin of Species" has generated a fair amount of skepticism, much of which Darwin anticipated.
Chief criticism is missing evidence: If natural selection modified all the species why don't we see more evidence of these earlier, or transitional, variations in the fossil record? He did admit that the geological record is spotty. "The crust of the earth is a vast museum; but the natural collections have been imperfectly made, and only at long intervals of time," he wrote.
We do not have a record of transitional species, as they do not live for long, after the favorable variation of the species takes hold, and quickly comes to dominate.
At least some of the gaps in the records can be attributed to the uneven ways at which the fossil record of evolution was recorded. Land rising from the sea will leave a great fossil variety; subsiding, breaking into the sea, it will leave little. Where sediment under the sea did not accumulate quickly enough to protect bodies from decay, no remains can be found.
In other words, during periods of subsidence, there will be much extinction of life. During the periods of elevation, much variation. Our notions of time do not take in the expanse of such cycles. “We do not make due allowance for the enormous intervals of time which have probably elapsed between our consecutive formations,” Darwin wrote.
Such vast expanses of time will be needed to support Origin’s other major assertion: that we, animals and plants alike, are all derived from a single creature. Variation, over time, created new species, and sub-groups of species, and on and on, each unique to some environmental factor yet all maintaining some basic fundamentals.
“What can be more curious than that a hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bar, should all be constructed on the same pattern,” Darwin writes.
The take-away from this and countless other examples offered in the book? “All the organic beings which have ever lived on this earth, have descended from some one primordial form, into which life was first breathed.”
All true classification is genealogical, a tracing back through countless variants, to that single first living being that geological record, though missing many chapters, is pointing back to.
“All past and present organic beings constitute one grand natural system, with groups subordinate to group,” Darwin writes “The affinities of all organic beings are due to inheritance or community of descent. The natural system is a genealogical arrangement.”
Finally, Darwin notes that appeals to the “the Plan of the Creator,” where someone “rejects the vera causa of ordinary generation with subsequent migration and calls in the agency of a miracle,” add nothing to our knowledge.
“Do they really believe that, at innumerable periods in the earth’s history, certain elemental atoms have been commanded suddenly to flash into living tissue?”
OTHER THOUGHTS:Sometimes a piece of writing so closely describes the truth, that it itself becomes the truth. Charles Darwin's " On the Origin of Species," first published in 1859, made its argument so thoroughly, so absolutely, it literally willed evolution into being in the human consciousness.
Once in plain sight, evolution made its own case, of course. But today the writing that first fully described evolution is anything but an emptied vessel.
Darwin piles on example after example variation, drawing from Chinese encyclopaedias, farmers and cattlemen, hobbyist animal breeders, gardeners, the Bible, even deriving them first-hand by breeding pigeons and studying the survival of weeds in a small field. At he was a species geek, and can wallow happily on some arcane variation of an ant, bee or flower.
The book crystalizes not one but two major drivers of evolution: natural selection and community of descent. Natural selection is the shaping of traits from an expanding population competing for fixed resources. The second idea, groomed by the natural selection, is that all living beings can be traced back to a single entity.
Driving the rolling roads of Virginia, I've often daydreamed of a hard-bitten tobacco farmer two centuries back sitting down at a heavy oak kitchen table during some winter nights to read this English Nat'rlist's recently published account of how his own livestock changed over time.
Darwin writes to make his case for this farmer. And for everyone. “This whole volume is one long argument,” he wrote. “Origin” is technical writing at its finest, writing about a concept so subtle and so complicated that it literally took the human race about 200,000 years to understand, and yet the writing is so clear that assumes no technical knowledge on the part from the reader, apart from basic fluency in the English language and some patience.
Quotes and ParaphrasesSpecies that are most numerous will have the best chance of producing favorable variation.
"Rarity is the precursor to extinction"
As new species are formed thru natural selection, others will become rarer & finally extinct.
The greater the diversity of the species, the better able to adapt to novel circumstances.
Geometric increase of species + Limited resources + Variation = Natural selection.
All species are adapted to their own climate; few inhabit both very hot and very cold climates.
Large beard, diminished waddles; Nature splurges in some places economizes in others.
Natural selection economizes: it won't profit the individual to build up its nutrient in useless structure.
The earth's crust is a vast museum, but its collections were taken at intervals of time vastly remote.
Forms in greater numbers will almost always be favored owing to their greater variability.
No one yet has pinpointed how much divergence there would be between two species that would limit them from breeding.
Some closely related species don't breed hybrids at all while some distant species readily interbreed.
The very process of natural selection constantly works to exterminate the parent and intermediate links.
A useful modification of one part will often have entailed on other parts diversified changes of no use.
The more diversified the descendants, the better their chances at succeeding in the battle for life.
Natural selection often produces structures for the injury of other species, such as the fang of the adder
While we don't see many transitional states in the fossil record, we should be cautious asserting that none existed.
Natural selection produces a perfection only according to the standard of the immediate environs.
It's a mistake to assume most instincts are generated by habit handed down to succeeding generations.
There is no fundamental difference between species and varieties.
Some cross breeding leads to vigorous new traits, though too extreme of cross-pollination will lead to sterility
Sans numerous connecting links, “it may be objected that time will not have sufficed for so great an amount of organic change.”
Natural Selection’s greatest weakness: The “extreme imperfection” of the geological record.
“The thickness & extent of sedimentary formations are the result & measure of the degradation which earth’s crust has elsewhere suffered.”
“He who most closely studies ... the sea on our shores will ... be most deeply impressed with the slowness with which rocky coasts are worn away”
“Our richest geological museums” have but a “paltry display”: Darwin on poor paleontological record of evolution
Land rising from the sea will leave a great fossil variety; subsiding, breaking into the sea, it will leave little
Where sediment under the sea did not accumulate quickly enough to protect bodies from decay, no remains can be found.
During periods of subsidence, there will be much extinction of life. During the periods of elevation, much variation.
“We do not make due allowance for the enormous intervals of time which have probably elapsed between our consecutive formations.”
“Continents may have existed where oceans are now spread out; and clear and open oceans may have existed where our continents now stand.”
“To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer”
“Of this volume only here & there a short chapter has been preserved. Of each page, only ... a few lines.”
“Species of different genre and classes have not changed at the same rate, or in the same degree.”
Natural Selection: The belief that each variety/species survives by “having some advantage over those with which it comes into competition.”
Means of dispersal for Species: change of climate must have had a powerful influence on migration.
The same species in distant points of the earth’s surface can be explained by each species having migrated from a single birthplace.
He “who rejects the vera causa of ordinary generation with subsequent migration & calls in the agency of a miracle”
Dried hazelnuts floated for 90 days, and afterwards, when planted, they germinated; an asparagus plant for 23 days
“I picked up in my garden 12 kinds of seeds, out of the excrement of small birds. Some of them ... germinated.”
Blown across vast distances by gales, birds can be highly effective agents in the transportation of seeds.
Some habitual actions do become instinctual through inheritance
“From the first dawn of life, all organic beings are found to resemble each other in descending degrees.”
“A classification founded on any single character, however important that may be, has always failed.”
Wide ranging species not only crossed barriers but were “victorious in distant lands in the struggle for life.”
A mollusk on a duck foot can last 12-20 hours, the time it’d take the duck to fly 600 miles.
“Nothing is thus added to our added to our knowledge” referring to “the Plan of the Creator”
The less any part of the organization is concerned with special habits, the more important it is for classification.
“What can be more curious than that a hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bar, should all be constructed on the same pattern.”
All true classification is genealogical; community of descent is the hidden bond naturalists have been seeking.
“This whole volume is one long argument”
“The innumerable species, genera, and families of organic beings, with which this world is people’d, have all descended, each within its own class or group, from common parents.”
Rudimentary organs, though largely useless, offer a clue as to the derivation of the species
“An organ useful under certain conditions might become injurious under others ... in this case natural selection would continue slowly to reduce the organ, until it was rendered harmless and rudimentary”
“Nothing can be plainer than that wings are formed for flight. Yet in how many insects do we see wings so reduced in size as to be utterly incapable of flight?”
Complex organs and instincts have been perfected by the mere “accumulation of innumerable slight variations, each good for the individual possessor.”
“All the organic beings which have ever lived on this earth, have descended from some one primordial form, into which life was first breathed.”
“I believe that animals have descended from, at most, only four or five progenitors. And plants from an equal or lesser number.”
“But do they really believe that, at innumerable periods in the earth’s history, certain elemental atoms have been commanded suddenly to flash into living tissue?”
“...To think we give an explanation when we only state a fact.”
“It can not be asserted that organic beings, in a state of nature, are subject to no variation. It can not be proved that the amount of variation, in the course of long ages, is a limited quantity.”
“All past and present organic beings constitute one grand natural system, with groups subordinate to group ... the affinities of all organic beings are due to inheritance or community of descent. The natural system is a genealogical arrangement..”
“But as all groups can not thus succeed in increasing in size, for the world will not hold them, the dominant groups beat the less dominant.”
“Dominant species, belonging to the larger groups, tend to give birth to new and dominant forms, so that each large group tends to become still larger and at the same time more divergent in character.”
But success will often depend on having special weapons or means of defense. Or on the charms of the male. And the slightest advantage will lead to victory.”
“The most vigorous individuals, or those which have most successfully struggled with their conditions of life, will generally leave most progeny.”
“But man can and does select the variations given to him by nature, and thus accumulate them in any desired manner. He thus adapts animals and plants to his own benefit and pleasure.”
“Man does not actually produce variability. He only unintentionally exposes organic beings to new conditions of life, and then nature acts on the organization and causes variability.”
“For very, very long periods of time, there will always be a good chance for wide migration by many means.”