The Origin of Species by Means of Natural Selection
On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life is a book by Charles Darwin published in 1859. It introduced the world to evolution through a process of natural selection. The main thesis was that different animal species were not independently created, and that similar species can result from natural variation followed by different survivability rates. Animals that are more adapted to their environments are more likely to survive. Alfred Russel Wallace wrote a similar theory independently, and had sent a manuscript to Darwin. From the fifth edition, published in 1869, Darwin also used Herbert Spencer's phrase "survival of the fittest", where "fittest" pertains to its Victorian meaning: that which is most suitable.
Human evolution is absent from Origin. Knowing of the opposition such a suggestion would face, Darwin confined his initial speculation to nonhuman animals. He covered the topic of human evolution in a later work, The Descent of Man and Selection in Relation to Sex.
Weaknesses in Evolution
Darwin in "On the Origin of Species" openly admitted that his theory had four major weaknesses, but expressed confidence that they would not prove fatal to his theory. These weaknesses were (1) the lack of transitional forms seen from the fossil record, (2) organs of unusual complexity, (3) refined instinct in nature, and (4) sterile offspring resulting from interspeciary breeding. A large portion of the book is actually devoted to addressing these problems. Chapter 6, Difficulties on Theory, addresses the 2nd problem. Chapter 7, Instinct, deals with the 3rd problem. Chapter 8, Hybridism, deals with the 4th problem (probably the least-known and least-addressed of the four after nearly a century and a half). Chapter 9, On the Imperfection of the Geological Record, deals with the 1st problem. As such, 4 of the 14 chapters in On the Origin of Species were actually aimed at confronting what Darwin acknowledged were serious weaknesses in his theory.
|“||"In the four succeeding chapters, the most apparent and gravest difficulties on the theory will be given: namely, first, the difficulties of transitions, or in understanding how a simple being or a simple organ can be changed and perfected into a highly developed being or elaborately constructed organ; secondly, the subject of Instinct, or the mental powers of animals; thirdly, Hybridism, or the infertility of species and the fertility of varieties when intercrossed; and fourthly, the imperfection of the Geological Record." (p. 6)||”|
|“|| "Long before having arrived at this part of my work, a crowd of difficulties will have occurred to the reader. Some of them are so grave that to this day I can never reflect on them without being staggered; but, to the best of my judgment, the greater number are only apparent, and those that are real are not, I think, fatal to my theory.
These difficulties and objections may be classed under the following heads:—
Firstly, why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms? Why is not all nature in confusion instead of the species being, as we see them, well defined?
Secondly, is it possible that an animal having, for instance, the structure and habits of a bat, could have been formed by the modification of some animal with wholly different habits? Can we believe that natural selection could produce, on the one hand, organs of trifling importance, such as the tail of a giraffe, which serves as a fly-flapper, and, on the other hand, organs of such wonderful structure, as the eye, of which we hardly as yet fully understand the inimitable perfection?
Thirdly, can instincts be acquired and modified through natural selection? What shall we say to so marvellous an instinct as that which leads the bee to make cells, which have practically anticipated the discoveries of profound mathematicians?
Fourthly, how can we account for species, when crossed, being sterile and producing sterile offspring, whereas, when varieties are crossed, their fertility is unimpaired?"(pp. 171-172)
CHAPTER 1. VARIATION UNDER DOMESTICATION
In this chapter, Darwin motivates the case for variation and selection by illustrating the variety among the natural and domesticated plant and animal worlds. Without knowing the details of inheritance (which would be demonstrated later by Gregor Mendel, James Watson, and Francis Crick among others) he shows its implications: like breeds like. Inheritance is what breeders use to direct the variation of species to some useful means. This is done by selection; the breeders' are keenly aware of the minor differences in the offspring populations of animals and exploit them to create new varieties. The variation of species is not simply due to crossings of existing varieties. He argues this by showing examples where it is unlikely or impossible, pigeons, dogs, and talks about recent domestication. Pigeon varieties completely different in appearance from the the wild rock pigeon show traits of the wild rock pigeon when crossed. He shows, through the works of breeders, that in fact even animals within the same breed show variation of which expert breeders are aware (consciously or subconsciously) and exploit to direct the traits of the offspring. This he shows convincingly, as breeders cannot control traits directly, but can exploit variation to make new breeds because they know the traits are inherited. During Darwin's time, species was not a well-defined category: animals may be regarded as species or varieties even among prominent naturalists of the time.
CHAPTER 2. VARIATION UNDER NATURE
CHAPTER 3. STRUGGLE FOR EXISTENCE
CHAPTER 4. NATURAL SELECTION
the cycle of natural section states that a predator will gain a advantage over prey then the prey gains a advantage over the predator and so on and so forth.
CHAPTER 5. LAWS OF VARIATION
CHAPTER 6. DIFFICULTIES ON THEORY
CHAPTER 7. INSTINCT
CHAPTER 8. HYBRIDISM
CHAPTER 9. ON THE IMPERFECTION OF THE GEOLOGICAL RECORD
CHAPTER 10. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS
CHAPTER 11. GEOGRAPHICAL DISTRIBUTION
CHAPTER 12. GEOGRAPHICAL DISTRIBUTION--continued
CHAPTER 13. MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY: EMBRYOLOGY: RUDIMENTARY ORGANS
CHAPTER 14. RECAPITULATION AND CONCLUSION
- ↑ Darwin, C.R. On the Origin of Species, 1st ed. London 1859, p. 6.
- ↑ Darwin, C.R. On the Origin of Species, 1st ed. London 1859, pp. 171-172.