Lecture 10_ The Origin of Species (famous book written by Darwin).pdf

Lecture 10: The Origin of Species (famous book written by Darwin) ● ● ● ● ● ● ● Darwin grew his famous beard in 1862. He spent 8 years working on Barnacles He published the Barnacles. The very same day he finished, he started working full time on The Origin of Species Not working on the book yet. B...

Lecture 10: The Origin of Species (famous book written by Darwin) ● ● ● ● ● ● ● Darwin grew his famous beard in 1862. He spent 8 years working on Barnacles He published the Barnacles. The very same day he finished, he started working full time on The Origin of Species Not working on the book yet. But working on unfinished thoughts Misunderstanding: Theory in general, but misconception that it is about human specifically Work on the species theory after finishing the barnacles books in 1853 ● Learning about people making the breeding ● Darwin convinced that they are all descended from the same ancestor ● Also conducted experiments on plants. He wants to be able to prove. ● Take seeds from different kinds of plants and put it on sea water and let them soak. To see how long it can survive. ● Working on a very big book but interrupted by Wallace’s writing. People asking Darwin for the overview of the theory. Project kept becoming bigger until it became unfit for a journal. Turns out to be the origin of species. ● Overview of the theory becomes the book. Some general remarks ● What the book is about o Evolution by natural selection explains a wide range of phenomena that are otherwise inexplicable ▪ Lyell’s gradualism underlies origin, long slow action of small natural causes that can accumulate to produce enormous changes ● Book does not address: o The origin of life o Does god exist? o Is god ultimately behind nature? (he strongly implies, yes) ● By then people already believe in laws of nature (like Darwin) but do not know where it comes fro, Publisher: John Murray ● John Murray published Darwin’s voyage of beagles. ● Published principles of geology. ● Respected publisher. ● He sent the books to be reviewed. ● Spent 18 months. Overview of 20 years of work. ● Published Nov 1859 Some general remarks ● Most important books in science and the most misunderstood book too. ● “Origin of species”. Not about humans, about all species. Where do species come from and change over time? ● Evolution by natural selection explains a wide range of phenomena that are otherwise inexplicable. o Lyell’s gradualism underlies Origin, long, slow action of small natural causes can accumulate to produce enormous changes. ● The book does not address on the origin of life itself. He had no idea, no concern. ● Nothing to do with whether god exist. The book does not depend on whether people believe in god or not. ● He was not an atheist when he wrote this book. He used the word ‘creator’. Believe in God. ● Book did not address: o What is the origin of life? o Does God exist? o Is God ultimately behind nature? (he strongly implies, yes) ● Addresses: o Species vanishing and new ones appearing. o Where and how do the new ones appear? What is their source? ‘What is the source of species’? o Short answer: descended from the earlier ones. ● Darwin didn’t use the word evolution at this time. But ‘The theory of descent with modification’ ● Many different kinds of evidence converge on his theory. No other theory can boast of this. ● Theory of Creation – not so straightforward theory ● Creation – doesn’t necessarily mean divinely created The Epigraphs ● These 2 quotations in front of the book. Epigraphs is there to give inspirations or ‘cover your back’ ● Darwin worried that the book will become controversial. Subsequent edition have 3rd quote. ● William Wrewell – Darwin’s contemporary ● Common philosophy – God is powerful and does not need to intervene all the time but he created natural law. E.g. gravity. ● The book – Darwin imply this book is nothing irreligious, just a natural law that explains how nature works ● Francis Bacon – No harm in studying nature as far as you go. These quotations imply nothing irreligious about the book CHAPTER I VARIATION UNDER DOMESTICATION. ● Variations are ubiquitous they are everywhere and constant. o Argument that everything changes, everything alive and extinct are all part of one gigantic genealogical tree of life. ● He began by using analogy of artificial selection of domesticated animals o o ● ● ● ● ● Breeds of domesticated animals and plants are analogous to new species. Natural variations are everywhere. If you look at things carefully, there are always tiny differences. o At that time. most breeders thought that the different breeds were descended from different ancestors. Darwin believed it all came from one ancestor. o Starts off with something everyone is familiar with to convince Artificial selection changes species – humans, by selecting certain breeds, change a species over time. Eg. Pigeons o Polish fowl bred to have huge plumes o Chicken bred to be fatter and fatter o Watermelon bred to have more flesh and less seeds o Ancon sheep bred to have short stumpy legs so they couldn’t jump fences o Strawberries bred to be large o Cavefish – Born without eyes 🡪 takes too much energy to grow eyes that would be useless in dark caves, hence eyes are totally useless, and it is sort of an advantage to not have eyes o E.g. wild ducks and domesticated ducks. Clear difference in the weight of the wing bones. Lost the ability due to disuse. Darwin joined these breeding clubs for pigeons. Very odd for well to do gentlemen to hang out with these men. He was interviewing them etc… learning about their culture of breeding. Next, he said plants and animals in nature vary just like domesticated ones, with no clear distinction between species and varieties o Process of changing is slow and gradual so things look like one another o Varieties are descended from species Tree of life makes sense of taxonomy (branch of science concerned with classification). Creation cannot. Natural selection – not a force or power, a shorthand name of any causes in nature. But it is not his sole explanation of change. Correlation of growth; Use and disuse. In modern day it’s called Lamarckism. CHAPTER II VARIATION IN NATURE. ● Plants and animals in nature vary just like the domesticated ones. ● Varieties descended from species. ● There is no clear distinction between species and varieties (members of one species) o It is an artificial, arbitrary line drawn by scientists, not an actual natural distinction or categorisation. o Subjective judgement. A little bit, a lot? What counts as a lot of differences? o Changes take place very slowly. Will overlap thus no clear difference. ● Tree of life diagram can make sense of taxonomy – gradual evolution over time (Creation cannot explain this) o Tree of life is the only diagram in the book o Similar to the tree diagram in Notebook B o Does not represent any specific family, just a generic diagram to illustrate the process. o Each space in between the lines connecting species may represent thousands of generations. o Split earlier = species will be more different, Dead end = extinct CHAPTER III STRUGGLE FOR EXISTENCE. ● Malthus: Given population growth, competition for survival is inevitable ● Geometrical population growth is inevitable o But this increase seldom happens because of checks o Since so few survive, competition is constant, only some manage to survive. But which ones? ● Only a few live – who survives? ● Any variation that has properties beneficial to the system in nature is more likely to live and give birth to offspring ● Natural selection not understood by majority, Natural preservation used instead ● Offspring with similar traits will likewise continue to pass down ● "Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection, in order to mark its relation to man's power of selection.” Origin of species, p. 61. ● Farmers and breeders: artificial selection ● In the natural world: natural selection ● Phrase used by Wallace. ● Probably got the phrase from Malthius. ● Important implications: Very few are surviving. There must be something special about these few. ● Geometric ratio of population increase is inevitable but seldom occurs due to competition. ● They are in fact naturally selected. ● Perhaps a better phrase is Naturally Preserved and not Naturally selected (Selection made people think that Darwin believes in a force behind it) CHAPTER IV NATURAL SELECTION. ● Sexual Selection ● Most visible in birds 🡪 Eg: peacocks have heavy, showy, large tails – doesn’t seem very practical in survival ● But they are the result of sexual selection – beautiful feathers are needed to attract a mate, and the showy traits are passed down ● Birds of paradise – picky females o Have caused males to evolve colourful plumes and elaborate mating dances. ● Pheasants – males have good singing voices due to female sexual selection ● Sexual selection – another means that contributes to change. I.e. Females choose which males to mate with. They are extremely discerning and choosy. They look identical but they are not. Not particularly popular among Victorians. ● Another sexual selection is male vs. male competition for females. ● How did the birds of paradise get those amazing colours/the peacocks get their long tails? ● Females choose which males to mate with – i.e. males parade/display while females are extremely discerning, what may look identical to us are actually very different in the eyes of the birds. (Colours show health/strength/territory etc.) ● They cut off the outer edge of the peacock’s tail (made the tail smaller) o He was the most attractive peacock but became mega loser – had no females at all, he was less attractive. ● Female preference over time led to evolution – this was very controversial because in the Victorian days, females had no choice. ● How do they know difference between species and varieties? ● Based on the degree of similarities. ● But Darwin said there is no clear distinction because they are not separately created types. ● The old question on how the giraffe gets its own neck. ● No mechanism that case one species modified for the good of another. ● Why are the gaps in the natural world? Intermediate forms will often go extinct. E.g. the finches, only 4 different type, what about the ones in between? ● What used to connect one group to another, doesn’t exist. ● Principle of divergence ● A bias in nature. Ecological bias towards descendants diversifying. The diagram from Origin of species (Tree of life) ● The only diagram in the book. ● Similar to the tree diagram in his notebook B. ● Doesn’t represent any particular family but the process he is arguing for. ● Each space in between lines may represent thousands of generations. ● The different letters represent the different species. CHAPTER V LAWS OF VARIATION. ● Laws of variation. Today called genetics. ● People can choose a particular feature to breed but the result turn different. Different factors in heredity. ● Throwbacks – sometimes organism born with something that belong to ancestors. ● Nothing sudden or dramatic that happen in Darwin’s theory. The process is really slow and gradual. ● We don’t see the change except in the farms. CHAPTER VI DIFFICULTIES ON THEORY.*** ● Objections people might have against its theory. ● Darwin took very seriously all the objections and problems that people might have in accepting his theory. ● 1) How could radical changes begin? – E.g. How could a whale or dolphin be descended from a land animal? How could a land animal become an aquatic one? Or bats and birds start to fly? What good is half an eye or half a wing? o Darwin says everything happens gradually by very many tiny gradual steps and selection. Many transitional forms are all around us. It could be a mammal with legs that have an aquatic (like hippos). ● 2) Darwin’s quote: Darwin was the first person to point out the reason why we can choke. The sad fact: air and food passages are shared. Because land living animals with lungs are descended from a fish ancestor with a swim bladder.(gas bag in the body that can be expanded to achieve neutral buoyancy in the water) Some fish that live in shallow or stagnant water with poor oxygen content are not able to get enough oxygen from the water with their gills. They can supplement this by going to the surface of the water to get a gulp of the air which can go into the swim bladder. They can absorb oxygen from the walls of the swim bladder. 🡪 origin of lungs. o Anatomy change but its basics still there 3) Darwin points out that any structures you might pick for example the human eye is perfect extremely complicated. It seems like it cannot come out gradually, in a series of gradual steps but Darwin says that we have many so many examples in the world today that have eyes in different stages -- Different levels of complexity found in living animals today. The eye had developed to become increasingly complex over a long period of time (it would only work if each stage of develop was an improvement was from before) like optic nerves with cornea etc 🡪 true a. People think this must have been designed, its too perfect… but Darwin says no b. All sorts of complexities of eyes we see today (gradual evolve at different stages) o Octopus have the same eye and lens as us. Can see same things as we do. ● 4) Imperfections 🡪 Why does a bee die after stinging? – seems a bit impractical. Because of their ancestry. Their stings originally had another function, but the sting eventually adapted to become a form of defence. The sting of a wasp was originally a tool for drilling into wood and plants and the wasp would inject a poison into a plant which then causes a genetic problem with the plant and the plant would grow a woody swelling and the wasp eggs are then injected into this ‘house’ and they live secure in this structure and munch on the plants from the inside. Drilling apparatus could be used as weapons because they are sharp and have nasty things inside that could be squirt out and that became stingers. The power of stinging is useful to the community. It would fulfil the requirement of natural selection, although it may cause the death of a few members. So, if having a family of bees in which some of them can sacrifice themselves to chase away an animal, the bees might die but the family would live. o Exist due to ancestry (inheritance) and is still useful ● Why are not all characters perfectly adapted? Why isn’t it absolutely optimal? (Like the choking – non-optimal structure.) – Characteristics which were formerly useful may persist due to inheritance ● Started off as one purpose, but became useful for others – Modification for something that was already there ● Why aren’t all features adaptive or useful? o Eg: why do mammals have an oesophagus and windpipe that share a common opening? Seems like poor design that makes choking risky o Land animals are descended from fish – had a hole that led to stomach and swim bladder o Descendants that evolved from the fish who came out of water have a breathing system that is similar to the predecessor o Features that are useless may just be left over from ancestors, and are just inherited CHAPTER VII. INSTINCT. ● Darwin attacked the idea that instinct is a miracle. There must be naturalistic explanations. ● Sterile workers can survive because they have a common mother. CHAPTER VIII HYBRIDISM. ● How does Hybrid work? ● Horse + donkey = mule ● Mule – sterile. Cannot have babies. ● Darwin showed Hybridism proved common descent. ● Showed the gradualism that Darwin proposed. CHAPTER IX IMPERFECTION OF THE GEOLOGICAL RECORD. ● Why isn’t there continuous gradation between all species when comparing the fossils? o Because we have incomplete picture and intermediate varieties go extinct. 🡪 accidental remains of what was once alive ● The Victorians were the first ones to learn of the fossil record in incredible detail. It was often tempting to think that they knew all the different things that have existed before even when they are finding new ones at the time. It was often thought that the records were quite complete. ● Darwin says that the fossil record is unbelievably fragmented. o Vast lapse of time, as seen in deposition and erosion o The (apparently) sudden appearance of groups of species thus explained ● Fossil record is incomplete. – widely interspersed occasional little fragments in between. o Because the occasions for fossil formation is extremely rare. o It only happens under certain conditions today and in the past and places. It does not happen everywhere. Most things die and rot and leave no trace. ▪ Must be fossilised before they are eaten etc. o o OR Rocks change so much after thousands of millions of years that fossils get melted/crushed when rocks are destroyed. 🡪 geological forces destroy it OR Most rocks are in the ocean or with we simply have no access to them. CHAPTER X. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS. ● Old and familiar topic. ● Modern creatures are descendants of the earlier ones. May not be exactly. ● Species once extinct never reappear. ● The succession (or continuation) of the same families within the same areas explained o Previous chapters, land big sloth to tree sloth etc CHAPTERS XI-XII GEOGRAPHICAL DISTRIBUTION. ● Biogeography – the most compelling evidence for evolution (why things are where they are) o Environment cannot explain distribution (Natural barriers and ways of contact and movement) ▪ Similarly, with the inhabitants of oceanic islands (not part of the continents, never connected to other lands but are islands that have always been out in the ocean, e.g. hawaii/galapagos). Why were there no amphibians on those islands? There was no naturalistic way for them to get there. (argument against for things being where they are because they are created there) They were not created there even though the environment was superb for them. Why weren’t they created to live there since the environment was so perfect for them? It was because they couldn’t get there naturally, couldn’t travel there so they were not found there. Frogs, salamanders, etc. have permeable wet skin and their eggs are killed when in contact with salt water. Amphibians don’t have the properties to travel there. 🡪 no natural way to get there o Animals and plants have moved about and diversified from ancestors, limited by natural barriers o Only evolution explains the distribution ● Continental islands – Singapore and Malaysia if sea level drops, become one island ● Oceanic island – risen out of the ocean and have never been part of land ● The distribution of living things around the world does not really make sense if we use older theories before Darwin that things were somehow formed/created to suit the environment where they live in. But if that is the case why are there different tropical species in the different tropical land masses. Why are they all not the same? ● Natural barriers: mountains/oceans etc. ● All these could only be explained by Darwin’s theory. ● Old theory – species created to suit the environment. 🡪 no CHAPTER XIII. MUTUAL AFFINITIES OF ORGANIC BEINGS: EMBRYOLOGY: [similarities between species] RUDIMENTARY ORGANS: MORPHOLOGY ● Evolution makes sense of all things. ● All living things fit in to these nesting categories. Linnean theory (non-evolutionist) o Embryology ▪ Established field before Darwin ▪ Embryos of different kind of animals look very similar in their early stages of development. 🡪 why? Darwin addresses this ▪ Earlier stage more alike, later stage more different. ▪ At some time during embryonic development all vertebrates have postanal tails and pharyngeal pouches ▪ The more closely related the creatures are, the more similar the embryo into later stages of development ▪ Eg: why do humans have a tail as an embryo? ● Leftover from common ancestors ▪ Why are they very similar? ▪ Q: did the whale embryo go through a stage of having teeth if they don’t need it (eventually born without teeth)?(Human embryos – completely covered in a coat of hair which is lost before birth.) A: This is because of common ancestry – there is no need for difference in this early stage of development. o Vestigial Organs (rudimentary organs) ▪ Structure that has no function ▪ Vestigial Organs are not like those in embryos where they vanish, but those that stay with the organisms for life. ▪ Teeth in the embryos of whales that are toothless as adults ▪ Why did the manatees have fingernails /toenails ? -- Remnants of the ancestors. ▪ Wings on flightless birds ▪ Pelvis in whales ▪ Pelvic spurs in boas (shows they have legs last time) ▪ All vertebrates share the same design – homologies. ▪ Human embryos grow tails but do not have it when given birth ▪ Ancestors left it o Homology ▪ Same structure in different species. (bone) 🡪 no reason for it but still exists ▪ Darwin’s explanation is better than Owen’s idea of archetypes (that there is some sort of model on which living things were based, that’s why different types in different families have the same structures/bones) ▪ Common ancestry/descent explains why the bone structures are similar yet so vastly different for function. ▪ E.g. frog hand, human hand, cat hand, whale, bird and bat etc. CHAPTER XIV. RECAPITULATION AND CONCLUSION. ● Common descent – evolution ● His main objective. ● Final remark, he mentioned human beings. Does the natural world reveal evidence of kind design or benevolent design? [LESS IN DARWIN BOOK BUT MORE ON THEORY OF PHILISOPHY] ● There is so much cruelty in the natural world. ● The living world does not show any evidence of kindness. ● Vast majority of what happens in the natural world is ruthless. ● Cruelty in nature seems contrary to what a benevolent and omnipotent god would do ● Eg: parasitic spiders, cats like to play with their prey, humans are cruel, wasps feed within the living body of caterpillar o Instincts for survival (like cats playing with mice 🡪 give them pleasure to play with mice, their prey) 🡪 so that they will survive if they enjoy ● Some other process of species creation must be happening ● “I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidæ [wasps] with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice.” - Darwin o He said to his friend ● Darwin say don’t just look like the nice happy life like in the previous saying 🡪 he say it is not benevolent ● But he is comforted that it is the result if laws of nature (working their way out) Ernst Haeckel’s tree of life from The Evolution of Man (1879). ● The traditional idea of human beings being the pinnacle of species as it was drawn here by Darwin’s follower 🡪 anti-Darwin. ● Incorrect representation of Darwin’s theory. o Exaggerated o Evolution is not a progress but a process of how things change (no direction also) ● This is different from what Darwin is saying, Darwin says that living things have evolved for the same period of time, so no species should be higher than the other unlike what the tree above is showing. ● Things have different pathways but everything living today is at the same stage. ● There is no direction or “higher and better” of the evolutionary progress – change, not progress! ● There is no inherent tendency for things to be more complex – rather, things change in response to the environment ● Six editions of Origin of species - it changed over time ❖ Book went through several editions ❖ The historical sketch added to the third edition (1861) 🡪 gave a sketch of other people that talked about evolution before him ❖ The fifth edition (1869) first used Herbert Spencer’s expression “the survival of the fittest” 🡪 survival of the context o Today: a misrepresented shorthand, as it leaves out the core idea of descent from ancestors ❖ Darwin thought a better term would have been “natural preservation” o “Natural selection” created confusion among his readers as it gave the impression that there was an agent doing the selecting, when there isn’t o Differential survival The famous conclusion to Darwin’s Origin of species: “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” 🡪 poetic on his theory of evolution and his view of life