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Charles Darwin |
This month is the 200th anniversary of the birth of one of the most influential thinkers in science history Charles Darwin developed the theory of how living things develop from simpler organisms over long periods of time that theory is known as evolution through natural selection how do new kinds of life come into existence for much of recorded history people have believed that organisms were created few people believe that living things changed what process could make such change possible these were some of the questions Charles Darwin asked himself over years of research in botany zoology and geology he was not the first person to ask them his own grandfather Erasmus.
Darwin believed that species evolved and others like the French naturalist Jean-Baptiste Lamarck had proposed ways this could happen but it was Darwin who identified and explained the process natural selection that causes life to evolve Charles Darwin was born in Shrewsbury England on February 12th 1809 his father Robert Darwin was a doctor Charles mother Susannah Darwin was the daughter of the famous Potter Josiah Wedgwood she died when Charles was only 8 years old young Charles was intensely interested in the natural world from an early age but his father wanted him to be a doctor at age 16 Charles was sent to study medicine at the University of Edinburgh but he did not like it he found medical operations especially horrible he later went to Cambridge University his father now hoped that Darwin would become a clergyman but at Cambridge.
Charles continued to follow his own interests there he met John Henslow plant scientist and clergyman the two became friends John Henslow suggested that Charles Darwin take the unpaid position of naturalist for a trip on the British ship HMS Beagle it sailed around the world from 1831 to 1836 the main goal was to make maps of the coastline of South America the British government paid for the voyage but another purpose of the trip was to collect scientific objects from around the world the beagles first stop was one of the cape Verde islands near the coast of Africa there Darwin noted that levels of rock extending high above the sea contained the fossil remains of shells
he thought that this was evidence that the bottom of the ocean had been lifted up by powerful geological forces over long periods of time the Beagle continued to the coast of South America in Valdivia Chile Darwin experienced an earthquake he collected examples of plants and animals he also collected the fossil remains of animals that had disappeared from the earth but it was on the Galapagos Islands off the coast of Ecuador that Darwin found creatures that made him wonder about how species develop and change there he saw giant tortoises and noted that the reptiles were different on each Island.
he collected Birds each with different beaks later after he had returned to England he would be shocked to find that these very different birds were all finches Darwin found lizards called iguanas that lived on land and ones that fed in the sea Darwin noted that all these species were similar to those found in South America but they all had differences or adaptations that helped them survive in the environment of the Galapagos Islands.
Darwyn sent much of what he collected back to England on other ships the Beagle met along the way by the time he returned to England in October of 1836 he was already a well-known geologist and naturalist within a few years he would be accepted into scientific organizations like the Geological Society and the Royal Society.
Darwin moved to London to be near other scientists he wrote a new version of the book about his travels he also edited works of others about the things he had collected on his trip Darwin also agreed to write several books including the zoology of the voyage of the HMS Beagle but in 1837 the pressure of the work caused his health to suffer.
he developed problems with his heart Charles Darwin had poor health much of his life he suffered headaches and problems with his skin and stomach no one was able to find out what disease he may have had during his lifetime recently some experts have suggested that he might have become infected with tropical disease other suggest.
Darwin's health problems were caused by conflict in his mind over his theory poor health would later force him to leave London and settle at down house near Kent England Darwin began work on a series of secret notebooks containing his thoughts about the evolutionary process he began to think that animals developed from earlier simpler organisms as early as eighteen 37 he imagined this process as a tree with branches representing new species.
unsuccessful branches ended but successful evolutionary changes continued to form new branches Charles Darwin's personal life was also expanding in 1839 he married Emma Wedgwood his cousin he told her his ideas about how species evolved over time what he called the transmutation of species Emma did not agree with her husband but the two had a strong and happy marriage they had 10 children together 7 of them survived Charles Darwin read widely and sought ideas from other fields of study he was influenced by Thomas Malthus's work an essay on the principle of population written in 1798 Malthus argued that populations are always limited by the food supply Darwin would later say that this work caused him to realize the struggle for limited resources was a fact of life.
He said small changes took place in individual animals changes that help them survive would continue but those that did not would be destroyed the result of this would be the formation of new species the British philosopher Herbert Spencer described this struggle as survival of the fittest but biologists used the term natural selection to describe the evolutionary process Charles Darwin developed his ideas slowly over more than 20 years.
He was concerned that he would lose the support of the scientific community if he revealed it he wrote to his friend botanist Joseph Hooker that speaking about evolution was like confessing a murder it was not until 1858 that Darwin was forced to release his theory to the public another naturalist Alfred Russel Wallace had independently written a paper that contained ideas similar to Darwin's concerning evolution Wallace said reached these ideas from his studies on islands in the western Pacific Ocean with help from Darwin's friends the two naturalists presented a scientific paper to the Linnaean Society of London in July of 1858 at first there was little reaction then in November 1859.
Darwin released the results of all his work on evolution the book was called on the Origin of Species by means of natural selection or the preservation of favored races in the struggle for life it was an immediate success the Origin of Species was praised by many scientists but religious leaders denounced it for them evolution opposed the explanation of creation found in the book of Genesis in the Bible today almost all scientists accept the theory of evolution but many non scientists are unsure about whether humans evolved over millions of years in the United States.
public opinion studies have shown that less than
Charles Darwin theory of evolution
I welcome in my series and science today we will talk about Charles Darwin's theory of evolution which is essentially the theory of how life came to be on this planet see any species cannot truly be cast as intelligent until it really starts to wonder where it comes from and these are very important philosophically questions and the answers can be very troublesome and there are myriad of answers available from scientific to religious today we will discuss what science has to say on this matter there are many possible hypotheses.
one of which is that life and the universe has existed as we see today in infinite time in the past there is another hypothesis of creationism that some external being has created life at some point in the past and the third hypothesis is rather interesting which says that at some point in the past life started originating or evolving from simple atoms which continued to evolve into much complicated in smart organisms that we see around us
today let's discuss these hypotheses the infinite past hypothesis seems philosophically troublesome particularly to me that that the universe has always existed just like as we see it today science believes the scientific view is that this is not the case that universe has not existed in the infinite past that it has a specific birth date and that a long time ago there was no earth there was no there were no stars and we'll talk more about this when we talk about the Big Bang in the origin of the universe, for now, this rules out the first hypothesis the second hypothesis is of creationism that at some point in the past in external being which we call God created life.
now it could be true but the problem that I find with it is that it does not really answer how intelligent life comes to be because you see if if an external being created us and the external being is intelligent how does that intelligent being come to be I mean it was he was the god do they have their own guards or do they happen to be around for infinite time in the past so you see it's not clear how intelligent life comes to be in this hypothesis because if God created us who created God and have they been around for the infinite time in the past or do they have their own words the third hypothesis is of evolution and this is very interesting
it says that it it is not necessary to have an external being or an external creator for life to happen that life can happen with working under the laws of the universe if you take simple atoms that these simple atoms can turn into molecules which can turn into single-celled organisms and then it can evolve slightly over time such that this becomes smarter and smarter and complex and complexes that they eventually become so smart that they one day start to wonder
where do I come from and that's that is one of the hypothesis that how humans have come to be in this planet today we will discuss that which of these hypothesis science believes is true the mystery of life has been called the mystery of mysteries and today we will try to resolve the mystery we will talk about Charles Darwin and his and his work of lifetime.
which he published in his book the origins of species he went on a voyage around the world for five years and he collected a lot of evidence and we will also discuss the basic insights that led him to his discovery let's talk about the worst before Charles Darwin one of the leading views at the time was that the species were immutable that God had created distinct
species man and then birds and then and then pigeons and then and then dogs and cats and lions etc and that the species had an order like there were plants and on top of which there were the animals and on top of the animals were the humans and up above the humans were gods in the skies similarly the famous botanist Carl Linnaeus
who was a Swedish botanist he started categorizing these various organisms he started his he led the foundation of the biological nomenclature that we see around and he first categorized the animals into species at a species was a categorized by the set of animals that could breed within themselves and within a species there were a lot of varieties or races now there were still some unanswered questions at that time in people and scientists realized that one of which was that if if God had created species in a particular order why were there so many variety of species
why we're there for example so many pigeons so many various pigeons why were there so many variety of dogs why were there so many we're idea of cares and secondly why could a particular animal be a source by just looking at a particular animal an experienced person could tell that I think this animal was originated in the Middle East why was it that different varieties of species tend to be associated with different locations let's talk about Lamarck so Lamarck proposed a very good idea
that species were not consonant and that they changed or evolved over time and he primarily focused on two main works one of which was that by using their organs very frequently animals tend to strengthen those organs for example if you use your hand a lot it will grow muscles if if and similarly if you don't use a particular organ and for example if you don't use your eyes for a long time if you live in a dark cave then eventually
the organs will get aureate and eventually they will they will go away similarly all the acquired the second thing he focused on was that all these characteristics that you acquire over lifetime they are passed on to your children those were the two main things now this work was however slightly incomplete and incorrect for example the first law really is just an exaggeration of saying that by by using a particular organ it strengthens but it doesn't really tell how an organism evolves he also made some wrong assumptions that he
said that organisms have a tendency to move to increase in complexity and move te ladder up in the progress but he it he didn't really answer why organism wanted to progress or wanted to become more complex it is primarily his second law or second world rule that is considered his legacy that characteristics acquired by animals are passed on via heredity to their children Charles Darwin was born in 1809 in England to a very wealthy family and his father wanted to make him become a doctor but he was more inclined to become naturalist.
he attended Cambridge where he was introduced to the various naturalist at the time and one of which was Paley who argued that because the organs of the human body were so complex that it was probably a good hypothesis to assume that an external being had created us, Darwin, when he graduated even though
he was supposed to go for further studies he decided to take an offer to go around the world on a research ship HMS speaker HMS Beagle left England in 1831 and it was supposed to go on this research mission for two years but it would not return for five he Darwin was an unpaid naturalist on the ship while on the ship the captain of the ship gave Darwin a very good book called principles of geology that was written by the geologist Charles Lyle Lyle argued that the surface of the earth here was not created by a flood or anything or any catastrophe
it was created or sculpted over long periods of time and it had gradually evolved over long periods of time so this very idea that the that something changes over time gradually so much that eventually, you don't recognize what it started from this idea had a profound impact on Darwin and his own experiences during the voyage back the geologists theories he the another thing that that astonished Darwin was that the variety of creatures or organisms that he met during his voyage for example in 1835 the bigger landed on the islands of Galapagos in near Chile and the creations of Galapagos really astonished
Darwin, for example, there were lizards who could swim and these were the only kind of lizards Darwin had ever heard of that could swim and there was a similar variety of lizards that lived on land there were oversized tortoises and which were unique to each Island I mean you could take a look at the eat or toys and you could tell that this particular tortoise comes from this island the other one comes from that Island and in particular in of particular importance are the species of bird which were finches the importance of which Darwin did not recognize at the time but he brought the specimen back with him to England and when these specimens were presented to the famous ordinary fellows John Goule
he announced that they were all finches and this really astonished Darwin because he had not thought of those specimens as connected at all he these birds were very different in shape and size and there was a huge range of variation between them so when Beagle returned to England in 1836.
Darwin began to assemble all the evidence that he had collected into a single coherent theory there were many things that he had noticed one of which was that the birds of Galapagos were all related and this argued that they once had a common ancestor similarly the fact that those tortoises came from different islands and you could tell that this total came from this island argued that they once had a common in system each family their eye from a common ancestor and that man himself was a member of the pigeon Club in London and he ran his own experiments on pigeon
he could find that you could change a species over time as well as those characteristics were then on to their children with high chance variation under domestication and this was also the first chapter in Darwin's book on the origins of species in this chapter Darwin argued that humans have shown that we can selectively breed animals with desired features for example we could breed a horse that could run very fast and or we could breed a dog with beautiful tails so and to be able to do this all you do is that you grow randomly a bunch of animals and then you selectively choose the ones that have desired features, in the end, you breed them this was artificial selection so Darwin was pretty convinced that species could modify and change over time and that you could artificially select them to have desired
characteristics but how did evolution work in nature how did a species change in nature because there was no artificial selection going on no one was picking them then how did species evolve over time and the answer to this came to Darwin after reading
Thomas Malthus who was a famous economist his book called the essay on principle of population Malthus said that any species multiplied very fast they multiplied geometrically but the supply for food or other resources necessary for their survival either remain constant or increase slowly so eventually what happened is that when the species had multiplied so much the resources necessary for survival became scarce and what this meant is that all the individuals of the species would be fighting for their survival to get the limited resources and what this meant is that and Darwin.
now saw the matter clearly that this man that the species competed to eat to reproduce to avoid predators essentially there was a game going on to survive because the resources were limited and so what happened is the following if by random chance some individuals were born which made their chances of survival better they would survive and those characteristics
would then be passed on to their children with a high chance and and that is how these characteristics would come to dominate the population oversight over several generations and this is when Darwin realized the natural selection the primary driver of evolution on the origins of species was the work of Charles Darwin that was published after almost a lifetime of Darwin's work that we knew that his theory was so mind-bending that that public would probably reject his hypothesis unless he made a very good case so he collected for almost 50 years evidence
before he put together his book to understand how his theory and how evolution works let's assume certain facts one is that offspring of any species slightly vary for example siblings that are born to the same parents have slightly different heights they have slightly different eye colors fact number two animal characteristics are passed on with a very high chance to their children, for example, pay children off tall parents are likely to be tall and the resources necessary for survival are limited that several individuals of a species are fighting to get them under these circumstances we assume that natural selection kicks in that individual that are born by random chance
I reiterate by random chance that makes them fit that make that make their chances slightly better they have a slightly better chance to survive or to win in this game and therefore they have a slightly better chance to reproduce and have off soon and because these characteristics are then passed on to their children the these characteristics which make them beneficial come to become to populate the majority but becomes the majority and this is how a species evolved for example take a look at a giraffe to let's say a giraffe who initially had a short neck and this is one of the theories
why giraffes have long neck is that initially giraffes used to have shorter neck but let's say they are born in an environment where fruits are high up in the tree if by random chance of giraffe is born that has a slightly taller neck then that giraffe will have a much better chance of survival while his peers will die out and that is and eventually his children will have two taller necks and this will continue to increase the long necks will continue to increase and there they have a company need to have an advantage over other people who are others struggling peers so next
we'll continue to rise the further evidence for natural selection is the evolution of peppered moth in England and this has been studied greatly evolution generally works over millions of years but under certain circumstances such that when the environmental pressure is very strong it can occur at a much faster rate for example originally in England
the moths were light-colored the majority of them and the this help them become this give them an advantage because think about this if they rested on a tree which was light-colored the dark-colored moth will appear out will stand out and will be eaten by the predator however the light-colored will be camouflaged successfully however during the Industrial Revolution what happened is that the light-colored plants died out and the trees became the dark by the suit by the population and this gave an advantage to the dark-colored and within a few decades the story completely changed upside-down the majority of the dark-colored moth became 98% in population
all this is good but we have still not answered how do we have understood how a species evolve over time but what we have not yet talked about is that how does a monkey evolve into a human being how do how do species change so that they become a completely different species and the answer to that is that in that means view there was no fixity of species to species were just too different was just such that one a long time ago there were children of the same parents it just so happens is that a particulars what is the species a species is just a population of animals
who can breed and they have an average set of characteristics and they are just variations on those average characteristics however over time these average characteristics can evolve if the environment changes if due to natural selection and evolution if however what happens is that due to some external factors these population is divided into two parts let's say a flood happens or the species migrate and then these two species
which are distinctly located in different environments over time there will ran chout so much that they will eventually become to be as two distinct species and will no longer be able to breed with each other and that is one of the cases with the Apes and humans that we once were Apes it's just that our ancestor decided to move out of the tundra and walk on the ground that they became humans and the Apes in the jungle remained Apes so concluding there has been widespread opposition to the theory however it is part of science and it is accepted people, for example, asked questions such as if man evolved from monkeys why are monkeys still around and also they asked that why don't we see evolution around us why don't we see a dog evolving into a wolf or a monkey evolving into a man
hopefully you now understand why these oppositions do not work of the three hypotheses that I discussed above science supports the third intelligent life can come to be from simple atoms on its own and the philosophical consequences of the theory of evolution are profound for example it rules out the nests the necessity of a creator may be around but it is not necessary to create life can come to be on its own by evolving under the laws of the universe the second thing which I found
very interesting is that no matter who you are if you are listening to my lecture if we go back in time we will find that we once had a common ancestor and it doesn't matter even if you are a chimpanzee or a fish if we go back in time long in a v1 we will find that V once had a common mother and father all life on this planet is connected it can be said that if an alien species land on earth the stick with which they will measure how intelligent we are they will simply ask themselves well have humans have they figured out evolution here and by that measure we would have proved to be intelligent thank you ...
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