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 believed 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 Lamark, 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 12 (twelfth), 1809 (eighteen-oh-nine). 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 eight 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 sixteen, 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 (priest, reverend, pastor). But at Cambridge, Charles continued to follow his own interests. There, he met John Henslow, a 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 H.M.S. Beagle. It sailed around the world from 1831 – 1836 (eighteen thirty-one to eighteen thirty-six). 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 Beagle's 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 (preguntarse) 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.
Darwin 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 (eighteen thirty-six), 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 H.M.S. Beagle." But in eighteen thirty-seven, 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 a tropical disease. Others 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 settled 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 thirty-seven, 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 eighteen thirty-nine, he married Emma Wedgwood, his cousin. He told her his ideas about how species evolve 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 ten children together. Seven of them survived.
Charles Darwin read widely and sought ideas from other fields of study. He was influenced by Thomas Malthus' work, "An Essay on the Principle of Population" written in 1798 (seventeen ninety-eight). 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 helped 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 use the term "natural selection" to describe the evolutionary process.
Charles Darwin developed his idea slowly over more than twenty 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 had reached these ideas from his studies on islands in the western Pacific Ocean.
With help from Darwin's friends, the two naturalists presented a joint scientific paper to the Linnean Society of London in July of 1858. At first there was little reaction.
Then, in November, eighteen fifty-nine, 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 Favoured 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 half the population believes in evolution.
Natural selection does not explain everything about why species evolve. Darwin did not know about Gregor Mendel's work on heredity. And the discovery of genetics and D.N.A. molecules took place long after his death. Yet, Darwin theorized in a world much different from the one we know. That is why scientists today wonder at the depth of his knowledge and the strength of his arguments.
Charles Darwin died on April nineteenth, eighteen eighty-two. He was buried at Westminster Abbey, in London, among other heroes of Britain.
a.) This (este, esta) These (estos, estas) b.) That ( aquel, aquella) Those (aquellos, aquellas)
Los adjetivos demostrativos se utilizan para determinar la posición de las cosas.
En español encontramos tres distintos grados de proximidad. Esto (para lo que está más cerca del sujeto). Eso (situado a media distancia) y Aquello (lejano).
En inglés, en cambio, solamente encontramos dos grados de proximidad.
This, que se utiliza para designar las cosas o personas relativamente cercanas y that, para las más alejadas.
This puede utilizarse también para presentarse a uno mismo (no personalmente) o para presentar a un tercero:
Hello. This is Craig. / Hola. Soy Craig (En una conversación telefónica) · Paul, this is Helen / Paul, ésta es Helen · Hello, Helen. Pleased to meet you / Hola Elena. Encantado de conocerte. · Hello / Hola
- This también se emplea coloquialmente para empezar un relato o para indicar el tamaño de algo:
This is the story of Ma Baker.... / Esta es la historia de Ma Baker... A man this fat / Un hombre así de gordo
- This / that / these / those pueden preceder a un sustantivo o ir solos.
This restaurant is expensive / Este restaurante es caro This is an expensive restaurant / Éste es un restaurante caro
- That sirve para indicar algo que ha ocurrido o algo que alguien ha dicho.
That was a wonderful film / Ha sido una pelicula maravillosa. You're an engineer, aren't you?; Yes, that's right / Es usted ingeniero, ¿no? ;Si, exacto
- Like this.... like that (así, de este modo, de ese modo)
Don't do it like that. Do it like this / No lo hagas así. Hazlo así (de esta otra forma)
Usamos pocos verbos cuando hablamos del tiempo. To Rain - Llover
It is raining. (Está lloviendo) It rained yesterday. (Llovió ayer) It will rain tomorrow. To Snow - Nevar It snows a lot in the mountains. It is snowing. It snowed yesterday.
The man walked down the trail on a cold, gray day. Pure white snow and ice covered the Earth for as far as he could see. This was his first winter in Alaska. He was wearing heavy clothes and fur boots. But he still felt cold and uncomfortable.
The man was on his way to a camp near Henderson Creek. His friends were already there. He expected to reach Henderson Creek by six o’clock that evening. It would be dark by then. His friends would have a fire and hot food ready for him.
A dog walked behind the man. It was a big gray animal, half dog and half wolf. The dog did not like the extreme cold. It knew the weather was too cold to travel.
The man continued to walk down the trail. He came to a frozen stream called Indian Creek. He began to walk on the snow-covered ice. It was a trail that would lead him straight to Henderson Creek and his friends.
As he walked, he looked carefully at the ice in front of him. Once, he stopped suddenly, and then walked around a part of the frozen stream. He saw that an underground spring flowed under the ice at that spot. It made the ice thin. If he stepped there, he might break through the ice into a pool of water. To get his boots wet in such cold weather might kill him. His feet would turn to ice quickly. He could freeze to death.
At about twelve o’clock, the man decided to stop to eat his lunch. He took off the glove on his right hand. He opened his jacket and shirt, and pulled out his bread and meat. This took less than twenty seconds. Yet, his fingers began to freeze.
He hit his hand against his leg several times until he felt a sharp pain. Then he quickly put his glove on his hand. He made a fire, beginning with small pieces of wood and adding larger ones. He sat on a snow-covered log and ate his lunch. He enjoyed the warm fire for a few minutes. Then he stood up and started walking on the frozen stream again.
A half hour later, it happened. At a place where the snow seemed very solid, the ice broke. The man’s feet sank into the water. It was not deep, but his legs got wet to the knees. The man was angry. The accident would delay his arrival at the camp. He would have to build a fire now to dry his clothes and boots.
He walked over to some small trees. They were covered with snow. In their branches were pieces of dry grass and wood left by flood waters earlier in the year. He put several large pieces of wood on the snow, under one of the trees. On top of the wood, he put some grass and dry branches. He pulled off his gloves, took out his matches, and lighted the fire. He fed the young flame with more wood. As the fire grew stronger, he gave it larger pieces of wood.
He worked slowly and carefully. At sixty degrees below zero, a man with wet feet must not fail in his first attempt to build a fire. While he was walking, his blood had kept all parts of his body warm. Now that he had stopped, cold was forcing his blood to withdraw deeper into his body. His wet feet had frozen. He could not feel his fingers. His nose was frozen, too. The skin all over his body felt cold.
Now, however, his fire was beginning to burn more strongly. He was safe. He sat under the tree and thought of the old men in Fairbanks. The old men had told him that no man should travel alone in the Yukon when the temperature is sixty degrees below zero. Yet here he was. He had had an accident. He was alone. And he had saved himself. He had built a fire.
Those old men were weak, he thought. A real man could travel alone. If a man stayed calm, he would be all right. The man’s boots were covered with ice. The strings on his boots were as hard as steel. He would have to cut them with his knife.
He leaned back against the tree to take out his knife. Suddenly, without warning, a heavy mass of snow dropped down. His movement had shaken the young tree only a tiny bit. But it was enough to cause the branches of the tree to drop their heavy load. The man was shocked. He sat and looked at the place where the fire had been.
The old men had been right, he thought. If he had another man with him, he would not be in any danger now. The other man could build the fire. Well, it was up to him to build the fire again. This time, he must not fail.
The man collected more wood. He reached into his pocket for the matches. But his fingers were frozen. He could not hold them. He began to hit his hands with all his force against his legs.
After a while, feeling came back to his fingers. The man reached again into his pocket for the matches. But the tremendous cold quickly drove the life out of his fingers. All the matches fell onto the snow. He tried to pick one up, but failed.
The man pulled on his glove and again beat his hand against his leg. Then he took the gloves off both hands and picked up all the matches. He gathered them together. Holding them with both hands, he scratched the matches along his leg. They immediately caught fire.
He held the blazing matches to a piece of wood. After a while, he became aware that he could smell his hands burning. Then he began to feel the pain. He opened his hands, and the blazing matches fell on to the snow. The flame went out in a puff of gray smoke.
The man looked up. The dog was still watching him. The man got an idea. He would kill the dog and bury his hands inside its warm body. When the feeling came back to his
fingers, he could build another fire. He called to the dog. The dog heard danger in the man’s voice. It backed away.
The man called again. This time the dog came closer. The man reached for his knife. But he had forgotten that he could not bend his fingers. He could not kill the dog, because he could not hold his knife.
The fear of death came over the man. He jumped up and began to run. The running began to make him feel better. Maybe running would make his feet warm. If he ran far enough, he would reach his friends at Henderson Creek. They would take care of him.
It felt strange to run and not feel his feet when they hit the ground. He fell several times. He decided to rest a while. As he lay in the snow, he noticed that he was not shaking. He could not feel his nose or fingers or feet. Yet, he was feeling quite warm and comfortable. He realized he was going to die.
Well, he decided, he might as well take it like a man. There were worse ways to die.
The man closed his eyes and floated into the most comfortable sleep he had ever known.
The dog sat facing him, waiting. Finally, the dog moved closer to the man and caught the smell of death. The animal threw back its head. It let out a long, soft cry to the cold stars in the black sky.
And then the dog turned and ran toward Henderson Creek…where it knew there was food and a fire.
