Theory of Evolution by Charles Darwin

After millions of years, it cooled down, and heavy rains started to fall. Gradually, water began to fill the lower depressions, forming the oceans, which became the cradle of life. Life began in water more than two billion years ago. From simple beginnings, life gradually acquired more complex forms. Such changes are together known by the term evolution.

Obviously, the most important result of the evolution of life is the human being. Human beings are two million years old, and that means we can be called the latecomers. But humans have already had a greater influence on Earth than any other living being. This is the debut post of FactLo tells you the great and exciting story of evolution.

The word ‘evolution’ and Charles Darwin

When you think of evolution, the first name that comes to one’s mind is that of Charles Darwin. However, the fact is that he was not the first person to put forward the idea of evolution. Lamarck had suggested it earlier, but the concept was not popular. In fact, a zoology professor, Robert Grant, lost his job because he supported Lamarck’s theory!

An anonymous work titled ‘The Vestiges of Creation’ was ridiculed. It was Charles Darwin who first made the theory acceptable, and he was able to do so because he supported it with a huge amount of evidence.

Darwin, an English naturalist, put forward his theory in a book titled ‘On the Origin of the Species’. He established that all species descended from common ancestors and that the different species evolved through a process he called natural selection. Darwin’s theory gained acceptance because it was able to explain the diversity of life.

Charles Darwin – a Fascinating Figure

Charles had an amazing life. He traveled the world, saw volcanoes explode, and earthquakes rode on the back of giant tortoises and went hunting for ostriches. When Charles was 22, he was invited to join a voyage round the world on a ship named ‘Beagle’.

When the Beagle stopped at the Galapagos Islands, in the Pacific Ocean, Darwin found some really strange animals. He collected lots of specimens while he was away, and when he returned home he started thinking about how animals and plants change through time.

He concluded that different individuals might survive better than others because they are a little bit bigger or better at something, and he called this ‘natural selection by survival of the fittest’. He also concluded that animals that do survive often have more offspring, and these young ones inherit their parents’ strengths.

In 1859, he finally wrote a book about what he had found out. It was called ‘On the Origin of Species’. It was a sensation! Charles’ ideas meant that humans weren’t special- they had evolved too, just like any other animal. Darwin had so much evidence that scientists decided he was right.

and Darwin’s Journey began?

Darwin’s voyage on the ship ‘Beagle,’ was a key turning point in his life. His role was to be a private naturalist. With its eager passenger aboard, the Beagle left England on December 27th, 1831.

The ship reached the Canary Islands in early January, and continued onward to South America, which they reached by the end of February 1832. During the explorations of South America, Darwin was able to spend considerable time on land, sometimes arranging for the ship to drop him off, and pick him up at the end of an overland trip.

He kept notebooks to record his observations. The Beagle reached the Galapagos Islands in September 1835. Darwin was fascinated by such oddities as volcanic rocks and giant tortoises. In January 1836, the Beagle arrived in Australia and then reached the Cape of Good Hope.

The Beagle sailed back to the coast of South America before returning to England, arriving at Falmouth on October 2nd, 1836. In the following few years, Darwin wrote extensively about his experiences. His experiences on this journey led to the publication of ‘On the Origin of Species,’ in 1859.

Two Tasks set by Darwin

Darwin had two goals in mind. First, he wanted to work out the mechanism by which evolution occurs. Secondly, he wanted to collect enough evidence to convince people of his theory of evolution. He sought information from his many contacts to help him refine his theory.

In 1837 Darwin began his first notebook on evolution. For several years, Darwin filled his notebooks with facts that could be used to support the theory of evolution. He found evidence from his study of the fossil record.

He observed that fossils of similar relative ages are more closely related than those of widely different relative ages. He consulted animal and plant breeders about changes in domestic species. He ran his own breeding experiments, and also did experiments on seed dispersal.

All of this varied information helped him formulate his theory of evolution and convinced him that the process of evolution which he expounded could, in fact, explain the patterns he saw in the natural world.

Darwin’s theory introduced the concept that organisms are modified over vast periods of time by naturally occurring processes, originating from common ancestors that lived tens of millions of years ago.

Darwin’s theory introduced the concept that organisms are modified over vast periods of time by naturally occurring processes, originating from common ancestors that lived tens of millions of years ago.

Evidence of Darwin’s theory

Most of the evidence for evolution comes from fossil records. Many living animals also support Darwin’s theory. For example, all Mediterranean bee orchids may look like. But they cannot interbreed, proving that they belong to different species, but have a common ancestor.

There is a strong resemblance between a bat’s wing and a dolphin’s flipper, suggesting a common ancestor once again. The arms and hands of chimpanzees are very similar to other vertebrates. The armadillo’s forelimb is short and sturdy to give it the power for digging, while horses’ legs have become adapted for running.

How did Darwin explain the distribution of plants and animals? Before Darwin’s Theory of Evolution was accepted, people believed that God created each species to suit the specifications of the area it lived in.

However, the puzzling distribution of plants and animals in South America and the Galapagos made Darwin question how species originated. If each plant and animal was created to match its habitat, why didn’t the same species appear in similar environments?

As Darwin would later come to realize, if the two species had arisen from a single common ancestor, it would make sense for them to live close together. The pattern of geographic separation he observed was exactly what one would predict if new species evolved from existing ones.

Darwin was able to show that migration and evolution are the most logical explanations for the patterns of distribution of plants and animals that are seen on the planet.

Fossil evidence and Darwin

Scientists at the beginning of the 1800s knew about some kinds of fossils. Charles Darwin studied fossils carefully to prove his theory of evolution. He found no strong evidence against evolution, and much in its favor.

When fossils are arranged in the order of their age, a continual series of change is seen, new changes being added at each stage. The fossil remains of the now-extinct reptile Mesosaurus found in Africa and South America provided one of the earliest clues to a former connection between the two continents.

Mesosaurus was a freshwater species, and so, clearly incapable of a transatlantic swim. Therefore, it must have lived in the lakes and rivers of a landmass that later became divided as Africa and South America and drifted apart.

Darwin’s concern about the age of the Earth

Charles Darwin is most famous for his work on natural selection, the idea that all species of life have evolved over time from common ancestors. This process involves favorable traits becoming more common in successive generations of living things, while at the same time, unfavorable traits become less common.

For Darwin’s theory to be correct, it was essential that the Earth be hundreds of millions of years in age because the process of natural selection is a long one needing enormous amounts of time. Darwin came into conflict with some scientists who calculated that the Earth was only 100 million years old or less.

Their claim troubled Darwin, as it went against his theory. However, later the confusion was cleared up, and it was accepted that the Earth was around 4.5 billion years old. This calculation supported Darwin’s theory.

Darwin’s interest in artificial selection

Darwin was interested in artificial selection. During his lifetime, new varieties of plants and new breeds of animals were bred through artificial selection. This involves breeding only those individuals that have desired qualities and rejecting the rest.

For example, animal breeders are often able to change the characteristics of domestic animals by selecting for reproduction those individuals with the most Evolution desirable qualities such as speed in racehorses, milk production in cows, trail scenting in dogs.

Over the years, those plants with desirable characteristics are grown by Man. Meanwhile, plants without these characteristics are less likely to survive. Eventually, the species of the plant will evolve. This supported Darwin’s theory that the strengths acquired by natural selection are indeed passed on to subsequent generations resulting in evolution.

Darwin as a part of the Beagle’s expedition

The HMS Beagle went on a lengthy scientific mission several years before Darwin came into the picture. On its second voyage, Captain FitzRoy was to command the ship. FitzRoy wanted to take along someone with a scientific background who could explore and record observations.

Inquiries were made among professors at British universities. Darwin’s former professor proposed him for the position aboard the Beagle. Darwin was very excited at the idea but his father was against it. Other relatives convinced Darwin’s father to let him go, and during the fall of 1831, the 22-year-old Darwin made preparations to depart England to join the Beagle team.

Darwin’s first interesting discovery

The H.M.5. Beagle arrived at the Cape Verde Islands on 16th January 1832, and anchored at Porto Praya, on the island of Santiago. It was here that Darwin discovered horizontal bands of white shells within a cliff face along the shoreline. This layer was more than thirteen and a half meters above sea level, and Darwin wondered how shells that are usually found under the ocean could be present so high up on land.

Since the layer was intact, any upward movement of the land would have to be very gentle, for violent movement would have broken up the layer. This discovery set Darwin thinking, and his thoughts would eventually lead to his theory about how ocean floors sank, and continents rose up.

Darwin visited Rio de Janeiro

On April 4th, 1832, the Beagle arrived in Rio de Janeiro. For ten weeks, while FitzRoy on the Beagle upgraded British charts of the Brazilian coast, Darwin lived in a cottage on Botafogo Bay in Rio de Janeiro.

While in that cottage, Darwin studied muddauber wasps which made clay, and then stuffed them ‘full of half-dead spiders and caterpillars’. He also saw a fight between a wasp and a spider that helped him understand ‘the struggle for survival’. Darwin wrote about the frogs, and ‘a pleasing chirp’ of crickets he heard there at night.

He also roamed all around the nearby countryside. Darwin collected many specimens of plants and insects during a trek up the coast and his collection exceeded anything he ever dreamed of.

Darwin’s stay in the Beagle Channel

One of the objectives of the Beagle’s Captain, FitzRoy, was to return three natives whom he brought from Tierra del Fuego to their homeland. These natives were known as Fuegians. Rev. Richard Matthews of the Anglican Church Mission Society, who hoped to establish a mission in the Fuegians’ land, would be accompanying them.

On January 18th, FitzRoy took the three Fuegians, twenty members of his crew, and Darwin in four boats down the Beagle Channel. This channel is a strait separating Tierra del Fuego from the extreme tip of South America, and it was named after the ship in one of its previous voyages.

On January 23rd, the four boats arrived at the Fuegians’ village where the mission was to be started. The next few days were engaged in setting up the mission, and the Reverend Mathews and the three Fuegians who had been trained under him were left to run the mission. For Charles Darwin, the trip down Beagle Channel was unforgettable, as it gave him his first glimpse of glaciers.

Darwin in the Falkland Islands

On March 1st 1833, HMS Beagle dropped anchor in Berkeley Sound, and Darwin had his first glimpse of the Falkland Islands. His first recorded impression of the Falklands was accurate enough ‘ … the land is low and undulating with stony peaks and bare ridges; it is universally covered by a brown wiry grass, which grows on the peat’, he wrote.

Darwin spent the next few weeks collecting fossils. He found that these fossils were very different from those that he had found in South America. This inspired him to do a comparative study of all the fossils, plants, and animals that he had collected.

These fossils were even more interesting than he imagined since they proved to be about 400 million years old, and an important link in the subsequent development of continental drift theories

Darwin’s experiences with the Gauchos

Notes from Darwin’s 1 833 expeditions to South America excitedly describe a rare breed of cowboys that he saw riding the open plains. These were the gauchos. In the summer of 1833, Darwin went inland with some gauchos in Argentina.

During his treks, Darwin dug for bones and fossils and was also exposed to the horrors of slavery and other human rights abuses. The Gauchos also had a lot of fun at Darwin’s expense, when they tried to teach him how to catch the game as they did. At the end of his time with them, Darwin had increased his specimen collection.

Darwin’s visit to Buenos Aires

Darwin arrived in Montevideo on Rio de la Plata on July 26th, 1832 on the Beagle. But he saw Buenos Aires only on September 20th when he arrived there, having traveled on horse-back from Bahia Blanca in the South. He collected natural history specimens from the area widely and carefully.

From South America, he collected complete suites of insects, small invertebrates, birds, spiders, corals, mollusks, mammals, and fossils when he could get hold of them. He had no scruples about buying specimens if he had the opportunity.

He knew he would never be able to visit again, and that he should not miss any chance to gather as much information as possible. He collected fossils of huge animals and wondered how these animals could survive on the sparse vegetation present. He was also puzzled as to how they had become extinct.

Darwin’s discovery at Punta Alta

Darwin’s search for fossils led to a very interesting find at Punta Alta. He found the fossil of a very large animal that was embedded in a cliff face below a layer of white seashells. This layer was very similar to a layer he had discovered a year earlier in Santiago.

This discovery puzzled him immensely and set him wondering what the creature was, why it had become extinct, and why it was not found anywhere else in South America. Darwin harvested from Punta Alta the remains of nine great mammals, all unknown, or barely known to science.

They were later proved to be extinct Pleistocene giants, unique to the Americas, in an age sometime before 12,000 years ago.

Darwin on his journey south

After leaving Montevideo, the Beagle, accompanied by the schooner Adventure sailed south. As the ships entered San Bias Bay, they were enveloped by a cloud of butterflies. This phenomenon puzzled Darwin, as there were no air currents at that time that could have swept the butterflies out to sea.

Later, the ships reached Port Desire, and Darwin went on shore to examine the landscape. He also used the time to write at length in his journal about the limited flora and fauna, especially the guanaco, a llama-like animal. Another feature that fascinated him was the river valley in the region.

After careful study, Darwin concluded that the river valley cliffs had once been under the sea, and had been slowly pushed upwards.

Darwin at Chiloe Island

The island of Chiloe is an island near the coast of Chile. The island was covered with evergreen forests and inhabited by native Indians who were very poor. Darwin found the place depressing because it was raining constantly!

The Beagle next sailed to the city of Valparaiso I in Chile. Here, the climate was much warmer, and the town was so pretty that Darwin soon cheered up. He went upon several long walks in the countryside, collecting specimens to add to his already impressive collection.

Valdivia – an unforgettable experience for Darwin

On February 20th, 1835, a massive earthquake hit Valdivia, and Darwin was right in the middle of the action. In his own words, ”This day has been remarkable in the annals of Valdivia for the most severe earthquake which the oldest inhabitants remember”.

He described the earthquake graphically with the words “An earthquake like this at once destroys the oldest associations; the world, the very emblem of all that is solid, moves beneath our feet like a crust over fluid”. The devastation was horrible – nearly every building in the area was destroyed.

On his arrival at the island of Quiriquina, when he explored around the island, he found areas of land that had risen a few feet due to the earthquake. Darwin became very excited because this was direct evidence that the Andes Mountains, and indeed all of South America, were very slowly rising above the ocean.

Darwin – explored the geology of Villavicencio

Charles Darwin visited Villavicencio in Argentina during his South American journeys in the 1 9th century and discovered a geological sequence that amazed him. He found that the local mountains were composed of lava flows that are usually found under the sea.

These lava flows were now found at a height of 1828 meters – and that too, 1126 kilometers from the coast. He was also wonderstruck by the fossilized coniferous trees that he found there, along with huge numbers of petrified trees, which are trees that have turned into stone over the ages.

It was obvious that this land had once been under the ocean, but Darwin wondered how the trees that had become petrified had ended up underwater. These discoveries led Darwin to develop geological theories of his own.

Darwin reaches Galapagos

Charles Darwin’s visit to Galapagos resulted in much attention being paid to these islands, and consequently, many fascinating things have been discovered about them. One of the main questions that excited him was how so many different plants and animals arrived on the islands in the first place.

The periodically changing currents may have allowed many different species to immigrate to the islands. Also, during the rainy season, rafts of vegetation break off and float out to sea. Most of the reptiles, the only terrestrial mammals and insects must have arrived by this route.

The light spores of many lower plants could have been blown in by the wind along with lighter seeds. Once on the islands, the various species established themselves, and determined territories. Evolution then set in, and many unique species, such as the finches that fascinated Darwin, were the result.

What were Darwin’s experiences in New Zealand? Charles Darwin’s ship visited New Zealand on December 1835. He was not particularly impressed with the countryside and was quite appalled by the natives because he felt that they had many vices, and practiced cannibalism.

After a few uncomfortable days visiting the local settlements, Darwin and the captain of his ship, FitzRoy were invited by eMS missionary William Williams to visit the Waimate mission. At Waimate, FitzRoy and Darwin were pleased to find an oasis of English civilization, complete with cups of tea and cricket on the lawn!

During his stay in New Zealand, Darwin collected insects, shells, fish, rocks, and a gecko. His detailed observations were carefully recorded in his journal of the Beagle expedition, which was published to much acclaim in 1839.

Flightless birds, giant snails, walking bats – many of New Zealand’s plants and animals are unique. There are almost no native mammals, but lots of frogs, lizards, and land snails. Some species are similar to plants and animals in the other lands once joined to New Zealand. What is the explanation for this?

About 85 million years ago, New Zealand broke away from the Gondwana supercontinent, carrying with it a cargo of plants and animals. Some of today’s plants and animals may have evolved from those living there at this time.

Many plants and animals have arrived more recently. This helps explain why there are few mammals. Only creatures that flew, or were light enough to be carried by the wind, or small enough to arrive on floating material, could cross the ocean between New Zealand and other lands.

Darwin’s visit to Australia

Charles Darwin arrived in Australia on 12th January, 1836. During the 61 days he spent in Australia, Darwin visited Sydney, the inland settlement of Bathurst, Hobart Town in Tasmania, and King George’s Sound in Western Australia.

Sydney’s roads, houses, and even the shops all met with Darwin’s enthusiastic approval. Beyond Sydney, he found the landscape arid and sterile, and the vegetation unappealing.

Bad weather delayed the Beagle’s departure from Hobart by 12 days, allowing Darwin to continue his natural history studies, and collect specimens of fossils, rocks, flora, and fauna. He collected shells, barnacles, 10 species of fish, and 66 species of insects, many of which were unknown to British scientists at the time, during the remainder of his stay in Australia.

Darwin’s writings are rich in observations of Australia’s landscape, fauna, flora, and people. These, and the insights he gained from his Australian associates, contributed to the development of his theories and ideas.

Variation, inheritance, and competition in Evolution

Charles Darwin’s theory of evolution through natural selection is based on variation, competition, and inheritance. The reason that variation is important is that there is competition among members of the same species for food and space.

Moreover, more offspring are produced than can be supported by available food and space. Variation refers to the fact that some combinations of traits will give some members of a species an advantage over others in this competition for survival. The offspring of the survivors in the competition inherit the strengths of their parents and this leads to evolution.

Theory of heredity and Darwin

Darwin believed that acquired characteristics are inherited, but gave more importance to variation and selection of the fittest in his theory of evolution. Darwin made a major mistake when he thought that the characteristics of parents were blended into their children.

If this were so, strong characteristics would be diluted, and the advantage gained by variation would be lost. However, Darwin was not able to come up with another explanation. Darwin conducted many experiments on the effects of crossbreeding and inbreeding in both plants and animals.

He noticed that when albino mice are crossbred with normal mice, the colors do not blend, but he thought that this was just an oddity. Darwin also found that inbreeding often resulted in weaker, sicklier descendants.

In his own life, he married his first cousin, and their children suffered the disadvantages of inbreeding. Three of his ten children died before they were 11 years old, and the rest were rather sickly. Darwin noticed that very often, children do not resemble their parents, but may look like their grandparents or other relatives.

He could not give an explanation for this. However, scientists later explained this by saying that all our characteristics are determined by our genes, and some genes are dominant while others are recessive.

All living things struggle for existence

Darwin suggested that an organism’s struggle for existence determines why some species survive, and others become extinct. The great number of variations in species has allowed plants and animals to become beautifully adapted to their environments.

Darwin provides examples of these adaptations. He mentions the beak of a woodpecker, which allows it to gather insects for food. Another example is the structure of a parasite, which allows it to attach itself to and feed off of another organism.

Darwin pointed out the ability of a beetle to dive into the water to gather food. These adaptations illustrate how unique characteristics of particular organisms have developed, allowing them to thrive in their specific environments.

The most advantageous characteristics are preserved and passed on to offspring. Darwin explains that the presence of these useful adaptations in organisms is the result of natural selection.

According to Darwin, although nature can provide an abundance of food and shelter to its inhabitants, it can also be destructive, causing a struggle for existence. The constant competition for existence compels all organisms and species to strive to outlive others, and successfully leave offspring for the survival of the species.

Natural selection

Natural selection is when a living thing is born with some feature that’s different from the rest of their species-for example more fur, or a longer neck or legs- that gives them an advantage, and helps them live better and longer in their environment.

These creatures pass on this difference to their offspring, and their offspring pass it onto their offspring until finally, a different species is formed. Here is an example of natural selection at work. Millions of years ago, the only vertebrate species in the world were fish, all of which lived underwater.

Competition for food was intense. Some species of fish that lived near the coast developed a strange mutation- they developed the ability to push themselves along in the mud and sand on the shore with their fins.

This gave them access to food sources that no other fish could reach. The advantage gave them greater reproductive success, so the mutation was passed along. This theory of natural selection is the basis of Darwin’s theory of evolution.