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What is the Darwinian Evolutionary Theory?

One of the most well-supported hypotheses in science is Charles Darwin's Theory of Evolution. But what is it, exactly?


Charles Darwin's book "On the Origin of Species," published in 1859, was the first to articulate the theory of evolution through natural selection. According to National Geographic, Darwin illustrates how creatures change over generations through the inheritance of physical or behavioural features in his book. The theory is based on the idea that there is variety in features within a population, such as beak form in one of the Galapagos finches Darwin investigated.

Individuals having qualities that enable them to adapt to their settings, according to the hypothesis, will help them survive and have more offspring who will inherit those traits. Individuals that are less adaptable are less likely to live to pass on their traits. The qualities that allow species to live and reproduce become more common in the population over time, and the population changes, or evolves. Darwin proposed that genetically distinct species could originate from a common ancestor through natural selection.

Darwin had no idea how qualities were handed down through the generations. He was unaware of genetics, the process through which genes encode for specific features and these traits are passed down from generation to generation. He also had no idea about genetic mutation, which is how natural variety is created. However, geneticists later discovered the process and added to the evidence for evolution by natural selection.

What is natural selection and how does it work?

Darwin used the phrase "natural selection" to contrast with "artificial selection," which involves animal breeders selecting for desired features. The natural environment, rather than a human person, is the one who selects in natural selection.

Simply put, the idea of natural selection evolution can be described as "descent with modification." The hypothesis is commonly referred to as "survival of the fittest," however this label is deceptive. The term "fitness" here refers to an organism's capacity to survive and reproduce rather than its strength or agility.

Natural selection can change a species in minor ways, such as changing the colour or size of a population over multiple generations. Microevolution occurs when this process occurs over a short length of time and in a single species or small group of animals.

Natural selection, however, can create wholly new species when given enough time and accumulated alterations, a process known as "macroevolution." Dinosaurs became birds, aquatic mammals (such as the Indohyus) became whales, and a common ancestor of apes and humans became the people, chimps, and gorillas we know today thanks to this long-term process.

Darwin also described a type of natural selection called sexual selection, which is based on an organism's ability to attract a partner. Peacocks' colourful plumage and male deer's antlers are both examples of features that arose through this form of selection.

What happened to whales when they evolved?

The development of whales is one of the best instances of natural selection available to biologists. Biologists discovered that the transfer of early whales from land to water proceeded in a sequence of predictable steps by utilising Darwin's theory as a guide and knowing how natural selection works.

For example, the evolution of the blowhole could have begun with random genetic mutations that caused at least one whale's nostrils to move further back on its head.

Because they wouldn't have had to entirely surface to breathe, whales with this adaptation would have been better suited to a marine lifestyle. These people were more successful and had more children. More genetic alterations happened in subsequent generations, causing the nose to move further back on the head.

Other aspects of early whales' bodies changed as well. The front legs were transformed into flippers. The back legs vanished. To better propel themselves through water, their bodies became more streamlined, and they evolved tail flukes.

Even while scientists could foresee the appearance of early whales, they lacked the fossil evidence to back up their claims for a long time. This lack was seen by creationists as proof that evolution did not occur, not only in the case of whale evolution but in general.

Scientists have discovered evidence from palaeontology, developmental biology, and genetics to support the concept that whales evolved from land mammals since the early 1990s. The hypothesis of evolution as a whole is supported by these similar lines of evidence.

Darwin theorised in the first edition of "On the Origin of Species" about how natural selection would force a land mammal to evolve into a whale. Darwin offered North American black bears (Ursus americanus) as a hypothetical example, who were known to capture insects by swimming in the water with their jaws open.

By natural selection, a race of bears became more aquatic in shape and habits, with larger and larger mouths, until a creature as gigantic as a whale emerged.

The proposal was not well received by the general public or other scientists. The swimming-bear passage was omitted from later editions of the book because Darwin was embarrassed by the contempt he received. Darwin had the right idea, but the wrong animal, according to scientists. He should have been looking at cows and hippopotamuses instead of bears.

Other evolution theories

Darwin wasn't the first or only scientist to propose an evolutionary theory. Alfred Russel Wallace, a British biologist, independently proposed the hypothesis of evolution through natural selection around the same time as Darwin. This, however, had little effect.

Because there was so much data collecting, the concept of evolution as a historical event was a hot topic among biologists and geologists prior to Darwin's book, but I suppose biological evolution hadn't really impacted individuals outside of the academic bunker. As long as science had no mechanism to explain how evolution occurred, it could be disregarded as a fringe theory.

Meanwhile, Jean-Baptiste Lamarck, a French scientist, claimed that an organism might pass on features to its progeny, but he was incorrect in several specifics.

Lamarck, like Darwin, thought that creatures adapted to their environments and passed those adaptations on to their offspring. He believed that creatures achieved this by changing their behaviour and, as a result, their bodies — similar to how an athlete works out and gets buff — and that these changes were handed on to offspring.

For example, Lamarck believed that giraffes had shorter necks at first, but as the trees around them got taller, they stretched their necks to reach the delectable leaves, and their offspring acquired longer and longer necks as a result. Lamarck also felt that life was compelled to evolve from simpler to more sophisticated forms over generations.

According to Understanding Evolution, Darwin did not believe that evolution necessarily moved toward greater complexity because he didn't know how traits were passed on. Instead, he believed that complexity arose through natural selection.

According to a Darwinian theory of giraffe evolution, giraffes had natural variety in neck lengths, and those with longer necks were better able to survive and reproduce in habitats with towering trees, resulting in more and more long-necked giraffes in following generations.

The primary difference between Lamarckian and Darwinian giraffe evolution theories is that the Darwinian explanation does not include giraffes lengthening their necks and passing on an acquired trait.

What is evolutionary synthesis in the modern era?

Darwin had no knowledge of genetics when he wrote his book. He was aware of the evolutionary pattern, but he was unaware of the process behind it. That emerged later, with the understanding of how genes encode certain biological or behavioural traits, as well as how genes are passed down from parents to kids. The addition of genetics to Darwin's theory is referred to as Synthesis of contemporary evolution.

Natural selection is enabled by physical and behavioural changes that occur at the level of DNA and genes within gametes, the sperm or egg cells through which parents pass on genetic material to their offspring. Mutations are the term for such changes. Mutations are the raw material that evolution works with.

Random errors in DNA replication or repair, as well as chemical or radiation damage, can result in mutations. Mutations are usually either detrimental or neutral, however in rare cases, a mutation may be helpful to the organism. If this is the case, it will spread across the population and become more frequent in the next generation.

Natural selection directs the evolutionary process in this way, maintaining and accumulating advantageous mutations while rejecting harmful ones. Although mutations are random, selection for them is not.

However, natural selection isn't the only way for creatures to evolve. When organisms migrate or immigrate, for example, genes can be transferred from one group to another, a process known as gene flow. Genetic drift is the term for when the frequency of specific genes changes at random.

The fact that learned features have little effect on the DNA of sperm and eggs is why Lamarck's theory of evolution is often incorrect. The gametes of a giraffe, for example, are unaffected by how far it stretches its neck; they simply reflect the genes passed down from its parents. Lamarckian components of evolution exist.

For example, a Swedish study published in the European Journal of Human Genetics in 2002 discovered that the grandchildren of males who were malnourished as children during a famine had better cardiovascular health than their grandparents. Although dietary deprivation does not modify the DNA sequences in the gametes, researchers believe that it may cause exterior DNA modifications that turn genes "on" or "off."

These alterations, known as epigenetic changes, do not affect the DNA sequence itself. For example, methylation, a chemical alteration, can affect which genes are switched on or off. These epigenetic modifications can be passed down to the next generation. In this sense, a person's experiences may have an impact on the DNA he or she passes down, similar to how Lamarck believed a giraffe craning its neck would effect the length of its offspring's neck.

What evidence is there for evolution?

The Theory of Evolution is one of the most well-supported hypotheses in scientific history. It is backed up by evidence from a range of scientific areas, including genetics, which demonstrates that different species' DNA is identical.

In palaeontology and geology, there is also evidence that supports the Theory of Evolution. This is accomplished through the fossil record, which demonstrates how ancient species vary from current species.

In developmental biology, there is also support for Darwin's idea. It has been discovered that species that appear to be very different as adults go through comparable stages of embryological development, implying a common evolutionary history.

According to a 2009 review published in the journal Evolution: Education and Outreach, the essential piece of evidence was uncovered in 1994, when palaeontologists discovered the fossilised bones of Ambulocetus natans, which means "swimming-walking whale." It had fingers and small hooves on its forelimbs, but its hind feet were gigantic in comparison to its size. The creature was definitely built for swimming, yet it could also move clumsily on land, much like a seal.

The ancient species swam in the manner of an otter, pushing back with its hind feet and undulating its spine and tail.

Modern whales use their horizontal tail flukes to propel themselves through the water, but A. natans still had a whip-like tail and had to rely on its legs to provide the majority of the propulsive force required to move through water.

More and more of these transitional species, also known as "missing links," have been identified in recent years, bolstering Darwin's theory. In 2007, a geologist unearthed the fossil of Indohyus, an extinct aquatic mammal with hooves and a long tail that was about the size of a cat.

Scientists believe the creature belonged to a type of cetaceans known as Ambulocetus natans. According to the National Science Foundation, this creature is a "missing link" between artiodactyls — a group of hoofed mammals (even-toed ungulates) that includes hippos, pigs, and cows — and whales.

Researchers knew whales were related to artiodactyls, but there were no known artiodactyls that shared physical traits with whales until the discovery of this specimen. Hippos, which are regarded to be the closest living relatives of cetaceans, are extremely different from whales. Indohyus, on the other hand, was an artiodactyl, as evidenced by its hooves and ankles, and also shared several features with whales, such as the form of its ears.

Genetic data also backs up the theory that whales descended from land mammals and sheds light on the evolutionary tree's exact branching. Hippos, for example, were whales' closest living relatives, according to genetic analysis of "jumping gene" sequences, which copy and paste themselves into genomes, published in the journal Proceedings of the National Academy of Sciences in 1999. Prior to 1985, scientists believed pigs were more closely related to whales, but a study published in 1999 proved them wrong.

In the journal Science Advances in 2019, researchers revealed which genes in the whale genome were inactivated during the creature's transition from land animals. Because traces of these genes, which the researchers refer to as genomic fossils, may be found in whale genomes, the researchers were able to determine that particular genes, including one involved in saliva production, had been inactivated. Whales are thought to have developed from a salivating monster.

Developmental biology has also revealed evidence of cetacean evolution. Because they are evolutionarily linked, creatures that are very diverse as adults share similarities as embryos, according to developmental biology. Cetaceans, for example, began to grow hind limbs as embryos, which disappeared later in development while the forelimbs remained and developed into flippers. Cetaceans are thought to have descended from a four-legged ancestor.

Is evolution a controversial theory?

Despite the abundance of evidence from the fossil record, genetics, and other fields of science, some people continue to doubt the validity of evolution. Some politicians and religious leaders criticise the notion, claiming that it relies on a higher being to explain the complicated universe of living things, particularly humans.

Boards of education argue whether evolution should be taught alongside other concepts like intelligent design or creationism.

There is no disagreement among mainstream scientists. There can be genuine reconciliation if many people hold strong religious views while still accepting evolution.

Many examples of changes in diverse species leading to the diversity of life seen today support evolution. The essential idea of modern biology is natural selection, or, to put it another way, variation, inheritance, and differential fitness. It's comparable to quantum mechanics and special relativity in physics, or the atomic model in chemistry.



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