Introduction to Evolution
Darwin: The Most Dangerous Man in England
Pre-Darwin
Over the years many people have taken an interest in animals and plants. Aristotle was one of the first people to study animals and catalogue them.
Many cultures had creation stories such as Aseops fables to explain the way animals are.
Domestic varieties, artificial selection.
Victorians knew that domestic breeds can be shaped by sexual selection. Choosing a parent animal with a specific feature often produced an offspring with the same feature. The more ancestors with that trait, the more likely the offspring is to inherit it.
Early man did not have pomeranians and chihuahuas. The fastest dogs were continuously bred to produce the greyhound. The biggest dogs were continuously bred to produce the great Dane. This all happened in the last 10,000 years.
Horses were bred to be faster or stronger. Cows were bred to produce more and more milk and sheep for more and more wool, chickens that lay more and more eggs.
Many of our fruits and vegetables have been selectively modified.
Mary Anning discovers Plesiasour & Ichthasaur 1812 & 1823
Iguanadon discovered 1825
A Swede, Carl Linnaeus wanted to create a table of all living things. He came up with the system we still use today to categorize all living things.
Kingdom
Animal, plant, fungi and bacteria
Class
Mammal, reptile, amphibian, fish and bird
Order
Carnivora
Family
Felidae
Genus
Panthera
Species
Panthers Leo (AKA Lion)
This gives you a forest instead of a single tree.
He was the first to assign bat as a mammal. However, he classified whales as fish.
It was known that animals could inherit traits from their parents but it wasn't known why. People didn't yet know about DNA. Europeans had been selectively breeding domesticated animals for centuries. Some people theorized that the offspring inherited traits that the parents had honed in life. Such as if a parent was a weight lifer, the child would be naturally strong as a result of the parents years of training. Although incorrect this showed that people were aware of decent with modification.
Humans had been breeding horses, dogs, cats, pigs, cows, sheep, and chickens for years. It was known as artificial selection.
Charles Darwin
Charles Darwin was born in Shrewsbury during the Victorian era. When charles turned 18 his father wanted him to become a doctor like him. However, when he attended medical school he couldn't stand the sight of blood.
Darwin still enjoyed studying biology. His grandfather Erasmus had been a naturalist and had introduced Charles to the basics. Darwin got taxidermy lessons from a black former slave living in Edinburgh named Edmonstone. The man had been owned by a naturalist in Guyana, South America and became free when he arrived in Scotland with his master. He used his experience collecting specimens withhis master in Guyana to teach the skill of taxidermy. Darwin wrote about Edmonstone in a letter to his sister.
"A negro lived in Edinburgh, who had travelled with Waterton, and gained his livelihood by stuffing birds, which he did excellently: he gave me lessons for payment, and I used often to sit with him, for he was a very pleasant and intelligent man."
Edmonstone charged Darwin one guinea for an hour every day for two months. As well as the time spent on instruction, the two must have conversed on the natural history Edmonstone knew first-hand from South America.
Darwin's father was worried about what Charles would do if he wouldn't be a doctor and enrolled him in a seminary to become a priest. “I did not then in the least doubt the strict and literal truth of every word in the Bible,” It was at this time that Darwin began courting a young lady whose family were friends with his. He also had his religious exams during time. Instead, he was obsessed with his beetle collection and it got in the way of having a girlfriend and becoming a priest.
The Voyage of the Beagle
One of Darwin's mentors reccomended that Charles see the world before settling down to get married and taking a job. So Darwin joined a government mapping ship called the HMS Beagle. They set sail 2 days after Christmas. His room was 9 ft by 11ft long and 5ft high. He was also very seasick which wasn't great since he was scheduled to spend the next 5 years at sea.
The HMS Beagle stopped at Cape Verde, a chain of islands off the African coast. Darwin observed marine fossils on a massive rock at the top of a hill. He wondered how they could've got up so high.
After 23 days they set off for Brazil. They travelled down the coast visiting ports and gathering specimens of plants and animals.
The crew of the Beagle mapped the Falkland islands which Britain had got from Argentina just months earlier.
Then they travelled around the strait of Magellan. Here he saw native peoples who still lived in the rainforests. In Victorian times these people were known as savages to the Europeans.
Darwin arrived in Chile just as they experienced a terrible earthquake. He observed that the rocks around the harbor were now raised out of the water. He thought back to marine fossils he observed up on a hill but still couldn't figure out how the two were connected.
South American Fossils
Darwin explored Patagonia and studied fossils the Chilean government had preserved. There he saw fossils of the Megatherium (Giant Sloth) Glyptodon (Giant Armadillo) and the Macrauchenia (Giant Llama). The similarity between these fossils and their modern counterparts caused him to conclude that they were related.
If these creatures that were so different were clearly related, what might the possibilities over a further time frame Darwin wondered. He began to sketch a tree of life and theorized a single tree of life with the words "I Think".
He applied this theory to all living things and called the theory evolution.
"the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth."
This theory was very controversial at the time. People believed that wild animals had always been the same. Charles Darwin was a Christian and struggled with his scientific findings and what he believed about the bible. He was worried about sharing his findings because he knew people would think it was contradictory to the bible.
Evolution is the theory that all the kinds of living things that exist today developed from earlier types and are all related. The differences between them resulted from changes that happened over many years. The simplest forms of life arose at least 3.5 billion years ago. Over time they evolved into the millions of species, or types, of living things alive today.
Other naturalists of the time were on the verge of creating the same theory. Such as Russell Alfred Wallace.
Galapagos Islands
He traveled to the Galapagos islands because he had heard about their variety of unique species. We now know that this is because they've been geographically isolated for a really long time. They're several islands far from the shore but separated from one another.
He observed the giant tortoises, salt water lizards called marine Iguanas. He also studied the birds on the islands. A small bird called a finch, he paid close attention to. He noticed that the finches were slightly different on each island.
He had the revolutionary idea that they weren’t always that way. Maybe these species had changed over time in response to their environment, he thought. Maybe they were all related to a common type of finch.
Darwin realized that the beaks were good for getting different kinds of food: big heavy beaks for crushing tough nuts that grew on one island; little beaks for eating fruit; sharp beaks for probing cactus; and long beaks for catching insects on other islands.
Birds with slightly heavier beaks did better on the island with nuts, and they laid more eggs and had more chicks than other birds. These chicks also had heavier beaks, and did better than other birds, and laid more eggs.
He called this “natural selection”. The strongest adaptation reproduces most often until the disadvantages forms go extinct. One of Darwin's friends coined the phrase "Survival of the Fittest" after hearing Darwin's theory.
"It's not the strongest species that survives, nor the most intelligent but the one most responsive to change" - Darwin
"As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form."
That is: the best adapted variants of a species are more likely to successfully reproduce and pass down their genes.
These variations occur mostly by chance as genes copy themselves to make new cells. Mistakes, called mutations, sometimes occur during the copying process.
Most changes in genes either harm the individual or do not matter much. But some changes help an individual to survive and reproduce. For instance, an animal may have better vision or faster legs. These traits may help it find food and avoid its enemies.
Return to England
When Darwin returned to England he married his cousin Emma Wedgewood and wrote an account of his voyage. It was hugely popular and made him a respected biologist. However, he was hesitant in releasing his most revolutionary idea because it contradicted the bible which he always believed to be literal and infallible.
His theory was that life is in a constant struggle to survive and reproduce. Those that survive are more likely to reproduce. If a slight difference in a lifeform makes it more likely to survive then that characteristic will become more common in the population.
Therefore, animals are not fixed creations but under constant change even in nature. This was controversial because practically everyone believed animals had been created by God into their current forms. He was starting to think God hadn't created them at all.
The last push to get Darwin to publish his finds was the face that a fellow naturalist named Alfred Wallace had written to Darwin. They had both been studying for years and they both agreed with the theory. Darwin and Wallace presented their findings together but Wallace later stood aside because Darwin had far more evidence gathered.
The scientific community was split and many were outraged.
https://youtu.be/l3eYb32AYGc
Let's Test his Theory...
Comparable Anatomy
The simplest of all is a visual assessment. Based just off physical features, we compare characteristics such as if they have hair, wings, teeth, scales, paws, whiskers, and can estimate how related two animals are. These structures are also all made of the same substance: Keratin.
Easy- alligator/cat - cat/dog
Medium- deer/horse/cow - bat-bird - ichthyosaur/dolphins
People used to classify a bat as a bird.
Hard- Whale/hippo - platypus/duck/opossum
1. Similar Structures in all animals
Investigate
What would we expect to see if all animals were related? Transitional species. Fish that look like amphibians, amphibians that look like reptiles, reptile like mammals, human like mammals.
Snake transitions
Fish to Amphibian
Walking Fish-
Siren - In contrast to most other salamanders, they have external gills bunched together on the neck.
Salamander to Lizard
Salamanders are often mistaken for lizards, but the two groups are very different. Though they both have similar body shapes, lizards are reptiles (along with turtles, snakes, crocodiles, dinosaurs and, yes, birds) while salamanders are amphibians (along with toads, frogs, and a weird and rarely seen group called caecilians). This means lizards have dry scaly skin, while salamanders have moist, porous skin. Lizards all must breathe with lungs, just as humans do. Salamanders, on the other hand, can breathe through their skin, via gills, via lungs, or in some cases via their skin and lungs!
Another major difference between lizards and salamanders is their reproduction. Lizards have leathery, partly calcified (shelled) eggs that are typically buried in sand or dirt, but in a few species are hatched while still inside the mother before birth. Salamanders, as amphibians, mostly lay their eggs in water where the larvae hatch and after some time usually metamorphose and return to land. Lizards can be found most anywhere on land, while salamanders must stay where they won’t dry out: under logs or leaves, underground, or directly in water.
Reptile to Mammal
A few reptiles give birth to live young. Skinks and Boas being two. Some Skinks have been observed laying both eggs and live young in the same pregnancy.
The platypus is a duck-billed, beaver-tailed, otter-footed, egg-laying aquatic creature native to Australia. If its appearance alone somehow fails to impress, the male of the species is also one of the world’s few venomous mammals! Equipped with sharp stingers on the heels of its hind feet, the male platypus can deliver a strong toxic blow to any approaching foe. Penis but only for reproduction.
Tegu is a seasonally warm-blooded lizard
The naked mole rats are cold-blooded.
Marsupial - placental mammal.
mouse - lemur - monkey - ape - human
Embryology
Human embryos normally have a prenatal tail that measures about one-sixth of the size of the embryo itself. At between 4 and 5 weeks of age, the normal human embryo has 10–12 developing tail vertebrae. By the 8th week of gestation, the sixth to twelfth tail vertebrae have disappeared via cell death, and likewise, the associated tail tissues also undergo cell death and regress. In extremely rare cases these tail growth switches fail to turn off and a baby is born with a tail. Also in super rare cases but babies have been born with full body hair. Scientists attribute this to genes that lay dormant in us that get turned on for whatever reason.
Paleontology/Fossils
One type of evidence comes from fossils, or the remains of living things preserved in the ground or underwater. Fossils show that many species that once existed were quite different from any kinds alive today. Dinosaurs are an example of this. Many fossils also show how certain living things changed over time. For example, the bones of horses from more than 50 million years ago show that early horses were about the size of modern dogs. Bones from several later stages of the horse show that they got bigger over time. In fact today there is a horse-like mouse called a Chevrotain that lives in jungles of south America.
Tiktaalik - 2004 - Laryngeal nerve, hiccups,
Synapsids - all one type reptile teeth to multi-use such as canines. Chewing teeth, reptiles don't chew. Forward facing pelvis shows they didn't give live birth. Tasmanian Devil and Opossums are close.
Archaeopteryx - 1874 -Gliding first, then flight.
"Had it not been for the rare accident of the preservation of footsteps in the new red sandstone of the United States, who would have ventured to suppose that, besides reptiles, no less than at least thirty kinds of birds, some of gigantic size, existed during that period? Not a fragment of bone has been discovered in these beds. Notwithstanding that the number of joints shown in the fossil impressions corresponds with the number in the several toes of living birds' feet, some authors doubt whether the animals which left these impressions were really birds. Until quite recently these authors might have maintained, and some have maintained, that the whole class of birds came suddenly into existence during the eocene period; but now we know, on the authority of Professor Owen, that a bird certainly lived during the deposition of the upper greensand; and still more recently, that strange bird, the Archeopteryx , with a long lizard-like tail, bearing a pair of feathers on each joint, and with its wings furnished with two free claws, has been discovered in the oolitic slates of Solenhofen. Hardly any recent discovery shows more forcibly than this how little we as yet know of the former inhabitants of the world." - Darwin on archeopttix
Whales - Why mammals in the ocean? Pakicetids, Ambulicitus, genetically closest to Hippos. Tapir can dive and eat underwater. Think otters, seals, pelvis' in whales.
"Direct" descendance. Like going to meet your great grandfather for the first time at a party and seeing a man about the right age and looks like you. You'd be expected to assume but the truth is that your grandfather might have brothers or cousins.
Fossilization takes very specific circumstances,
Also, consider that evolution is a slow process with no direction or intent. Are you different today than you were yesterday? The purpose of natural selection is to reproduce and carry on your genes. If every day of your life were like a reproduced organism, you feel the same every day but be only slightly different. 365 days x 18 years is 6,570 generations. A son, father and grandfather would all look the same but their descendance be vastly different from them. In that time your body would develop from a baby, unable to walk or crawl to an adult. 6,570 generations at an average lifespan of 30 years (in the paleolithic era) would take less than 200,000 years. A Caterpillar's DNA has the blueprint to change to a butterfly.
Geologic Timescale
Vestigial organs
Some body parts of creatures give clues in themselves. Often animals will have body parts that they don't use but scientists believe they used to use.
Some horses grow extra toes. Back fins in dolphins. Such as tiny legs on the boa constrictor from when it had legs. Pelvis on whale from when it had legs. Eyes of a blind mole-rat. Underground creatures lose pigmentation and eyesight. Wings on birds that can't fly but used to. Vestigial Organs don't have to be useless to be vestigial. Anhinga - No waterproof wings, density helps drive and catch fish
DNA and Genetic Inheritance
Although the discovery of DNA occurred in 1869 by Swiss-born biochemist Fredrich Miescher, it took more than 80 years for its importance to be fully realized.
DNA is self-replicating material that’s in every living organism. It contains the instructions needed for organisms to develop, grow, survive, and reproduce.
Human DNA is unique in that it is made up of nearly 3 billion base pairs, and about 99 percent of them are the same in every human.
You can find the relatedness of two living things by testing their DNA. A DNA test can prove who your parents are. Or more impressively, show where your ancestors came from. The amount of difference between the DNA sequences of two animals tells us how closely they are related
When you take our our observations of physical appearance and set up predictions for DNA similarity, the majority of the time those results come back supporting the prediction.
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