Now to present all of the evidence for evolution would take eons, and would bore even Darwin, Dawkins and Jay Gould, and so if you’re really interested in reviewing all of the overwhelming evidence for evolution, then this video isn’t it… what it is, however, is just nine lines of evidence from several fields of study which by themselves alone make a very convincing case.
So, where to begin? Well, the first two lines of evidence that I’m going to present both come from the comparative anatomy of whales to land mammals.
- We’ve long known that despite whales looking like fish, they’re mammals, because just like mammals, and unlike fish, they give birth to live young; feed their young milk via their mammary glands; breathe through two lungs rather than gills; have skin and hair rather than skin and scales; and they’re warm blooded.Now this alone strongly implies that they share a common ancestor with land mammals, but what really makes this suggestion even more compelling, and what I’ll offer as a first line of evidence, is the curious bone structure of their flippers…
Within their flippers, whales have, just like the forelimbs of land mammals, finger, hand, wrist, and arm bones, which can be easily explained if these bones are repurposed forelimbs, but are remarkably hard to explain if they’re not, as after all, these bones have very little in common with non-mammal fins, and yet a great deal in common with the forelimbs of land mammals.
- Furthermore, and to invoke a second line of evidence, whales have strange bones that look like shrivelled hip, thigh and shin bones where land mammals have hind legs, and some of these bones, such as these from a bowhead whale, even have what appears to be a ball and socket joint… further still, palaeontologists have found numerous species within the fossil record that have unique similarities with whales, but also varying sizes of hind legs.
Now once again, these bones make perfect sense if they’re vestigial and / or repurposed, but they’re very peculiar if they’re not.
- Talking of vestigial traits, and to present a third line of evidence, a superb example of one can be found in all mammals (including you), and it’s called the left recurrent laryngeal nerve. Without getting to technical, this nerve runs from the brain to the voice box, which should be a distance of a few inches, but instead it goes down into the chest, loops around a main artery, and then goes back up to the voice box, which in the case of the giraffe results in a 15 foot detour… “A mistake that no engineer would ever make!”
However, in animals without a neck, such as fish, the most direct route for this nerve is indeed by navigating round the artery, and hence, if mammals evolved from fish-like ancestors, we can easily explain why this absurd design exists. But if, on the other hand, we want to insist that it was deliberately created this way by a designer, then, well, we certainly can’t call this designer intelligent…
- Now the fourth and fifth lines of evidence I’m going to present both come from DNA sequencing, which for those you unaware, is the process of determining the precise order of nucleotides within a DNA molecule, which put simply means that we can compare the DNA of one organism to another, and in doing so, see exactly how closely related they are.
Needless to say, by doing this we have made many outstanding discoveries, but perhaps the most extraordinary, and what I offer as a fourth line of evidence, is that all living things are related, and that therefore all living things share a common ancestor. Seriously, the genetic similarity between you and a chimpanzee is 97%; with a cow it’s 80%; with a fruit fly it’s 60%; and with a banana it’s 50%.
Now most of us have heard this fact before and treated it like it’s just a bit trivia (including myself), but it’s far more than this – it’s unimpeachable proof that all living things share a common ancestor, and considering that all living things don’t look the same, it’s also overwhelming evidence of evolution.
- And the second line of evidence from DNA that I’ll present (and is the fifth in this video), is that the closest living relative to cetaceans (which is a class that includes whales), is the hippopotamus, a land mammal that just so happens to share many very rare commonalities with cetaceans. For example, both mammals are nearly hairless, do not have sweat glands, have remarkably thick bones, are encased in dense fat, have multichambered stomachs, give birth to their young underwater, feed their young under water, and communicate with their kin under water.
Now all of these similarities once again make perfect sense if cetaceans and hippos share a common ancestor (as their DNA screams, let alone suggests), but if they didn’t evolve from a common ancestor then all of these similarities are one hell of a coincidence, and DNA is greatest troll in history!
- The sixth line of evidence I’ll present is the artificial selection of domestic dogs. It’s no secret that most breeds of dog have the specific traits that they do because humans have deliberately (or artificially) selected which dogs get to reproduce, and in doing so, which traits are passed on to subsequent generations. For example, greyhounds have powerful legs, deep chests, flexible spines, and slim builds because humans have deliberately bred dogs with these attributes. The same is true of the tiny height of Chihuahuas – they are the result of humans breeding smaller and smaller dogs; and the same is also true of giant height of Great Danes – they are the result of humans breeding bigger and bigger dogs… it may not seem like it, but domestic dog breeds alone not only suggests evolution, they demonstrates it.Now as we’ve just explained, the selective pressure in the case of domestic dog breeds is artificial – it’s humans deliberately selecting which dogs get to reproduce – but this raises the immediate question of what exactly selects which organisms get to reproduce in nature, and the answer is… nature.
To further explain this, and to give you a few fascinating examples, I’m going to have Thomas from Holy Koolaid jump in – enjoy!
- The Peppered Moth: This first example is a bit of a celebrity in the world of evolutionary biology: the peppered moth. During the industrial revolution coal plants pumped out enough air pollution to kill the light-colored algae on trees and coat the foliage with soot. The light-gray moths which once blended in against the bark of the the trees were now exposed and were picked off by birds and other predators, but a small percent of the population had a rare genetic mutation that led to dark-colored wings. This beneficial mutation gave them a survival advantage, allowing them to camouflage in with their changing environment. Before long, the majority of the peppered moth population were the darker variety. But in the 1950s, clean energy reform reversed this trend causing the dark moths to be more vulnerable, leading to a resurgence in the lighter colored moths, who were still the dominant variety in the less-polluted countryside. Now that genome sequencing has become available and affordable for scientists, researchers at the University of Liverpool have pinpointed the exact mutation that caused the color change.
- Silent Crickets: Another excellent example of evolution in action is the silent crickets of Hawaii. To attract a mate, male crickets on the island of Kauai would rub their wings together creating a chirping noise. Several years ago a parasitic fly entered their ecosystem, honing in on the noisy crickets and laying larvae inside them that would eat them from the inside out. A rare mutation on the X chromosome caused some crickets to develop without the ridges on their wings required to chirp. Natural selection did its thing, and within just 20 generations, 95% of the crickets on the island were silent. When the flies migrated to Oahu a few years later, crickets there independently underwent the same lifesaving evolutionary change, via a different mutation.
- Ring Species: That’s all fine and dandy, creationists might argue. “But those are all examples of ‘micro-evolution’ not ‘macro evolution.’ Animals never change species or reproduce outside their kind.” Which brings us to ring species. For this, we’ll take a look at the Greenish Warbler of the Himalayas. Which biologists believe migrated south to north, branching east and west around the mountains. As time passed, they evolved and adapted to their new environments, and by the time they met up north of the Himalayas, they were so different that they were no longer able to interbreed. Each bird could reproduce with its southern neighbors all the way back around the loop. But they could not reproduce with each other – a textbook example of evolution in progress if I’ve ever seen one.
To learn the truth behind 9 misconceptions about evolution, check out the counterpart of this collaboration here: 9 Misconceptions about Evolution (Ft. Rationality Rules). If you enjoyed this video, please subscribe to Rationality Rules. Let’s see if we can get Steve up to 12,000 subscribers by the end of the week.
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