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Happy Darwin Day: Top 10 Evolutionary Facts

February 12, 2014

Today is the 205th birthday of naturalist Charles Darwin. So let’s look into one of my favorite branches of science: evolutionary biology. Evolution requires Darwin’s discovery of natural selection, the process whereby organisms better adapted to their environment tend to survive and produce more offspring. Here is a list of my top 10 favorite pieces of evidence of evolution.

#10. Tiktaalik

Illustration of a restored Tiktaalik

When you see those evolutionary charts of a fish crawling out of the ocean for the very first time, the creature it’s referring to is the Tiktaalik. In 2004, fossilized remains of this adorable guy were found in Canada, dating back 400 million years. Tiktaalik isn’t just a funny looking fish, either. It’s fins have wrists and fingers, and it’s limbs could bear weight. It’s head could move on a neck, unhindered by gills. It also had primitive nostrils and lungs inside a broad ribcage.

Tiktaalik also happens to be one of my favorite words to say. Use it in Scrabble!

#9. Whale Feet

Whales and dolphins (cetaceans) are unique in that they are the only aquatic mammals that, well, look like fish. If mammals evolved independently of other sea animals on land, how did these mammals find their way back into the sea? Why do they look so much like fish? Where did their back legs go?

Well, their back legs are still there, in vestigial form. If you examine the skeleton of a modern whale, you will find floating bones where their hind legs used to be, 50 million years after returning to the ocean. Modern whales share a common ancestor in Indohyus, a small deer-like herbivore that found success hunting for food in water. So how did biologists connect this creature to whales? A unique bony structure around the ear that is found in both whales and Indohyus.

#8. Dandelion Sex

Photo of a dandelion puff

We all know how sex works, right? When a mommy and a daddy love each other very much, they both contribute genetic material in the production of a new life form. It’s important for natural selection because it introduces genetic variation. But not all living things rely on sexual reproduction to keep the species going. In other life forms, they have the equipment for sexual reproduction, but they never use it.

Dandelions have the usual sex organs found in plants that sexually reproduce: the stamen and pistil. But they actually reproduce asexually through a process known as apomixis. This means that at one point in time, dandelions produced offspring by exchanging pollen, but has since evolved the ability to go it solo. That’s right: dandelions have vestigial sex organs.

#7. Goosebumps

Photo of an arm with goosebumps

Erector pili are small muscles connected to the hairs of mammals that allows the fur to fluff up and insulate when cold, or to appear larger when threatened. It’s part of the autonomic nervous system, meaning it’s involuntary. Furry animals’ hair stands on end in reaction to outside stimuli like cold or fear.

We humans lost our fur millions of years ago, but our erector pili stuck around. Today we have goosebumps, a vestigial autonomic response. Goosebumps don’t make us any warmer, and they sure don’t make us look any scarier to an enemy. There is no point in our having them, but they’re still around, like our coccyx and our appendix, remnants of our every continuing evolution. It’s cool to be reminded of this every time I get a chill.

#6. Puppies!!

PUPPY IN A TEA CUP. SO CUTE.

The wide variety of dog breeds today is an example not of natural selection, but rather of artificial selection. It’s still a great example of how evolution works. In artificial selection, people select and breed traits, rather than the environment. Let’s be honest, the cutie above would last about ten minutes in the wild.

When we first began to domesticate dogs, we chose animals that were kinder and gentler towards humans. These domesticated puppies had small genetic variations, be it fur color or size. Larger dogs were bred with other large dogs, small dogs with other small dogs, and in a few thousand generations we have the wildly different Great Dane and Chihuahua. Darwin said of canine artificial selection, “The key is man’s power of accumulative selection: nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to make for himself useful breeds.”

#5. Antibiotic Resistance

Antibiotics are available only through a prescription, and even then doctors are hesitant to prescribe them. But why? They work, they are safe, and they are the only way to treat a variety of bacterial infections. The problem is we’ve unknowingly created a much more powerful bacteria that is resistant to our medicine.

Natural selection says that only the most well adapted creatures survive, and when it comes to antibiotics, that means only bacteria that is not effected by antibiotics will survive. Since this resistant bacteria is left behind, it breeds new generations of bacteria with this same trait. Today, over 24% of gonorrheal bacteria in the U.S. are resistant to at least one kind of antibiotic, and 98% of gonorrheal bacteria in Southeast Asia are resistant to penicillin.

The yearly evolution of the flu virus is also why you need a new flu shot every year.

#4. Lucy

Photo of the skeletal remains of Lucy

About 3 million years ago, Lucy walked the earth. Also known as Australopithecus afarensis, Lucy here is a very old member of our family tree, as well as an important link to our roots. She’s about one third our size, and has characteristics from both apes and humans. She walked upright on two legs, but it’s also believed that she spend a large amount of time in trees.

When she was discovered in Ethiopia in 1974, she was the most complete early hominid skeleton ever found, and she made major advancements in our understanding of human evolution. Her decent from the trees to the ground on two feet was one of the first steps (har har) to the evolutionary advantages that made humans one of the most successful animals on the planet.

Also, she’s named after a Beatles song.

#3. Feathered Dinosaurs

Archeyopteryx Fossil

The popular theory today is that the small dinosaurs who survived the extinction event went on to become birds (or rather, they were already on their way to becoming birds by the ti,e the asteroid hit). Dinosaurs didn’t disappear, they’re still here in bird form! There have been a few transitional fossils found, such as Archeopteryx, but where did those feathers come from?

The change from scales to feathers is a few simple genetic switches that natural selection flipped along the way (we’ll come back to this in a moment). Scales became filaments, and then feathers. Rather than grow horizontally, the scales began to grow vertically into long, hollow tubes. These filaments would eventually begin to branch, grow into different shapes and colors, and become more and more elaborate.

#2. Darwin’s Finches

Illustration of finches with different beaks.

These birds are often pointed to as Darwin’s version of Newton’s apple. After spending time on the islands of the Galapagos observing the wildlife, Darwin noticed the very different beaks in these otherwise similar birds. The finches on one island had thin, needle like beaks, while the finches on another island had large, powerful beaks. Why?

Well, on the first island, the most readily available food source was cactus nectar, while on the second island, the most common food source was seeds. One finch was best adapted to drink nectar, while another was best suited to crack hard seeds. Was it possible that finches who did not have the proper beak shape for the food sources on their respective islands starved and died off, and only those with the proper beak shape for their environment survived?

Tada, natural selection!

#1. Chickens into Dinosaurs

Illustration of a chickensaurus

Science requires that it’s theories be observable, testable, and repeatable. While we can witness evolution in small life forms like bacteria, in larger life forms it’s a bit more difficult, since it can take millions of years.

But now that we’re tinkering with genetics, it might actually be possible to show evolution in action… in reverse. Earlier we talked about a flipped genetic switch that turned scales into feathers. What if we were able to turn it off again? Or play with the code that turned a long tail into a shorter one? Or the switch that turned off teeth? The basic development for all these characteristics is still present in modern day birds, such as chickens. Right there in the genetic code, and even in embryonic development, there is evidence of these genetic switches getting flipped on and off. Developmental biologists are trying to reverse engineer a dinosaur. They’ve already managed the teeth.

Of course, the next natural question is what did dinosaurs taste like…?

Happy Darwin Day everybody!!

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