Species go away forever for a lot of different reasons: ice ages, catastrophic meteor collisions ... and, of course, there's the persistent threat of one particular predatory, parasitic, highly adaptable species: Homo sapiens (that would be you and me).
We didn't do all these species in, but we've certainly had a hand in some of their demises.
1: The Dodo (Raphus cucullatus)
Oh, dodo. Poor dodo. The flightless bird, native to the island of Mauritius, in the Indian Ocean, was known to mankind for less than 100 years ... but that's all it took for us to eradicate the species.
It wasn't so much that humans killed the stubby, rotund birds directly, but our decimation of their habitat and food source did an awful lot to hasten their demise.
And then there are the pigs, dogs and other predators that we introduced to the isolated island, where they ravaged the birds' nests and generally harassed them.
The last dodo died sometime in the late 17th century. Since then, the bird (a relative of pigeons and doves) has become a poster child for extinction and a reminder of the havoc we can wreak as human beings.
2: The Dinosaurs, all of them
They were gone long before the first human graced the planet, yet they've still managed to capture the hearts of school kids across the globe, thanks to the toys, cartoons and museums full of skeletons extolling their prior existence.
And wouldn't it be nice if the dinosaurs all lived together like they do in the movies, playing, fighting and hunting? Think more The Land Before Time and less Jurassic Park, more plant-eaters and fewer Velociraptors. The reality is that many of the more famous dinosaur species never even crossed paths.
Stegosaurus lived way before Triceratops showed up; Tyrannosaurus wasn't feasting on Apatosaurus (he had been extinct for millions of years by that time); and they were all gone by the time human beings came around. But never mind that.
They've captured our hearts in a way that no other extinct animals have ... and when it comes down to it, we should probably just be thankful that we never knew those Velociraptors, right?
3: Passenger Pigeon (Ectopistes migratorius)
How do you go from being the most common bird species in North America to being nothing more than a sad footnote in American history?
Well, it helps if you taste good.
While passenger pigeons were hunted as a crop nuisance for years, it wasn't until pigeon meat got popular that things took a turn for the worst. It also sure didn't help that westward-bound settlers were chopping down the birds' habitat at an alarming pace.
Over less than 100 years, the species that once blackened the sky as it roamed in flocks numbering in the billions was suddenly in a lot of trouble.
The last passenger pigeon died in a Cincinnati zoo in 1914. Her name was Martha.
4: Great Auk (Pinguinus impennis)
At nearly 3 feet tall, the great auk was a large bird, indeed, but a story involving one of the last living auks was perhaps more unusual than its size.
The last known auk in Scotland was executed in 1840, after local villagers thought that it was a witch. Really.
While the auk was unlikely actually a witch, the penguin-like species was the last flightless bird in the Northern Hemisphere and once inhabited islands off the coast of northern Europe and northeastern North America.
Hunted as food and bait, the last auks were observed in 1844 off the coast of Iceland. The nesting pair were killed by fishermen, who made sure not just to kill the birds for their pricey meat, but also to crush their lone remaining egg. Thanks, guys.
5: Tasmanian Tiger (Thylacinus cynocephalus)
The thylacine looked like something of a cross between a tiger (due to its stripes) and a dog (in terms of its build). However, it was in fact a carnivorous marsupial, complete with pouch.
Native to Australia, the thylacine was last seen on that mainland over 2,000 years ago. The tiger was hunted to extinction by the indigenous population, but had a safe haven of sorts in the island of Tasmania ... or at least it did until Europeans showed up.
Their heavy-handed hunting, prompted in part by farmers' protection of their livestock, brought the animal to minimalist numbers by the early 20th century. By then, efforts to protect it were too late.
The last one was caught in 1933 and died three years later in a zoo in Hobart, Australia.
6: Large Rodents (Josephoartigasia mones)
If you've spent much time in a large city, you've probably seen those large, inflatable rats that striking workers put up while protesting. Ever wonder what it would be like if that rat came to life?
The rodent that lived in South America between 2 and 4 million years ago was closer in relation to a guinea pig than a rat; however, fossilized remains discovered in 1987 indicate that Josephoartigasia monesi was 10 feet long and likely weighed over 1,000 pounds.
Yikes. Good luck finding an exterminator for that one.
7: The Saber-toothed Tiger (Smilodon)
Though there were once many species of saber-toothed cats, the most famous is Smilodon.
He's the cat you see in picture books about prehistoric times, the one that got trapped (and preserved) in the La Brea tar pits while hunting mammoths. He's been gone from the Earth for over 10,000 years now, but those huge canine teeth, now believed to be used primarily for (eek) ripping open prey, still inspire awe.
The cat itself was about the size of a modern-day lion (if not a bit shorter), but far more robust. Since the fierce predator once roamed freely in the grasslands and forests of North and South America, we should probably just be happy we're not living in the Ice Age.
8: Baiji White Dolphin
The Baiji white dolphin is one of the most recent species to fall victim to human civilization.
Native to the Yangtze River in China, the freshwater dolphin was nearly blind and quite intelligent. A 2006 expedition searched the Yangtze for six weeks, but didn't find any Baiji, marking an end to a species that had been a part of the river since ancient times.
The aquatic mammal had fallen prey to hunters and fishermen, as fishing boats, complete with their entangling gear, began to crowd the river in the 1950s and '60s. A reported sighting in 2007 raised hopes, but most scientists argue that if a few of the Baiji do still exist, their numbers are most likely so small as to make them "functionally extinct," meaning they're beyond a comeback.
9: The Quagga
Once upon a time, the quagga was standard fare in European zoos. The caramel brown zebra subspecies has been missing from the planet since the 19th century, but that hasn't stopped some from trying to resurrect it.
Since 1987, the South Africa-based Quagga Project has been using selective breeding among plains zebras to mimic the animal's unique markings -- most notably, its distinctive striping pattern, which starts at the head but extends back only as far as mid-body.
Native to South Africa, the original quagga was hunted to extinction for its meat and hide. The last one died in an Amsterdam zoo in 1883.
10: Steller's Sea Cow
Land cows eat grass, but these "sea cows" once grazed on kelp in the Bering Sea.
A relative of the smaller, much-beleaguered manatee, the gentle sea cows were over 25 feet long and may have weighed as much as 10 tons.
By the time German naturalist Georg Steller found and described them in 1741, their population was already threatened, perhaps due to hunting by indigenous peoples.
Their extermination would quickly continue with the arrival of Alaska-bound European fishermen and seal hunters. The sea cows were rapidly hunted for food, skins (used to make boats) and oil (for lamps), and by 1768, less than 30 years after Steller found them, the Steller's sea cow was extinct.