Neil Shubin has greatly expanded our knowledge about the origins of life. This week Shubin, a professor at the University of Chicago, unveiled an incredible discovery: the missing link between ancient sea creatures and the first creatures to walk on land.
"The world is filled with puzzles, all kinds of interesting questions and it's our challenge to figure them out," Shubin said. "It's not just like this static file cabinet of things that human beings know. It's ever expanding."
Shubin said his find opens "a remarkable window on one of the major events of the history of life on Earth. We are dealing with the transformation from life in water to life on land. Those animals that took the first steps on land are the animals that evolved limbs."
Shubin's discovery is a 375 million-year-old fossil called tiktaalik. Many scientists agree that tiktaalik further proves Darwin's theory that some sea dwellers evolved to become land dwellers.
"Tiktaalik has bones that correspond to shoulder, elbow and wrist," Shubin said. "We can see what the joints looked like, and we can put those joints together to understand how the fin worked, how the animal moved. And when we did that we found that this was a fish that could do a form of push-up."
Shubin and several colleagues spent six years scouring the Canadian Arctic for evidence of the missing link.
"The Arctic is a real promising hunting ground," he said, "and I think that is why we stuck with it for so long."
It was promising also because no one had really looked there before. It is a very difficult place to work. For all but one month a year, it is covered in snow.
"Another thing to get used to in the Arctic is being in the food chain," Shubin said. "There are polar bears there, and polar bears eat people. So we carry weapons."
A 45-year-old father of two, Shubin grew up near Philadelphia. His love of archaeology began there, where he searched for remnants of America's origins. While at college in New York, he spent most of his time at the Museum of Natural History where his curiosity about evolution began to evolve into a lifetime of work. "I was interested in the big steps, the big jumps," he said. "How did fish evolve? How did things evolve to walk on land? How did birds evolve to fly?"
Twenty-five years later, he has shed some light on one of nature's best kept secrets.
"The transition from life in water to life on land is a piece of our own past," he said. "We are uncovering our own past, our own past when we were fish."
ABC News' Elizabeth Vargas reported this story for "World News Tonight."