“A zoo offers a great variety of creatures that are all distinct in many ways. But let’s not focus on what makes them distinct; to pull off our prediction, we need to focus on what different creatures share. We can then use the features common to all species to identify groups of creatures with similar traits”

One of the central tasks of biology is to group similar creatures together, creating categories of species based on what traits define a group of different animals. Evolutionary biologists such as Shubin can then use these groupings to deduce which creatures evolved from which, assuming that creatures with more singular characteristics (like humans who walk on two legs) evolved after other animals. 

“Every rock sitting on the ground has a story to tell: the story of what the world looked like as that particular rock formed. Inside the rock is evidence of past climates and surroundings often vastly different from those today.”

Shubin’s work as a paleontologist and evolutionary biologist is often based on analyzing rocks for information about the Earth’s ancient history. Since rocks form in particular climates and time-periods, each rock contains its own story about life on Earth long ago.

“Like a fish, it has scales on its back and fins with fin webbing. But, like early land-living animals, it has a flat head and a neck. And, when we look inside the fin, we see bones that correspond to the upper arm, the forearm, even parts of the wrist”

This passage describes Shubin’s Tiktaalik fossil. The creature is unique as it shares characteristics with both fish and reptiles. The fossil offers important information about how ancient fish began to evolve limbs and leave water to walk on land.