Our environments demand that we evolve constantly and also determine what we evolve into. Since our environments are constantly changing, we are in a constant state of evolutionary trial and error. Genetic mutations improve each individual formula by finding what does and does not work. The Darwin documentary gives many great examples of this process, from the 350,000 kinds of beetles and 28,000 species of fish known to be on Earth, to the masseter muscles of humans allowing for larger brains versus those of chimpanzees. These are all beautiful marvels of diversity, but everything has to do with the environment.
For instance, the ancient Tiktaalic creature, a fish with eyes on the top of its head and the leg power to flop onto land, is thought to have evolved out of necessity due to an underwater environment filled to bursting with predatory fish. For the Tiktaalic, the situation required it to, “get bigger, grow armor, or get out of the way.” This revolutionary, evolutionary act of avoidance became the spider-webbing source of all land-walkers. One need go no farther than the most commonly used example of adaptation—the peppered moth during the industrial revolution—to see how Tiktaalic’s response prevails to this era. Or even the mice of Arizona mentioned in the video, which have either black fur or tan fur depending on the color of desert soil they roam.
Some traits remain behind, but the tried and true stay universal. For instance, Homeobox genes govern the body plans of all creatures along their anterior-posterior axis, ensuring the wings, arms, and legs all go in the right places. On the other hand, unneeded genes are tossed out, such as the spikes of the lake-occupying Stickleback Fish, which no longer has stickles on its back. Its ocean counterpart, however, still has these namesake pointy protrusions due to an open, dangerous environment with bigger mouths to foil. Even the whale is a good example: its vestigial leg bones have diminished due to the ocean’s demand for a more streamlined form and fins only. Small changes in the recipe equal better navigation of the world.
Therefore, our environment truly does determine what we are and who we will become. What will humans look like in 2,000 years? How will we slowly adapt to an environment in which constant physical exertion is no longer pivotal to the survival of larger and larger portions of the population? Will other species evolve bigger brains and begin to run aside humanity? These are fascinating questions that, as the video demonstrated, will only be answered in the vast oceans of time.