Too often, our perception of evolution seems to be a romanticized version of “Oh, a couple hundred of million years ago there were the fish, dinosaurs, amphibians, and reptiles- then the mammals came, and from then us humans came into existence.” Not only is this overly simplistic, but our sense of chronology leads us to overlook a major question in science today: how has evolution been so quick?

First, in general, evolution seems to be a very slow process. It can take 100,000 years from one species to evolve for another. An example of the long length of time evolution can take is respecialization. For example, our human toes evolved from the toes that apes have for grasping onto branches or swinging—but now, their purpose is different. This little change by itself took about 10 million years to emerge.

On the complete opposite end of the spectrum, evolution seems to abnormally fast at times. From sixty five million years ago, mammals first started evolving. Yet, the mammals in existence today are extremely diverse, not to mention the millions of species that have become extinct since sixty five million years ago. Even further back in time, evolution occurred at 4 to 4.5 times its normal speed during the Cambrian Explosion.

The best example of this quick evolution is ourselves—or more importantly, our brains. Homo sapiens evolved from Homo erectus about two million years ago, but our brain size has doubled twice and we’ve added fifty billion neurons to the Homo erectus brain. So unless we somehow added hundreds of thousands of new neurons to our brains every decade or so, we still don’t have an answer to how this took place.

This question of rapid, intense evolution can be looked at from a genetic viewpoint. It could be that only one gene mutation can cause intense differences. In a 2002 study, scientists modified a single mouse gene and created mice with brains 50% larger than normal. Perhaps this shows how our brains evolved so quickly. This theory of rapid evolution caused by genetic mutation is backed up by today’s theory: mutation occurs, and if it is favorable, that particular type of organism will naturally be selected to represent its species.

Another viewpoint altogether is that “quick” evolution is normal, and the question we should be asking is “Why is evolution so slow?” It takes about one million years for a lasting genetic change to take place, according to Josef Uyeda, and rapid genetic changes can take place within hundreds or thousands of years. His team thinks that because of these timespans, diversity and evolutionary change is actually much slower than what we’d expect it to be. Therefore, they concluded to reject that genetic mutations are the basis for evolution: rather, environmental change, predation or anthropogenic disturbance have to accumulate for true evolutionary change, which may take a long time.

Simply because we humans haven’t been around long enough, we are still struggling to find out exactly what rate of evolutionary change is “normal”. It’s very possible that a combination of all factors and theories may be the best answer we have for answering this question—but until we have the technology and research to back up our theories more, the question remains at this frustrating standstill.