by James Morris
How much do you know about evolution? Take the following quiz to find out.
This week was the start of the semester at Brandeis and many other colleges. On the first day of a class on evolution, I began by asking the students a series of questions to try to get them curious about what we will be studying together. Then I asked the students to close their notebooks, take out a pencil and sheet of paper, and answer seven true-false questions about evolution.
This had a chilling effect in the classroom – a pop-quiz on the first day? But I had something entirely else in mind.
Here is the quiz. Try it for yourself before reading the answers.
For each of the following statements, indicate whether it is true (T) or false (F).
_____ Humans evolved from chimpanzees.
_____ The only mechanism of evolution is natural selection.
_____ Evolution explains how life originated.
_____ A child growing up and the leaves of a tree changing color in the fall are examples of evolution in action.
_____ Organisms become more complex as they evolve over time.
_____ Mammals are the most diverse group of organisms alive today.
_____ If you watch the history of life on Earth play out over 60 seconds, the first modern humans would come on the scene at the very end, around 50 seconds.
Ready for the answers? Here they are:
__F__ Humans evolved from chimpanzees.
__F__ The only mechanism of evolution is natural selection.
__F__ Evolution explains how life originated.
__F__ A child growing up and the leaves of a tree changing color in the fall are examples of evolution in action.
__F__ Organisms become more complex as they evolve over time.
__F__ Mammals are the most diverse group of organisms alive today.
__F__ If you watch the history of life on Earth play out over 60 seconds, the first modern humans would come on the scene at the very end, around 50 seconds.
As you can see, it turns out that none of these is true; they are all false. In fact, these are common misconceptions that many of us have about evolution. How did you do?
I didn’t actually grade the quizzes, or even collect the answers. But that moment of fear that we all feel when a pop-up quiz is announced had a real effect: Students took it very seriously, and then were surprised to learn that they too carry around at least some of these misconceptions.
Let’s consider each in turn:
- Humans evolved from chimpanzees.
Chimpanzees are the closest living relatives of humans. What this means is that humans and chimpanzees share a common ancestor, and that this ancestor lived more recently than the common ancestor of humans and any other organism, about 5-7 million years ago. However, we didn’t evolve from chimpanzees, since chimpanzees are alive and well today.
This slip of the tongue reveals a fundamental misunderstanding of the way that evolution works. It would be like saying that you are descended from your cousin, when in fact you both share a common ancestor – your grandparents.
- The only mechanism of evolution is natural selection.
This one is a bit more complicated. Most of us understand that natural selection is a mechanism of evolution. There is variation; some of this variation is passed on to the next generation; and some of this heritable variation gives organisms a slight edge in terms of survival and reproduction. The result is that populations change and organisms become better adapted over time.
However, natural selection is not the only mechanism of evolutionary change. In the early 1900s, Godfrey Hardy and Wilhelm Weinberg independently recognized that the genetic make-up of a population tends to stay the same under certain conditions and therefore evolution occurs when these conditions are not met. There are five of these conditions (and therefore five mechanisms of evolution).
Selection, it turns out, is just one of the five. The genetic make-up of a population can also change, for example, due to chance over time. But selection is particularly important, and receives most of the attention, because only selection results in adaptations, the close fit between an organism and its environment.
- Evolution explains how life originated.
How did life begin on Earth? This is a question fraught with uncertainty. How did life evolve once there was life? This is much better understood.
The two questions are both interesting, both the subject of lots of research. But the questions (and the answers) are fundamentally different. The reason is that the processes by which we get life from non-life are not the same by which life changes over time. However, by conflating the two, it makes it seem that our understanding of evolution is just as uncertain as our understanding of origin of life. It’s not.
- A child growing up and the leaves of a tree changing color in the fall are examples of evolution in action.
A child growing up into adulthood and the leaves of a tree changing color in the fall are both examples of change over time, but they are not examples of evolution. Evolution by natural selection is a theory about populations, not individuals. In other words, populations change over time, and this change is evolution.
Individuals may change over time. But, this change is not evolution because, for the most part, these changes are not passed down to the next generation. For example, if you suffer an injury or get a tattoo or color your hair, you won’t pass these traits on to your children.
However, many popular visualizations of evolution show changes occurring in an individual over time, just like the leaves of a tree. There is a well-known Guinness advertisement showing three people at a London pub taking a sip of beer and then morphing backwards over time until they are fish (mudskippers, to be exact), ending with the line, “Good things come to those who wait.”
And Homer Simpson goes forward through the entire history of life, from a single-celled organism to a human, while staying unmistakably Homer. Marge asks, as Homer finally arrives on the couch, “What took you so long?”
These are fun, but problematic because they depict changes in individuals, not populations over time.
- Organisms become more complex as they evolve over time.
This one is based on the erroneous, but stubborn, idea of evolution as progress. Evolution doesn’t proceed toward a goal and doesn’t make organisms “better” than they were. Natural selection leads to adaptations. And, as environments change, so do organisms. In addition, there are many examples of reversals in evolution. For example, cave-dwelling mammals lose eyes and the ability to see, and marine mammals lose limbs.
- Mammals are the most diverse group of organisms alive today.
Mammals are familiar to us, but are not the most diverse group of organism in terms of number of species. That prize goes to the insects, and specifically to beetles. There are perhaps 5,500 species of mammals that have been named, compared to about a million species of insects. Among the insects, fully half are beetles. So beetles make up a quarter of all named species on Earth! This is why J. B. S. Haldane, when asked about what he learned about the creator after a lifetime of study, quipped, “He must have had an inordinate fondness for beetles.”
- If you watch the history of life on Earth play out over 60 seconds, the first modern humans would come on the scene at the very end, around 50 seconds.
Modern humans arrived late in the history of life on Earth. Very late. First life evolved about 4 billion years ago, and modern humans about 200,000-300,000 years ago. If the history of life played out over 60 seconds, we wouldn’t even have a second time.
How can we unseat strong misconceptions that many of us hold? In The Unschooled Mind, Harvard professor Howard Gardner found that schooling often does little to budge misconceptions that are in place before school starts. He famously asked students schooled in science seemingly simple questions such as what causes the seasons or the phases of the moon, and found that they often reverted to explanations that were in place as five-year-olds.
One way to have students literally sit up and pay attention is to surprise them with a pop-quiz that forces them to confront these misconceptions head on. But the mind is powerful and tends to seek simple ways to understand the world around us over more complicated or subtle ones.
So it’s a bit of an uphill battle. Against gravity, which we can’t see, even though we see its effects everywhere, everyday.
Just like evolution.
© James Morris and Science Whys, 2015