Evolutionary Mismatch Explained
A palm tree in New York and a fish out of water.
Posted May 29, 2019
This past week, I had the good fortune of teaching a group of nearly 100 bright and eager students at Chongqing University of Education, deep in the heart of China.
The class that I teach here introduces students to the basics of evolution (e.g., natural selection, adaptation, heritability, etc.) and it includes a large component that applies evolutionary ideas to issues of the human condition (e.g., physical health, mental health, education, etc.).
As a teacher, it is very important to me that my students understand the concepts that I am presenting. There is something of a language barrier, as these students are not native English speakers and their language differs from English in many significant ways. With this in mind, I regularly solicit feedback to make sure that the ideas I am teaching are understood. I also use stories or vivid examples to demonstrate many ideas.
The other day, several students reported that they did not fully grasp the idea of evolutionary mismatch (see Giphart and Van Vugt, 2018). In short, this idea pertains to conditions in which the current conditions of an organism are, in important ways, mismatched from the ancestral conditions of the organism that existed during the lion's share of that organism's evolutionary history.
As I write that now I think, "That makes a lot of sense!" But when I wrote this all up on the board and looked my students from Chongqing in the eyes, I came to realize that there is quite a lot of jargon and technicality in such a standard definition of mismatch. It occurred to me that some simple examples could shine a light on this concept for a broader audience. Following are the examples I put out there for my students:
A Palm Tree Will Die if You Transplant it in Upstate New York
In Chongqing, palm trees are pretty common. The city is generally hot and winter never brings ice and snow. Palm trees evolved in temperate, sub-tropical, and tropical zones around the world. They have long green fronds designed to soak up the sun's energy all year long, with no worries about needing to change into a state of hibernation during the cold winter months. There are not cold winter months. The nature of palm trees tells us about the ancestral conditions of palm trees. We can surmise that the ancestral conditions were warm and temperate. Palm trees evolved "for" such conditions.
What would happen if I grabbed a palm tree next time I visit Florida, put it in my luggage, and tried to cultivate that tree in my yard in upstate New York—a yard that is covered with about a foot of snow for about three months each year? You guessed it: It would die. That is because my yard is mismatched from the conditions that these trees evolved to exist in.
Monkeys Don't Do Well in Small, Isolated Cages
In 2012, the Bronx Zoo closed its famous Monkey House. Worse, perhaps, it converted the space into administrative offices. The closing of the Monkey House was part of a worldwide trend designed to reduce animal cruelty. Armed with insights from evolutionary science, we now know that all kinds of primates evolved under conditions that were highly social in nature. Further, their natural conditions include large expanses of land. Putting a primate in a small cage alone is no different than putting a human into solitary confinement (see Harlow & Suomi, 1971). Monkeys raised in isolation do not develop well in terms of their social and emotional responses.
A small cage at the Monkey House in the Bronx Zoo is, thus, highly mismatched from the environmental conditions that surrounded the evolution of the various primate species that were represented there. Monkeys don't do well in isolation because, under ancestral conditions, monkeys of various types lived in highly social conditions. These are the conditions that shaped the nature of monkeys that exist today.
A Fish Out of Water
For any students who did not understand the idea of evolutionary mismatch based on these first two examples, I came up with a little story that was designed to be simple and powerful in explicating the concept of evolutionary mismatch.
Imagine a little 5-year old girl. She has a pet fish in her room. She loves that fish and will do anything for it. One night, her grandmother reads her a bedtime story and then says good night.
The little girl gets to thinking: Wouldn't it be great to snuggle with her fish at night? The little girl had a net near the fish tank that was designed to scoop the fish up. She turned on a small light on her desk and she went scooped up her fish. (Remember, she is only 5.) She put the fish on her pillow and went to sleep.
I then ask my students this: What is the little girl going to wake up to? And why?
Here, all of the students understand the issue fully. Unfortunately, there will be a dead fish on the girl's pillow in the morning. This is because fish evolved under aquatic conditions. Fish evolved a suite of adaptations, including gills, so as to survive and thrive under water. These same features of fish are not adapted to terrestrial life. Gills are good for breathing in water. They are not good for breathing on land.
The fish dies due to evolutionary mismatch.
Humans in Modern Urban Settings
From this point in the lesson, all of the students are ready to think about mismatch as it applies to humans. Especially humans in large modern cities (such as Chongqing). How is life in a large modern city mismatched from the ancestral conditions that surrounded our ancestors?
We came up with several ways, including:
- People are now surrounded by many strangers.
- People now only live near a handful of kin.
- A high proportion of modern diets includes processed food.
- Modern education systems do not match ancestral ways of learning.
Evolutionary mismatch is a powerful concept to help think about modern human problems. As I found out teaching students in Chongqing, the terminology included in a standard definition of evolutionary mismatch may be difficult for non-native speakers to understand. But the concept is so accessible and can be demonstrated using various simple, vivid examples such as planting a palm tree in New York or trying to have your pet fish sleep on your pillow overnight.
Giphart, R. & Van Vugt, M. (2018). Mismatch. Robinson.
Harlow, H. F., & Suomi, S. J. (1971). Social Recovery by Isolation-Reared Monkeys. Proceedings of the National Academy of Science of the United States of America, 68, 1534-1538.