From Bananas to The Bomb: The Strength of Diversity
My friend has two dogs. One is a purebred pug with a cute pushed in nose and a charming personality. The other is a sleek, and playful husky-lab cross. She loves to run fast and dig holes. The pug cannot keep up with his mutt friend because he has some serious health issues. He comes from a long line of parents who were too closely related. The Husky-Lab Mutt has no health problems and is brimming over with energy, in part because her parents and grandparents were different genetically. She has what scientists call Hybrid Vigor.
Hybrid vigor refers to hybridization or crossing of different variations of a plant or animal. It was observed by plant and animal breeders long before we understood the genetics involved. But today we can explain at least some of the genetics of hybrid vigor. All higher plants and animals have two pairs of genes, one set from each parent. You can think of it as a backup system to ensure that the all-important genetic material has each needed instruction for the cell. These gene pairs have dominant genes which are always expressed and recessive genes which are only expressed when it is teamed with another recessive gene. When a recessive gene codes for a disease, a dominant partner becomes especially important because it can compensate for the disease-causing gene. This is the most obvious example the mechanics of hybrid vigor. But there are many other gene combinations that have more subtle effects on the health and vigor, also called fitness. Inbreeding is the opposite of hybridization. Purebreds like the pug have ancestors bred for generations with close relatives. Here the recessive genes tend to pair up more and more so they can be expressed leading to things like heart defects and skeletal deformations. These specific problems are found in our shrinking population of Florida Panthers who are forced to inbreed.
Hybrid vigor is one example of biodiversity which can exist at many different levels in nature. We just looked at genetic biodiversity. But it is also important at the level of the groups of animals or plants of the same species called populations. Diversity at this level helps make the population more stable and more apt to survive a change in the environment. The opposite of this is what we call a mono-culture in modern day agriculture. This can be a field of corn, or a forest, or a banana plantation. The more identical the genes are in these populations the more vulnerable the organisms are to disease or other types of environmental variations like temperature and rainfall. If a disease attacks a forest that has been planted from cloned trees with identical genes and all those trees are easily killed by that disease organism, you may lose the whole forest instead of a percentage of it. There are no “Outlier” trees whose genetic diversity make them more resistant to disease. One sad example of this is happening right now in banana plantations around the world. They are losing their trees to a fungus disease that is killing off whole fields of cloned banana trees. Unfortunately, the entire world uses one particular banana variety that was high yielding until a fungus evolved that could kill them all. Don’t expect cheap abundant bananas in the coming years because farmers around the world will be struggling with reduced yields and the need to transition to a resistant banana strain or a new crop. We don’t seem to learn from history as this is the third global round of banana clones wiped out by disease. Remember the song “Yes There Are No Bananas”? That was the first banana apocalypse back in the 1930’s. More diversity could have made these losses less apocalyptic
An entire ecosystem made of many populations living together is also more stable when it is diverse. A natural environment where many species live together is more stable than environments like our cloned banana plantation or corn field with identical plants and fewer species. In a diverse ecosystem, environmental change may remove a few organisms but enough remain that it continues to function and the system can recover.
Can we apply these biological terms to human society? Is a diverse human society more stable in terms of surviving changes and more apt to thrive and meet new challenges? Should modern societies value diversity or should we work to become a purebred mono-culture? Nature certainly suggests that diversity is strength. And we know it is true for human health. A classic example of this is Queen Victoria and her close relatives who ruled Europe in the late 19th Century. Arranged marriages for political reasons were common. Like the pug and the panther, arranged marriages led to inbreeding so all the rulers in Europe were close cousins. Consequently, certain diseases caused by recessive genes began to show up. Queen Victoria’s granddaughter Alexandra married Tsar Nicholas in 1894, cementing an alliance between Britain and Russia. A deadly gene inherited from Queen Victoria and carried by Alexis and many of her royal cousins across Europe showed up in her only son. Because his genes were the male XY form there was no protection from a dominant companion X gene inherited from Alexis. His mother and sisters were unaffected as they had a healthy X chromosome from their female XX chromosomes to cover up the devastating effects of the disease. The little prince suffered from Hemophilia, a disease that prevents clotting of the blood. The active child was constantly ill. Any bruise continued to bleed and there was no way to stop it using medical techniques of the time. The prince was often in terrible pain and nearly died multiple times. Some historians say that the royal family ignored the signs of the coming Russian revolution in part because they were so distracted by the health struggles of their only son.
But can we take this further? What does biodiversity at the ecosystem level tell us about how well a diverse society functions versus one where the kinds of people and the kinds of behavior acceptable is narrowed to meet standards of “purity”? Do we want to encourage a diverse environment in hopes of seeing hybrid vigor at the level of our social ecosystems? Great innovation and artistic achievement in history appears to correlate with active trade, the mixing of ideas, and mixing of populations. For example, the world in the 6th century BCE civilization flourished because trade, migration and mixing of ideas produced new ways of thinking and seeing the world. This is the time of the golden age of Greece, The rise of Buddhism in India, and Confucianism in China. The scientific revolution in the 13th to 18th centuries in saw Europe open up to an increase of trade in ideas and goods on the silk road from the East, and through Moorish Spain from the middle East and Africa. These contacts influenced scholars and craftsmen and gave them tools like Indian numbering systems, Chinese paper and Arabic Algebra. The philosophy and mathematics of ancient Greece were rediscovered through Arabic translations. These diverse contacts provided foundations for the rise of modern science and the industrial age.
Finally, what does biodiversity tell us about the value of immigration and conversely about banning immigrants or excluding certain human groups from a society today?
Let’s look at production of The atomic bomb in World War II. There was a race between US and Nazi allies to produce the bomb and win the war. Opposing leadership of the bomb building teams were Heisenberg on the German side and Oppenheimer in the US. In the US over 100 gifted scientists who were refugees from Nazi Germany worked on the Bomb together with many Americans. Roosevelt trusted science and his scientists and the US poured all their resources behind this project. On the other hand, the Nazis did not fully trust Heisenberg because of his ties with Jewish scientists. Essential support was withheld. The diverse American team produced a working bomb when the Nazis were still years behind. The immediate results were a clear win for the US allies in World War II and no atomic bomb in Hitler’s hands.
In the long term nuclear energy and weapons are, to say the least, problematic. But is it better to have such scientific power in the hands of a few who think that most of the world’s humans are inferior and expendable, or under the control of a diverse society that can bring many points of view and skills to bear?
To some extent these factors are now under our control. Do we want a constricted purebred culture to be the norm in the US or are we looking for hybrid vigor in our ideas, in our commerce and in our human capital?