Back to Science: DNA: Survival of the Cooperative

0
316

England’s Royal Society—the world’s oldest scientific academy in continuous existence—announced in July 2017 that The Selfish Gene topped their poll of 1,309 respondents as the most influential and inspiring science book of all time. Written by British zoologist Dr. Richard Dawkins and published in 1976, the main premise of his book is that genes—not the organisms in which genes reside—are the basic units of evolution upon which natural selection operates.

According to Dawkins, genes are the true “replicators.” As they evolve to ensure their own survival, they eventually create new species. The species they create, including Homo sapiens, are merely “survival machines—robot vehicles blindly programmed to preserve the selfish molecules known as genes.”

His gene-centered view of evolution was grounded in the worldview promoted by the Nobel Prize winning research team of James Watson and Francis Crick two decades earlier. In 1953, Watson, Crick, and their fellow researchers elucidated the double-helix structure of DNA, the primary molecular component of genes. At the time of their discovery, Crick proclaimed they had “discovered the secret of life.” By the end of the 1950s, scientists had deciphered the genetic code stored within the arrangement of nucleic acids in DNA, and the world of genetics and molecular biology inhabited by Dawkins came into being.

I wish to use Dawkins’ popular and influential ‘selfish gene’ perspective as the backdrop against which to contrast the evolutionary vision promoted by the American zoologist, the late Lynn Margulis. Let me first introduce her to you before I describe her insights into the evolution of life through symbiogenesis, the theory that independent and disparate organisms merge to form new species.

Lynn Margulis described herself as a “very bad student” while she was at O’Keefe Elementary School located in the south side of Chicago. “I couldn’t do what I was supposed to do, and I had to stand in the corner a lot.”  “I was getting in trouble because I was bored.”  After being “afraid of [losing] her life in Hyde Park High School,” her parents, Morris and Leona Alexander, transferred their young teenage daughter to the University of Chicago Laboratory Schools.

In this new, stimulating academic setting, the inquisitive Lynn “found life so interesting.” She went on to earn advanced degrees in zoology from several universities. During her distinguished teaching and research career, Dr. Margulis was elected to the National Academy of Sciences, became a fellow at the American Academy of Arts and Sciences, and was one of the very few American members of the Russian Academy of Sciences. President Clinton awarded her the National Medal of Science “for her outstanding contributions to understanding of the development, structure, and evolution of living things, for inspiring new research in the biological, climatological, geological and planetary sciences, and for her extraordinary abilities as a teacher and communicator of science to the public.”

Dr. Margulis’ interest in Russian science exposed her to the work of Konstantin Mereschkowski, a Russian biologist and botanist.  His research on lichens revealed that, contrary to their appearance, lichens are not themselves individual ‘plants,’ but a composite community of fungi interwoven with algae or cyanobacteria (or both). This biological pattern of cooperation among dissimilar lifeforms resulting in a ‘single’ organism exhibited by lichen- inspired Mereschkowski, in 1910, to propose the theory of symbiogenesis: evolution of larger, more complex cells (such as those found in plants and animals) can arise through establishment of interdependent relationships among smaller, less complex cells (such as bacteria).

Drawing upon the discoveries and theories of Mereschkowski and others (and before Richard Dawkins wrote his famous book), Lynn Margulis proposed that mitochondria and chloroplasts—specialized organelles with their own DNA found in the cells of animals and plants—were once free-living microbes. In the very distant past, small microbes entered the larger cells of the forebearers of today’s animals and plants. Instead of destroying or being destroyed by their host, mutually beneficial interactions developed. Today, mitochondria and chloroplasts—the remnants of these ancient microbes—have become essential components of animal and plant cells, respectively.

Think of that. Living within the cells of our bodies are the descendants of alien creatures that possess their own independent, bacteria-like genome! We cannot live without them, and they cannot live without us. We cannot survive and reproduce based upon our 23 chromosomes alone. We need the vital information stored within the mitochondrial chromosome as well. We are alive because our DNA and their DNA have learned to cooperate and carry out the vital metabolic and reproductive processes of life.

And this is to say nothing about the role played in maintaining (or disrupting) our health by the trillions of microflora that live in our gut. Their collective microbiome (the total number of different genes they possess) outnumbers our own human biome by about a factor of 100 to 1. Our good heath (and theirs) absolutely depends upon our DNA getting along with their DNA in a cooperative way. 

In summary, Margulis argued that development of symbiotic relationships is the major driving force behind evolution. In contrast to the classical Darwinian “Nature, red in tooth and claw” view of evolution powered by cutthroat competition for survival among individuals or groups of organisms (or their genes, if Richard Dawkins’ theory is correct), she felt “life did not take over the globe by combat, but by networking.”

I must say as fascinating and thought-provoking as these theories are, as a human being they leave me a little cold. At this season of Advent in the Christian calendar, I am reminded of a different, less materialistic worldview of life, ancestry, and genealogy. In the opening chapters of the Gospels of Matthew and Luke, we are given accounts of the forebearers of Jesus of Nazareth. Through these narratives, we are offered the sense that each and every one of us are more than reproductive machines. In addition to being vehicles for DNA as science tell us, we also are bearers of the sacred; and my heart is warmed by this affirmation of life. 

LEAVE A REPLY

Please enter your comment!
Please enter your name here