Huge tracts of our planet have been in a deep freeze for tens of thousands of years. After the most recent ice age, some of the most northerly land masses in the Northern Hemisphere remained frozen. These were referred to as permafrost regions, the Earth’s deep freezer. Over the past few decades, global warming is decreasing how much of the planet has permafrost: the deep freezer is defrosting. What is left of the permafrost holds answers about the state of our planet tens of thousands of years ago. Scientists can drill into the permafrost to retrieve frozen relics of a world long gone. Modern equipment can determine if the material retrieved was frozen 500 or 50,000 years ago. Aside from providing a window on our planet’s past, permafrost samples have made us confront unexpected consequences of global warming.
A recent sample from Siberia revealed some very old life forms that flourished 24,000 years ago. One of the creatures frozen in time was a microscopic animal, called a rotifer. Rotifers are tiny creatures, less than a millimeter long, but they are in every sense animals. They have a head, a body, and a foot. They eat, move, defecate, and make baby rotifers. There is evidence that they arrived on the surface of our planet at least 25 million years before our distant relatives stopped dragging their knuckles on the ground. Finding a rotifer in the Siberian permafrost was not surprising. Everything sitting outside without a heavy coat or a campfire in that region 24,000 years ago would quickly transform into an icicle. The rotifer was no different. It had no antifreeze or self-heating system to protect it. It was frozen solid for 24,000 years. To the amazement and probable horror of the scientists studying this speck of life, a little heat revived it. Having been unequivocally dead for 24,000 years, the rotifer somehow restarted its engine and started eating, moving, defecating, and making baby rotifers.
Science fiction writers anticipated this version of the Undead as early as the 1950s. A low budget horror movie, entitled The Thing, depicted the re-animation by way of an electric blanket of an unfriendly, alien creature frozen in the Arctic ice. The creature proved to be a blood-sucking plant-like organism “from another world.” (Fun fact: the monster was played by James Arness, an actor more famous for his role as Marshall Matt Dillon in the long-running television series Gunsmoke.) The plant demon did not wilt with freezing and produced seeds that could grow into nasty weeds just like their flash frozen father. The men and women faced with this extra-terrestrial legume decided to save the world by sautéing it.
Just as worrisome as the crash landing of a blood-sucking plant on our shores are the implications of the more humble rotifer’s resuscitation. If a tiny and innocuous animal frozen in ice for 24,000 years can re-awaken and join the life forms now crowding our planet, what are the implications for viruses, bacteria, and less friendly creatures being released from their lengthy slumber in the Earth’s deep freeze? Instead of searching for the Covid-19 virus in exotic animal markets, perhaps we should check the mud we just scraped off our boots from the recently unfrozen Arctic plains.
Rotifers are thousands of times more complex than bacteria, and bacteria are thousands of times more complex than viruses. If the rotifer could make it through a 24,000 year winter, the viruses and bacteria that flourished long before humans started burning down the rain forests and sharpening sticks to kill each other should have no problem re-emerging from the primordial muck of Siberia or Alaska.
Humans have died by the millions when exposed to unfamiliar viruses and bacteria. Covid-19 is only the most recent of these grim reapers. No organism has yet proven adequately lethal to kill off our species, but some have come close. Before the development of effective antiviral agents, only one in twelve people infected with the human immunodeficiency virus (HIV) had natural resistance sufficient to protect them from developing AIDS. Antibiotics are now available that limit the spread and lethality of the bubonic plague, a rapidly lethal bacterial infection spread by infected fleas. Armies have been defeated by the influenza virus, and entire societies have been erased by the smallpox virus.
With every epidemic, there have been survivors equipped with genetic peculiarities that have allowed them to live on and pass their natural resistance to their offspring. That some of us will survive every pandemic is not a sure thing. The more similar our genes are in communities around the world, the more vulnerable we are to a germ (bacteria) or virus that can kill every person exposed to the infectious agent. If your parents came from opposite ends of the earth, you are likely to have picked up from one of them a gene that conveys protection against a long forgotten infectious agent. Conversely, if your parents were closely related, you will lack the gene diversity that may be vital during a pandemic.
The interbreeding of widely diverse communities has helped assure the survival of our species, but the gift of genetic resistance is not a sure thing, especially if the infecting organism is different from anything that humans have previously faced. With HIV, we were fortunate to have and to develop antiviral agents. We were fortunate to have people resistant to the virus. I do not doubt that in the not too distant future a vaccine against HIV will be developed. In the absence of antiviral agents, containment measures, and individuals with resistance, this virus might well have killed all humans. Nature finds a way to spread unfriendly things.
As the permafrost disappears, our natural resistance to ancient infectious agents will be tested. This challenge will be complicated by changes in our atmosphere: the melting permafrost is also releasing large amounts of trapped methane, a green house gas much more potent than carbon dioxide. Innumerable species in our environment have already succumbed to these global changes. If we can stop the global warming we are currently causing before it becomes irreversible, our great grandchildren will have a world much like our own. If we do not stop the global warming, it is unlikely our great grandchildren will survive long enough to have their own great grandchildren. I believe we can and shall find a way, but we must recognize that Nature has no more affection for us than it had for the dinosaurs or, for that matter, for the rotifer.
Dr. Lechtenberg is an Easton resident who graduated from Tufts University and Tufts Medical School in Massachusetts and subsequently trained at The Mount Sinai Hospital and Columbia-Presbyterian Medical Center in Manhattan. He worked as a neurologist at several New York Hospitals, including Kings County and The Long Island College Hospital, while maintaining a private practice, teaching at SUNY Downstate Medical School, and publishing 15 books on a variety of medical topics. He worked in drug development in the USA, as well as in England, Germany, and France.