Tracing back to a Lewis contemporary in my family--my children's great-great-great-great-great-great-grandfather, Thomas Saunders, born in 1787--Meriwether Lewis's America was but seven generations ago, seven along an ancestral path that is incontestably human for several hundred thousand generations. These most recent seven generations, a minuscule fraction of human evolution, have witnessed dramatic change. Indeed the world of Meriwether Lewis was more similar to that which existed in the early years of human existence than to what we now know just seven generations after his.
This is true in many ways, for Lewis lived before the Industrial Revolution, before mechanized transportation, before human flight, before electrons starting moving down wires for commerce, before antibiotics, before petrochemicals fueled bulldozer engines, before Darwin, Pasteur and Einstein, before Arrhenius foresaw global warming, before Thomas Midgely, Jr., invented chlorofluorocarbons or Paul Müller discovered the insecticidal properties of DDT or David Letterman happened across unexpected uses for Velcro and Ronald Reagan extended Teflon's use into politics.
The transformations wrought in these last 7 generations have changed human life--for many of us, especially in the developed world, for the better. Lifespan is longer. Child survivorship is higher. Some diseases have been vanquished, utterly. Communication is instantaneous, worldwide. The trip from Albemarle County to the mouth of the Columbia River can be done, including plane transfers and driving time plus twenty minutes to handle car rental in Portland, in fewer than 9 hours.
But the changes go far deeper than the superficial factors which let me get to Astoria, Oregon, in a hurry or even that have allowed the last two generations of Americans to grow up without fearing polio or small pox. In these last seven generations, indeed largely within the last 3, humans have irrevocably, profoundly changed our relationship with the planet. Before, our actions were no more than minor fillips on the surface, passing impacts of limited extent. Now we play at a scale capable of affecting the planet's condition.
There are many manifestations of this change. One, about which Professor Edward Wilson has written on these pages, is the current extinction crisis. More plants and animals will disappear forever as a result of human activity within the next century than in any comparable time period within the last 65 million years. And as biologist Norman Myers observes, this loss will diminish human prosperity for all generations to come.
A second involves human-caused changes in atmospheric concentrations of trace gases and their impact on the planet's heat and light budget. The Earth is warming. The climate is being disrupted. Excess ultraviolet light is passing through the stratospheric ozone shield. These two very different physical impacts will alter life and ecosystems on Earth.
A third stems from the dispersal into ecosystems of pollutants and other toxic chemicals. Some of these are metals or other chemicals that have been part of Earth's chemistry for eons but whose entry into biological systems has been discrete, limited and except for largely local conditions, at trace levels. Others are novel. They have never existed before, anywhere. Now they are everywhere, quite literally, and at levels that evoke concern.
Everywhere? Scientists studying the global distribution of organochlorine pesticides last year reported that samples even from the most remote areas are contaminated... "Almost all of the organochlorines measured in this study are ubiquitous on a global scale..."
Everywhere? Consider polychlorinated biphenyls, or PCBs, compounds proven to disrupt the embryonic development in fish, birds, reptiles and mammals, including human. Some of their impacts include lowering disease resistance, altering reproductive characteristics, and impairing behavior and intelligence. Studying these effects in people living along the St. Lawrence River downstream of Buffalo, Ottawa and Toronto, medical experts went to the high Canadian arctic to find a control population, people so remote from the sources of contamination that they should be clean, unaffected, and thus good baselines against which to compare the residents of the St. Lawrence. What the researchers found instead in remote Canada was even more severe contamination, even more severe health impacts, because the pollutants had spread by atmospheric and oceanic transport and then been concentrated as they moved up the food chain.
The pervasive spread of this contamination makes me think again of Meriwether Lewis and the age in which he was born. His era, and every single one of those myriad generations before him, differs from ours today in this respect: Our bodies, and those of our children and those of babies in the womb, carry several hundred synthetic chemicals hitherto unknown to human body chemistry. Some of us carry fewer, some carry more, but none born today have none, anywhere on earth.
Some of these novel chemicals will prove benign. Others will not. Science at this moment has been able to test only a small fraction of them for a limited number of effects, with testing almost always done at high contamination levels that are largely irrelevant to the conditions prevailing in the real world. What is available from low dose studies is enough to give deep pause: that at least for some contaminants and for some types of impacts, particularly those related to behavior, reproductive capacity, and resistance to disease, low level effects....very low level...are real. They cause material damage. They are having an impact in today's world on people and on wildlife.
If that weren't enough, none of the science on which protective standards are based consider interactions among chemicals. Yet again, that is just the way in which we encounter them in the real world. New results published this spring demonstrate that interactions take place at low levels and can multiply the impacts by over 1000-fold.
When Meriwether Lewis set forth across the American continent, he entered unknown territory. That is where we are headed, into an experiment that--because of the scale of the human enterprise--involves the planet and all life on earth. Lewis's exploration put at risk only a few tens of men and one woman, yet he planned in exquisite detail, with caution and an attempt to foresee the unknown. Our experiment involves much more--it involves the external world of the planet's ecosystems and the internal chemical workings of our own bodies. Surely we owe it to succeeding generations to apply caution and planning proportional to the scale of the risks entailed. Had Lewis proceeded with the blithe ignorance that guides our current course, he would have foundered before reaching St. Louis. And that was the easy part.