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impressed her superiors, and in 1936,she became the second woman to be hired at the Bureau full time.In 1941, she published the first of three books on the ocean,combining science with lyrical meditations on underwater worlds.These explorations resonated with a wide audience.In Silent Spring, Carson turned her attention to the ways human actions threaten the balance of nature.

She began to make inquiries through government contacts from her years working in the United States Bureau of Fisheries.She asked: hat has already silenced the voices of spring?In 1962, Carson published her findings in Silent Spring.Her book documented the misuse of chemicals and their toll on nature and human health.Silent Spring immediately drew both applause and impassioned dissent along with vicious personal attacks on the author. 07

In 1958, Rachel Carson received a letter describing songbirds suddenly dropping from tree branches.The writer blamed their deaths on a pesticide called DDT that exterminators had sprayed on a nearby marsh.The letter was the push Carson needed to investigate DDT.She had already heard from scientists and conservationists who were worried that rampant use of the pesticide posed a threat to fish, birds,and possibly humans.

In 1969, under pressure from environmentalists,Congress passed the National Environmental Policy Act that required federal agencies to evaluate environmental impacts of their actions.To enforce the act,President Richard Nixon created the Environmental Protection Agency.And in 1972, the EPA issued a partial ban on the use of DDT.Long after her death, Rachel Carson continued to advocate for nature through the lingering impact of her writing.

She rejected the prevailing belief that humans should and could control nature.Instead, she challenged people to cultivate aturity and mastery, not of nature, but of ourselves.Carson died of cancer in 1964,only two years after the publication of Silent Spring.Her work galvanized a generation of environmental activists.

Former Secretary of Agriculture Ezra Taft Benson demanded to know why a spinster with no children was so concerned about genetics?and dismissed Carson as robably a Communist.A lawyer for a pesticide manufacturer alluded to Carson and her supporters as inister influences aiming to paint businesses as mmoral.In reality, Carson had focused on the dangers of chemicals because they weren't widely understood, while the merits were well publicized.

She suggested that exposure to DDT might alter the structure of genes,with unknown consequences for future generations.The response to Silent Spring was explosive.For many people the book was a call to regulate substances capable of catastrophic harm.Others objected that Carson hadn't mentioned DDT role controlling the threat insects posed to human health.

In spite of this and other mishaps, the US Department of Agriculture and chemical companies extolled the benefits of DDT.There was little regulation or public awareness about its potential harm.But Carson showed how the overuse of chemicals led to the evolution of resistant species which, in turn, encouraged the development of deadlier chemicals.Since DDT does not dissolve in water,she asserted that over time it would accumulate in the environment,the bodies of insects, the tissues of animals who consume those insects,and eventually humans. 7

DDT was originally used during World War II to shield crops from insects and protect soldiers from insect-borne diseases.After the war, it was routinely sprayed in wide swaths to fight pests,often with unforeseen results.One attempt to eradicate fire ants in the southern U.S.killed wildlife indiscriminately,but did little to eliminate the ants.

How did this mild-mannered biologist and writer ignite such controversy?Carson began her career as a hardworking graduate student,balancing her studies in biology at John Hopkins University with part time jobs.Still, she had to leave school before completing her doctorate to provide for her ailing father and sister.Carson found part time work with the Bureau of Fisheries writing for a radio program on marine biology.Her ability to write materials that could hold the general public attention.

So odds are our soot will still be here 66 million years from now,easy enough to find for any aliens who care to look.Of course, there's an important difference between us and an asteroid.A space rock has no choice but to follow gravity.We can choose to do differently.And if we do, there might still be some kind of human civilization thousands or even millions of years from now.Not a bad record to hope for.

That smudge corresponds with a meteoric rise in the amount of carbon dioxide in the air,now beyond 400 parts per million,or higher than any other Homo sapiens has ever breathed.Similar soot can still be found in ancient rocks from volcanic fires of 66 million years ago,a record of the cataclysm touched off by an asteroid at the end of the late Cretaceous epoch.

That goes for people, too.If the microscopic plants of the ocean suffer as a result of too much carbon dioxide, say,we'll lose the source of as much as half of the oxygen we need to breathe.Then there's the smudge in future rocks.People's penchant for burning coal,oil, and natural gas has spread tiny bits of soot all over the planet.

That also means that even if people were to disappear tomorrow,evolution would be driven by our choices to date.We're making a new homogenous world of certain favored plants and animals,like corn and rats.But it's a world that's not as resilient as the one it replaces.As the fossil record shows,it's a diversity of plants and animals that allows unique pairings of flora and fauna to respond to environmental challenges,and even thrive after an apocalypse.

This die-off started perhaps more than 40,000 years ago as humanity spread out of Africa and reached places like Australia,kicking off the disappearance of big, likable, and edible animals.This is true of Europe and Asia,think woolly mammoth,as well as North and South America, too.For a species that has only roamed the planet for a few hundred thousand years,Homo sapiens has had a big impacton the future fossil record.

Those elements will last in the rock record,even in our bones and teeth for millions of years.And in just 50 years, we've made enough plastic,at least 8 billion metric tons,to cover the whole world in a thin film.People's farming, fishing, and forestry will also show up as a before and after in any such strata because it's those kinds of activities that are causing unique species of plants and animals to die out.

Even New York or Shanghai may prove hard to find buried in the rocks a million years from now.But humans have put new things into the world that never existed on Earth before,like plutonium and plastics.In fact, the geologists known as stratigraphers who determine the geologic timescale,have proposed a start date for the Anthropocene around 1950.That's when people started blowing up nuclear bombs all around the world and scattering novel elements to the winds.

That would be a new unit in the geologic time scale that stretches back more than 4.5 billion years,or ever since the Earth took shape.Modern humans may be on par with the glaciers behind various ice ages or the asteroid that doomed most of the dinosaurs.What is an epoch?Most simply, it's a unit of geologic time.There's the Pleistocene,an icy epoch that saw the evolution of modern humans.

Or there's the Eocene, more than 34 million years ago,a hothouse time during which the continents drifted into their present configuration.Changes in climate or fossils found in the rock record help distinguish these epochs and help geologists tell deep time.So what will be the record of modern people's impact on the planet?It doesn't rely on the things that may seem most obvious to us today,like sprawling cities.

Imagine aliens land on the planet a million years from now and look into the geologic record.What will these curious searchers find of us?They will find what geologists, scientists, and other experts are increasingly calling the Anthropocene,or new age of mankind.The impacts that we humans make have become so pervasive,profound,and permanent that some geologists argue we merit our own epoch.