Odd way to start a chapter of geologic ages, you say. Bear with me.
The International Commission on Stratigraphy are the gate-keepers for the definition - and dating - of the various geologic epochs. This keeps self-absorbed geologists for naming a geologic age after themselves, among other things. The responsibility they have also assures that everyone worldwide is referring to the same thing when they say, for instance “Eocene” (the period ranging from 55.8 to 33.9 MY ago). This stratigraphic boundary-marking is normally done by looking for a marker bed - some particular layer that is seen all over the world that marks some profound change in climate or animal populations.
Here's an example: the end of the Permian Epoch and the start of the Triassic Epoch (251 MY ago) is marked by a mass extinction: about 95% of all life forms disappeared from the geologic record. This is called the Permian Extinction (for obvious reasons) and geologists are still trying to figure out what caused it.
For the end of the great Cretaceous Epoch, there actually is a “smoking gun”: a huge crater in the northern part of the Yucatan Peninsula (it runs offshore into the modern Gulf of Mexico) that marks the asteroid impact that ended the age of the dinosaurs. Think of it: a rock about 10 km (just six miles) in diameter made a crater ~170 km to ~300 km in diameter (depending on which scientific paper you read) and scooped debris into a sub-orbital trajectory that came down in Montana. The marker bed for this event is a thin layer of clay that is distinctive worldwide: it is loaded with iridium, a “sidereal element” similar to platinum, and not normally found on earth - but commonly found in asteroids. There are also huge tsunami deposits on Haiti and elsewhere in the proto-Caribbean.
About 10 years ago, a Nobel Laureate chemist named Paul Crutzen suggested the name “Anthropocene” for the Age of Man. Yes, it’s pseudo-Greek, but most of these things are. This was intended to spur debate over human influences in the world, and they are substantial.
To put things in perspective:
* We are presiding over the largest and most rapid mass extinctions of animals in millions of years.
* The International Energy Agency reports that anthropogenic carbon dioxide emissions for 2010 reached 30.6 Gigatonnes. That represents a 5% increase in just two years!
* We are seeing the beginning effects of major climate change: a dramatic increase in atmospheric carbon that if left unchecked will acidify the oceans, destroy coral reefs, and drown cities like Miami and New York by the middle of this century.
* There are land features on Earth now that can be discerned from space - human-made features.
Major and abrupt changes to soils worldwide (you can count the Walmart parking lot asphalt acreage) might meet the traditional definition of when a geologic boundary is crossed. When do you date the change to the Anthropocene, however? There is ice-core evidence for accelerating changes in the atmosphere dating to roughly 1800 - when the Industrial Age began to roar. However, there are radio-isotopic changes in soils dating from 1945, when nuclear weapons began to detonate in the atmosphere.
Which would you choose?
Man is now the Top Predator on the Earth. In fact, with the ice-free Arctic coming on we are killing off even the polar bears. To human over-hunting we apparently owe the extinction of the Mammoths and Mastodons, the North American Camel, the Ground Sloth, and other “Charismatic Megafauna” in the past 12,000 years. To human over-fishing we also owe the collapse of the world Cod population and the imminent collapse of nearly all large fish stocks in the oceans that humankind depend on for protein.
In that sense, we could say that humankind “owns” the Earth because of our enormous and highly visible impact in its surface.... but we still are not as important to the planetary biosphere as, say, microorganisms. Destroy all microorganisms, and everything on the planet stops. Not so if H1N1 killed off most humans.
We certainly don’t control the Earth, however. Virtually all governments recognize that the uncontrolled and accelerating growth of fossil fuel burning will cause terrible changes to our world, from monster hurricanes and continental-scale wildfires to drowned coastal cities. But humankind seems unable to do anything about it.
Which gets me back to the syphilis analogy. If we are an infection that is destroying the Earth as we know it... will we “evolve” fast enough politically to keep from poisoning our planet? LDS people are fairly unique in that we recognize the Earth to be a living thing. Since 1978 (at least) we have been told that we must not “mess it up” - we cannot continue to consider the Earth’s bounty to be limitless, or to pollute it. In 1834, Joseph Smith instructed the Saints that it wasn’t necessary to kill a Massassauga rattlesnake that they encountered near one of their camps on the Zion’s Camp march. That was quite an interesting first step in an environmental movement that most people attribute to Rachel Carson’s 1962 book “Silent Spring.”
We were getting instructions more than a century before that. Have we been listening?