## Monday, January 28, 2008

### Anthropocene: a postmodern geological period

Anthropocene.
The beginning of the year 2008 brought us two new papers defending this concept: see some news from Australia. It is almost certainly becoming a topic of serious discussions between the people who have the power to modify textbooks. I mostly think that the idea is silly. But let us begin with some basic facts describing the eons, summarized in the (hopefully) most transparent way you have ever seen:
• Hadean (eon): 4.6-3.8 Gyr BC, named after Hades, a Greek god of the underworld
• Archean (eon): 3.8-2.5 Gyr BC (also "prahory" or "urhills" in Czech), divided to these eras:
• Eoarchean: 3.8-3.6
• Paleoarchean: 3.6-3.2
• Mesoarchean: 3.2-2.8
• Neoarchean: 2.8-2.5
• Proterozoic (eon): 2.5-0.54 Gyr BC (Rodinia supercontinent, oxygen created, preparing for complex life, also "starohory" or "old hills" in Czech)
• Paleo-: 2500-1600 Myr
• Meso-: 1600-1000 Myr
• Neo-: 1000-542 Myr
• Phanerozoic (eon): 542 Myr BC - today (Greek for "visible life"):
• Paleozoic (Greek for "old animals"; also "prvohory" or "Primary"): 542-251 (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian)
• Mesosoic (dinosaurs and reptiles; also "druhohory" or "Secondary"; Greek for "middle animals"): 251-65 (Triassic, Jurassic, Cretaceous)
• Cenosoic (mammals; Greek for "new animals"): 65 Myr BC - today:
• Tertiary ("třetihory"): Paleogene: 65-23 Myr BC:
• Paleocene, Eocene, Oligocene
• Neogene: 23-today
• Tertiary: Miocene: 23-5.3 Myr BC
• Tertiary: Pliocene: 5.3-1.8 Myr BC
• Quaternary: Pleistocene: 1.8 Myr - 9600 BC
• Quaternary: Holocene: 9600 BC - today

Note that Tertiary covers both Paleogene as well as a part of Neogene while Quaternary ("čtvrtohory") roughly coincide with the broader human race. Now, there are hundreds of other facts that the mankind has learned that you might expect me to reproduce here. But I won't. Let me focus on more general facts.

Each geological eon, era, or period is associated with some geological events as well as with some epochs in the evolution of life. But because all of them are geological periods, it should be the rocks that determine the natural boundaries.

Continental drift and the creation of various mountains and other huge structures belong to the defining events of the geological classification. Life is added as a cherry on a pie. Its fossils are confined within the rocks.

Journey to Prehistory ("Cesta do pravěku", Karel Zeman, Czechoslovakia, 1955): brontosaur in Mesosoic

If we look at very ancient eras, it is clear that our time resolution diminishes a little bit. For example, the Hadean lasted nearly for one billion of years and it has no official subdivisions. The fact that the recent subdivisions are finer has two major reasons:

• subjective ones: I mean our inability to learn the distant past in detail
• objective ones: I mean the fact that the events on Earth are speeding up

I guess that the objective aspect dominates in the very recent periods. In principle, we can measure time rather accurately even for events that occurred tens of millions of years ago. But we simply don't divide those events to as short periods as one million of years or thousands of years because we are not aware of too many dramatic events that occurred a long time ago.

It is not just that we are aware: many of us are convinced that the frequency of events worth human attention was limited, indeed.

Life occurred rather quickly after the Earth was created. While there has been a lot of rather sophisticated life on Earth in Phanerozoic, it doesn't mean that there was no life in the previous eons. In fact, you can find life not only in Proterozoic but even in Archean.

Consider modern life with internal membranes in cells and cytoskeleton, those that usually have the nucleus. These life forms are called "eukaryotes". Well, what is the evidence for the oldest eukaryote? It wasn't found by your humble correspondent but it was found by Jochen Brocks, his former roommate, and it probably lived 2.7 Gyr BC, in Neoarchean.

That's when the Earth was roughly 50% younger than today.

Only in Phanerozoic, in about the most recent 10% of the Earth's life, we could see abundant life forms around. And only in Cenosoic, the most recent 1% of the Earth's life, there have been mammals around. In the most recent 0.1% of the Earth's history, we saw some kinds of humans around. The white race as defined by the SLC24A5 mutation has only existed for the last 0.0001% of the Earth's history.

Things seem to be speeding up.

Well, it is plausible but unlikely that a similar acceleration occurred in the past and dinosaurs or other distant cousins were driving their SUVs around - before they were destroyed. Let us assume it is not the case and the Quaternary is the first geological period when the evolution of intelligent life forms started to speed up exponentially.

Fine.

But now the main point. With all my admiration for the unbelievable progress that life has recently made, I think that we - the mammals, humans, or whomever you want to include - have a very limited impact on the features of our planet that geologists will be able to study in the year 10,000,000.

I think that the notion of an anthropocene is arbitrary, its beginning is ill-defined, its justification is not really based on geology, and one could invent even newer, more recent eras associated with another kind of human progress.

Note that according to the classification above, we already live in Phanerozoic as well as Cenosoic as well as Neogene as well as Quaternary as well as Holocene. Holocene, the shortest period, approximately coincides with the existence of oldest civilizations as we know them. Do you really want to add Anthropocene to the list?

I don't see too many qualitative geological events that occurred in the last 200 years but that would distinguish us from the ancient Greeks or Romans. Honestly speaking, I consider myself to be much closer to some old people in Greece or the Roman Empire than most politically correct loons who live in the "Anthropocene".

Will we also have to add Microprocessorocene, Multiculturalismocene, or something else? Please stop this insanity. Create new mountains. If you can't do it, please wait until Mother Nature does it for you. Then you can start a new era. ;-)