It’s been unseasonably cool and rainy here. In the middle of August we are leaving the doors open during a time that the house is typically closed with the air conditioning running. Last winter was warm and spring came early. So, is this evidence of global warming? Not necessarily. Weather is not climate change. Weather change is to climate change as a bad week on Wall Street is to a worldwide depression. The difference is a the presence of e trend, not just over days or weeks, but over quarters in the case of the market and decades in the case of climate.
Whether or not, and to what degree, humans are responsible for the current climate change, it is definitely happening. The area where we live in Northeast Georgia (the state not the nation) has historically been firmly in gardening zone 7 with even Atlanta being part of zone 7. We are at the edge of gardening zone 8 now, and may already be there. What will happen to us? What will happen to Homo sapiens as a result? It’s hard to predict. One possibility is that we will become extinct.
Evidence of mass extinctions has been observed at multiple times in earth’s history. There have been 5 or 6 in the history of the planet. The causes include volcanism, impact events, climate change, sea level change, and fluctuations in atmospheric oxygen levels.
Obviously, these causes are interrelated. For example, Toba, a giant volcano in Indonesia, erupted about 73,000 years ago creating a huge ash cloud that blocked sunlight. As a result, the earth’s temperature dropped about 9 degrees. Nine degrees may not sound like much, but such a change is huge. Homo sapiens almost became extinct as a result. We went from a population of tens of thousands to a handful of individuals. It was a squeaker. So, the earth’s temperature fell. What effect would that have? For one thing the temperature at and near the poles would be sufficiently lowered to create glaciers. Glaciers trap huge amounts of water. Sea levels drop. The predominant vegetation changes from forest to savannah. Savannahs favor large grazers. Large grazers favor large predators. Lions and tigers and bears, Oh No!
Woolly Mammoths largely became extinct about 10,000 years ago, but some lived until as late as about 4000 years ago. No one know exactly what happened. Maybe it was a change in vegetation due to the beginning of the current interglacial period. Maybe it was disease.
“The last glacial period was the most recent glacial period within the current ice age, occurring in the Pleistocene epoch, which began about 70,000 and ended about 12,500 years ago. The glaciations that occurred during this glacial period covered many areas of the Northern Hemisphere, and have different names, depending on their geographic distributions: Wisconsin (in North America), Devensian (in Great Britain), Midlandian (in Ireland), Würm (in the Alps), Weichsel (in northern central Europe) and Llanquihue in Chile. The glacial advance reached its maximum extent about 18,000 BP. In Europe, the ice sheet reached northern Germany.” Wikipedia
Genetic studies show that about 50 – 60,000 years ago our ancestors did something new. They began to move from Africa. One group migrated from the south eastern portion of Africa moving up the continent, across into Southeast Asia, ultimately settling in Australia. Another somewhat later group moved across to Europe and on into Asia. The rate of movement was spectacular. Within 35,000 years that migratory group had populated all of the European and Asian continents.
So, what caused the sudden movement? The eruption of Toga marked the beginning of the current ice age. (We are in an interglacial period of this ice age.) Remember that that happened 10,000 years earlier. There are a number of theories about the impetus for the migration out of Africa.
Richard Leakey has a theory that our ancestors developed language at that time thus providing the tools for communicating ideas and concepts. Perhaps. Remember that Chimpanzees, our nearest cousins, have no language but seem to cooperate fairly well. Gorillas within a band follow the direction of the leader, and those directions are not spoken. Even wolves cooperate in a fairly complicated way during a hunt. Most social animals have worked out a system of communication. But, it could have been language.
Another theory has to do with a receptor for dopamine, one of the signal transmitters in the brain. Some individuals have a variation of the DRD4 gene that has been called the “Adventure” gene or the “Migration” gene. Individuals with that gene are drawn to novelty. They want to try new things, are less startled by the new, and calmer in the face of danger. Demographics show that individuals with that variant gene are about twice as common in Europe as Africa. Four times as common in North America and six times as common in South America. Why is this gene so common? Genetic mutation only increases in frequency if the change produces some advantage to the population. The effect may be a disadvantage to individuals, but advantageous to the group as a whole.
Moving must have been a good thing. Perhaps the savannah dried up in East Africa making a hunter/gatherer’s existence harder. Certainly living in multiple areas of Earth would favor the chance of a group surviving if war, or famine, or disease wracked another area.
Individuals with this gene frequently get diagnosed with ADHD. Loving novelty, though, they may become researchers or entrepreneurs. Low tolerance to risk may make them mountain climbers or animal trainers. Low tolerance to risk can get you killed, but get the group more land or a woolly mammoth. I'm fairly sure that I have this gene. I wouldn't have wanted it any other way.
So, maybe it was a mutation.
Recently David P. Goldman (“Spengler”) has predicted mass extinction of humans for a most interesting reason. Goldman studies demographics. What he has noticed is that the birthrate has been dropping not just in Europe but among Arabs. Particularly, it has dropped in countries where there is a high rate of education among women, coupled with an aging population and decreased opportunity for occupation. Goldman imagines that this fall in birth rate is due to despair, a loss of hope, a loss of faith in a benevolent creator. This lack of hope and vision of a loss of family and culture results not only in individual suicides, but in suicide bombings. A culture that thinks it will become extinct, no matter what, may start a war that will end in mutual destruction.
Goldman is a secular Jew who writes from a Judeo-Christian perspective. He may be right about the lack of hope. However, mass extinction may result from multiple causes. The population of earth is 7 billion now. It is projected to double by 2050. This doubling does not take into account food and water shortages, drought, war with a country with nuclear weapons that sees its glory days as the cultural center of the mid-east at an end. A people who produced Omar Khayyam, ornately beautiful mosques and the concept of the zero may decide they have nothing to lose against nations that want to subjugate and humiliate them by assuring mutual destruction.
I think that Goldman sees the collapse as being more like a loaf of bread that has simply risen too high, collapsing in the middle after the influence of the yeast runs out.
One thing is certain; there is no “out of Africa” option. We occupy every area of earth. Migration to a distant star is not an option.
In the meantime I’m going to look backward as anthropologists and geneticists work to figure out how we got to where we are. Backward is a lot more beautiful than forward.
Woolly Mammoth extinction: http://www.bbc.co.uk/news/science-environment-11000635
Mass extinctions: http://dsc.discovery.com/earth/wide-angle/mass-extinctions-timeline.html