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Humans Nearly Went Extinct 70,000 Years Ago
Josh Fink brings us a CNN story discussing evidence found by researchers which indicates that humans came close to extinction roughly 70,000 years ago. A similar study by Stanford scientists suggests that droughts reduced the population to as few as 2,000 humans, who were scattered in small, isolated groups. Quoting:
"'This study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species' history,' said Spencer Wells, National Geographic Society explorer in residence. 'Tiny bands of early humans, forced apart by harsh environmental conditions, coming back from the brink to reunite and populate the world. Truly an epic drama, written in our DNA.'"
The rest of humanity spread out across the globe, the Genography project has some nice maps of how the genetic markers show humanity to have moved. They do make one error when it comes to Europe. Europe was settled at least twice - once by a long-headed hunter-gatherer people and then later by a rounder-headed farming people. The long-headed people are the ones who developed lactose tolerence and anyone who can digest cheese or milk in any quantity is descended from the long-heads. In order for that to make sense, the long-heads must have migrated with cattle or goats, much as many nomadic tribes do today. The Iron age "Ice Man" (central Europeans give them such boring names - at least Britain's bogman was called Pete Marsh) was, if I remember the description correctly, one of the round-headed people. He was also left-handed, but that probably doesn't signify anything of interest. He was either a trader or a trapper and there can't have been many tools in either trade that were designed with a specific hand in mind.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Maybe it's because I pay attention to genetics and genealogy (and I thought people were geekier than I am here) but I clearly remember this news from 2006. Why is it getting recycled now, two years later?
The end of this article seems to cover that. Basically, this is a completely independent set of data (taken from the Genographic Project) that further confirms a theory that's been kicking around for a while.
This guy's the limit!
So yeah, maybe there is some input that we haven't yet discovered that explains the warming trend. Lord, that would be nice. But until some evidence of that is uncovered, I'm going to trust the nice, testable, repeatable climate models over people's thought experiments, untestable claims, and "what-ifs".
P.S. - why don't ordered and unordered lists work anymore?
W..w..W - Willy Waterloo washes Warren Wiggins who is washing Waldo Woo.
And I have to wonder if the author even read the original peer-reviewed article - which can be found at:
http://www.ajhg.org/AJHG/abstract/S0002-9297(08)00255-3
The actual study contrasts two complex hypotheses on early human populations in Africa. The major points are:
1. (Presented as the current consensus). Early humans lived in a one population in eastern or southern Africa. Around 90,000 years ago, this population splits. One of the daughter groups is the primary source of the Khoisan (a South African ethnic group with many "early" maternal lineages). The other is the source of the out-of-Africa migration 60-70,000 years ago. After the out-of-Africans leave, there is renewed migration between the two African groups.
2. (The new hypothesis proposed in this paper). Early humans split into two largely separate African groups starting around 150,000 years ago. Again, one of these is the primary source of the Khoisan and the other is the source of the out-of-Africans. Again, there is renewed migration between these groups after the out-of-Africans leave. (Also, this second hypothesis requires some limited migration from the Khoisan ancestors to the other group around 90,000 years ago to make the patterning of genetic variation work out).
The data which these hypotheses are trying to account for - in part - is that there is significantly more diversity in maternal lineages in Africa than out. In fact, all of the maternal lineages outside of Africa are a subset of *one* of the African lineages. So any explanation of this has to somehow derive a non-diverse population (the rest of the world) from a very diverse source population (Africans). Both of these hypotheses try to do this in fundamentally the same way (population splits in Africa), but the new paper argues that in order for the pattern to be as it is, a longer time of separation of populations in Africa is required.
There are no new population size estimates in the paper whatsoever. There is no discussion (other than an off-hand mention or two) of population sizes in the paper.
The CNN/Associated Press article is sensationalistic at best and misleading at worst.
And as an aside, whatever the "separate study by researchers at Stanford University" is - I couldn't figure out which one it was in the reference list - it is certainly about *effective* population size, which is _very_ different than census population size. For instance, the long-term effective population size of the entire human species is generally estimated to be around 10,000 *effective* individuals.
Urm? This is a new one. See pretty pictures here: http://data.giss.nasa.gov/gistemp/graphs/. You also missed the time frame on the extreme predictions - about 50 to 100 years out. So far, what little predictions have been made have turned out to be too conservative.
Those who can, do. Those who can't, sue.
The global outright ban was an overreaction, but we were just spraying the stuff willy nilly and it was spreading throughout the environment. The stuff is carcinogenic. In the US, where a person is more likely to die of cancer than malaria, it doesn't make sense to use it.
The Global Cooling theory was actually fairly accurate. It just came at the end of a cold spell. But much like the GW theories of today, people look at a graph and see it going in a particular direction and draw a straight line in that same direction to predict the future. Today, it's called the "hockey stick" graph, because that's what it looks like. Global cooling was never mainstream. Yes, it merited some brief consideration, but even back in 1970, most people considered global warming a more serious threat than global cooling. Predictions today are based on much more sophisticated models of global climate that consider both the cooling effects of aerosols and the warming effects of greenhouse gasses. Pollution/Smog was a problem in LA. Not so much in Raleigh NC. The problem is that people who never left LA assumed the whole country was like that made predictions based on what they saw. Many of the global cooling theories was based on this (smog blocks the sun and leads to GC). Pollution controls have helped LA. They've done nothing for Plano TX. Actually, they have reduces carbon monoxide, respirable particulate, ground level ozone, NOx, and diesel particulate throughout the nation. Not every area had concentrations that exceeded EPA standards, but reducing the concentrations further lessens health impacts from air pollution. The Ozone layer was shown to be "growing back" even before any ban on CFC's could have an effect. Then it shrank again. Then it grew back again. It's a cycle. The problem is that we discovered it during the shrinking phase and freaked out, much like today. Yes, the ozone layer goes through seasonal fluctuations. It's much like the CO2 concentration in that way. However, the low, high, and average concentrations each year all showed downward trends.Uhh, dude, even if I don't mention ice cores and other geological evidence, you do realize that we have "usable records" older then 2,000 years, right?
Records survive from the Roman Kingdom -- which is over 2,500 years old. Ditto for records from the Roman Republic (2,000 - 2,500 years old). Some surviving artifacts and records from Babylon are at least as old (moreso in many cases). The Iliad is around 2,800 years old. The Torah is over 3,000 years old. The Egyptian pyramids and associated artifacts/records are even older than that. All of which have survived to the present day.
I want peace on earth and goodwill toward man.
We are the United States Government! We don't do that sort of thing.
Which might explain why the GP said that records from the Roman Kingdom were over 2500 years old and that after that they had the Roman Republic. You should have kept reading after you saw the phrase Roman Kingdom.
Famine: Well, there's a lot of Africans who still don't get enough to eat.
Floods: Might as well include storms, so think about the number of hurricanes in the last couple of years, and many people in Europe have been experiencing SOME flooding.
Rising water: that's a really slow effect. Mind you, eroding shore lines are a sure sign of this phenomena.
Just because you don't see it happen instanteously doesn't mean its not happening.
AND you should be GLAD its not happening instanteously!