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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.'"
I don't think it's that high, and that would be in the short term. Over time variation is introduced into the gene pool from different combinations of sexual partners, 'genetic drift' / mutations. An extreme example would be northern elephant seals or cheetahs. Obligatory wikipedia reference; http://en.wikipedia.org/wiki/Population_bottleneck#Examples
Interesting.
...the human population was once chopped down to much less than 2000 survivors. Try only 8 survivors.
And some number of generations before that, it all started out with only two humans, and very shortly before that, there was only one, and before that, none.
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!
I really don't think global cooling was a 1 time tabloid issue. Looking at the always reliable wikipedia, looks like more than a single 1970s article...
http://en.wikipedia.org/wiki/Global_cooling
So I am a skeptic. Stick with some theory for more than a couple of decades and I will buy in.
The research doesn't even show evidence of a population crash. What this story is doing is attempting to resurrect the Toba eruption myth of a few years ago. There was a supervolcano eruption at Toba, Indonesia, about 75 to 77 thousand years ago and Stanley Ambrose got Henry Harpending to publicly mutter that it was vaguely possible that there had been a population crash at that time, at which point the BBC immediately did a special on the Toba eruption and the near extinction of humanity. Harpending had had the chance to do the math by that time and found that there was no genetic evidence of a bottleneck, rather that there was geographic isolation of genetically homogeneous groups for a time.
He told that to the BBC.
Guess which version of the story they ran.
I presume that you love America? And perhaps by extension that you love our national symbol, the bald eagle? Well the only reason you can see them in the wild today is because of the DDT ban. They are one of the few species to ever come back after being placed on the endangered species list, and it's directly due to environmental action. So I'd hope you'd show a little gratitude. The worldwide DDT ban has caused the deaths of millions worldwide. Even if DDT were to make the bald eagle extinct, which is highly doubtful, the lives of millions of men, women, and children is more important to me. Other than that... Global Cooling was not actually a mainstream theory. Pollution/Smog was a serious problem, ask anyone who lived in L.A. in the 80s and now compared to now thanks to their emissions regulations. The ban of CFCs has had a demonstrably positive effect on the condition of the ozone layer. 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.
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.
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. So you're basing your decision to not believe in Global Warming based on a series of things which mostly turned out to be completely true? No. You have it all wrong. My decision not to freak out of global warming is due to an understanding of all the freaking out that has been done in the past when people discover something and over react, before the cyclical nature of the even is fully understood.
The climate changes... always. It is either going up or down 100% of the time. If it were going down, we'd be freaking out over global cooling and blaming pollution and smog and putting all kinds of limitations on "pollution contributing substances", like fossil fuels!
There is no "I disagree" mod for a reason. Flamebait, Troll, and Overrated are not substitutes.
Do you have anything to back that up? Last I checked, hunting was the major reason for the drop in bald eagle population. The DDT ban did screw Africa - they used enough of the stuff that DDT resistant skeeters are around, but not enough to kill them all.
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
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.Well if you're on the internet, chances are you're not black, you are literate, and are male. Though I suppose some illiterate black lady is going to post to prove me wrong now.
Give me Classic Slashdot or give me death!
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.
"Their is no doubt that temps are going up"
Actually there is. The stations we rely on for the temperature aren't exactly placed where they should be nowadays.
Good blog on the subject - that actually bothers to _check_ the station surroundings!
http://wattsupwiththat.wordpress.com/
it's in my head
Oh, it's a distinct possibility. However, it requires two things:
* All solid models of global warming require a considerable amount of time, as the insulating effect of greenhouse gases is very small, and operate on a timescale of centuries. It's possible we were wrong, and if the temperature truly leaps, that becomes more likely.
* It also requires an actual warming trend, rather than the patchwork we see now. We see glaciers melting, as well as polar icecaps. We also see cooling trends in some of the hottest places on earth. We're seeing record high temperatures all over the world, but also record lows.
Logically, this suggests not warming, but instability. Did people think we lived in a magic time when the world we knew would remain the same forever - even though history shows that there is no "norm"? This can also be caused by human causes, and I assure you within the next hundred years that will be reality, but I'm honestly more afraid of the unusual tectonics and solar activity we started seeing at right around the same time than I am about CO2.
Also, one additional bit of info. Please feel free to verify. CO2 has increased by 31% since the start of the industrial revolution - and is projected to require far higher amounts to have any appreciable effect. Methane has a far higher GWP than CO2, meaning it's more damaging greenhouse-wise. It has increased by 150% - primarily due to agriculture (both plant growth and livestock). You don't hear much about methane because it serves no political motives to fight it.
In other words, while fossil fuels are a major factor in greenhouse gas emissions, it plays a very small role compared to the agricultural requirements of supporting 6+ billion people. That doesn't make for great news, though. In the short run, anyway. In the long run, CO2 has more lasting effects than any of the other GG's - so don't worry, Big Oil will be properly blameable for the next few centuries.
Again, please verify, then go watch An Inconvenient Truth, analyze it's logic (or lack thereof) and then go compare it to REAL ecology like Silent Spring (which has scared the living hell out of people for decades, and backed up it's assertions with verifiable evidence).
Do not confuse "Freedom of Choice" with "Free Will".
http://en.wikipedia.org/wiki/Deluge_(mythology)
You too can do basic research in just minutes!
How we know is more important than what we know.
If you put some cold water with some ice cubes in a glass, how fast does the temperature of the water change while the ice is melting? How fast does the temperature change after all the ice is melted?
Laissez lire, et laissez danser; ces deux amusements ne feront jamais de mal au monde. - Voltaire
First, you are not quoting science, but headlines of popular newspapers and magazines that need to grab your attention to sell
In 1895, quotes from geologists describing the relatively recently (at the time) discovered geological record that suggest past cycles of ice ages and supposing that it will happen again is not in the same category as predicting climate change from models considering man-made inputs
Besdies the fact that '30s headlines stating that the earth is steadily growing warmer are correct (at least for some suitable length of time-averaging), that period in the US was known as the dustbowl for the lengthy droughts, so such headlines were understandable
Also, that major cooling was seen in the early '70s as widely inevitable should be no shock, as the cycles of ice ages IS widely seen as inevitable, in the geological sense of 100,000 year, 41,000 year, and 23,000 year cycles in the light of evidence that was just becoming understood in the '50s and '60s. http://earthguide.ucsd.edu/virtualmuseum/climatechange2/03_1.shtml/
Same for the sensationalist TIME headline in the middle of a cold snap.
Of course, you think that the above makes current warnings about global warming probably "just as worng", even though the "science" referred to in your quotes was NOT wrong and does not contradict current theories with "better" computer models (were any of the headlines before the last one based on theory from computer models?) and a "little better" (in the sense of "much greater") data gathering capability.
"CO2 is a minor greenhouse gas"
Incorrect. Aside from water vapor, carbon dioxide has the largest radiative forcing of the green house gases in our atmosphere. The others, in order, are methane, nitrous oxide, and CFC-12. To add to this, the lifetime of carbon dioxide in the atmosphere is quite long, unlike gases sucha as methane.
"The amount of CO2 re release into the atmosphere is pathetic compared to the other gases - a mere 0.28%"
Incorrect. CO2 currently makes up over 72% of greenhouse gas emissions from anthropogenic sources.
"The hottest years on record predate the industrial revolution."
Of course they do. How could they not, given the IR started 250 years ago? If you're going to bring up the argument of "natural cycle", you're still mssing the point. At best, we are merely contributing to change that, on the whole, we haven't really prepared for.
"There are a number of other factors such as the above that you can't/don't give an explaination for (solar activity being one)"
And obviously you haven't even performed a rudimentary review of the (quite large) amount of data collected on the climate. You could start by reading the IPCC report, which summarily dismisses you claims.
As far as solar activity goes, again, you need to read more. NASA is currently collecting terabytes of solar data. If the sun so much as burps, we'd know about it. According to the IPCC report, solar activity levels have not contributed to the current climate change.
You are, of course, free to bury your head in the sand or ignore the people who have dedicated their lives to studying the climate. Frankly, I'm more inclined to listen the people who study climate than some idle slashdotter.
But to make you happy, I'll just say that all this climate crap is a worldwide group of scientists operating in collusion in a multi-national scheme to bilk world governments out of billions of dollars for their own personal profit.
Tin foil hats are available at the door.
~X~
~X~
Global average temperature is approximately 15C, NOT ZERO! Even during ice-ages, it averages around 10C.
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!
BBC Take on it. http://news.bbc.co.uk/2/hi/science/nature/7358868.stm Tim S
This has been around for several years. http://www.andaman.org/BOOK/originals/Weber-Toba/ch5_bottleneck/textr5.htm
Tisha Hayes
Rabies comes pretty close. Lucky for us it isn't very contagious (not through air/aerosols) and there are vaccins.
A virus can easily kill 100% of it's victims and survive because for most viruses the victims are not the carriers. For example plague is pretty good at killing humans but doesn't seem to eradicate rat populations...
I Am Not A ________