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 way things are going

[clonan (64380)]

we will actually reach that population level again.

Environmental damage here we come!

Re:The way things are going

[shbazjinkens (776313)]

we will actually reach that population level again. Environmental damage here we come!

Hear that Kelly Kapowski? Not if I was the last man on Earth, eh?

it all sounds like a lame plot from a porno

[EmbeddedJanitor (597831)]

2000 person orgy to save the species.

Re:The way things are going

[brunokummel (664267)]

Mother nature must have said:
"Darn it, that was close, I'll get them next time!"

Re:The way things are going

[clonan (64380)]

The problem with global warming is three fold....

#1 it is unequally balanced..the temp changes more at the poles where the ecosystem is more sensitive to temperature. Therefore a small global change will mean dramatic changes in isolated areas.

#2 if you look through history, the average GLOBAL temperature over a one year period has typically hovered around 0 deg C for most of history. I hear that is an important temperature for something..... Anytime the temperature strays from freezing dramatic changes happen to the global environment.

#3 Consistency. So much of our modern society is based an the extremly mild conditions the earth has experienced over the last 20,000 years. Most of Europe is inhabitable ONLY because of the gulf stream and atlantic currents. Agriculture is ONLY possible because the temperature has been consistant year to year. We are in a sweet spot environmentally that is very unusual in earths history. screwing with the temperature is not going to help.

Re:The way things are going

[Knara (9377)]

AFAIK things like ice cores can give us indirect (but very usable) evidence of temperatures for much longer time periods. Of course, with all the ice shelves/glaciers melting, that particular method might not be all that useful for much longer. However, I imagine that other geological methods can also give us indirect, usable evidence of climate over longer periods than, say, just using tree rings or the like.

Re:The way things are going

[NeutronCowboy (896098)]

They might not be optimal, but they sure are what we've optimized our agriculture for. Deviations from expected values will cost money.

Re:The way things are going

[Shakrai (717556)]

History constitutes less than 2000 years. Thats the farthest back for which there are any usable records.

Uhh, dude, even if I don't mention ice cores [wikipedia.org] 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.

Re:The way things are going

[MightyYar (622222)]

Considering ice ages last between 40,000-100,000 years, that doesn't seem too significant to predict the climate.

They have ice core data that goes back over 100,000 years. I suppose it could be a coincidence that:

• The most dramatic CO2/Temperature increase in history just HAPPENS to coincide with mankind figuring out that they could burn shit from underground.
• Scientists have developed models that match this historic data quite well, and even when set to be as conservative as possible, STILL predict a warming trend based on CO2 input.

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?

Re:The way things are going

[morcego (260031)]

So yeah, maybe there is some input that we haven't yet discovered that explains the warming trend. Lord, that would be nice.

Do you really think that ? I don't.

Considering human acts the main cause of global warming (or whatever other catastrophe you want) is very comforting. Why ? Because we can do something about it.

On the other hand, if humans are not the cause, we have a really big problem. Imagine it is some kind of change on the sun. How do we handle that ?

These days, I take a great deal of comfort on the idea we are destroying out planet, our "natural" disaster are due to humans doing this or that.
 

Re:The way things are going

[NeutronCowboy (896098)]

Do you also ask a physicist to tell you about the black plague? You also miss the fact that changes in temperatures will also change where deserts occur. In other words, warmer temperature will not necessarily mean more arable land, and it certainly does not mean that it will be in similar places.

Re:The way things are going

[LithiumX (717017)]

I agree but I would also add that there is absolutely no proof that we are contributing significantly to the warming trend. I'm sure we have some effect, *all* lifeforms affect their environment. I'm also sure it's a good thing to cut down on pollution, but it's NOT a good thing to play chicken little when we haven't a clue about the climate long term and have very little history to compare it to.

Be careful saying that. You're likely to get yourself harassed, blacklisted, and shunned for such politically incorrect remarks.

I fully believe that the greenhouse effect is a simple matter of physics. I also believe that the effects, as we know them, do not occur rapidly. I also know that, historically, the climate is NOT stable - whoever said that it's been stable for most of history simply does not know history (Nineteen-hundred-and-froze-to-death being one example, the total environmental collapse of mesoamerica and the middle east, the sudden shift that made Europe more habitable and helped lead to the Rennaisance, etc etc etc).

In other words, yes our pollutants will have a very real effect on our climate. There is no free lunch. But, those effects belong to our children and grandchildren - what you see today is the normal cycle of change - but in a highly connected world prone to panic and fantasy, and overly willing to lay blame anywhere it can.

It may not be all bad though... it might scare us into actually controlling ourselves - before the bill actually shows up.

Re:The way things are going

[drakaan (688386)]

How about the people who busily insist that can't possibly be anything other than a wholly human-caused phenomenon, and that we can definitely stop it. What if we can't? Plans, anyone?

Seriously, I want my interstellar settler permit and associated vehicle already...oh, wait...we can't even go to the moon anymore.

Re:The way things are going

[cheater512 (783349)]

Well if what we are doing right now is the best we can do, and we are causing global warming, then we are completely screwed.
Might as well give up now and save a few billion dollars.

I'm of the opinion that GW is natural and we are just giving it a teeny tiny push.
Next they'll blame the next ice age on human activity as well.

Re:It bothers me

[NeutronCowboy (896098)]

Urm? This is a new one. See pretty pictures here: http://data.giss.nasa.gov/gistemp/graphs/ [nasa.gov]. 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.

Re:It bothers me

[mosb1000 (710161)]

What I'm saying is: if we're already half way there, where are the effects we should be seeing today? Where are the droughts and famines and floods that everyone is talking about? Is there some reason to believe that there's a threshold value, and once we cross it the problems will begin. It seems to me that if the CO2 if trapping heat, we should see the temperature rise with CO2. That would mean that we can expect another 1/2 degree rise at the most in the next 50 years.

Re:It bothers me

[MetalPhalanx (1044938)]

I'm giving up modding to point this out, but perhaps you might want to consider that many systems in nature tend to be a kind of check-and-balance. There are effects in the system which dampen the issue, things which remove carbon from the air and bind it. If we continue to increase the CO2 levels, we will overwhelm those checks and then all hell will break loose.*

The other thing I'd like to mention is that there really are more things to consider than just CO2 levels in terms of global warming. I don't think that human carbon dioxide emissions will be the end of us, but it could trigger the chain of events that leaves our planet much less hospitable to us. Have you heard of the methane hydrates in the cold sea bed?** It's possible that a small shift caused by our increasing carbon dioxide emissions - even if they have to increase by another 30% or maybe more - will push the temperature over a critical threshold and trigger a cascade which will again cause all hell to break loose.

So in a way, you are right. Except in climates which are around a sensitive temperature (e.g. Those areas where the temperature hovers near 0 degrees C) there is very little change right now. That could be that CO2 emissions are having a very minimal effect on the temperature, or more likely IMO, that's just that we haven't quite overwhelmed the checks that are in place. /rant

* (IANA Environmental Scientist, so there may be a margin of error in the direness of my predictions)
** http://dsc.discovery.com/news/2008/02/26/methane-global-warming.html [discovery.com]

Re:It bothers me

[Xyrus (755017)]

You're not seeing ocean level rise because most of the ice is still land-locked. Even worst case scenarios only have ocean levels rising catastrophically over the course of centuries. The ice at the north pole has almost no impact on ocean levels as it's already in the ocean.

The biggest short term impact of northern cap melting away is albedo. The caps radiate away a far amount of energy because of the snow and ice. Less snow and ice, means more darker surfaces which means more energy is retained. This becomes a feedback loop that rapidly (relatively speaking) ends up warming the northern hemisphere.

You're writing like you don't understand how significant even small changes in global temperatures can have large impacts. Do yourself a favor and read the IPCC reports. Better yet, go enroll yourself in a university and major in climatology. Then you will understand exactly how much energy a 1 degree rise in temperature world-wide can have, and why it should be a concern.

And stop confusing climatology with meteorology. The climate doesn't shift over the course of a week. The changes people are concerned about will be happening over the coming decades and centuries. We only have a hope of preparing for it if we start early.

~X~

Re:It bothers me

[Shakrai (717556)]

Though I personally believe we'll still end ourselves before nature does (over population is so much more of a threat)

How would overpopulation end us? Even if you aren't optimistic enough to assume that technology will provide a solution (it always has in the past -- think you could support modern day population density with the agricultural technology of ancient Rome? Hint: You couldn't), how will overpopulation end the human race?

The absolute worst case scenario that I could envision is a global war for resources that the poorer/less-well-armed nations would lose. Even in that scenario I don't see the end of the human race -- it's unlikely that even a global nuclear exchange would end the human race, though it would certainly set us back a few centuries.

That's definitely a problem I have

[Sycraft-fu (314770)]

This idea that we can prevent it, and then everything will be fine. Well there's two big problems with that:

1) What if even though we are the source, we can't stop it? What if it turns out there's just no way now to turn things around, we are too far down the road? What then?

2) Assuming historical extrapolations are right, the world has been much hotter and colder than it is now. Thus it is likely that will happen again. Thus no matter what we do, we are probably in for a big temperature change at some point.

So then if we assume it is true that a temperature shift of a few degrees will really screw us over, then we need to be preparing for it and figuring out how to deal with it. It really seems like a case of not if but when. Even if we are the cause and have the power to prevent this current change, a change that we can't will happen at some point. Also, just because we are the cause, doesn't mean we can prevent it.

Either way, the most sensible thing would seem to be to figure out what we need to do to be able to survive a temperature shift, not concern ourselves with what the cause is because unless we are extremely incorrect about past temperature, it is not a static function over any time period, and thus is not likely to remain so, regardless of what we do or don't do.

Re:The way things are going

[WindBourne (631190)]

In the 60's, greenies like myself fought against pollution from companies. If we had allowed the companies to continue, we would look FAR worse than parts of china or old USSR does today (and have significantly far worse health issues, akin to china's).
The global cooling issue was a 1 time tabloid issue. It was never in the science world other than 1 article. Only idiots point to that.
In the 80's, it was reagan trying to roll back the environmental changes (interestingly, the majority of the environmental laws esp EPA was from the pubs). It was the beginning of the ozone issue.
In the 90's, it was solving the Ozone issue. And just all the other ones was a problem. Fortunately, it is being saved because the freon was stopped. But we still have a hole in the south pole, that is slowly receding.

And since the 90's, global warming has been an issue. Back in the mid 90's, the neo-cons said that the earth is not warming. Now they say that man can not be behind the warming.

Do not buy it. Just quit polluting and forcing your shit on me and mine.

Re:The way things are going

[Chris Burke (6130)]

The DDT ban was one of the most successful examples of environmental policy in our history.

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.

I've heard convincing arguments that an outright ban on DDT went too far, and allowing small-scale controlled usage would have been beneficial. However the large scale cause-and-effect of spewing tremendous amounts of DDT everywhere -> bald eagle populations dropping, and banning DDT -> bald eagle populations recovering is indisputable. We know it was the DDT; we could measure it in the corpses of their prematurely dead young.

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.

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?

Good job!

Re:The way things are going

[KnightNavro (585943)]

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.

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.

Re:The way things are going

[Planesdragon (210349)]

1. CO2 is a very minor greenhouse gas

Link?

2: The amount of CO2 [we] release into the atmosphere is pathetic compared to the other gases

The relevant question is "amount we add to the atmosphere that was not there before." What other gases do we dig up and throw into the environment in a larger quantity?

3: The hottest years on record predate the industrial revolution

A: Link?

B: Yes. The era of planet formation was pretty hot. Your point?

C: The industrial revolution predated worldwide temperature monitoring. The "record", such as it goes, it incomplete.

4[a]. 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)

The sun isn't providing enough additional power to the Earth to explain the observed increase in temperature. Yes, we are watching the sun.

4[b]you simply resort to either the "your workin for big oil" or the "i'm more rightgous than you" defense, neither of which is a valid scientific defense.

An ad hominem attack is no more valid in a scientific political discussion than any other discussion.

I'll have to beg your forgiveness; the "global warming isn't a threat / is not our fault" line has been embraced by the same slice of the body politic that claims DDT doesn't hurt baby eagles, smoking doesn't cause cancer, and you can cut taxes forever and still pay for a war.

If when you argue on the same side of an issue as those who have long since ceded any claims to credibility to the scientific method, you get associated with their tactics until argued otherwise. "Silence implies consent", and all.

Re:The way things are going

[Reality Master 101 (179095)]

Good old fashion starvation and disease. For reference, see the current food prices and how these are liked in the developing world. Biofuel mania has something to do with it, but increased consumption by people and animals people eat is the major problem.

Yes, it's entirely possible to get crop failures leading to starvation. But how many deaths? 1M? 10M? Not even a small dent in human population.

The flaw in your thinking is very common -- it assumes a static world that does not adjust. If people are dying by the millions, then things will adjust. Hunger is by far a distribution problem, not a food production problem.

Re:The way things are going

[BiggerIsBetter (682164)]

Hunger is by far a distribution problem, not a food production problem.

I've read this sentiment many times, and although I agree with the latter statement, I can't agree with the former. In my view, it's not a distribution problem, it's an economic problem. We could distribute enormous amounts of food anywhere on the globe, but we don't. Why? It's too expensive. Hungry people are often poor people, and poor people can't pay enough to meet our expectations of a return (or even no loss) on labor, fuel, vehicles, storage, and other distribution resources. So, we make this choice: they're just not valuable enough to us to bear the cost of sending food (of course, aid agencies disagree and do exactly this).

Re:The way things are going

[icebike (68054)]

If starvation kills off 50% there is twice as much food left for the remaining 50%. Starvation is a self limiting mechanism. You have a lot more homework to do to get down to 2000 remaining individuals.

As for diseases, there is no earthly disease that kills 100% of its victims, (because such a disease would then itself become extinct).

I think you've been watching too much Science Fiction.

You are not legend.

Re:The way things are going

[Reality Master 101 (179095)]

Volcanism. With global warming, the melting of the polar ice will result in a major redistribution of mass. The planet will want to conserve angular momentum. Something will have to give.

Huh? I suggest going to look up the mass of the earth, compared to the mass of all the water. The mass of ALL the water is proportionally tiny, much less the mass of just the ice. Then try and remember that the world goes through periodic ice ages that redistribute water mass all the time.

Re:The way things are going

[maxume (22995)]

Just don't let him back out.

Damn those Cylons

[Dzimas (547818)]

I guess only 2,000 survivors made down to the planet's surface from the Battlestar Galactica. They should have listened to Starbuck earlier.

The concept of races

[PIPBoy3000 (619296)]

This event probably ended up establishing the concept of "races", meaning small groups of geographically isolated humans ended up having a lot of genetically distinct features. As their populations grew, they seemed very foreign to each other and only in modern times those barriers to gene flow seem to be falling.

I look forward to the day when people stop saying "I'm X race" and instead say "I carry the genetic markers for A, B, and C." Well, perhaps it's unlikely, but an ex-biologist can dream, can't he?

Re:The concept of races

[Kelz (611260)]

Or perhaps instead of saying "I'm X race" just say "This is my speciality and these are my accomplishments!" Once you get to a certain average prosperity level worldwide, it eventually stops mattering.

Re:The concept of races

[Digi-John (692918)]

Speaking as an American, as long as dumbasses think they're special because some of their ancestors came from Ireland 8 generations ago before proceeding to mix with every other background in the US, we're going to hear a lot more "I'm Irish" or worse "I'm 1/16 Cherokee, 1/2 Irish, 2/7 Italian..." crap.

Conversation with government clerk....

[by Anonymous Coward]

Conversation with government clerk filling out official forms...

Clerk: Full name please?
Me: Allen Dale Douglas
Clerk: Date of Birth?
Me: June 12th, 1981
Clerk: Place of birth?
Me: In a hospital.
Clerk: Which city and state, Einstein?
Me: Oh, Dallas TX, Presbyterian Hospital
Clerk: Sex?
Me: Sometimes.
Clerk: (rolls eyes ) Sex?
Me: Male.
Clerk: Race?
Me: Human.
Clerk: No, I mean what ethnicity are you?
Me: Texan.
Clerk: (rolls eyes again, tosses pencil up into the air and walks away)

Re:The concept of races

[lottameez (816335)]

I would agree with you were it not for my Scottish stubbornness.

Re:The concept of races

[jd (1658)]

Oh, it would have taken more than one such event, but we know that more than one such event occured. There have been other reports of other droughts nearly killing off humanity and the bottlenecks showing up in the DNA. Once humanity fragmented globally, however, mutations would have stayed reasonably local, and this also created races. (The two African tribes mentioned in the article formed from the drought mentioned and the Australian aborigines formed from early geographic isolation, making the three very special examples of humanity, but that should not lead anyone to conclude they should be treated as ouside humanity - they've a greater right to the title than most extremists.)

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.

Re:The concept of races

[flyingsquid (813711)]

I'm not entirely sure that I buy the reasoning behind their claims. OK, let's assume that they're right that all modern humans descend from a very small population, of about 2,000 people. It does not follow that the entire global population of H. sapiens was, at some time, 2,000 people. Perhaps there were 200,000 total, but only 1% of the people developed sophisticated technologies and cultures which allowed them to expand, eventually wiping out the remaining 99%. You still have a bottleneck, but your total population never goes below 200,000. For example, if the Neanderthals are considered a subspecies of H. sapiens, then you could have had 198,000 Homo sapiens neanderthalensis, and slowly that 1% of the species which is Homo sapiens sapiens expands and wipes them out. Certain populations of the species may have gone through bottlenecks, but the species as a whole has a stable population. Did that happen? I don't know, but you'd have to address this possibility before you go around waving your arms about the species being on the brink of extinction.

Also, keep in mind that the genetic evidence is just one line of evidence, and that's it's difficult to interpret. If their conclusions are correct, then other lines of evidence should corroborate their story. In particular, if humans nearly went extinct 70,000 years ago, then shouldn't we expect to see that in the archeological evidence, with stone tools becoming less common for a period?

Re:The concept of races

[jd (1658)]

You are correct to be suspicious. The other event I mentioned was much stronger - there was a definite genetic bottleneck, there was a geologically determinable drought, there was a reduction in human activity, and humans were still more-or-less in one region and thus much more likely to be affected by a drought. Numbers can be calculated directly from evidence of remains, but also by looking at what would have existed in the way of food and water, then calculating the maximum supportable population. You can do that with a single cluster.

This newer claim must be treated with caution, because it involves humans that have spread out (less likely to find remains, less likely the humans would have been affected catastrophically) and it's much harder to calculate numbers, because it's much harder to determine what would have been available to whom and what level of trade would have existed when levels of critical resources differed between human-inhabited areas.

DNA is also a dangerous thing to go by. We know there was a mitochondrial Eve, and we know a date but not whether it was the date of the event horizon (the point at which all surviving humans were descendents of Eve, within a timeframe in which differences in mtDNA would not yet be significant in the only regions we have really mapped for such purposes) or the point of singularity itself (when Eve lived). We also don't know why homogenious mtDNA occured - unless it conveyed such dramatic advantage as to be always selected (mtDNA handles energy conversion in cells), there's nothing that makes it obviously preferential, so all mtDNA lines should have survived on a completely random distribution.

Only twelve descendent lines exist in the whole of Europe and Asia. Another eight pretty much covers the rest of the planet. I say "only", but remember at least one actual catastrophic drought and this supposed one happened much later than mtDNA Eve. If a uniform, homogenous strain was preferential, we should not be getting such divergence now. It's not a simple picture.

(Also, dating an event by mutations is dangerous, since mutations can revert, not all markers mutate at the same rate, and all kinds of other factors make such calculations extremely messy. On the DNA mailing list, people often point out that the margins of error on last common ancestor calculations are so broad as to make the calculation worthless.)

It's a Douglas Adams kind of situation: even if we knew for certain, we wouldn't really know what it was we were certain about, or indeed that we were even certain about it.

one arkload

[0WaitState (231806)]

Isn't 2000 people about the capacity of Golgafrinchan Ark Ship B?

Just saying...

If by 70,000 years ago

[monoqlith (610041)]

you mean 6000 years ago, and if by a drought you mean a flood, and if by 2000 human beings, you mean one bad-ass yachtsman named Noah and his hot wife Jessica Alba, then I would be inclined to agree. Otherwise I'm afraid this is just another godless article passed off as 'science' by Lucifer-worshipping scientists and their ilk over at CNN.

Seems a bit shaky to me

[NewsWatcher (450241)]

This whole article seems to rest on the premise that humans left Africa en masse about 60,000 years ago. This is likely, but still a hotly contested theory. A rival theory contends that modern humans (Homo sapiens sapiens) originated about the same time from Homo erectus, whose bones have been found in Asia and Africa (the multiregional theory).

It stands to reason that the tests on mitochondrial DNA of a group in Africa is only useful if you assume everyone left Africa sometime after 60,000 years ago.

Given there are numerous sites in Australia that claim to have artefacts stretching back at least that far (and possibly 176,000 years ago) it is very likely there were pockets of humans in other parts of the world much earlier than 60,000 years.

This research actually only shows that there is evidence of a population crash in Africa. Not that homo sapiens across the world had a population crash.

70,000 is co-incidental with another event...

[puppetman (131489)]

the explosion of the Toba volcano, in Indonesia, that was believed to take humans to the brink of extinction: [nasca.org.uk]

Across the world the last eruption of a super volcano was the Toba volcano in Indonesia. This erupted around 75,000 years ago spewing out tremendous quantities of rock and ash and is thought to have reduced global temperatures by up to 21 degrees centigrade.

CNN article is a complete mischaracterization

[raaum (152451)]

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 [ajhg.org]

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.

Re:Are we SO sure?

[BobMcD (601576)]

I have a whopping 10 mod points, but would rather participate in this discussion instead, so here goes:

I think that this is actually plausible. Things to mull over that could make this an interesting topic:

1) What evidence, 70000 years later, would decisively display the difference between a flood and a drought?

2) Could the Noah story be an allegory written after the fact to describe this event, with only the details mixed up? If so, what does that tell us about this story?

3) What remnants of an Ark would one expect to find 70000, or even 5000 years after the fact? Conversely, what evidence could be shown that would decisively PROVE OR DISPROVE that the event happened? And I'm talking about scientific evidence here. Not anecdotal faith-based cruft. Not even science-based faith-based cruft, if you please...

Love these topics. Go people, go!! :P

Re:Are we SO sure?

[taniwha (70410)]

actually the whole almost dieing out thing just reeks of a total lack of intelligent design

Re:So...the Neanderthals could have wiped us out

[diablovision (83618)]

Actually the study can't support the statement that there were only 2,000 of us at that time. What it does say is that only 2,000 of us alive at that time managed to pass down their genes until today. There might have been a larger population whose genes we have lost in the intervening time (e.g. during the Bubonic plague).

The problem with these studies is that there isn't any DNA record of the humans that didn't make it. The only evidence we could hope to find of the humans that have died out is fossilized remains, which are few and far between.

Re:So...the Neanderthals could have wiped us out

[diablovision (83618)]

Because the inheritance graph of humans is a DAG flowing backward in time (thus cannot create cycles), with each individual having exactly two parents. These research results estimate the number of unique nodes of this graph at a specified point in time by essentially tracing backwards from who is alive today.

People don't "intermingle", they have children. If the children die, or all the children's children die (or all the children's children's children die, ad inifinitum), then your unique genetic code is erased (except the portion of your genetic code that you shared with other individuals who got it through a different path in the graph).

In fact, it's slightly more complicated than that because when you have children you only pass on (an essentially random) half of your genetic code. You might have the dumb luck that none of the unique mutations in your code gets passed on to your children because they never land in your children's 50%. You therefore might have had a unique mutation that cannot ever be detected in the future genetic record because by chance you passed on the "common" portion of your DNA code and not the unique mutation.

So yes, branches of this DAG can and do die off. Nothing "points" to them, so they die. In fact, this is the very mechanism by which natural selection and speciation occurs.

The arguments they use in the article are statistical and even though they account for many factors, in the end they can only work on information available from surviving DNA.

Re:So...the Neanderthals could have wiped us out

[Kenja (541830)]

And now we're an over-weight, not-too-bright, not-too-strong, disease-ridden, sorry-assed bunch of H. Sapiens.

What a difference 70,000 years makes!

Re:Old News

[gEvil (beta) (945888)]

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 [nationalgeographic.com] 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.

Re:The flood!

[QuantumG (50515)]

Floods typically do follow droughts.. so I wouldn't be surprised if an oral tradition was formed around how the global flood (which is a legend in most every culture) was passed on for 70,000 years or so.