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Have Humans Come Close To Extinction?
waytoomuchcoffee writes "According to a new study, our virtually identical DNA indicates humans were close to extinction about 70,000 years ago. Another take on the same study tells how being lactose intolerant in adulthood was normal, and being able to digest lactose became a survival advantage after dairy farming was invented."
Think about it. A chimp troop can consist of up to 60-70 chimps for a big troop. Assume all but around 30 troops are killed off leaving around 2000 chimps. If a single troop of those chimps could have more genetic diversity than all of humanity - ie. more than the 2000 people who sired us then 2000 chimps would have around 30 times more diversity. (Or more than that depending on how much more diversity in a chimp troop than there is in humanity.)
So, either humanity dwindled down by chance to 2000 people who happened to have little genetic diversity, or there was some common genetic trait that selected for those specific people. Or something. But then who knows... maybe chimps are just naturally genetically diverse and we're not... or maybe I just missed something that the writer thought was too technical for the article.
Still, the numbers bothered me.
So do your part to ensure diversity, and make sweet love with someone genetically different (read: hot) under some power lines near a microwave running with the door open. "For the sake of the species" never made a better pick-up line.
(Just don't give her your name--she might expect you to help raise your special freak).
Thinking about that, I didn't make myself clear on something. What I was trying to say was that if a single troop of 60 to 70 chimps can have X diversity, shouldn't a group of 60 to 70 humans - a close relative of the chimp - also have X diversity. What struck me about the article is that their implication is that those 2000 people they say sired us had less diversity than 60 to 70 chimps.
Makes you wonder if it has something to do with human females being fertile year round. If I recall, chimp females are not. Because chimps can only mate at certain times, there is less oppurtunity for one male to sire all the children in a troop. In a human harem type social group, this could be easily accomplished which would cut down the genetic diversity considerably. Do this for a couple of generations and you might end up with a population with a depressed gene pool. Anyway, just arm chair theorizing off the top of my head. (Gotta use that anth degree for something.)
Arguably, in spite of our numbers, we're close to extinction now.
Hey, good to know we got out of it last time.
Sunlit World Scheme. Weird and different.
Here is the abstract from the The American Society of Human Genetics article, and here is Stanford's press release on the story.
And are the web pages of Marcus W. Feldman and Noah Rosenberg From Rosenberg's research page, here is access to a PDF of the journal article.
Anyway, farts is the problem, but indirectly. If you are lactose intolerant, you're body can't break down lactose, so you get few calories from it. The energy is wasted on fart generating bacteria.
Hey, I never knew you could watch a post drop each time you hit preview!
'SBEMAIL!' is better than a goat!!
But being lactose intolerant was an advantage once fart-lighting was invented.
Do you even lift?
These aren't the 'roids you're looking for.
According to a new study, the old study was right!
-BM
http://melbournephilosophy.com/
The thing that should have bothered you is the utter ambiguity of such a claim. This is just one of those "newspaper statistics" that sound as though they mean something but don't.
What is the diversity of all humans? Is it more than the diversity between the two most different humans? What is the means of quantifying difference? Is there some standard, or are there lots of standards, or are there just countless ways, each of which yields a different answer?
What about the diversity in a group of chimps? Is that a family of chimps, or a small group randomly chosen from all chimps, such as one might find at some zoos?
I'm just not sure how to interpret the comparison of diversity between a small group (of chimps) and a large group (all humans). Size of group wouldn't have been mentioned, presumably, if it weren't part of the equation. What part?
Unless you know what it is they really mean, I'm not sure it makes much sense to go looking for deeper meaning.
"Those who have never entered upon scientific pursuits know not a tithe of the poetry by which they are surrounded."
being able to digest lactose became a survival advantage after dairy farming was invented.
So at some point some humans said:
"Hey lets invent dairy farming!"
"Hmm, but we're all lactose intolerant..."
"What the heck, if we take this crap every day we'll eventually mutate and some generations down they will be thanking us."
Nice long-term thinking there, thanks!
Within the next 50 years, about half of us will be dead!
I'm not sure I buy the article's argument that "humans" came close to extinction. I think another possibility is that what they're looking at is a speciation event: that's the point that homo sapiens sapiens branched off from immediate predecessors. If that group had been killed, we wouldn't be here, but I'm not sure the homo genus would have died off.
"I dare you to drink that."
"No, I dare you."
"Ok, we all dared, so we all drink."
Then they all got sick except one who not only brained them with a club and sired children with thier wives... After that, he taught his sons how he got all the foxy wives and they went to neighboring villiages...
Robert K. Wayne of UCLA has estimated that we may have domesticated wolves as much as 100,000 years ago.
What if it was 70,00 years ago? Did our partnership with dogs save our species?
The BBC had one of their unevitably brilliant documentations about the rise of mankind a few weeks again on German television where they pointed out that humanity must have been really, really close to the gutter before it exploded. Then this big, black rectangle came and showed them how to use the thigh bone of a pig to kill...oh, never mind...
Could the biblical story of Noah's ark explain this, as a worldwide flood leaving only a single family of eight alive will achieve this effect of everyone having similar genes.
Before you mod me down into oblivion for sounding like a self-righteous Creationist, do note that other cultures have references to a catastrophical flood (such as the Chinese, apparently the character for ship is that story).
Please direct all bug reports to
Could it be possible that we are the decendents from a crashed spacecraft? Maybe I played Homeworld too often, but doesn't it seem funny that we are the only primates that can:
(A great site that goes into more detail is: Here.)
At times we have more anatomically in common with a Seal than an ape. Not enough to make me buy a tinfoil cap, but precisely how does an otherwise aquatic creature "evolve" on an Savanna, and then ddevelop their first civilization in the middle of a desert?
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
It's shocking how much better the San Francisco Chronicle article is to the BBC article.
Clearly both writers had the same source to work with, but the sfgate article was much more researched, thought-out, and nicely tied together. Even when I had only read the BBC article, I was shocked at how poorly structured the article was.
If you're only going to read one of the two, read the sfgate piece.
Genetic lactose intolerance (= hypolactasia = non-production of lactase enzymes past weaning) has a hereditary component (Sahi 1994) The Cambridge World History of Food (2000) has a good article on the science and geography of lactose intolerance. This problem is not caused by the gene that creates lactase but instead by another gene (LAC*R (lactase restriction)) that kicks in later and ramps down the primary gene. (The other allele LAC*P allows lactase production to persist) However that article says:â¦However in 2002 the LAC*P gene was identified and sequenced within a Finnish population and was found to be the same as those in the rest of the world. This means that genetic adaptation for adult milk drinking evolved early and all milk-drinkers have ancestors in some early population in the middle-east or Africa.
The problem with equating lactose intolerance with genetics is that people will see this as an either/or situation â" either you can eat it or you can't. The fact is that most intolerant people can consume small to medium amounts of lactose with no problem. Major milk problems are more often the result of allergies.
Eventually there is the issue of culture. Fermented milk products (e.g. yoghurt and cheese) may be easier to digest than raw milk. Do the cheese/yoghurt eaters have a cultural advantage? Or have they disadvantaged other cultures?
(Without reading the article...)
:)
I don't know much about genetics but....
IIRC genetic diversity also indicates how
old a 'species' is.
Hence, given the widespread genetic diversity in chimpansees and the low genetic diversity in humans, you can deduce that chimpansees have been around much longer than humans.
The other explanation could be that a single group of humans were so succesfull at some point in the past that we are all descendants of that group.
(oops, thats the same as coming close to extinction - just phrased a different way
There are groups of people in the world that are very much genetically distinct from the rest of us. (Eh, Read "The Naked Ape" by whatshisname...)
( Isolated pockets of genetic diversity...stuff like that )
Another explanation could be the life span of chimpansees...anyone know how long they life in the wild? Short lifespan? Females are almost constantly pregnant. Now compare that to humans...long lifespan...relatively low pregnancy rate ( welll...) That could also explain the difference in genetic diversity?
Phrased another way - for an equivalent period of time there might have simply been more generations of chimpansees compared to generations of humans.
Could that account for the difference in genetic diversity (as well)?
I don't expect the BBC to do an exhaustive search of all the peer review journals every time they do a science story, but they should at least check their own archives to help explain an curious conundrum like this one.
The date given for the bottleneck, ~70,000 years ago, coincides perfectly with the largest volcanic explosion in the last half million years. One that spewed thousands of times as much ash as produced in the 1980 Mt. St. Helens eruption.
The explosion of Toba in Indonedia around 74,000 years ago probably caused a greater than 5 degree drop in average global temperature that lasted over 6 years. 5 degrees may not seem like much but that global average may translate to over a 15C drop in the summertime temperatures in the temperate regions and would have devestating effects on many of the plants we relied on for food.
Point is that most of what I just mentioned (and much more) can be found in a few articles on their own web site:
"There is a thin line between ignorance and arrogance, and only I have managed to erase that line." - Dr. Science
This "news" is pretty old. There was even a Learning Channel (or Discovery) show a couple of years ago about the idea of "supervolcanoes", one of which could rest beneath Yellowstone and one (Toba) that, they think, blasted ~70K years ago, causing global average temperatures to drop and nearly causing our species to become extinct. Interesting stuff.
I don't know what happened to the cows. I do know that the Masai do, indeed, drink blood and milk mixtures. Having lived with a Jewish roommate, i can remember the look of horror on her face as she tried to interpret it into kosher food concepts.
Lactose Intolerance is not the only intolerance out there... Gluten intolerance hits 7% of the population (including me.) More women than men, mostly northern european descent. Me with my scottish pale skin and my german grey eyes, it's got my grandmum, my mum, my sister, and me. Skipped both brothers.
Part of my point being - there are genetic variations that are gender specific, there are genetic variations that are region-specific, and there are genetic variations that we're only just discovering. Another part of my point being- Lactose intolerance is unbelievably common. And i miss ice cream and milk. Lactase tablets aren't enough for a lot of people out there, that's how severe we're talking... I think maybe there are a number of changes that happened regionally, and now we're seeing the results as cultures blend. My dentist talked about it all the time, how asian teeth and african teeth and european teeth are similar but jawlines differ, and when you get different genes kicking in for jawbone and teeth it sometimes leads to really good combinations and sometimes leads to surgical correction so that the kid can chew. He said this in a completely nonracist way; he thought it was a great idea to blend genetic and cultural groups together, so he was more than happy to help correct the results of problem combinations, because they could usually be helped and their appearance meant that new combinations were always being created.
Oh, and about the Masai. Don't mess with a people who kill lions by hand. These are the people from the movie the ghost and the darkness- flushing out lions by shouting and beating the brush...
"I'd say 'Have a good time,' but arson is still illegal.
I'm surprised that article didn't pick up on the theory that the bottleneck in the genetic line about 70K years ago might well have been due to the eruption of the Toba supervolcano that was regarded as one of the most significant eruptions in the last 2 million years. That kind of climatic change from such an eruption could well be responsible.
"Provided by the management for your protection."
Wear uranium underwear!
Eat at Joe's.
As I remember from high school biology, doesn't only a small percentage of our DNA code for useful information? The reset was just junk that is cut out during protein synthesis (introns? extrons? I forget the terms...) Is this included in the study? Could it be that chimps are also extremely genetically uniform in the areas that matter, but they have more diverse "junk" material than us? Then again, I seem to remember someone saying that the "junk" DNA plays a vital part in evolution? Argh, guess I shouldn't have slept through those classes! Now we'll all become extinct!
Lactose intolerancy is a little bit more than just some farts... it's not like eating chili or something :)
It can really mess your day up... the major side effect of lactose intolerance is massive gastrointestinal issues stemming from the lactose not being broken down. I have it, and believe me it's not just gas or I could definately handle that.
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In 1959 Koshima macaque monkeys learned to swim, ever since then the entire group can swim...
Also in American colonial times the only human swimmers were witches...
The other arguments are interesting, but the swimming one is weak.
"I'll have a Guinness, no wait, make that a Coors Light" -Grad student I work with, who shall remain anonymous...
Why didn't they domesticate goats for milk production instead of cows? Goats don't produce lactose in their milk. We can't easily switch now because goat milk tastes too different from cow's milk. We are too used to the taste. Cow milk is kind of like the QWERTY of milk.
Table-ized A.I.
Leave it to an anthro major to pull out bullshit like that.
Meanwhile, in the scientifc world, diversity has a specific technical meaning that can be measured using "H," or entropy, from Claude Shannon's information theory -- which is similar the measure of entroy in physics.
H(p) = - sum[i=1..X] (pi * log pi)
Just take Shannon's equation, plug in allele frequencies for the population (maybe use log base 4 for 4 base pairs?) and presto, a quantity of diversity
From the Ontario Goat Milk Producers' Association
It seems physically(not trying to get in a social debate) that dark skin would only be advantageous(you don't burn as bad), less skin cancer?
Ideas either way.
I believe those with darker skin need more sunlight to produce enough Folic Acid and Vitamin D. Thus the adaptation to lighter skin when we moved North to the Cloudy Continent.
-Ansel.
G=C800:5