We Dodged Extinction

ABCNews ^ | Lee Dye

[Sabertooth]

We Dodged Extinction
	‘Pruned’ Family Tree Leaves Little Genetic Variety Just one group of chimpanzees can have more genetic diversity than all 6 billion humans on the planet. (Corel)

Special to ABCNEWS.com
A worldwide research program has come up with astonishing evidence that humans have come so close to extinction in the past that it’s surprising we’re here at all.
    Pascal Gagneux, an evolutionary biologist at the University of California at San Diego, and other members of a research team studied genetic variability among humans and our closest living relatives, the great apes of Africa.
     Humanoids are believed to have split off from chimpanzees about 5 million to 6 million years ago. With the passage of all that time, humans should have grown at least as genetically diverse as our “cousins.” That turns out to be not true.
     “We actually found that one single group of 55 chimpanzees in west Africa has twice the genetic variability of all humans,” Gagneux says. “In other words, chimps who live in the same little group on the Ivory Coast are genetically more different from each other than you are from any human anywhere on the planet.”

The branch lengths illustrate the number of genetic differences, not only between species, but among species as well. The pruned bush for humans shows how little genetic diversity exists. (Marco Doelling/ABCNEWS.com)

The Family Bush
“The family tree shows that the human branch has been pruned,” Gagneux says. “Our ancestors lost much of their original variability.”
     “That makes perfectly good sense,” says Bernard Wood, the Henry R. Luce Professor of Human Origins at George Washington University and an expert on human evolution.
     “The amount of genetic variation that has accumulated in humans is just nowhere near compatible with the age” of the species, Wood says. “That means you’ve got to come up with a hypothesis for an event that wiped out the vast majority of that variation.”
     The most plausible explanation, he adds, is that at least once in our past, something caused the human population to drop drastically. When or how often that may have happened is anybody’s guess. Possible culprits include disease, environmental disaster and conflict.

Almost Extinct
“The evidence would suggest that we came within a cigarette paper’s thickness of becoming extinct,” Wood says.
     Gagneux, who has spent the last 10 years studying chimpanzees in Africa, says the implications are profound.
     “If you have a big bag full of marbles of different colors, and you lose most of them, then you will probably end up with a small bag that won’t have all the colors that you had in the big bag,” he says.
     Similarly, if the size of the human population was severely reduced some time in the past, or several times, the “colors” that make up our genetic variability will also be reduced.
     If that is indeed what happened, then we should be more like each other, genetically speaking, than the chimps and gorillas of Africa. And that’s just what the research shows.
     “We all have this view in our minds that we [humans] started precariously as sort of an ape-like creature” and our numbers grew continuously, adds Wood. “We’re so used to the population increasing inexorably over the past few hundred years that we think it has always been like that.”
     But if it had, Gagneux notes, our genetic variability should be at least as great as that of apes.

A Stormy Past
Gagneux is the lead author of a report that appeared in the April 27 issue of the Proceedings of the National Academy of Sciences. The study, carried out with researchers in Germany, Switzerland and the United States, is the first to examine large numbers of all four ape species in Africa.
     “We can do that now because new technology allows us to non-invasively take some hair, or even some fruit that these apes chew, and then we get their DNA from a couple of cells that stick to a hair or a piece of fruit they chewed.”
     Then they compared the DNA variability of apes and chimps to that of 1,070 DNA sequences collected by other researchers from humans around the world. They also added the DNA from a bone of a Neanderthal in a German museum. The results, the researchers say, are very convincing.
     “We show that these taxa [or species] have very different amounts and patterns of genetic variation, with humans being the least variable,” they state.
     Yet humans have prevailed, even though low genetic variability leaves us more susceptible to disease.
     “Humans, with what little variation they have, seem to maximize their genetic diversity,” Gagneux says.
     “It’s ironic,” he notes, that after all these years the biggest threat to chimpanzees is human intrusion into their habitats. When he returned to Africa to study a group of chimps he had researched earlier, Gagneux found them gone.
     “They were dead,” he says, “and I mean the whole population had disappeared in five years.”
     Yet as our closest living relatives, chimps still have much to teach us about ourselves.

Lee Dye’s column appears Wednesdays on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

[Sabertooth]

I don't argue for a young Earth, and I'm not claiming this as evidence for the Flood, I'm just enjoying the convergence of the near extinction stories.

[John H K]

The effects of the eruption would have been the LEAST negative on humans in Equatorial Africa....where chimps lived in the first place. It's hypothesized that most of the humans that survived also lived in Equatorial Africa; this is why Africa has more human diversity, much more, than anywhere else; A Norwegian and an Italian are more gentically similar, in many cases, than an African in one tribe and an African in another tribe a few miles down the road.

It's not unusual for extinction events to have a larger effect on some animals compared to others. For one thing, they tend to affect animals more the larger they are (witness dinosaurs and mammals) and humans are a little bigger than chimps.

[realpatriot71]

A grand statement totally unsupported by any evidence whatsoever!

I ask you again which statement did I make that is unsupported by any evidence?

[Doctor Stochastic]

...but the eruption didn't effect chimps?

That would depend on where the populations resided and the relative numbers. If (for example) Toba were the culprit and a large portion of humans lived in Asia while a large portion of the chimps were in Afrika, the effect on humans could have been much greater. It's also possible that there were more chimps around then so killing 90% would still live the chimps with more individuals. There's no reason to expect similar effects on the different species.

[Sabertooth]

You've just ended the entire debate, Baby. Science and Creation are both wrong....

All is evil and madness!

[Rushian]

Maybe the three wives were identical triplets! You have to look at all the statistical possibilities.

[Victoria Delsoul]

LOL!!!

[Sabertooth]

BUT each of these had a genetically different wife.

Maybe, but probably not...

Who was the wife of Seth, son of Adam and Eve? His sister. You know that later, Sarah was Abraham's sister, as well as his wife, right? Prohibitions against incest did not come until later, under Moses I believe.

According to the Genesis story and Hebrew legend, there was much sexual perversion and comingling with demonic seed among the antediluvians... Noah's family was untainted. It's likely that the wives of Noah's sons were closely related.

[realpatriot71]

Maybe the three wives were identical triplets! You have to look at all the statistical possibilities.

Grasping at straws. Besides the Bible does not say they were sisters. I guess you have to skew the facts at every chance to fit your model of origins - most people call that intellectual dishonesty.

You still have not pointed to any statement I have made that is not supported.

[Captain Shady]

Human extinction ? First ,the flood--Now ,my mother-in-law.

[Rushian]

If the flood happened between 10,000 and 4000 years ago, there is no where near enough time for this much non-deletrious mutation and recombination to occur in order to see the differences that we do. This is the statement you grandly provided for the evolutionaryly deprived.

[Sabertooth]

It's not unusual for extinction events to have a larger effect on some animals compared to others. For one thing, they tend to affect animals more the larger they are (witness dinosaurs and mammals) and humans are a little bigger than chimps.

Barely. This is weak. We're not talking aboout anything like the size difference between a Triceratops and possum.

[realpatriot71]

According to the Genesis story and Hebrew legend, there was much sexual perversion and comingling with demonic seed among the antediluvians... Noah's family was untainted. It's likely that the wives of Noah's sons were closely related.

I've heard this speculation before, and I'm not doubting it, but I feel that the first part of Genesis 6 is rather obscure, and could mean any number of things, including God chose Noah because he was righteous.

Ok, here's something else to think about. God made two individuals. Obviously humanity had to come from these two, and then from their children. Adam and Eve would have had to of been quite different genetically in order for their children's children not to have problems. If this is the case then, God must have created genetic diversity into the human race as a way to avoid problems with the genetics of bother/sister pairings. In this way it still goes against the data, people should still have more genetic diversity.

Another possible idea I just thought of, was that there was no such thing as a recessive trait until the fall of man. Man's gene's were perfect, but became over time more and more imperfect due to exposure to mutagens. Imagine the possible amount of muation a germ line could take up when the people were living 900+ years. This could possibly help explain the genetic diversity we see with the chimps..

[razorbak]

There is evidence worldwide for a massive flood. Those who rule our a universal flood explain the evidence by positing many large local floods. Life that dies on the surface decays and disappears. If it is suddenly trapped and encased by sediment at high pressure it produces raw petroleum. Fossils themselves are evidence of a flood. The highest peaks on earth feature fossils of marine life. Unless mollusks are really good mountain climbers the anti-catastrophists have an immense problem.

[Sabertooth]

Another possible idea I just thought of, was that there was no such thing as a recessive trait until the fall of man. Man's gene's were perfect, but became over time more and more imperfect due to exposure to mutagens.

Here's where I have a problem with Evolution... where is the evidence of mutagenic speciation? Let alone randomly mutagenic evolution?

[vikingchick]

There's no way that I descended from a knuckle-dragging, hairy ape. Alec Baldwin, maybe, but not I. :)

[Rushian]

Don't understand. The fall of man took place in the first generation. And the age differences was the point I made earlier to explain the greater changes in the chimp descendants from Noah's two.

[Sabertooth]

There's no way that I descended from a knuckle-dragging, hairy ape.

Here's how I look at it...

Whether or not my forefathers were apes, Jesus' mother was a virgin.

[jlogajan]

God must have created genetic diversity into the human race as a way to avoid problems with the genetics of bother/sister pairings.

Why? You think if he was such an all powerful being, he could make DNA that didn't have sibling problems. You make him sound like a hacker banging out a quick and dirty work around to a bad initial design.

[Sabertooth]

You think if he was such an all powerful being, he could make DNA that didn't have sibling problems. You make him sound like a hacker banging out a quick and dirty work around to a bad initial design.

Why would the capacity for genetic diversity be an indicator of bad initial design?