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.

[dead]

Barely.

[realpatriot71]

Chimps are HARDLY clean! Ask a rabbi if he'd eat one. Sheeesh.

Lev. 11:1-8

[MeekOneGOP]

Yep!

[AndrewC]

I don't believe in Cleveland. Yet Cleveland exists.

A good example of self-contradiction.

be·lieve (b-lv)
v. be·lieved, be·liev·ing, be·lieves
v. tr.

1. To accept as true or real:

re·al¹ (rl, rl)
adj.

1. 1. Being or occurring in fact or actuality; having verifiable existence: real objects; a real illness.
   2. True and actual; not imaginary, alleged, or ideal: real people, not ghosts; a film based on real life.
   3. Of or founded on practical matters and concerns: a recent graduate experiencing the real world for the first time.

ex·ist (g-zst)
intr.v. ex·ist·ed, ex·ist·ing, ex·ists

1. To have actual being; be real.

[another cricket]

Chimps are HARDLY clean! Ask a rabbi if he'd eat one. Sheeesh.
Lev. 11:1-8

I think that non-carnivorous animals were considered "clean" at this point in time. After all, the only two commandments given after the flood were:
1.) If a man sheds another mans blood, then by man shall his blood be shed.
2.) Every living creature I have given to you as meat but the blood that is the life you shall not eat.

No mention of the split hoofed, cud chewers being the only clean animal allowed for dinner.

A. Cricket

[John O]

I stand (possibly) corrected. While chimps are not clean according to Mosaic law, what was the definition to Noah (who was dead well before Moses was born)?

(Of course this is drifting off topic just slightly.)

GSA(P)

[John O]

Yah, what another cricket said!

(Thanks AC)

GSA(P)

[realpatriot71]

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.

I didn't make God sound like anything. I was throwing out ideas. You're the one making inferences.

A perfect creation, I would imagine, had one one set of traits per gene, all dominant. However, because the affects of time, the enviroment, and sin in the world after the fall of man, mutations, in an otherwise perfect creation, manfested themselves as recessive traits, and sometimes as dominant traits.

[realpatriot71]

I was hasty, and forgot about the generation times of chimps. I'm still searching how much affect generation time has on rate of mutation, and whether this is enough to give the significant amount of variation seen in chimps versus humans from a gene pool the size of that after the flood.

[Baseballguy]

A Stormy Past

Noah!!! God is a real part of our being.

[realpatriot71]

Well the next place we read about clean and unclean animals is in Lev. 11. I would personally think, that the nature of God, as expressed in the Bible, would be one that is not arbitrary. I would think that an unclean animal in Levitcus was unclean before then, and still is today. I would thik that it would be quite silly for it to be otherwise.

[Sabertooth]

I didn't make God sound like anything. I was throwing out ideas. You're the one making inferences.

Bingo. See my post at #113.

Interesting that it's the dogmatists on both sides who are quickest to grind the theological axes. Desperation is a funny thing, isn't it?

[AndrewC]

Interesting that it's the dogmatists on both sides who are quickest to grind the theological axes.

God rated parts of creation "good" and his total creation "very good", thus not perfect.

Gen 1:4 And God saw the light, that [it was] good:
Gen 1:10 And God called the dry [land] Earth; and the gathering together of the waters called he Seas: and God saw that [it was] good.
Gen 1:12 And the earth brought forth grass, [and] herb yielding seed after his kind, and the tree yielding fruit, whose seed [was] in itself, after his kind: and God saw that [it was] good.
Gen 1:18 And to rule over the day and over the night, and to divide the light from the darkness: and God saw that [it was] good.
Gen 1:21 And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that [it was] good.
Gen 1:25 And God made the beast of the earth after his kind, and cattle after their kind, and every thing that creepeth upon the earth after his kind: and God saw that [it was] good.
Gen 1:31 And God saw every thing that he had made, and, behold, [it was] very good.

[another cricket]

I would personally think, that the nature of God, as expressed in the Bible, would be one that is not arbitrary. I would think that an unclean animal in Levitcus was unclean before then, and still is today. I would thik that it would be quite silly for it to be otherwise.

When the Law was given to Moses it was refined from the simple commandments given before and immediately after the flood. The Law clearly laid out what meant what, with all ifs, ands or buts covered.

Take rule one for example.

1.) If a man sheds another mans blood, then by man shall his blood be shed.

Very simple and basic. However in the Law of Moses you find many examples of where the rule is refined. Cities of Refuge and the difference between Homicide and Involuntary Manslaughter being just two examples.

2.) Every living creature I have given to you as meat but the blood that is the life you shall not eat.

Rule two has many of the same refinements.

Prior to the flood there were clean and unclean animals but the rule had nothing to do with eating the animal. Another refinement, if you will. Arbitrary? No. Refined? Yes.

A. Cricket

[John O]

I would personally think, that the nature of God, as expressed in the Bible, would be one that is not arbitrary. I would think that an unclean animal in Levitcus was unclean before then, and still is today

We are not talking about the nature of God changing. We are talking about the nature of animals changing.

I find nothing scriptural that details what is clean and unclean prior to the flood. Seems that the only command was that quoted by AC earlier. Every beast is for food.

GSA(P)

[Torie]

Here's my layman's theory. Humans are very agressive and mobile. The varient of human that had a competitive advantage in rather short order wiped out all competitors to its niche.

[JerseyHighlander]

It might not be PC, but has anyone postulated that those chimpanzee communities are extremely inbred, and the inbreeding has caused huge amounts of genetic mutations over the millenia. Looking at it in this light, it seems more to represent differing methods of population propagation between humans as opposed to chimpanzees and Saddam Hussein's clan.

[jlogajan]

However, because the affects of time, the enviroment, and sin in the world after the fall of man, mutations, in an otherwise perfect creation, manfested themselves as recessive traits, and sometimes as dominant traits

So God neglected to think ahead. Kind of a flawed super-being you have there. But continue to make excuses for him. It is fun to watch.

[jlogajan]

The varient of human that had a competitive advantage in rather short order wiped out all competitors to its niche.

That sounds reasonable. But I think a lot of DNA variation doesn't really manifest itself outwardly. For instance, two DNA divergent chimps might look very similar. So not much to select each other for or against.

However, I do agree that aggressive humans were pretty good at "trimming" divergent branches (killing strangers.) Humans are effective and practiced killers of themselves.

[realpatriot71]

Honestly, I feel you guys are rationalizing. My point about the nature of God is that he doesn't change, so why would God's list of clean and unclean animals change? What were the criterea for clean and unclean before the flood, if not consumtion, then what?