When Humans Faced Extinction

BBC ^ | 6-10-2003 | Dr David Whitehouse

[blam]

When humans faced extinction

By Dr David Whitehouse
BBC News Online science editor

Humans may have come close to extinction about 70,000 years ago, according to the latest genetic research.

From just a few, six billion sprang

The study suggests that at one point there may have been only 2,000 individuals alive as our species teetered on the brink.

This means that, for a while, humanity was in a perilous state, vulnerable to disease, environmental disasters and conflict. If any of these factors had turned against us, we would not be here.

The research also suggests that humans (Homo sapiens sapiens) made their first journey out of Africa as recently as 70,000 years ago.

Little diversity

Unlike our close genetic relatives - chimps - all humans have virtually identical DNA. In fact, one group of chimps can have more genetic diversity than all of the six billion humans alive today.

It is thought we spilt from a common ancestor with chimps 5-6 million years ago, more than enough time for substantial genetic differences to develop.

The absence of those differences suggests to some researchers that the human gene pool was reduced to a small size in the recent past, thereby wiping out genetic variation between current populations.

Evidence for that view is published in the American Journal of Human Genetics.

Oldest members

Because all humans have virtually identical DNA, geneticists look for subtle differences between populations.

One method involves looking at so-called microsatellites - short, repetitive segments of DNA that differ between populations.

These microsatellites have a high mutation, or error, rate as they are passed from generation to generation, making them a useful tool to study when two populations diverged.

Researchers from Stanford University, US, and the Russian Academy of Sciences compared 377 microsatellite markers in DNA collected from 52 regions around the world.

Analysis revealed a close genetic kinship between two hunter-gatherer populations in sub-Saharan Africa - the Mbuti pygmies of the Congo Basin and the Khosian bushmen of Botswana.

First migration

The researchers believe that they are "the oldest branch of modern humans studied here".

The data also reveals that the separation between the hunter-gatherer populations and farmers in Africa occurred between 70,000 and 140,000 years ago. Modern man's migration out of Africa would have occurred after this.

An earlier genetic study - involving the Y chromosomes of more than 1,000 men from 21 populations - concluded that the first human migration from Africa may have occurred about 66,000 years ago.

The small genetic diversity of modern humans indicates that at some stage during the last 100,000 years, the human population dwindled to a very low level.

It was out of this small population, with its consequent limited genetic diversity, that today's humans descended.

Small pool

Estimates of how small the human population became vary but 2,000 is the figure suggested in the latest research.

"This estimate does not preclude the presence of other populations of Homo sapiens sapiens (modern man) in Africa, although it suggests that they were probably isolated from each other genetically," they say.

The authors of the study believe that contemporary worldwide populations descended from one or very few of these populations.

If this is the case, humanity came very close to extinction.

[Doctor Stochastic]

Actually, Jenner based his work on Turkish practices. Of course, the resistance to smallpox is different from allergies.

[Aric2000]

Well, I know that 45% of scientist believe in theistic evolution.


Since I am not a scientist though, I am pleased to be a part of your group as well Cobalt.

[dsc]

"fantasy, folk tale, or maybe even science fiction story"

Well, you know, Einstein said something to the effect that science consisted of thinking God's thoughts after Him.

[Fiddlstix]

Bump

[ffusco]

Yup. I did mean those two particles.

[ffusco]

What Turkish practices? Like caling The Saint Sofia the hagai Sofia-Preteners All.

[stuartcr]

To me, it doesn't make sense that if someone can believe that God is the creator of all, how can they not believe that He created stuff in the beginning, then that stuff evolved. Seems like a no-brainer.

[Doctor Stochastic]

The Turkish practice of exposing people to cowpox to induce smallpox immunity. It was based on observed immunity of milkmaids. Jenner expanded and improved the idea. This is discussed in history of medicine books.

[Mike Darancette]

There are different types of sperm that have different functions - killers, blockers, and egg-getters.

Like a little Hockey Team in there. :)

[JosephW]

It's actually the Hagia Sophia.

Hagia comes from the Greek Agios (pardon mis-spellings) which means holy or saint.

Hence Hagia Sophia is Saint Sophia.

Those that carry their laundry on their head do not refer to it by this name, they have picked something else (which I do not remember nor care to know). They did however bastardize it by placing minarets around it and other alterations.

[js1138]

Fascinating concept, which would make a great fantasy, folk tale, or maybe even science fiction story.

That was a premise in Arthur Clarke's 2001, the book (not made clear in the movie).

[CobaltBlue]

>> Seems like a no-brainer.<<

I agree. My home page on my web browsers (all of them, I use IE, Netscape, and Opera - my favorite is Opera but some web pages don't recognize Opera) is NASA's Astronomy Picture of the Day. Very cool way for the layman to learn cosmology.
http://antwrp.gsfc.nasa.gov/apod/astropix.html

I know that the evolution of the Universe and the evolution of life forms are not related, but in my mind they are analogous. The Universe started out as gas and became more complex over time. A couple of days I learned the theory that the Sun is a Third Generation star - which I gather means that our Sun is made up, in part, of material from dead stars, two generations of dead stars.
http://www.physlink.com/Education/AskExperts/ae465.cfm

When I first heard the term Intelligent Design, I thought it might mean that people had discovered that a drive towards complexity was somehow programmed into physical matter, which I have seen in science fiction, and that they had somehow decoded that, but unfortunately, that's not the case.

Nobody really knows the First Cause.

[CobaltBlue]

Brandywines are heirloom tomatoes, first developed by Amish farmers near Brandywine, Pennsylvania.

People in Alabama do grow heirloom tomatoes. Here is a link to a thread on the Alabama Gardening forum on Gardenweb.com.
http://forums.gardenweb.com/forums/load/alabgard/msg0218462815146.html

I post on Gardenweb as Msilaine. Probably should change it to CobaltBlue just to be consistent.

[CobaltBlue]

Your mama probably grew Creoles. I am from New Orleans and that's the tomato that everybody grows in New Orleans. They get huge and RED and are tangy and strong tomato flavor. They don't crack too much when it rains.

Hybrid tomatoes just don't taste as good, but they are disease resistant.

I had to turn my tomato bed into a flower bed because of viruses and there is no other really sunny place for tomatoes except along the sidewalk leading to the front door, so I am not growing tomatoes this year.

[CobaltBlue]

On second thought, if your mama saved her seeds every year, no telling what she grew, it could have been something she developed all on her own. If you grow the old style tomato, not the hybrid kind, but the kind they call heirloom now, they are open pollinated and so you can get new varieties due to pollination, especially if you grow different varieties.

Evolution in your tomato bed. ;^)

[ffusco]

Thanks. Typical behavior of a bastard culture.

[CobaltBlue]

Conquerors have appropriated the religious sites of vanquished foes throughout history - long before recorded history.

[stuartcr]

I agree with your analogy. When you think about the amount of time that is involved with a third generation star, you begin to realise that we are speaking about time periods that are virtually incomprehensible to humans. If God truly is the creator of all, then we can begin to realise just how tiny a part in all this, we have.

[Mamzelle]

Oh, please don't post your CV.

When a discussion board thread devolves into dueling credentials, it becomes a dead bore.

If you're so teddibly smart, why bother even talking to me?

[CobaltBlue]

I have no idea whether I am smarter than you, not that it matters. Facts are facts.

Real scientific research doesn't rest on hands waving. It may rest on faulty assumptions, but that's what the next generation of scientific researchers is for. Learning never stops.