Archaic Genes in Modern People?

Science Magazine | 2005-04-22 | Elizabeth Culotta

[Lessismore]

MILWAUKEE, WISCONSIN--About 1200 researchers gathered near the shores of Lake Michigan here from 5 to 9 April to discuss early Englishmen, the birth of modern humans, and Stone Age weapons.

In the past 15 years, a flood of genetic data has helped propel the Out of Africa theory into the leading explanation of modern human origins. DNA from mitochondria (mtDNA), the Y chromosome, and ancient humans each suggest that the ancestors of all living people arose in Africa some time after 200,000 years ago, swept out of their homeland, and replaced archaic humans around the globe without mixing with them. But at a genetics symposium, two independent groups presented data from the X chromosome hinting that modern humans interbred with other human species: The teams found possible traces of archaic hominids in our genes. "Just as the Y and mtDNA data seemed to have settled it, the new data revive the question [of interbreeding]," says Stanford University's Joanna Mountain, co-organizer of the symposium. "The controversy is not settled." Geneticists Makoto Shimada and Jody Hey of Rutgers University in Piscataway, New Jersey, presented an intriguing haplotype--a set of genetic mutations inherited together--that appears to have ancient roots in Asia rather than Africa. Shimada sequenced a 10.1-kilobase noncoding region in 659 individuals from around the world. Overall, the genetic variations were most frequent in Africa, just as expected if our ancestors were a subset of ancient Africans who migrated out of that continent. But one rare variant, appropriately named haplotype X, appeared in nine individuals from Europe to Oceania but was entirely absent in Africa. Shimada estimated that the haplotype arose 1 million years ago, long before the modern human exodus from Africa. "Haplotype X is difficult to explain by the recent African origins model," says Shimada. "It's very old, it's rare, and it is widespread outside of Africa."

In independent work, geneticist Michael Hammer of the University of Arizona in Tucson offered a similar example. Hammer and postdoc Dan Garrigan identified a 2-million-year-old haplotype in the RRM2P4 region of the X chromosome that is common in East Asia but vanishingly rare in Africa. Their work, published 2 months ago in Molecular Biology and Evolution, raises the possibility that the haplotype arose in very ancient Asian populations, presumably of Homo erectus, an ancient human once found across Asia. "This is what you'd expect if you had introgression" between modern humans and H. erectus, Hammer said.

But at this point several other explanations are possible. Hey of Rutgers acknowledges, for example, that haplotype X may be present in Africa but was missed by spotty sampling in that continent. "Simply observing those [examples] is not sufficient to rule out one model or another," cautions Mountain. "What you need is 10 or 50 loci--one or two is not sufficient." Hammer, for one, thinks that these preliminary data do "speak to some archaic admixture. The few [loci] we've done so far are so suggestive that it gives me great excitement to continue sequencing more loci."

[dread78645]

Also, I've read that the brain size of Cro-Magnon Man was larger than modern humans. And, someone mentioned on another thread that Homo-Erectus and Neanderthal had larger brains too but, I suspect this is incorrect.

Cro-Magnon is about the same height, a larger brain case (~1500cc), and probably larger in body size than modern humans (we got smaller around the start of agriculture 15,000 - 10,000 ya). But anatomically, they were modern humans.

Brain capacity, in general:

• A. afarensis 375-550
• A. africanus 420-500
• H. habilis 550-725
• H. ergaster 750-900 (remained in Africa)
• H. erectus 800-1225 (migrated out of Africa)
• H. heidelbergensis 1200-1300
• H. sapien neanderthalensis 1350-1750
• H. sapien sapien 1300-1500

[<1/1,000,000th%]

Now we're going to start having some fun.

[blam]

" I'm not sure about Cro-Magnon, although my impression was that they are all but indistinguishable from modern humans. "

The only one I'm certain about are the Cr-Magnon, they had a larger brain than moderns. The jury is still out on all others.

Here's an info filled article, Human Origins, I read down to where it said that Neanderthals had a larger brain than moderns(us).Gotta do something else now, back later.

[blam]

Characteristics of Neanderthals:

1. Brain size average 1500 cc (larger than ours).
2. Thicker, more robust bones.
3. Cranium large, long, low with marked brow ridges.
4. Forehead higher than Homo erectus but lower than Homo sapiens.
5. Face projecting forward; nose large.
6. Front teeth large, heavily worn as if used as a vice to hold objects.
7. No chin

[b_sharp]

"Make that two of us, out of Africa is bogus."

"What's your evidence for that conclusion?"

He really, really wants it to be.

[Frumious Bandersnatch]

hinting that modern humans interbred with other human species

But, but, but I thought that one of the (nearly) sacred definitions of a sexual species was that it could not breed true outside of itself.

[b_sharp]

"Jessy Jackson, Al Sharpton, Louis Farrakhan , and all the race baiters are all sadden now. "

"Yes, they will be sadden now that there maybe evidence that humans came from SE ASIA and not from Africa and will target their racism more towards Asians now instead of Caucasians."

You might want to reread the post. Apparently you mis-understood it the first time.

[b_sharp]

"I guess it comes down to a battle between natural evolution and human-directed evolution. Which will win?"

There is no winning against natural evolution. Until we can completely control our environment, including pathogens, we will be unable to overcome or even just surpass natural evolution.

Even our technology and societal structure causes undirected, natural evolution, we simply cannot get away from it.

[js1138]

But, but, but I thought that one of the (nearly) sacred definitions of a sexual species was that it could not breed true outside of itself.

That would be a creationist definition of species.

In real biology, it's more complicated.

[Frumious Bandersnatch]

Sorry, but it seems to be, in point of fact, an evo argument. Whenever speciation is inferred by these people as a result that either the species will not mate outside of their own group, that they cannot mate outside of their own group or they cannot produce non-sterile children outside of their own group.

This, of course applies to sexual species only.

[PatrickHenry]

Characteristics of Neanderthals:
1. Brain size average 1500 cc (larger than ours).
2. Thicker, more robust bones.
3. Cranium large, long, low with marked brow ridges.
4. Forehead higher than Homo erectus but lower than Homo sapiens.
5. Face projecting forward; nose large.

[narby]

Thanks for the ping PH.

Good post and good responses all around.

[js1138]

Whenever speciation is inferred by these people as a result that either the species will not mate outside of their own group, that they cannot mate outside of their own group or they cannot produce non-sterile children outside of their own group.

OK, but that isn't what you originally said. It's still more complicated than this. The most common cause of speciation is geographical isolation. There are such things as ring species, whose territories span great distances. Any two individuals separated by short distance can and will mate, but individuals from the extreme ends of the range will not mate if given the opportunity.

Specises is not a clean and tidy concept.

[Doctor Stochastic]

Doesn't work that way. The "center" gets the most mutations. Same for language. English has more variations in London than in India.

[Frumious Bandersnatch]

That's exactly what I said, only with more words. And you are right that speciation is not neat and tidy. It is often times in the eye of the beholder. IOW, what one person claims is a species another person claims is not.

However, it is generally agreed amongst evos that if two disparate sexual groups are able to interbreed as a matter of course, and their offspring can also breed, then the two groups are of the same species.

That's my point. How can two separate species of humanoids interbreed and produce non-sterile offspring. My argument here, would be that both groups are of the same species and that they are probably of different races, certainly no more than different sub-species.

[js1138]

However, it is generally agreed amongst evos that if two disparate sexual groups are able to interbreed as a matter of course, and their offspring can also breed, then the two groups are of the same species.

No, that's a very confused statement.

Of course individuals that routinely breed are of the same species, but there are populations that are genetically capable of producing fertile offspring that seldom or never interbreed. You are asking questions that imply the word species somehow determines reality. Species is just a word with fuzzy edges. Darwin called species a strong variety. He also used the term race interchangeably with species. They're just words.

[Frumious Bandersnatch]

Actually, it is very clear. Reread it. It appears to me that either you don't understand what the statement "as a matter of course" means or you missed it in your reading of my post.

That said, I reiterate that I'm not trying to start a flamefest here. I'm just pointing out that amongst evos, speciation is often a matter of opinion that has nothing to do with the ability to crossbreed. The article implied that different species of humanoids interbred routinely. According to your own statement, this means that these humanoids were not of different species.

[Protagoras]

Evolution is amazing... I wonder who invented it?

[Protagoras]

I know people who have skulls like that now. I wonder what they will think if they are all dug up in a few thousand years?

[SunkenCiv]

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