Ice Age Ancestry May Keep Body Warmer and Healthier

NY Times ^ | January 9, 2004 | NICHOLAS WADE

[neverdem]

A team of California geneticists has found that many of the world's peoples are genetically adapted to the cold because their ancestors lived in northern climates during the Ice Age. The genetic change affects basic body metabolism and may influence susceptibility to disease and to the risks of the calorie-laden modern diet.

The finding also breaks ground in showing that the human population has continued to adapt to forces of natural selection since the dispersal from its ancestral homeland in Africa some 50,000 years ago.

The genetic adaptation to cold is still carried by many Northern Europeans, East Asians and American Indians, most of whose ancestors once lived in Siberia. But it is absent from peoples native to Africa, a difference that the California team, led by Dr. Douglas C. Wallace of the University of California, Irvine, suggest could contribute to the greater burden of certain diseases in the African-American population.

Other experts praised the findings about adaptation to cold but said the role of mitochondria, relics of captured bacteria that serve as the batteries of living cells, in these diseases was less certain.

The genetic change affects the mitochondria, which break down glucose and convert it into the chemical energy that drives the muscles and other body processes. But the mitochondria will generate heat as well, and less chemical energy, if certain mutations occur in their DNA that make the process less efficient. Just such a change would have been very helpful to early humans trying to survive in cold climates.

Dr. Wallace and his colleagues have now decoded the full mitochondrial DNA from more than 1,000 people around the world and found signs of natural selection. By analyzing the changes in the DNA, they have been able to distinguish positive mutations, those selected because they are good or adaptive, from negative or harmful mutations. In today's issue of the journal Science, they report that several lineages of mitochondrial DNA show signs of positive selection.

These lineages are not found at all in Africans but occur in 14 percent of people in temperate zones and in 75 percent of those inhabiting Arctic zones. Dr. Wallace and his colleagues say this correlation is evidence that the lineages were positively selected because they help the body generate more heat.

Until now, most genetic change in the human population since it left Africa has been thought to be either random or just the elimination of harmful mutations. The evidence of the new analysis is that positive or adaptive selection "played an increasingly important role as people migrated out of Africa into temperate and Arctic Eurasia," the California team writes.

One implication is that everyone is adapted to a particular climate zone, and that moving to different zones may cause certain stresses. Mitochondria of the lineages found in Africa, Dr. Wallace suggests, may contribute the extra burden of certain diseases found among African-Americans, like diabetes and prostate cancer.

His reasoning is that African lineage mitochondria have never had to develop a mechanism for generating extra heat. So when an African-American and a European-American eat the same high calorie diet, the European's mitochondria burn some calories off as heat but the more efficient African mitochondria are liable to generate more fat deposition and oxidative damage, two results that could underlie the higher disease rates, Dr. Wallace said.

Separately, some of the European mitochondrial lineages appear to protect against Alzheimer's and Parkinson diseases and to be associated with greater longevity.

"Therefore," the California team writes, "to understand individual predisposition to modern diseases, we must also understand our genetic past, the goal of the new discipline of evolutionary medicine."

While many scientists study the genes of the human cell's nucleus, Dr. Wallace has focused on the tiny mitochondrial genome for 33 years. Along with the late Dr. Allan Wilson, he has pioneered the tracing of the 20 or so mitochondrial lineages found in the human population, all of which link back to a single individual known as the mitochondrial Eve.

Several other experts said that Dr. Wallace's ideas were promising but that the role of mitochondria in degenerative diseases had yet to be established. "It's a very attractive idea and may well turn out to be right, although the biochemical evidence of uncoupling differences between the mitochondrial lineages has yet to be nailed down," said Dr. Lawrence Grossman, a mitochondria expert at Wayne State University.

Dr. Mark Seielstad, a population geneticist at the Genome Institute of Singapore, said the positive selection was likely to have been a "major architect" in shaping mitochondria and that Dr. Wallace's work should throw open discussion of the subject.

Two experts on mitochondrial disease, Dr. Michael Brown of the Mercer University School of Medicine in Macon, Ga., and Dr. Gino Cortopassi of the University of California, Davis, said Dr. Wallace's ideas about African mitochondria made sense but had yet to reach practical significance. "We've not yet got to the stage of being able to give advice to African Americans," Dr. Brown said.

Dr. Wallace says that climatic selection may have operated on the human population from the moment it moved north of the African tropics. Most such pioneers died but two lineages, known as M and N, arose in northeast Africa some 65,000 years ago and might have been adapted to temperate climates. Almost everyone outside of sub-Saharan Africa has mitochondria descended from the M and N lineages.

[ruoflaw]

I know a guy that spent a year studying archaeology in Scottland and he just loved Haggis...but I just don't think I could eat it much less look at it!

[blam]

"Where's your son been lately?? "

He doesn't come onto FR very often. He's a space scientists in SOCAL.(PhD physics). My only child.

[cyborg]

If I was a space scientist I'm sure I'd be busy too. Understood!

[raynearhood]

"Shocking. How can this be? The creationists keep insisting that all mutations are harmful."

Actually, that is incorrect, sir. Just that where there are beneficial mutations there has never been, nor is mathematically possible to have, enough subsequent beneficial mutations to actually cause any adaptive species change. A dog is a dog is a dog, and never will be otherwise.

"By analyzing the changes in the DNA, they have been able to distinguish positive mutations, those selected because they are good or adaptive, from negative or harmful mutations. In today's issue of the journal Science, they report that several lineages of mitochondrial DNA show signs of positive selection."

Another thing of which one must be careful. Beneficial mutations occurring are often presented as fact when it is, in fact, the extrapolated interpretation of observation by scientists based on the model of science they use. This is called THEORY.
Another scientist could interpret the facts this way:
"By analyzing the changes in the DNA, they have been able to distinguish positive changes, those caused by the specimen's ability to genetically vary within its kind, from negative or harmful mutations."

In the end, neither creationism nor evolutionism is proved or advanced.

Sorry to all.

Present undeniable, observable fact for either side, and I'll bite.

[neverdem]

I frequently scan the Slimes science section. I can't believe they didn't can this story. Sometimes I'll post their articles when I see something that's worth the trouble of posting. I ping you when I do unless you Freepmail me otherwise. No offense would be taken.

[VeritatisSplendor]

Unmentioned here is a very interesting point about mitochondrial evolution. The mutations are transmitted infallibly from mother to child, and not shuffled with the chromosomes. The concepts "dominant" and "recessive" don't apply. This allows for more efficient selective pressure, but only acting through females.

[JudyB1938]

If it's not too much trouble, I would appreciate your adding me to your ping list. Thanks.

[Ernest_at_the_Beach]

Very interesting!

Please add me to your ping list, thanks!

[Notforprophet]

Great article, thanks for posting it.

NFP

[SunkenCiv]

Just updating the GGG information, not sending a general distribution.

Please ping me to other topics which are appropriate for the GGG list. Thanks.

Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)

[SunkenCiv]

· join list or digest · view topics · view or post blog · bookmark · post a topic ·
	Gods Graves Glyphs	Just updating the GGG info, not sending a general distribution. To all -- please ping me to other topics which are appropriate for the GGG list. GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach
·Dogpile · Archaeologica · ArchaeoBlog · Archaeology · Biblical Archaeology Society · · Discover · Nat Geographic · Texas AM Anthro News · Yahoo Anthro & Archaeo · Google · · The Archaeology Channel · Excerpt, or Link only? · cgk's list of ping lists ·

[neverdem]

Thanks for resurrecting the thread, SunkenCiv. See comment# 65. It started my health & science ping list. JudyB1938 and fourdeuce82d have passed away. fourdeuce82d and I were in the same heavy mortar platoon, 1st Battalion, 504th Parachute Infantry Regiment, 1st Brigade, 82nd Airborne Division in the early 1980s.

There's supposed to be a handle on that flaming sword. I didn't notice one at the link.

The early airborne divisions included glider infantry regiments. Don't ask me what's the difference between a brigade and brigade combat team. Army combat brigades were always mixes of combat arms battalions, i.e. infantry and artillery and maybe armor(tanks), plus support troops.

Effects of Purifying and Adaptive Selection on Regional Variation in Human mtDNA

A phylogenetic analysis of 1125 global human mitochondrial DNA (mtDNA) sequences permitted positioning of all nucleotide substitutions according to their order of occurrence. The relative frequency and amino acid conservation of internal branch replacement mutations was found to increase from tropical Africa to temperate Europe and arctic northeastern Siberia. Particularly highly conserved amino acid substitutions were found at the roots of multiple mtDNA lineages from higher latitudes. These same lineages correlate with increased propensity for energy deficiency diseases as well as longevity. Thus, specific mtDNA replacement mutations permitted our ancestors to adapt to more northern climates, and these same variants are influencing our health today.

If you want to register, not subscribe, you can access the whole article. I posted the article as breaking news. They made it chat!

I corrected the spelling in my tagline since then. In Vietnamese it means I'm sorry sweetheart.

[Ernest_at_the_Beach]

Well...this is new to me.,...thanks for the revival.

[GOPJ]

Interesting post, neverdem. Thanks for the ping.

[SunkenCiv]

Yet another way is hot cocoa. :’)

[SunkenCiv]

Glad I could do it.

[SunkenCiv]

the classics never wear out:

The Neandertal Enigma
by James Shreeve
in local libraries

Frayer's own reading of the record reveals a number of overlooked traits that clearly and specifically link the Neandertals to the Cro-Magnons. One such trait is the shape of the opening of the nerve canal in the lower jaw, a spot where dentists often give a pain-blocking injection. In many Neandertal, the upper portion of the opening is covered by a broad bony ridge, a curious feature also carried by a significant number of Cro-Magnons. But none of the alleged 'ancestors of us all' fossils from Africa have it, and it is extremely rare in modern people outside Europe." [pp 126-127]