News Article on Genetic Mutation and Evolution

[Guest guest]

I just stumbled on this article a few minutes ago in today's news. I

am posting it, not because of the article itself, but because of

some of the comments in it by so-called " scientists. " In one of my

two long psychic connections posts, I talked about " enigmas " and the

closed-mind thinking that tends to prevail in all academic and

scientific disciplines. If something doesn't fit the

established " theory, " don't question the theory, question the

whatever it is that doesn't fit.

This article is a perfect example. Of particular interest is the

comment by C. Owen Lovejoy of Kent State University " Such a claim is

counter to the fundamentals of evolution. "

I also found the following " criticism " interesting in light of what

I know to be true from cranialsacral therapy regarding fusion or non-

fusion of the cranial bones.

" Also, if large jaw muscles were eliminated, the plates that form

the skull would have fused and the brain compartment would not have

expanded. "

And it is just this kind of closed thinking that drives me nuts

regarding a lot of the conventional, westernized approaches to

health care and their resistance to alternative or complimentary

therapies. " Our minds are made up - don't confuse us with facts. "

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Gene Mutation Said Linked to Evolution

Wednesday, March 24, 2004

Touching off a scientific furor, researchers say they may have

discovered the mutation that caused the earliest humans to branch

off from their apelike ancestors — a gene that led to smaller,

weaker jaws and, ultimately, bigger brains.

Smaller jaws would have fundamentally changed the structure of the

skull, they contend, by eliminating thick muscles that worked like

bungee cords to anchor a huge jaw to the crown of the head. The

change would have allowed the cranium to grow larger and led to the

development of a bigger brain capable of tool-making and language.

The mutation is reported in the latest issue of the journal Nature

(search), not by anthropologists, but by a team of biologists and

plastic surgeons at the University of Pennsylvania and the

Children's Hospital of Philadelphia.

The report provoked strong reactions throughout the hotly contested

field of human origins (search) with one scientist declaring

it " counter to the fundamentals of evolution " and another

pronouncing it " super. "

The Pennsylvania researchers said their estimate of when this

mutation first occurred — about 2.4 million years ago, in the

grasslands of East Africa, the cradle of humanity — generally

overlaps with the first fossils of prehistoric humans featuring

rounder skulls, flatter faces, smaller teeth and weaker jaws.

And the remarkable genetic mutation persists to this day in every

person, they said.

Nonhuman primates — including our closest animal relative, the

chimpanzee — still carry the original big-jaw gene and the apparatus

enabling them to bite and grind the toughest foods.

" We're not suggesting this mutation alone defines us as Homo

sapiens, " said Dr. Hansell Stedman of the University of Pennsylvania

School of Medicine (search). " But evolutionary events are

extraordinarily rare. Over 2 million years since the mutation, the

brain has nearly tripled in size. It's a very intriguing

possibility. "

University of Michigan biological anthropologist Milford Wolpoff

called the research " just super. "

" The other thing that was happening 21/4 million years ago is that

people were beginning to make tools, which enabled them to prepare

food outside their mouths, " he said. " This is a confluence of

genetic and fossil evidence. "

Other researchers strenuously disagreed that human evolution could

literally hinge on a single mutation affecting jaw muscles, and that

once those muscles were reduced, the brain suddenly could grow

unfettered.

" Such a claim is counter to the fundamentals of evolution, " said C.

Owen Lovejoy of Kent State University. " These kinds of mutations

probably are of little consequence. "

Others sought to find some middle ground in the debate.

University and commercial laboratories rapidly are comparing the

human genome with that of chimpanzees to determine what makes people

human, and how the earliest transitional creatures known as hominids

split from Old World apes and monkeys some 6 million years ago.

So far, perhaps 250 genetic differences have been flagged for

further study.

Jaws have been a focus of evolutionary research since Darwin, and

the mutation offers a tantalizing theory. But it is unlikely that

one mutation — even at a crucial evolutionary juncture — would make

a person, some skeptics said.

" They have successfully nailed a genetic mutation that works to

deactivate these jaw muscles, " said Potts, director of the

Human Origins Program (search) at the sonian Institution. " But

their suggestion connecting it to the brain is way too speculative. "

In their experiment, the Pennsylvania team isolated a new gene in an

overlooked junk DNA sequence on chromosome 7. It belongs to a class

of genes that express production of the protein myosin, which

enables skeletal muscles to contract.

Originally the scientists were concentrating on determining the

biological underpinnings of Duchenne muscular dystrophy, a muscle-

wasting disease. But once they isolated the mutation, they spent the

next eight months deciphering its evolutionary implications.

Different types of myosin are produced in different muscles; in the

chewing and biting muscles, the gene MYH16 is expressed.

In primates like the macaque, the jaw muscles are 10 times more

powerful than in humans. They contain high levels of MYH16, and the

thick muscles attach to bony ridges of the skull.

But the Penn researchers discovered humans have a mutation that

prevents the MYH16 from accumulating, and our jaw muscles are

smaller.

As for when this genetic split occurred, the researchers came up

with a calculation based on the widely held belief that genetic

mutations occur at a constant rate.

Then they looked deep into the fossil record to determine when the

jaws of human ancestors started looking smaller and more

streamlined. What they found confirmed their estimate.

As far back as 2.4 million years ago, Homo habilis, or " handy man, "

emerged as the earliest known species to show distinctly human skull

and jaw traits, while retaining an apelike physique.

Its brain grew by about 25 percent over that of its more primitive,

nonhuman relatives Australopithecus and Paranthropus. This brain

increase may have coincided with the first known use of manufactured

stone tools, perhaps to extract marrow from animal bones.

The Homo line flourished, and finer-boned Homo varieties also

developed over the years. Modern humans, or Homo sapiens, appeared

about 150,000 years ago.

The Penn researchers said the jaw muscle mutation opened an

evolutionary struggle in which brain conquered brawn, although it

probably took another million years for Australopithecus and

Paranthropus to disappear, leaving the world to the Homo lineage.

Critics said the study takes several wrong turns.

Under the pressures of natural selection, mutations occur at

differing rates. So the jaw muscle mutation might have occurred far

earlier.

Also, if large jaw muscles were eliminated, the plates that form the

skull would have fused and the brain compartment would not have

expanded.

Many additional — and simultaneous — mutations probably are needed

to explain all the changes seen in Homo fossils, they said.

" The single mutation would have reduced the Darwinian fitness of

those individuals, " said anthropologist Bernard Wood of

Washington University. " It only would've become fixed if it

coincided with mutations that reduced tooth size, jaw size and

increased brain size. What are the chances of that? "