Free Republic
Browse · Search
News/Activism
Topics · Post Article

Skip to comments.

Gene May Be Key To Evolution Of Larger Human Brain [Evolution]
ScienceDaily Magazine ^ | 13 January 2004 | Staff

Posted on 01/13/2004 10:50:50 AM PST by PatrickHenry

Howard Hughes Medical Institute researchers have identified a gene that appears to have played a role in the expansion of the human brain's cerebral cortex -- a hallmark of the evolution of humans from other primates.

By comparing the gene's sequence in a range of primates, including humans, as well as non-primate mammals, the scientists found evidence that the pressure of natural selection accelerated changes in the gene, particularly in the primate lineage leading to humans.

The researchers, led by Howard Hughes Medical Institute (HHMI) investigator Bruce Lahn at the University of Chicago, reported their findings in an advance access article published on January 13, 2004, in the journal Human Molecular Genetics. Patrick Evans and Jeffrey Anderson in Lahn's laboratory were joint lead authors of the article.

"People have studied the evolution of the brain for a long time, but they have traditionally focused on the comparative anatomy and physiology of brain evolution," said Lahn. "I would venture, however, that there really hasn't been any convincing evidence until now of any gene whose changes might have contributed to the evolution of the brain."

In this study, the researchers focused on a gene called the Abnormal Spindle-Like Microcephaly Associated (ASPM) gene. Loss of function of the ASPM gene is linked to human microcephaly – a severe reduction in the size of the cerebral cortex, the part of the brain responsible for planning, abstract reasoning and other higher brain function. The discovery of this association by HHMI investigator Christopher A. Walsh and colleagues at Beth Israel Deaconess Medical Center is what prompted Lahn to launch an evolutionary study of the gene.

Lahn and his colleagues compared the sequence of the human ASPM gene to that fromsix other primate species shown genetically to represent key positions in the evolutionary hierarchy leading to Homo sapiens. Those species were chimpanzee, gorilla, orangutan, gibbon, macaque and owl monkey.

"We chose these species because they were progressively more closely related to humans," said Lahn. "For example, the closest relatives to humans are chimpanzees, the next closest are gorillas, and the rest go down the ladder to the most primitive."

For each species, the researchers identified changes in the ASPM gene that altered the structure of the resulting protein, as well as those that did not affect protein structure. Only those genetic changes that alter protein structure are likely to be subject to evolutionary pressure, Lahn said. Changes in the gene that do not alter the protein indicate the overall mutation rate – the background of random mutations from which evolutionary changes arise. Thus, the ratio of the two types of changes gives a measure of the evolution of the gene under the pressure of natural selection.

Lahn and his colleagues found that the ASPM gene showed clear evidence of changes accelerated by evolutionary pressure in the lineage leading to humans, and the acceleration is most prominent in recent human evolution after humans parted way from chimpanzees.

"In our work, we have looked at evolution of a large number of genes, and in the vast number of cases, we see only weak signatures of adaptive changes," said Lahn. "So, I was quite surprised to see that this one gene shows such strong and unambiguous signatures of adaptive evolution -- more so than most other genes we've studied."

By contrast, the researchers' analyses of the ASPM gene in the more primitive monkeys and in cows, sheep, cats, dogs, mice and rats, showed no accelerated evolutionary change. "The fact that we see this accelerated evolution of ASPM specifically in the primate lineage leading to humans, and not in these other mammals, makes a good case that the human lineage is special," said Lahn.

According to Lahn, among the next steps in his research will be to understand how ASPM functions in the brain. Studies by Walsh and others hint that the protein produced by the gene might regulate the number of neurons produced by cell division in the cerebral cortex. Lahn and his colleagues plan functional comparisons of the ASPM protein among different species, to understand how this gene's function or regulation changes with evolution.


TOPICS: Culture/Society; Miscellaneous; Philosophy
KEYWORDS: brain; crevolist; evolution; genetics
Navigation: use the links below to view more comments.
first 1-2021-25 next last
Everybody be nice.
1 posted on 01/13/2004 10:50:51 AM PST by PatrickHenry
[ Post Reply | Private Reply | View Replies]

To: *crevo_list; VadeRetro; jennyp; Junior; longshadow; RadioAstronomer; Physicist; LogicWings; ...
PING. [This ping list is for the evolution side of evolution threads, and sometimes for other science topics. FReepmail me to be added or dropped.]
2 posted on 01/13/2004 10:51:48 AM PST by PatrickHenry (Everything good that I have done, I have done at the command of my voices.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: PatrickHenry
I don't believe the size of the brain has much to do with it. It is in the structures.
3 posted on 01/13/2004 10:53:40 AM PST by RightWhale (How many technological objections will be raised?)
[ Post Reply | Private Reply | To 1 | View Replies]

To: PatrickHenry
Please add me to it. Thank you.
4 posted on 01/13/2004 10:56:08 AM PST by brazucausa
[ Post Reply | Private Reply | To 2 | View Replies]

To: PatrickHenry
Even Kierkegaard wuld have needed a jet pack to make the major leap of faith required to believe this....WHOA.....
5 posted on 01/13/2004 10:57:59 AM PST by joesnuffy (Moderate Islam Is For Dilettantes)
[ Post Reply | Private Reply | To 1 | View Replies]

To: PatrickHenry
"pressure of natural selection accelerated changes in the gene"

Could someone please explain this to me one more time? How does 'natural selection' cause a 'changed gene' to override the existing gene?

6 posted on 01/13/2004 10:58:46 AM PST by MEGoody
[ Post Reply | Private Reply | To 1 | View Replies]

To: PatrickHenry
Just wild speculation, but I suspect the number of mutations necessary to produce the human brain size will turn out to be surprisingly small.
7 posted on 01/13/2004 10:59:07 AM PST by js1138
[ Post Reply | Private Reply | To 1 | View Replies]

To: brazucausa
You joined FreeRepublic yesterday. That's fine. Welcome. But I'll need to see some of your posts before I can add you. (The list is only for the evolution side of these debates.)
8 posted on 01/13/2004 11:03:05 AM PST by PatrickHenry (Everything good that I have done, I have done at the command of my voices.)
[ Post Reply | Private Reply | To 4 | View Replies]

To: PatrickHenry
One reason for the lack of study is that only W.S.Gilbert could have made good lyrics from Abnormal Spindle-Like Microcephaly Associated .

It should also be noted that nowhere in the article is it claimed that humans descended from chimpanzees, gorillas, orangutans, gibbons, macaques or owl monkeys.

9 posted on 01/13/2004 11:10:55 AM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
[ Post Reply | Private Reply | To 1 | View Replies]

To: PatrickHenry
In a related study, researchers discovered that women wearing low-cut genes cause men's brains to shrink.
10 posted on 01/13/2004 11:12:42 AM PST by Roarkdude (no tag line entered)
[ Post Reply | Private Reply | To 1 | View Replies]

To: MEGoody
The owners of the existing gene don't reproduce as effectively as the owners of the selected gene.
11 posted on 01/13/2004 11:21:40 AM PST by Junior (Some people follow their dreams. Others hunt theirs down and beat them mercilessly into submission)
[ Post Reply | Private Reply | To 6 | View Replies]

To: MEGoody
The owners of the existing gene don't reproduce as effectively as the owners of the selected gene.
12 posted on 01/13/2004 11:21:44 AM PST by Junior (Some people follow their dreams. Others hunt theirs down and beat them mercilessly into submission)
[ Post Reply | Private Reply | To 6 | View Replies]

To: Junior
Posting is weird today. Many server errors.
13 posted on 01/13/2004 11:32:49 AM PST by js1138
[ Post Reply | Private Reply | To 12 | View Replies]

To: Junior
If you say it three times, does that make it true? ;^)
14 posted on 01/13/2004 11:38:56 AM PST by CobaltBlue
[ Post Reply | Private Reply | To 12 | View Replies]

To: CobaltBlue
"There's no place like home. There's no place like home. There's no place like home."

Nope.

15 posted on 01/13/2004 11:43:37 AM PST by Junior (Some people follow their dreams. Others hunt theirs down and beat them mercilessly into submission)
[ Post Reply | Private Reply | To 14 | View Replies]

To: MEGoody
Could someone please explain this to me one more time ["pressure of natural selection accelerated changes in the gene"]? How does 'natural selection' cause a 'changed gene' to override the existing gene?

It was sloppily worded. The gene under discussion is presumably a mutated version of one which exists in more primitive primates. Natural selection (i.e., death by incompetence or other inability to survive and reproduce) gradually filtered out those individuals who did not possess the mutated gene, thus assuring the predominance of the changed gene in the population. There is no "override," to speak of. Just a higher reproductive success rate for those possessing the mutation.

16 posted on 01/13/2004 11:47:06 AM PST by PatrickHenry (Everything good that I have done, I have done at the command of my voices.)
[ Post Reply | Private Reply | To 6 | View Replies]

To: Roarkdude
In a related study, researchers discovered that women wearing low-cut genes cause men's brains to shrink

No, we're talking about the genes having to do with reproduction-- I mean, we're talking about how they control the brain-- forget it.

17 posted on 01/13/2004 12:24:01 PM PST by expat_panama
[ Post Reply | Private Reply | To 10 | View Replies]

To: PatrickHenry
"Natural selection (i.e., death by incompetence or other inability to survive and reproduce) gradually filtered out those individuals who did not possess the mutated gene, thus assuring the predominance of the changed gene in the population."

Hmmm. . .then that question that gets laughed at by evolutionists so much comes to mind. If 'natural selection' means death by incompetence or other inability to survive and reproduce, why are there still apes? Shouldn't they have ceased to exist based on these criteria? If not, why wouldn't some forms of life between apes and man exist? Why would they be less 'competent' to survive than apes?

18 posted on 01/13/2004 2:18:00 PM PST by MEGoody
[ Post Reply | Private Reply | To 16 | View Replies]

To: PatrickHenry
Take a look at this page http://www.ncbi.nlm.nih.gov:80/sutils/blink.cgi?pid=38155724&tax=0&org=0&pdb=0&sort=1&cut=100&all=0 it shows how the "abnormal spindle-like microcephaly-associated protein" is related to some other species.

and here is the gene http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=259266
19 posted on 01/13/2004 2:35:21 PM PST by AdmSmith
[ Post Reply | Private Reply | To 1 | View Replies]

To: js1138
Once heard that the size of a human's head is limited by the size of the birth canal.

That we would have larger heads and larger brains if the woman's body could accommodate it.
20 posted on 01/13/2004 2:43:48 PM PST by dhs12345
[ Post Reply | Private Reply | To 7 | View Replies]


Navigation: use the links below to view more comments.
first 1-2021-25 next last

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
News/Activism
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson